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Mycofoam Insulation for Zero House

One of the most exciting developments in the field of sustainable building is the use of biological processes to literally grow building materials. While experiments in this realm abound, the folks at Ecovative is one of the first to become available. Currently Ecovative is focused on packaging materials and other non-construction uses for Mycofoam, but its use as a building material is supported by a number of ASTM tests that show it to be a feasible building insulation material (see data sheet below). We are very excited to be an early adopter of this technology!

This spring, we acquired some bags of Ecovative’s Grow-It-Yourself material to experiment with forming our own building insulation panels. We are happy with the results, and will be casting some larger panels to be used on our Zero House project.

 

We look forward to growing the larger sheets of Mycofoam for the Zero House project. And we definitely look forward to the day when Mycofoam is widely available to builders everywhere!

Thatch Roof Basics

Thatch roofs may seem like a romantic and foreign notion in North America, but they are entirely feasible in a wide range of North American climates. No other roofing is annually renewable, carbon-sequestering and non-toxic. A thatch roof may not be for everybody, but it’s worth considering…

This introduction to thatch roof basics is adapted from the book Making Better Buildings by Chris Magwood:

Thatch roof basics

Applications for system

– Roofing for roofs with a minimum pitch of 10:12

– Wall cladding

Basic materials

– Long-stemmed reeds or straw

– Strapping

– Twine or wire to fasten thatch to strapping

 

How the system works

 

While it may seem strange for modern builders to think that a bunch of dried grass stems can provide a thoroughly water-resistant and long-lasting roof, thatch roofs have a long and successful history across a wide range of climatic zones. Thatching techniques have been developed worldwide, adapting the basic principle to suit available materials and to work in specific climates. Modern thatched roofs are installed in almost every region of the world, though in relatively small numbers.

The system of thatching used in many wet and/or cold climates involves fastening bundles of long, thick reeds or straw to the roof strapping in successive courses, each overlapping the preceding course. The thatch is laid at a thickness (which can range from 8–20 cm / 3–8 inch) that prevents water from working its way through the layers. Thatched roofs have very steep pitches to aid in this drainage.

Traditional thatch was hand-tied to the roof strapping using twine or rope. Modern thatchers often use screws and wire to provide attachment. Regardless of regional variations in material and technique, the thatch is held in place by securing a horizontal member across the thatch and tying that member back to the strapping through the thatch. The next course of thatch then covers the tie point as the roof is built upward. At the edges of the roof, the thatch is laid at a slight angle to encourage runoff to leave the edge of the roof and to provide a consistent appearance.

Thatching on flat sections of roof is relatively straightforward, but the same cannot be said for ridge, hip and valley sections. These areas take considerable knowledge and experience to execute in a weather-tight and long-lasting manner.

Many modern installations use a fire-resistant (often fiberglass) membrane under the roof strapping to prevent the spread of a fire from inside the building to the roof. Eavestroughs are not typically installed with thatched roofs, making them incompatible with rainwater harvesting.

 

Tips for successful installation

  1. Thatching methods vary widely with the type of thatch material being used and the tradition of thatching used in the region. Ensure that the reed or straw being used is compatible with the climate and the installation technique.
  2. Be sure you are able to obtain the material and expertise required to create a thatched roof. It is a rare type of roofing in North America, and must be well researched before deciding to proceed.
  3. Plans for a thatched roof must be properly detailed before construction. The uncommon thickness of the roofing, the steep pitch required and the particular details at hips and valleys must be incorporated into the drawings to ensure the roof will work when built.
Thatch roof Canada

Dormers, hips and valleys require much more skill than simple gable roofs

Pros and cons of thatch roofs

Environmental impacts

Harvesting — Negligible to Low. Thatch that is harvested regionally will have the lowest environmental impact of any roofing material. The plants that produce useful thatch are annual grasses, making it the only annually renewable roofing. Some reeds that are suitable for thatching do not need to be manually seeded, but occur naturally on marginal lands that are otherwise not suitable for agriculture and aren’t sprayed or treated in any way. Most modern grain plants have been bred to have much shorter, narrower stalks than their genetic ancestors and are not suitable for thatch, but less common grains (spelt, rye, etc) still have stalk lengths and diameters that may work for thatch. Farmed grains may have environmental impacts associated with the use of herbicides and/or pesticides.

Manufacturing — Negligible to Low. Thatch requires little to no processing other than cutting, cleaning and bundling. These processes are done on a small scale and with minimal machinery and fossil fuel input. There are no toxic by-products created.

At the most intensive, a thatch roof will use a small amount of metal wire and screws and a layer of fiberglass matting that has high energy input and some toxic by-products. At the least intensive, round wood strapping and natural fiber twine is used.

Transportation — Negligible to High. Some thatch projects in North America are completed using thatch imported from Europe, because there are no commercial suppliers on this continent. This adds high transportation impacts to an otherwise low-impact roof. Many thatch roofs are made with locally, manually harvested material, keeping impacts very low.

Installation — Negligible. Thatch is largely installed without the use of power tools and does not create any problematic waste or by-products.

Embodied energy & carbon

Thatch roof Canada

Waste

Compostable — All reed or straw thatching, natural fiber twine.

Recyclable — Polypropylene twine, metal wire.

Landfill — Fiberglass matt offcuts, if used. Quantities can be negligible to low.

 

Energy efficiency

Historically, thatched buildings relied on the fairly significant amount of air trapped in the thatch to insulate the roof of the building. However, thatch allows for a lot of air infiltration and would not be considered adequate insulation or airtight enough to meet codes or modern comfort levels on its own. Modern buildings with thatched roofs rely on an insulation layer independent from the roof sheathing.

A thatch roof can have some beneficial effects by reducing summertime warming of the attic space quite significantly. Thatch roofs will also eliminate the issue of condensation on the back side of the roof sheathing as the material will not have the low surface temperatures of more dense sheathing and is able to adsorb and absorb moisture without condensation.

 

Labor input

Working at heights to install roofing has inherent dangers. Proper setup and safety precautions should always be taken when working on a roof.

Thatch roofing is unique in that, for most North American builders, harvesting the material is likely to be a necessary preliminary step. While suitable materials are widely available, harvesting and preparing them can be a very labor-intensive process, easily requiring more hours than the installation itself. In areas of the world where thatch material is harvested commercially and available for delivery to a job site, the labor input is obviously much lower.

Thatching is the most labor-intensive form of roofing. An experienced thatch crew can move at a speed that approaches that of an experienced cedar shingle crew. Beginners will move a great deal slower, as the process of laying thatch is very particular and must be done accurately and correctly.

 

Skill level required for the homeowner

Thatching requires a good deal of skill. In European countries, it takes many years of apprenticeship and experience to obtain the title of “Master Thatcher.” Beginners are advised to start with a very small roof, such as a small shed, and to keep roof shapes to simple gables or sheds. Hips and valleys add a lot of complexity to the thatching process, and should be left to those with plenty of experience.

 

Sourcing/availability

Both the material and the expertise to build a thatch roof can be difficult to source in North America. A few master thatchers practice in the U.S. and they tend to import their thatch material from Europe.

A homeowner wishing to attempt a thatch roof will have to resort to harvesting thatch material locally and learn from books or by taking workshops with experienced thatchers and bringing the skill back home.

 

Durability

Thatch roofs are surprisingly durable. In northern European climates, they can last for forty to eighty years. Depending on the style of ridge cap used, the ridge may need repair or replacing every ten to twenty years. A thatched roof at the end of its lifespan is not typically replaced; rather new thatch is built over top of the existing thatch.

 

Code compliance

No building codes in North America address the use of thatch roofs. Proposing a thatch roof will likely require a fair bit of documentation and persuasion, as there are few examples of thatched roofs on which a code official can base an assessment. The historical and modern use of thatch in Europe means that a lot of code-related testing and documentation exists to support it. A building department may be willing to consider a thatch roof with the right amount of documentation and some assurance that the installation is being done properly. The few master thatchers working in North America have been able to have their work approved, as have a small number of owner-builders.

 

Future development

There is no reason for thatch to be disregarded in North America, as it is a viable, durable roofing option that is remarkably environmentally friendly. As the costs of conventional roofing materials rise with the price of fuel to make them, thatch will start to look better and better. The machinery required to mechanically harvest and bundle thatch is not complicated or expensive, and viable thatch material grows in many places on the continent. There will always be limitations to the use of thatch roofing in urban areas, as fire safety concerns would limit the density of thatched roofs. But there are many locations where thatched roofs are feasible, appropriate and the best possible environmental choice. It will take many dedicated homeowners willing to push the boundaries and create a market in which thatch may start to take the kind of foothold where it creates a viable niche market, similar to cedar shingles.

 

How does it rate?

Thatch roof Canada

 

Resources for further research

Billett, Michael. The Complete Guide to Living with Thatch. London: Robert Hale, 2003. Print.

Fearn, Jacqueline. Thatch and Thatching. Aylesbury, UK: Shire Publications, 1976. Print.

Sanders, Marjorie, and Roger Angold. Thatches and Thatching: A Handbook for Owners, Thatchers and Conservators. Ramsbury, UK: Crowood, 2012. Print.

Composting Toilet Basics

Composting toilets are the most misunderstood element of an ecologically friendly building. There’s no need to be scared!

This introduction to composting toilet basics is adapted from the book Making Better Buildings by Chris Magwood:

 

Composting Toilet Basics

Composting toilets collect urine and feces — referred to as humanure in the rest of this chapter — and treat it completely on-site, until it is transformed into useful compost or humus.

This category of treatment system does not include common pit outhouses, which do not provide ideal conditions for the conversion of humanure to compost, though given enough time the material in a pit toilet can undergo this transformation.

There are three common types of composting toilet:

 

Bucket toilet — This low-tech version of the composting toilet uses a bucket or similar portable receptacle placed under a seat/container to receive humanure deposits. Sawdust, wood shavings, chopped straw or another form of cellulose material is used to cover each deposit in the toilet, helping to reduce odor, absorb urine and provide aeration. Once full, the bucket is emptied into an outdoor compost heap. Here the material is layered and mixed and covered with more cellulose material, providing the right conditions for the natural conversion to compost/humus.

The indoor toilet construction is usually provided with passive or active ventilation, but no water connection or flushing action is used.

Self-contained toilet — These units provide a seat over an integral composting tray in a single, self-contained structure. Humanure deposits are received in the tray and provided with the appropriate conditions for composting action within the unit. These toilets all use some form of mechanical ventilation to reduce odor. Excess urine may require a separate handling system, or heat may be used to speed evaporation. Due to limited storage capacity, these toilets normally use some form of mechanical action and/or acceleration for the composting process and are only suitable for low numbers of users or for intermittent use.

The compost tray is removed from the unit when processing is complete or when the tray is full. It is often necessary to have an outdoor compost heap to receive material from these units, as it can prove difficult to complete the composting process within the unit.

Some models of self-contained toilet use chemicals or high heat to “cook” the humanure into a benign state. The material from these toilets is not useful compost, as the biological activity that creates rich, useful soil has been killed off.

Remote chamber toilet — A toilet (dry chute or low-water flush) sits above a large, enclosed chamber that receives humanure. The chamber is of sufficient capacity and design to contain and process a high volume of completed compost.

Units handle humanure in various ways. Some use heat and/or evaporation to rid the chamber of excess urine and water and speed the composting process, while others retain and process all material. Mixing or stirring capabilities, misting sprayers and rotating trays are options offered by certain manufacturers. Vacuum flush, allowing the toilet to be level with or below the height of the chamber, is also available.

Some units gather excess urine after it has passed through the bulk material in the chamber and retain this liquid as a high-quality fertilizer. This makes best use of the potential value of all material entering the toilet, as up to 80 percent of the nutrient value in toilet waste is in the urine. Once transformed into nitrites and nitrates after passing through the biologically active compost solids, the liquid can be a safe and low-odor fertilizer.

All chamber-style toilets provide humanure with enough time and adequate conditions to fully convert to compost before being removed from the unit. These are the only units that do not require additional outdoor composting capacity.

 

Types of waste handled

– Black water (though most systems are waterless)

 

Tips for successful installation

  1. Understand the maintenance requirements of any type of composting toilet before committing to installation. All require some maintenance, and dealing with humanure is not for everybody. Some units require infrequent maintenance, others daily.
  2. Check local codes before planning for a composting toilet. They are an accepted solution in some codes but not in others.
  3. Check local codes for the legal status of composted humanure. Though a good deal of documentation exists to show the material is biologically benign, some jurisdictions require compost to be treated as hazardous waste.
  4. Some types of composting toilets require specific layout arrangements that must become part of the home design.
  5. Mechanical ventilation is part of most composting toilets, requiring an exit tube that passes through the roof of the building with as straight a run as possible.
  6. Plan for an easily accessible route from the point of removal to the outdoors, to facilitate emptying of the toilet or chamber.
  7. Be sure there is sufficient provision on the property for units requiring outdoor composting facilities, and that the process of finishing humanure compost outdoors is well understood.
  8. When using commercially produced units, follow the manufacturer’s instructions for successful installation.

 

Pros and cons

Environmental impacts

Composting toilets are the only form of toilet that does not treat human excrement as waste, and rather as a potentially regenerative material for amending soils and fertilizing plants. A large environmental problem is thereby transformed into a solution to soil depletion, creating more robust growing environments.

The composting of humanure is not without issues, and untreated or partially treated material can be contaminated with pathogens that are potentially dangerous to humans and animals and can contaminate soil and ground water. There is a growing body of evidence that complete composting of humanure is relatively easy to accomplish reliably, but the correct conditions must be understood and created.

 

Material costs

Simple bucket toilets and appropriate outdoor composters can be built for as little as a hundred dollars. Complete remote chamber toilet systems can cost between four and eight thousand dollars.

 

Labor input

Depending on the type of composting toilet, labor input can vary greatly. Other toilets do not require direct ventilation, and even the simplest composting toilet has more components and longer installation times than a conventional flush toilet.

 

Skill level required for the homeowner

Installation — Moderate to Difficult. Multiple components and connections can complicate installation.

Use — Easy.

Maintenance — Moderate to Difficult. Some form of regular maintenance is inevitable with composting toilets. Bucket toilets can require daily maintenance to transfer full buckets to the compost pile. Chamber units may only need monthly inspections and annual emptying.

 

Sourcing/availability

There are many commercially available self-contained and remote chamber toilets. These are typically sold directly from the manufacturer or in specialty shops. Bucket toilets are homemade, with plans readily available online or in books.

Plumbing for any composting toilet system are standard components available through any plumbing supply outlet.

 

Durability

The simpler the toilet system, the greater the durability. Units with heaters and moving parts are more prone to durability issues. Consider the accessibility of parts that may need repair or replacement; if they are in difficult locations (especially if they require emptying of the toilet’s contents) they will be unpleasant to service.

 

Future development

Interest in composting toilets is just beginning to grow, and the technology is likely to develop rapidly in coming decades. There has been a significant shift in understanding about humanure, from a sense of revulsion and the certainty of contamination and illness to an appreciation of the simplicity and value of composting. It will be some time before this shift affects a broad constituency of builders and homeowners, but the research and experience currently being gained in this field by early adopters will be valuable contributions to a technology that is potentially transformative. There is little else in home-building practice that could so radically improve the environmental impacts of our homes.

 

Resilience

Build and operating a composting toilet system in a low- or no-energy scenario is straightforward. The bucket toilet is an excellent example of resilient technology, as it not only replaces an energy- and resource-intensive practice, but does so in a way that gives back valuable nutrients to the ecosystem.

 

Resources for further research

Jenkins, Joseph C. The Humanure Handbook: A Guide to Composting Human Manure. Grove City, PA: Joseph Jenkins, 2005. Print.

Del Porto, David, and Carol Steinfeld. The Composting Toilet System Book: A Practical Guide to Choosing, Planning and Maintaining Composting Toilet Systems, an Alternative to Septic Systems and Sewers. Concord, MA: Center for Ecological Pollution Prevention, 2007. Print.

Darby, Dave. Compost Toilets: A Practical DIY Guide. Winslow, UK: Low-Impact Living Initiative, 2012. Print.

Envirolet vacuum flush toilets

Phoenix composting toilets

Residential Heating System Basics

Residential Heating System Basics

The ability to employ mechanical systems to automatically modulate the temperature (and often humidity levels) of our homes is a radical change from the previous centuries of human habitation. Our heating and cooling systems are often complex and high performance devices that give us fingertip control over indoor climate that would have been unthinkable less than a century ago. Until quite recently, the devices we used to achieve stable temperatures were functional but quite inefficient, using large quantities of fuel to meet our thermostat settings. A lot of development has gone into increasing efficiency, and in many cases this has come with increased complexity and cost. The following residential heating systems basics will help you understand your options.

Though most heating devices are intricate systems, it is quite easy to understand the basic technology behind each of them. It is worthwhile as a homeowner to understand these systems, and not leave it to company reps or installers to provide selling points.

It is easiest to think of heating and cooling systems as falling into categories of means of heat production and means of heat delivery. From this understanding, it is possible to narrow down the pool of options to those that suit the needs of a project.

Means of Heat Production

Despite all the competing products in the heating and cooling market, there are just four kinds of heat production. Details for each system are provided individually later in the chapter.

1) Solar Heat

In effect, all sources of heat are based on solar energy, as the fuels used in every heating system are the result of captured and stored solar energy. However, this classification of heating systems is based on direct harvesting of solar energy in real time. Heat from the sun can be collected (and sometimes concentrated) in, on or near the building and distributed for use throughout the building.

There are three basic types of solar heat, which may be used in any combination.

Passive Solar – A building may be designed with sufficient glazing on the sunny side of the building to allow for a measurable increase of indoor temperature when the sun is shining.

Active Solar Air – Collector units are used to gather and concentrate the sun’s heat in a flow of air that is supplied to a heat exchanger or directly to the building.

Active Solar Water – Collector units are used to gather and concentrate the sun’s heat in a flow of liquid that is supplied to a heat exchanger or directly to the building.

This category of heating devices does not include photovoltaic cells, which use solar energy to generate electrical current, and not directly to produce heat. Heat created by solar electric current is considered in the category of electric resistance heating.

Solar energy systems may appear to have low efficiency rates, with figures ranging from 10-70%, depending on ambient temperatures and type of collector, among other factors. These figures represent the percentage of available potential energy from the sun: approximately 1000 Watts per meter squared (W/m2) for a surface perpendicular to the sun’s rays at sea level on a clear day. A reduced figure of 800 W/m2 is often used in generating comparative figures for solar devices. While it is beneficial to increase efficiency rates to produce more heat from less collector area, the efficiency rates aren’t directly comparable to those of combustion devices as no sunlight is actually “wasted” and no harmful byproducts are generated by the solar energy that is not absorbed by the collector.

Solar heating systems do not generate emissions, fuel extraction and transportation impacts or air pollution, with the exception of those systems that use non-solar energy to drive small pumps or fans.

2) Combustion Devices

This category of equipment is by far the most prevalent. Regardless of the type of system and fuel used, all combustion devices burn a fuel and extract heat from the flame. All these devices rely on a supply of oxygen to react with the fuel and create the flame, an exhaust to allow spent combustion gasses to exit the unit and the building and a heat exchanger that passes the heat from the flame to the delivery system that supplies heat to the home. There are two broad categories of combustion devices:

Gas/Liquid Fuel Combustion – These are the dominant players in the market, and include all the various forms of fossil fuel such as natural gas, propane and oil, as well as bio-fuels like biodiesel and vegetable oil.

Solid Fuel Combustion – This group includes wood burning devices, as well as those that use other forms of biomass such as compressed pellets.

Combustion devices have efficiencies that range from 50% for some wood burning devices to 98% for some new gas burning devices. This means that less than all of the heat potential of the fuel is captured and used to supply the building.

Exhaust gasses from combustion devices differ depending on the fuel used and the combustion efficiency and conditions, but all devices release CO2 and a host of other byproducts with environmental effects.

3) Heat Pumps

This category of equipment is widely used in the form of air conditioners, and has started to capture a larger portion of the heating market. These systems use the refrigerant cycle to transfer latent heat from a source and deliver it to a destination or heat sink. It can be difficult to understand exactly how a heat pump works, but it is worth figuring out the principle at work in order to decipher manufacturer claims. Heat pumps can seem like they magically make heat from no heat if the refrigerant cycle is unclear.

heat pump explained

Heat pump explained

Mechanical energy (usually in the form of an electric motor) is used to cycle a volatile refrigerant that is chemically designed to boil and condense in the expected operating temperature range of the heat pump. The refrigerant is in its liquid state when it absorbs latent heat from a source (air, ground or water for most residential purposes). This heat does not need to be in a temperature range that feels warm or hot to the touch, as the refrigerant’s chemical properties will ensure its boiling point is at or near to the source temperature. Once the refrigerant has passed through the heat collection exchanger, the electric compressor pressurizes the warmed refrigerant, which is at or close to its boiling point. The pressurization causes the refrigerant to become a hot vapour. This hot vapour passes through a heat exchanger where the heat generated from pressurization is dispersed. The refrigerant condenses as the heat is removed. Condensed refrigerant now passes through an expansion valve where the pressure is released and the refrigerant returns to its liquid state and returns again to the exchanger and repeats the cycle until a thermostat indicates the proper room temperature has been reached.

It is the process of boiling and condensing a refrigerant under different pressures that creates the heat exchange. Useful heat exists in this boiling/condensing cycle, regardless of the actual boiling point of the refrigerant. As long as heat collection side is above absolute zero, there will be heat to extract. Consider the home refrigerator: cold is not being generated in the freezer, rather heat is being extracted from the freezer and released via the heat coils on the back of the fridge.

The refrigerant cycle can happen in either direction, and some types of heat pumps are designed to work as both heating and air conditioning units by reversing the direction of flow of the refrigerant.

There are three broad categories of heat pumps for residential use:

Ground Source Heat Pumps (GSHP) – The source of heat is the stable temperature of the ground (below the frost line in cold climates). Base ground temperature is very reliable and steady, and the ground provides a large surface area and capacity for heat exchange. Most GSHPs are reversible and can provide heat and cooling.

Air Source Heat Pumps (ASHP) – The source of heat is the ambient air temperature outside the building. As this temperature can be quite variable, different refrigerants and/or pumps are used to continuously extract useful heat from changing air temperature. Most ASHPs are reversible and can provide heat and cooling.

Air Conditioners (AC) – The source of heat is the uncomfortably warm air that is affecting comfort. These units provide cooling only.

Efficiencies for heat pumps far exceed those of combustion devices. The amount of energy input to provide compression of the refrigerant is significantly lower than the amount of heat energy that is extracted from the process and this how manufacturers claim efficiencies ranging from 200-500%. The heat is not “free” as some claim, but for every one unit of electrical energy applied to the system, 2-4 units of heat are returned. The systems don’t work without the electric motors, but they are much more efficient than combustion devices.

While there is no combustion and therefore no exhaust gasses from heat pumps, environmental impacts will vary depending on the source of electricity used to power the system. The refrigerants used can also be powerful greenhouse gasses, though stricter regulations are resulting in less damaging formulations.

4) Electric Resistance Heat

Electrical current can be passed through a resistive conductor to produce heat. This type of heat production is known as resistive, Joule or ohmic heating. The heat produced is proportional to the square of the current multiplied by the electrical resistance of the wire or element. The amount of current supplied can be adjusted to vary the heat output. Heat energy may be supplied through convection and/or infrared radiation depending on the kind of heating element used.

Efficiency of electrical resistance heating is considered to be 100%, as all the potential energy in the current is converted to heat. However, many sources of electrical power are less than 100% efficient, so overall system performance must take into account the type of generation used to supply the electricity.

The type of generation will also determine the environmental impacts, which can range from high for coal-fired power plants (with delivered power efficiencies as low as 35%) to negligible for renewable energy streams like solar, wind and microhydro.

Means of Heat Delivery

Heat flow always moves from a warmer object to a colder one. Heat flow can occur in three ways:

Conduction – Heat energy is transferred from a warmer object to a colder one by direct contact.

Convection – Heat energy is transferred from a warmer object to the air surrounding the object and then to cooler objects in contact with the warmed air. Warmed air become less dense and rises, creating convection currents that affect objects in the path of the current.

Radiation – Heat energy is transferred from a warmer object to a cooler object by electromagnetic waves, caused by energy released by excited atoms.

Heat transfer

Heat transfer

These neat categorizations do not adequately describe heat delivery systems in buildings, as any heating system will warm a space in all three ways to varying degrees. Consider the element on an electric range: anything that touches the hot element will be heated by conduction. At the same time, air near the element will be warmed, become buoyant and warm objects near the range by convection and the heated element will radiate heat to nearby cooler objects, warming the surface of the range and nearby utensils that are not touching the element nor in the path of heated air.

Certain heating systems will rely on one of these methods of heat flow more than others, but cannot be categorized by a particular kind of heat flow.

Instead, it is more useful to consider heating systems in regard to the medium of delivery, of which there are two. Almost any kind of heat production can be twinned with any kind of delivery system.

1) Air Delivery

Passive Air Delivery – These systems rely only on natural convection currents to move heat from a source to the desired locations in the building. No fans or ducts are used to direct warmed air.

Active Air Delivery – These systems use some form of mechanical energy to force air movement in a desired direction. Ductwork is often used to deliver a concentrated stream of warmed air to a particular location.

Air can be an effective medium for delivering heat in some circumstances. It is not very dense, and it is therefore easy to change the temperature of a large volume of air quite quickly. The energy required to move air from one location to another is low, as it flows and changes direction easily and large volumes can be moved quickly. Natural convection loops of rising warmed air and falling cool air can be exploited to good effect to contribute some or all of the required flow.

Occupants in buildings will feel heated air against their skin and have an immediate awareness of warmth and perceived comfort.

These advantages of air as a heating medium are also the disadvantages. The low density of air means that it loses its heat very quickly to more dense objects; raising the temperature of objects in a building via air flow can take a long time, and often objects and the surfaces of the building remain significantly cooler than the ambient air temperature. This can lead to discomfort as the warm occupants in the home will unwittingly be trying to heat the building’s surfaces radiantly, one of the reasons it’s possible to feel a “chill” even in a warm building.

The convection loops associated with air delivery ensure that the warmest area of the building is at the ceiling and the coolest is at the floor. Since occupants reside on the lower side of this balance, some heat is “wasted” by being concentrated outside the contact zone for occupants. Convection loops can also cause cool air to move against occupants in some areas of the building, causing the feeling of chilly drafts even in an air tight building.

In forced air systems with ductwork and fans, the layout must be done carefully if it is going to be efficient. Limiting the number of bends and restrictions increases flow, and proper positioning of outlets can reduce unwanted convection loops and create a relatively even distribution of heat.

Air heating systems will move a significant amount of dust and allergens as it flows. In forced air systems, inline filtration is highly recommended. For natural convection systems, an active filtration system is worth considering.

2) Hydronic Delivery

Using a fluid (typically water) to transfer heat from a source to a destination is a strategy with a long history. Water has a high capacity for absorbing and releasing heat in the range of temperatures used in buildings, and its high density means it can store a lot of heat.

Hydronic heating systems are often called “radiant” heating systems, especially when the heat is delivered to an entire floor area, but this is not an accurate description. Floor heat is conducted through feet, and a very even and useful form of convection accompanies the radiant transfer of heat.

Hydronic heat delivery can be achieved via a radiator that has a lot of surface area. Radiators can be the floor, walls and/or ceilings of the building, or purpose-built radiator systems. Water-to-air systems use a radiator inside forced air ductwork to create a hybrid system.

In all of these systems, produced heat is absorbed into the transfer fluid and moved through pipes through the action of a mechanical pump. The fluid is delivered through branch pipes to the point(s) of delivery where the heat is released, before being recirculated to the heat source again.

Hydronic heating systems will take a longer time to deliver perceptible heat, as the water requires more heat input to reach a perceptible temperature change. Once delivered to the radiator, the quantity of heat in the mass of the water and radiator creates much slower release times. The mass of air (and in some systems, even people) in the building will be lower than the heated mass, and all will rapidly be warmed to the radiator’s temperature without “draining” the radiator of its stored heat, resulting in longer but less frequent cycling of the heating system compared to air systems.

The design of hydronic systems needs to account for the surface area and distribution of the radiator(s), the length of piping and head, and the temperatures required to provide comfort based on the radiator layout. Systems can be quite simple, with a single pump and just a few radiator loops, or they can be complex with multiple pumps and valves responding to individual thermostats in each radiator zone.

Heating System Design: Heat Loss Calculation

Regardless of type of heat production and means of delivery, the design of an effective heating system starts with an accurate assessment of the expected heating needs for the building. This is achieve through the completion of a heat loss calculation. Many building codes now require such a calculation, and even if it is not a legal requirement it is recommended. Oversized or undersized heating systems are not efficient, and will cost a lot more than the calculation.

There are free, simple spreadsheets that can be used for heat loss calculations. These involve gathering dimensions for wall, floor, ceiling, window and door surface areas from the building plans and assigning each its expected heat loss rate (U-value or R-value). These figures are tallied and factored with the number of degree days and minimum anticipated temperature. The results include the hourly heat loss for the coldest expected day (expressed as BTU/hr) and total yearly heat loss (in millions of BTU).

More complex and comprehensive computer modeling programs will include more variables in the calculation, giving consideration to solar gain, thermal bridging in the building enclosure, anticipated air leakage rates and occupant behaviour among other factors. The more detailed the calculation, the more useful the resulting figures for sizing heating systems.

The hourly heat loss figure determines the maximum required output of the heating system, and the total yearly heat loss helps to anticipate energy requirements and costs. Figures from a good heat loss calculation also allow the design of the building to be tweaked for maximum efficiency at the design stage, as variables can be adjusted to determine ideal levels of insulation, window size and quality and air tightness.

With the parameters established by the results of the heat loss calculation, the particulars of the system can be designed to meet these needs in the most efficient and comfortable way.

Making Better Buildings book

This content is based on the book Making Better Buildings by Chris Magwood. 

Rammed Earth Construction Basics

Rammed earth construction basics

How does rammed earth construction rate? This introduction to rammed earth construction is from the book Making Better Buildings: A Comparative Guide to Sustainable Construction for Homeowners and Contractors, by Chris Magwood from the Endeavour Centre. The book gives unbiased information about all the different sustainable building material options.

Applications for rammed earth wall systems

  • Load-bearing wall systems
  • Interior walls
  • Built-in furniture, benches
  • Decorative elements

Basic materials

  • Earth
  • Stabilizer (cement or lime where required)
  • Insulation (where required)
  • Water-resistant finish (where required)

Control layers

Water control  — The finished rammed earth is typically the water control layer. It is possible to use vapor-permeable, water-resistant finishes on the rammed earth surface or to include water-resistant additives in the earth mix before ramming. Additional cladding over the rammed earth is feasible but rarely done. We all know the danger of water damage to a home. If for some reason, water damage occurs, you need to reach out to a professional like Flood Proof Florida LLC.

Air and vapor control — Solid, continuous and dense, rammed earth is an effective air and vapor control layer.

Thermal control — A rammed earth wall requires an additional thermal control layer in hot or cold climates (see Thermal Mass vs. Insulation sidebar). This layer can be on the interior, exterior or center of the wall, and is typically a rigid insulation.

How rammed earth construction works

A lightly moistened earth mix with a relatively low clay content (10%–30% is common) is placed into forms in lifts, then tamped heavily to achieve a desired level of compaction. The soil mix varies by region and builder, but it is common to “stabilize” the mix with a small amount (3%–9%) of portland cement or other hydraulic binder.

The walls are built up in continuous lifts to full height. Often they are built in sections, so that formwork is not needed continuously around the building.

Window and door openings are usually created using a wooden “volume displacement box” or VDB. These VDBs hold the place of the window or door as tamping occurs around them. Once the wall is complete the VDB is removed, leaving a well-formed opening in the wall.

For large openings, lintels of wood, concrete or steel can be used above the opening; these are often buried in the rammed earth so they cannot be seen in the finished wall.

Electrical wiring and switch boxes (or conduits to receive them) are placed in the formwork before adding earth and tamping, and are formed right into the wall. Surface mounting after construction is also possible.

At the top of a rammed earth wall is a bond beam made of poured concrete, wood or steel. The beam is fastened to the top of the wall to provide a continuous attachment point for a roof. The method of fastening will depend on expected wind and seismic loads.

In hot or cold climates, insulation is part of a rammed earth wall system. The insulation can be a continuous wrap on the interior or exterior of the wall, but more commonly it is centered in the wall. Types of insulation used will vary with climate, availability, compressive strength and environmental factors.

Rammed earth walls are usually left exposed to provide the finished surface. A variety of sealants can be used on the raw earth to leave it visible but add protection from water. Plasters and others sidings are rarely used but are possible finishes.

Tips for successful rammed earth walls

  1. Formwork is the key to building with rammed earth, and the better the formwork the faster and more accurate the construction. Forms must be able to withstand the considerable forces of ramming the earth within and be able to be assembled and disassembled with a minimum of effort. Formwork that is reusable can help keep costs down. Check with experienced builders to see what formwork systems are being used successfully.
  2. Soils used for rammed earth must be very well mixed and not too wet. An even distribution of clay and any additional binders (cement, slag, lime, fly ash) is crucial to final wall strength. Rammed earth mixes do not benefit from the plasticity that water adds, and require plenty of mechanical mixing to achieve best results instead.
  3. Test potential soils before using. The makeup of the soil is critical to the performance of the wall. A lot of soil is required to make a rammed earth wall, and changes in its composition will mean that mixes may need to change too. Compact samples of the earth and use reliable sources to determine whether or not you will need stabilizers, and which ones are most appropriate for the soil type.
  4. Plan mechanical systems and wall openings carefully, as modifying rammed earth walls is time-consuming. If services are to be run within the walls, consider using conduit so that you can make changes and repairs without opening the wall.
  5. Avoid finishes that will reduce or eliminate the permeability of the rammed earth wall.
  6. If you are building your own home, consider buying the equipment you will need to dig, mix and tamp the earth. It can be much less costly to buy used equipment and re-sell it at the end of a project than to rent it for a long period of time.

        Pros and cons of rammed earth construction

Environmental impacts

Harvesting — Negligible to Moderate. Site soil can be harvested with negligible impacts. Amending materials like sand and cement have low to moderate impacts including habitat destruction and water contamination from quarrying.

Steel for reinforcing bar is extracted in a high-impact manner, with effects including habitat destruction and ground water contamination.

Manufacturing — Negligible to Moderate. Soil can be extracted and processed with negligible to low impacts.

Portland cement, if used, is fired at extremely high temperatures and has high impacts including fossil fuel use, air and water pollution and greenhouse gas emissions.

Steel reinforcement bar is made in a high-heat process that uses a lot of fossil fuel, and has impacts that include air and water pollution.

Transportation — Negligible to Moderate.

Sample building uses 79,410 – 105,666 kg of rammed earth:

74.6 – 99.3 MJ per km by 35 ton truck

Soil, cement and steel are heavy materials, and accrue significant impacts proportional to distance traveled.

Installation — Negligible to Moderate. The process of ramming the soil mixture can be done manually with negligible impact. More often, hydraulic machinery is used, with moderate impacts depending on power source.

Embodied carbon & energy of rammed earth construction:

rammed earth construction embodied carbon

Waste from rammed earth construction: Low

Biodegradable/Compostable — All leftover earth materials.

Recyclable — Metal reinforcement bar.

Landfill — Manufactured insulation offcuts, cement bags.

Energy efficiency of rammed earth: Low to High

A rammed earth wall has a lot of thermal mass and can easily be an airtight wall system, but it has no inherent insulation value (see Thermal Mass vs. Insulation sidebar). The overall energy efficiency of a rammed earth wall system will depend on the insulation strategy. Insulation can be placed on either the interior or exterior of the wall or a double wythe system can have insulation in the middle of the wall.

Insulation on either side of the wall will force a builder to create a finished surface over the insulation, which adds cost and complexity to the wall system and isolates all of the available thermal mass on one side or the other. Core insulation is more effective and leaves the rammed earth as the finish on both sides, but complicates the forming and tamping process and limits choice of insulation to materials that can resist the compressive forces of the tamping process.

Material costs of rammed earth construction: Negligible to Moderate

Components for good rammed earth may be sourced on site at negligible cost, but pre-mixed versions with Portland cement stabilizers may be moderately expensive. The addition of rigid foam insulation between two wythes of rammed earth will raise costs considerably.

Labor input of rammed earth construction: High to Very High

Rammed earth construction is labor intensive. The use of machinery can reduce the amount of labor involved in excavating, mixing and tamping earth, but even machine time can be extensive. Building, erecting and disassembling formwork takes a lot of time regardless of tamping method. However, when used as the finished wall surface, a rammed earth wall eliminates the need for steps often required to sheath and finish other walls.

Skill level required for rammed earth construction: Moderate to High

Mixing and tamping soil does not require prior experience, but the creation and use of formwork does, as does the operation of excavation and dirt-moving machinery. A first-time builder will want some training or experience prior to undertaking a major rammed earth project.

Sourcing/availability of rammed earth materials: Easy to Moderate

Soils suitable for rammed earth construction are widely available, as are the ingredients for amending soils that are not inherently suitable. The equipment used for excavating and tamping earth is common to other more conventional construction activities and should be easy to source.

Insulation materials will vary in availability depending on type and location.

Durability of rammed earth construction: Moderate to High

Rammed earth buildings have a long history in many parts of the world, with some examples lasting well over a thousand years. Erosion and/or spalling caused by excessive wetting are the main causes of failure. Creating adequate roof overhangs and site drainage can control this. Water repellents are sometimes mixed into the rammed earth or applied over exposed surfaces. These must not affect the strength of the mix or overly reduce permeability. Plasters and other forms of siding can also prevent moisture damage.

Rammed earth, like all soil-based construction types, can be repaired quite easily if damaged, by the addition of new soil mix.

Code compliance of rammed earth construction

Rammed earth construction is an accepted solution in some building codes, in regions where the technique has historical precedent. A good deal of testing and modeling of rammed earth walls has been done around the world, and the available data is usually sufficient to justify the use of rammed earth as a load-bearing wall for one- and two-story structures. A structural engineer may be needed to approve drawings to obtain a permit.

Indoor air quality of rammed earth construction: High

Uncontaminated earth is generally agreed to have no inherently dangerous elements and is consistent with the aims of high indoor air quality.

Soil contamination, from natural sources like radon or synthetic sources like petrochemicals, is possible, and it is wise to inspect and/or test soils carefully before using them to build a house.

Future development of rammed earth construction

Code development for rammed earth is moving forward in several countries, including the US and Australia. Widespread code acceptance is likely to encourage more rammed earth construction.

As the basics of rammed earth construction have remained the same for thousands of years, revolutionary developments in technique are unlikely. However, processes to reduce labor input for formwork and soil mixing and tamping are likely to be streamlined, making the system more affordable.

How does rammed earth construction rate?

rammed earth construction

 

Resources for rammed earth construction

Walker, Peter. Rammed Earth: Design and Construction Guidelines. Watford, UK: BRE hop, 2005. Print.

Easton, David. The Rammed Earth House. White River Junction, VT: Chelsea Green, 1996. Print.

Minke, Gernot. Earth Construction Handbook: The Building Material Earth in Modern Architecture. Southampton, UK: WIT, 2000. Print.

Rael, Ronald. Earth Architecture. New York: Princeton Architectural Press, 2009. Print.

Morton, Tom. Earth Masonry: Design and Construction Guidelines. Bracknell, UK: IHS BRE, 2008. Print.

Jaquin, Paul, and Charles Augarde. Earth Building: History, Science and Conservation. Bracknell, UK: IHS BRE, 2012. Print.

Keefe, Laurence. Earth Building: Methods and Materials, Repair and Conservation. London: Taylor & Francis, 2005. Print.

McHenry, Paul Graham. Adobe and Rammed Earth Buildings: Design and Construction. Tucson, AZ: University of Arizona, 1989. Print.

 

Jumbo bales and hempcrete – together!

Fifth Wind Farms wanted to create a building that could reach the energy efficiency requirements of the Passive House standard without resorting to the use of foam, mineral wool or other materials with a high carbon footprint. While straw bale buildings can have excellent energy performance, typical straw bale construction does not meet the Passive House standard without the addition of an extra layer of insulation (see our “Straw-Cell” project for a different take on this idea).

Jumbo straw bale duplex home

First jumbo bale in place (on a bed of Poraver insulation)

The building owner proposed the use of “jumbo bales,” which are produced from the same local straw and by the same low-carbon machinery, but are of dimensions that greatly increase their thermal performance. While typical straw bales are 14″ x 18″ x 32″, the jumbo bales used for this project measure 32″ x 32″ x 60″! At a nominal R-value of 2.0 per inch, that would give a jumbo bale wall a rating in the range of R-60, more than enough to help the building meet any energy efficiency rating.

However, the jumbo bales provide some issues when it comes to window and door openings… with a wall that thick, window sills and returns are extremely deep, creating not just aesthetic concerns but also concerns about air flow in the deeply recessed bays and the likelihood of condensation forming on the windows in cold weather.

Our solution was to form the window sections at a wall depth of 16″ using double stud framing and hempcrete as the infill insulation. This would keep us on track as far as low carbon footprint is concerned, and the hempcrete would be used to create the tapered window returns to meet the full depth of the bale walls. As a bonus, the hempcrete would completely fill any voids at the ends of the jumbo bales.

One issue with using jumbo bales: they weigh over 500 pounds each! We used a boom truck to install them in the building. With the bales in place and the top plate secured over the bales, we then mixed our hempcrete (you can find our recipe here) and tamped it into the framing and around the jumbo bales. The two materials are very complimentary, with the easily-formed hempcrete able to compensate for the uneven ends of the jumbo bales and creating smooth window returns.

 

The building is currently being prepared for plastering… more posts to follow soon!

Building a roof on the ground

At Endeavour, we tackle some fairly large building projects with our Sustainable New Construction program. This means completing a entire building from the ground up in just 5-6 months, from breaking ground to final finishes. Time is always at a premium, as is the safety of our students. For both these reasons, we often choose to build our roof structures on the ground and lift them into place with a crane.

 

Building on the ground allows us to have a team working on the roof right from the beginning of the project, rather than only starting the roof once the foundation and walls are completed. This kind of “multi-tasking” shortens the entire build cycle, as the mostly-completed roof is set in place as soon as the walls are ready to receive it. The building receives immediate weather protection and the project moves into the finishing phases very quickly.

The process of building the roof is also appreciably faster when it’s done close to the ground. Much less time is spent going up and down ladders and scaffolding, and the accuracy of the work is improved because workers feel comfortable and safe and can take their time to do jobs properly.

And of course, doing the whole project at ground level is a much safer way to learn to how to measure, mark, layout and install all the components of a roof. Much of the work can be done with feet planted firmly on the ground, and even when working at the peak the heights are limited.

For our jumbo straw bale duplex this year, we are again employing this technique, and this time the process includes full construction of the soffits, fascia and gable end siding.

 

The more complex the roof and roof details, the more sense it makes to build this way. None of our roof lifts have required more than 4-8 hours of crane time, which makes it a very affordable process (ranging between $750-1200), especially considering the time savings during construction.

And the day of the lift is exciting, a bit nervous, and a great sense of accomplishment as the building goes from open walls to full enclosed structure.

Building a roof on the ground

Relaxing after the excitement of lift day!

Sustainable Building Essentials from Endeavour and New Society Publishers

The Endeavour Centre is partnering with New Society Publishers to bring natural building enthusiasts a new series of books intended to cover the full spectrum of materials, systems and approaches to natural building.

Sustainable Building Essentials books

Called the Sustainable Building Essentials series, the books cover the full range of natural and green building techniques with a focus on sustainable materials and methods and code compliance. Firmly rooted in sound building science and drawing on decades of experience, these large-format, highly-illustrated manuals deliver comprehensive, practical guidance from leading experts using a well-organized step-by-step approach. Whether your interest is foundations, walls, insulation, mechanical systems or final finishes, these unique books present the essential information on each topic.

The first three titles in the series are now available for pre-order from the publisher, with a 20% discount:

Essential Hempcrete Construction

Essential Building Science

Essential Prefab Strawbale Construction

Upcoming titles in the series include:

  • Essential Straw/Clay Construction
  • Essential Green Home Design
  • Essential Rainwater Harvesting
  • Essential Natural Plasters
  • Essential Cordwood Construction
  • Essential Composting Toilet Systems
  • Essential Green Roofs
  • and many more…

We hope that this series helps continue Endeavour’s mission to bring affordable, accessible and accurate sustainable building information to a wide audience!

Light clay straw insulation

On April 10, a workshop at Endeavour led participants through the theory and practice of making wall insulation from light clay straw (also known as straw/clay, slipstraw, or EcoNestTM).

This is an insulating technique we’ve used numerous times on building projects at Endeavour, and we appreciate the extremely low carbon footprint, simplicity, lack of toxicity and simple installation process of this insulation.

Here is an introductory slide show about light straw clay insulation:

Clay slip versus dry mixing
During our workshop, we used the typical mixing approach for light clay straw insulation: mixing our clay into water until we had a thick, “melted milkshake” consistency. This slip is then poured onto the straw and mixed in until the slip evenly coats all of the straw, so that a handful of straw can be squeezed into a shape that reasonably retains its shape. Whether mixed by hand, in a mortar mixer or in a purpose made straw/clay tumbler, this is how we and other straw/clay builders typically prepare the insulation.

 

For this workshop, we also tried a mixing technique more similar to that we use for hempcrete. When mixing hempcrete, the hemp hurd and the binder are added together when dry, mixed until the powdery binder coats all the hemp, and then lightly misted with water to make the binder sticky. So we tried sprinkling dry powdered clay over the straw, stirring, and then adding water. This didn’t work so well, as the clay powdered sifted down through the straw and ended up at the bottom.

Dry mixing, version 2
For our next batch, we reversed the process and gave the straw a light misting of water and then sprinkled in the clay powder and stirred. This seemed to work very well, as we ended up with a clay coating on the straw that was much stickier than slip mix and allowed the clay/straw to be packed into the forms easily. This process used 25-50% less clay, and more importantly 25-50% less water, which should reduce drying time in the wall dramatically. Having placed both slip-mix and dry-mix side-by-side in the same wall system, there was no appreciable difference in quality in the finished appearance of the insulation, but the dry-mix showed about 25% moisture content on our moisture meter, and the slip mix was up at 36%. Given that slow drying time is the main hang-up for straw/clay insulation, we will use this technique in the future to reduce the wait for the insulation to dry!

NEXT STRAW/CLAY WORKSHOP: OCTOBER 30, 2016

Hempcrete developments

On April 9, a workshop at Endeavour brought participants together to explore hempcrete insulation materials.

The workshop looked at well-used options for these materials, but also explored some interesting new approaches.

Endeavour has continued to develop the use of homemade hydraulic lime binders as a means to eliminate carbon-heavy cement from our building materials and to create locally-sourced binders for cement replacement. At this point, our homemade hydraulic lime binder is well-tested and we feel it works as well as any of the imported (European) hempcrete binders, at a fraction of the cost and with locally-sourced ingredients.

Hempcrete mix
Our hempcrete binder is composed of 50% hydrated lime (most easily accessible to us is Graymont’s Ivory Finish Lime) and 50% Metapor metakaolin from Poraver (created as a by-product of the company’s expanded glass bead production).

We mix our hempcrete at a ratio of 1 part chopped hemp hurd by weight, with 1.5 parts of the binder by weight. After translating these weights to volume measurements, it was 4 buckets or hemp hurd going into the mixer with 1 bucket of binder (1/2 lime, 1/2 metakaolin).

 

hempcrete insulation

Weight ratios are converted to bucket measurements: 1/2 bucket of lime, 1/2 bucket of metakaolin, 4 buckets of hemp hurd

 

The hemp hurd goes into the mortar mixer first and then we sprinkle in the binder and allow it dry mix until the hurd is well coated with binder powder.

hempcrete insulation

A horizontal shaft mortar mixer is used to dry-mix the lime binder and the hemp before water is misted into the mix

Water is then misted (not sprayed) into the mixer until the mix is just moist enough that if we pack it like a snowball in our gloved hands it keeps its shape, but is still fairly fragile (ie, can be broken with a bit of a squeeze). It is important to not over-wet the hempcrete, as this will greatly extend the drying time once the hempcrete has been packed into a wall. If too much water is added, the mix can’t be recovered by adding more dry ingredients as the hemp hurd will quickly absorb excess water and there won’t be any free water for the new dry ingredients. So, add water carefully and gradually!

hempcrete insulation

When packed like a snowball, the hempcrete should just hang together

Hempcrete is placed into formwork on a frame wall, using light hand-pressure to compact the mix just enough to ensure that the binder will stick all the individual pieces of hemp together.

hempcrete construction

Hempcrete is placed into forms and lightly pressed into place. The forms are leap-frogged up the wall.

Our workshop crew was able to mix and place enough hempcrete to fill a 4-1/4 inch deep wall cavity that was 4-feet wide and 13-feet high in just under 3 hours! That’s over 6 cubic feet of material per hour!

Hempcrete recycling
We have long touted the no-waste benefits of hempcrete. We’ve speculated that even when the insulation is being removed from a building during renovations or demolition, that the hempcrete can be broken up and recycled into a new mix with new binder added. We put that theory to the test at the workshop, as we demolished one of our small sample walls and added the broken up hempcrete into our new mixes at a ratio of 3 parts new hemp to 1 part recycled hempcrete. The resulting mixes were impossible to distinguish from the all-new mixes, and confirmed that hempcrete can easily be re-used!

hempcrete insulation

Hempcrete that had already been mixed into a wall was broken up and added into a new mix… Fully recyclable!

Hempcrete book forthcoming
If you are interested in hempcrete insulation, Endeavour’s Chris Magwood has just finished a book called Essential Hempcrete Construction that will be available in June, 2016. It contains recipes, sourcing, costing, design and installation instructions and will be very valuable to anybody considering a hempcrete project.

hempcrete insulation

New book includes everything you need to know about building with hempcrete

Hemp-clay shows lots of promise!
Hempcrete insulation is almost always done using a lime-based binder. But at the Natural Building Colloquium in Kingston, New Mexico last October, we were doing a hempcrete demonstration right next to a straw/clay demonstration, and we took the opportunity to mix up a block of hemp hurds with a clay binder.

hemp clay construction

A sample block of hemp-clay showed the potential for this material combination

The success of that demo block led us to try this combination on a slightly larger scale, and we machine mixed the clay and the hemp to fill one tall wall cavity with this hybrid material. Using the same mixing methodology as typical hempcrete, we added the hemp hurd and dry bagged clay to the mixer and allowed it to dry mix, before misting with water. Interestingly, we were able to use half the amount of clay binder compared to lime binder (1/2 bucket of clay to 4 buckets of hemp hurd) and the resulting mix was stickier and easy to form and pack than with the lime, and with the addition of noticeably less water.

hemp clay construction

The hemp-clay mix has great binding power, and keeps its shape with very little pressure required

The key difference between the two binders is in their manner of setting. Hydraulic lime binders cure chemically, and consume water to change the chemical structure of the mix as it solidifies. Clay binders simply dry out and get hard. So the lime-based versions should be drier and harder sooner. However, the smaller quantity of water required in the clay-hemp mix may mean that drying times end up being similar… we’ll report back when we know.

hemp clay construction

A close-up of the hemp-clay mix formed into the wall. It keeps its shape within seconds of being placed into the forms

Clay binder with hempcrete offers some advantages over lime-based options, including a significantly lower carbon footprint and none of the caustic nature of lime that can cause skin burns when handling. The clay-based binder creates a mix that is much stickier during installation, which means less packing/tamping to get the material to cohere in the forms. Less water means that it was almost impossible to over-compact the mixture. We will definitely be exploring this option in a serious way!

hempcrete insulation

Having placed 18.5 cubic feet of hempcrete in a few hours, the crew stands in front of their work. The lighter coloured hempcrete is our homemade hydraulic binder, the darker mix is Batichanvre, a binder imported from France.

NEXT HEMPCRETE WORKSHOP: OCTOBER 29, 2016

Repairing Clay Plaster (with toilet paper?…)

Questions concerning the durability of clay plaster – especially as an exterior plaster, and even more especially in cold and wet northern climates – get raised any time we suggest using clay plaster to a client. We recently had the experience of returning to the first building we clay plastered, back in 1994. What we saw and learned greatly increases our confidence in the use of clay plasters!

What do we mean by “durable?”
When we talk about durability, what do we really mean? Let’s say we’re comparing two kinds of exterior siding: clay plaster and vinyl siding. Intuitively, we’d probably say that the vinyl siding is more durable. But scratch the surface a bit… no material is indestructible, so what we really mean is “how long before it needs fixing or replacing.” Vinyl siding can last quite a long time before it wears out or breaks. But it does wear out and break, and when it does what can be done? Typically, nothing. It gets removed, taken to landfill, and replaced with new material.

The clay plaster may be more susceptible to wear (especially if it’s placed too close to the ground, as we’ll soon see!). But when it is damaged, it can be easily repaired at almost no cost and made as good as new, with no landfilling and no need for replacement.

Using Clay Properly
The first step in making clay plaster durable is to plan properly. The worst section of damage on this 12 year old home was next to the utility door on the north side. The building is way too close to grade… we recommend 8-12 inches minimum, but didn’t do that here. It was also unprotected by a roof overhang… despite the whole building have wide overhangs, this northern corner protrudes out to be almost in-line with the roof. Two strikes! And yet, here in the worst possible scenario – with rain hitting it, snow piling against it and no sun striking it to help dry it out – the plaster was still intact and still protecting the bales, it just didn’t look pretty anymore. Other places on this building saw some cracking, a result of not using enough fiber in the mix. Our clay plasters have for years now featured high quantities of fiber and we’ve avoided these kinds of cracks.

Getting the repairs going
We addressed the two areas that had seen a fair bit of erosion with new clay plaster. But clay plaster mix is terrible for filling cracks… the large aggregate and high fiber content that make for great plaster also makes for a mix that does not want to be pushed into long, narrow cracks.

Even though we opened up all the cracks with a pallet knife, the openings were nowhere near the size needed to push in an actual plaster mix. In fact, a mix with almost any aggregate (sand) in it does a lousy job. Even if it fills the crack adequately, there is always sandy mix left on the surface of the plaster calling attention to the repair forever after. And if we used straight clay, the shrinkage would be extreme and there would be micro-cracking along the crack.

Toilet paper to the rescue!
As we contemplated how to make a mix that would adhere to the existing clay, but would have such a fine aggregate that it could be wiped off the surface, we started to think about cellulose… little paper fibers that would be very fine but still add a lot of strength to the repair mix.

Earthen plaster repairs

Toilet paper provided the cellulose fiber we needed, and mixed in the blender with clay (and a bit of talc) created a smooth mix!

We came up with a highly scientific formula: 6 arm-spans of toilet paper (two-ply) to 2 cups of clay, with a bit of talc powder and water to the desired consistency. What we got was a sticky mix that was easy to work into cracks, that bonded well with the existing clay, didn’t shrink at all and was very easy to work with!

We were able to fill all the cracks to their full depth using a putty knife and pulling back and forth across the crack until it wouldn’t accept any more material. Then one pass with the putty knife left the surface scraped back cleanly to the original plaster.

Low impact repairs… like, really low impact!
The materials we needed to do all the repair work were right on site. The clay that had been leftover from the initial plastering in 2004 was left in a small mound near the house. Slowly, that mound became a “garden” of sorts. We were able to shovel clay from the back side of the pile and leave the garden undisturbed. Some natural pigment, some sand (and some TP in the cracks)… that’s all that was required.


I don’t think we could even calculate a carbon footprint or embodied energy for these repairs!

Mixing and applying a new clay paint
The largest area of the house had a red clay paint applied 12 years ago. There were enough cracks and repairs on this section that we decided to re-coat it with a coarse clay paint. We mixed 20 parts of the site clay with 10 parts of fine sand and 3 parts of pigment, and applied this runny mix using a sponge float.

A wetter mix with only 3 parts of fine sand was brushed onto the narrower bands of colour at the top of the wall. It was easy to cut a smooth line with this paint, making for crisp lines between the colour bands.

Fast work, faster next time
There were enough areas that needed attention on this house that we decided to completely re-paint the whole building. From first arrival at the site to colour matching the mixes to application and final clean-up, we spent a total of 3 days for 2 people (about 42 hours) on these repairs.
When this plaster needs work again in the future, there will be a paint mix in all three colours ready to be re-hydrated and applied. And since the colours match, spot repairs can be done instead of a whole new coat. If we’d been smart enough to do this the first time around, we could have cut the time for the job in half! We don’t expect cracks to re-open again, as no new cracks opened up on the building after the first couple of years.

A final layer of protection
One of the reasons we feel this clay plaster held up so well – despite being a less than ideal mix placed too close to the ground – was the inclusion of a top-coat of Primasil, a silicate paint primer from PermaTint.

Though it isn’t intended to be used as a “clear coat” finish, we have applied it this way on several buildings and it has done a great job of protecting the plaster from water damage while remaining highly permeable. In the future we will experiment with adding PrimaSil to our finish plasters and clay paints instead of water and see if building the silicate right into the material has a positive effect.

An endlessly repairable finish
The beauty of clay plaster is its ability to be maintained and repaired indefinitely. We had no waste from these repairs other than some sand and clay on the ground, and we had no expense other than a bit of pigment and a roll of toilet paper. And the pigment will be suitable for about a century’s worth of repairs of this extent! Now the plaster is once again gorgeous to look at and ready to handle another decade or two of keeping out the elements… Try doing that with vinyl (or anything else!).

Why We Love Earthen Floors

Take one step – especially with bare feet – on an earthen floor and chances are you will be sold on the idea. You will want an earthen floor of your own. And not only will you be making happy feet when you choose an earthen floor, you’ll be making one of the most radical-yet-simple sustainable building choices… one that could dramatically reduce the environmental impacts of the built environment in a meaningful way.

earthen floor workshop and how-to

Clay, sand, fiber… that’s it!

A true game-changer
With the construction industry touting just about every option as being “eco-friendly” these days, it can be hard to know what choices really do make a difference. Earthen floors are a truly eco-friendly option. Using just four basic, natural, chemical-free and abundant materials that are minimally processed on site, an earthen floor creates a durable, healthy finished floor with the lowest possible environmental impacts. Mix the right proportions of clay, sand, natural fibers and drying oils and you’ll have a floor that is as beautiful as it is planet-friendly. The embodied energy of a 3/4″ thick earthen floor is 0.16 MJ/square foot, a tiny fraction compared to 3 MJ/square foot for hardwood, linoleum and concrete flooring of the same thickness, and 10-25 MJ/square foot for tile.

Really, a dirt floor?
It is often difficult for anybody in the “developed” world to consider an earthen floor as part of a clean, modern home. But earthen floors can be the visual showpiece of a home. A well-made earthen floor is a thing of beauty, bringing a texture and visual impact that cannot be replicated with any other material. Natural clay colours or natural pigments offer a wide palette, and a variety of fiber options can be used to great effect. And then there are the oil finishes which can add a rich lustre and additional colour options.

Are hearten floors durable?
Earthen floors are not a common option, and therefore most people do not have experience with seeing an earthen floor wear over time. In fact, these floors have very similar wear characteristics as most other natural floor materials like wood, bamboo and linoleum. All of these floor types can have a long lifespan under typical use conditions, although all are susceptible to scratching and gouging if mistreated, and all will require occasional refinishing to protect and enhance the surface of the material. Earthen floors are no different, and are quite easy to repair and refinish should some damage occur. I witnessed the earthen floor at Arts Centre Hastings spend a night under water after a large cooler full of melted ice broke, and yet after mopping up the spill the floor was not affected at all!

Place them wisely in the building
Though durable, it is wise to place them appropriately. Entryways, especially those that will see a lot of salt from snowy boots, can stress an earthen floor. Areas which will see a lot of dragging of chairs and furniture may not be appropriate. But if the use of the floor is for interior foot traffic, they hold up very well.

How does it work?
The clay/sand/fiber mix of an earthen floor may not seem like an ideal combination in a heavy-wearing scenario like a floor. These elements combine to make a substrate that can be easily packed and levelled. A typical earthen floor mix is 1 part of clay, 4 parts of sand, and 1 part of finely chopped fiber. As clays and clay soils can have different properties, it is always good to experiment with new materials before pouring an entire floor. Once this mix has been poured and troweled level, it is allowed to dry. Then the real magic occurs: several coats (anywhere from 2-6) of natural oil finish is applied to the floor. The oil penetrates into the clay/sand mixture and hardens around it, creating a tight and water-resistant finish that is very durable. The process is similar to natural linoleum, where linseed oil is mixed with sawdust. As with linoleum, the result is surprisingly solid.

Where can an earthen floor be used?
Earthen floors can be laid over many typical floor bases, including concrete slabs and plywood sub-floors. As

earthen floor clay floor how-to

A living room with a wood stove is a great place for an earthen floor

long as the floor base is stable and doesn’t have excessive flex or deflection, then an earthen floor can be laid. Typical thickness for a finished earthen floor is 3/4″, though it is possible to make them thicker. The floors can be laid over hydronic heating tubes, or used under wood stoves or other sources of heat. Simple substrate preparations are used if the base is either very smooth and shiny or if it is water absorbent.

It’s easy to learn to make an earthen floor
The steps involved in mixing, laying and finishing an earthen floor are very straightforward. If you think an earthen floor might be in your future, you can check out our upcoming earthen floor workshop, where you’ll get a chance to mix, pour, level and finish a complete earthen floor.

All About Natural Paint

There is no easier or better place to shift away from toxic petrochemicals and move to using natural, non-toxic options than with the paint we put on our walls.

Anybody Can (and Should) Do This
We hear from many people who wish they could build a home with natural materials, but because they live in an existing home they seem to feel there is no way for them to use natural materials. But using natural paints is something that anybody can do, at any time, in any home, and on any wall surface. And the benefits are profound. In terms of your family’s health, it can be better to have a non-natural home painted with natural finishes than to have a natural home painted with toxic petrochemicals. Natural paints are also better for the planet.

Why Not Just Use No-VOC Paint?
By all appearances, the paint industry seems to be getting “greener.” So why not just choose a good no-VOC paint and use that? Turns out, there are quite a few reasons. Firstly, paints labelled as “Low-VOC” or “No-VOC” are far from being non-toxic. Secondly, the petrochemical paint industry has a huge environmental and carbon footprint.

The Dirty Secret About No-VOC Paintdisturbing paint facts
The impetus to reduce the quantities of volatile organic compounds (VOCs) from paints actually had nothing to do with human health concerns. VOC reductions were imposed on the paint industry because they contributed to smog, and only those VOCs that directly contribute to low-level ozone production are covered by these regulations. The US Environmental Protection Agency (EPA), the body that first imposed VOC restrictions, has this to say after testing a range of paints that qualify as low-VOC and finding surprisingly high concentrations of VOCs:

“EPA Reference Method 24 is probably not an adequate method for measuring the VOC content of low-VOC latex paints. …Current bulk analysis and emission test results showed that the VOC contents of low-VOC latex paints are well within the uncertainty range of Method 24, and the method is apparently not precise enough to accurately define the VOC content of those paints.” –Inside IAQ EPA/600/N-98/003

What If It’s Labelled as “Green”
There are some labelling programs that do ensure acrylic (commonly called “latex”) paints are less harmful to occupants. However, the most common labels do not. GreenGuard and Ecologo are the labels most commonly seen in paint stores. They are administered by Underwriters’ Laboratories (UL). Here’s what that standard has to say about its commitment to human health:

“1.14 While this practice lists specific chemicals and associated maximum allowable concentrations, as required by criteria indoor air procedures and specifications, it does not assess the human risk involved with use of the materials either as an installer and/or as an end user.” –UL 2821

green seal logoIf you want to trust a label, find paints certified by GreenSeal GS-11. This is the only standard I can find that actually excludes a wide range of toxic chemicals and has a direct concern for human health.

And Even If It’s Got a Good Green Label…

Despite the fact that they are called “water-based,” all acrylic paints are made from petrochemicals. Coatings consumption worldwide reached 80 billion pounds and $120 billion in value in 2013, according to “Global Paint & Coatings, 2013-2018,” by polymer and chemical market researchers Kusumgar, Nerlfi & Growney. That means that our use of petrochemical paint carries with it the same environmental impacts as any use of crude oil. Don’t like offshore drilling, oil sands, pipelines, greenhouse gas emissions, oil spills, etc? Every time we use acrylic paint, we contribute to all those impacts.

From raw material harvesting through production and end-of-life waste, the 80

From raw material harvesting through production and end-of-life waste, the 80 billion pounds of paints produced annually have a massive impact on the environment.

The embodied energy and embodied carbon emissions of acrylic paint are also very high. Using data from the Inventory of Carbon and Energy V2.0, the paint needed to coat the interior of a typical 2,000 square foot home (primer and two coats of finish) would use about 7,300 megajoules (MJ) of energy to produce, and emit 303 kg of carbon dioxides (or equivalents). That’s the energy in 1.5 barrels of crude oil or 61 gallons of gasoline required to paint every home, and somewhere in the neighbourhood of the same weight in CO2 emissions as the combined weights of the home’s inhabitants!

Now the Good News!
Don’t want to inhale toxic chemicals or contribute to oil spills and climate change? The good news is that there are plenty of accessible, affordable and practical paint options available that are non-toxic and low-impact. Most of the paint manufacturers listed here provide full disclosure of their ingredient lists, meaning that there are no hidden toxins. All have been recommended by people with chemical sensitivities.

Natural paints come in a number of different categories, based on the type of binder they use, and each type of paint has a range of different surfaces it may be used on:

Natural Oil Paints

  • Drying oils (linseed, sunflower, tung, etc) polymerize when exposed to air
  • Some natural oil paints are emulsified with water
  • Indoor & outdoor use
  • Used on almost any substrate

Although many people will have an initial negative reaction to the idea of “oil paints,” these bad associations are from very toxic petrochemical oil paints. Natural oil paints are a whole different breed. The emulsified oil paints are the most straightforward natural paints to use, and give results that are consistent with modern petrochemical paints. Washable, durable and tinted to any available colours, these paints can be used to replace conventional acrylic and alkyd paints with no change to expectations about application, coverage and durability. All the brands we’ve used are non-toxic and fully bio-degradable. Most can be obtained in just about any imaginable tint.

Auro Wall Paint, available in Canada from Tockay
Allback Linseed Oil Paint available in Canada from Living Rooms
AFM Safecoat Naturals available in Canada from Living Rooms
Kreidezeit Wall Paint, available in Canada from Tockay

Lime Paints

  • Calcium carbonate binder, often with additional natural binders
  • Indoor use (outdoor use for lime washes)
  • Most wall substrates, surface prep may be req’d

Lime paints have been used for thousands of years, and the modern versions are excellent products that can be used on most wall surfaces. Naturally anti-septic, these paints come in a variety of textures from quite smooth to quite grainy. They add a depth and beauty that is hard to explain but is immediately obvious upon seeing them. They are durable and do not wash away with water. They are an excellent choice for any wall that receives light to heavy contact, and are available in a wide range of colours.

Kreidezeit Lime Paint, available in Canada from Tockay
Auro Lime Paint, available in Canada from Tockay

Clay Paints

Non-toxic paints

Kreidezeit clay paint can be brushed or rolled onto wall surfaces primed with a casein primer

  • Natural clay binder, often with additional natural binders
  • Indoor use only
  • Most wall substrates, surface prep may be req’d

Clay paints are the champions of low-impact and low-toxicity. The fact that they are gorgeous to look at is an additional bonus! A variety of grain sizes and tints are available. They are durable (no dusting, will not brush off the wall) but are not washable. They can handle some direct wetting, but will wash off with scrubbing or constant abrasion. Good for use on any wall that does not receive direct wetting or a lot of touching/contact.

Kreidezeit Clay Paint, available in Canada from Tockay

Casein Paints

  • Milk or vegetable casein binder, often with additional natural binders
  • Indoor use only
  • Most wall substrates, wood

Casein paints can be made from vegetable or milk casein. Similar to the clay paints, they are capable of dealing with some wetting and abrasion, but shouldn’t be used in places where this will happen consistently. A wide variety of tints are available. They can be used on walls, and also on raw wood.

Homestead House Milk Paint, available from Homestead House
Kreidezeit Vegetable Casein Paint, available from Tockay

Mineral Paints

Non-toxic paint

Eco-House silicate dispersion paint can be used on interior and exterior mineral surfaces

  • Potassium or sodium silicate (“waterglass”)
  • Indoor & outdoor use
  • Mineral substrates only (plaster, brick, concrete, etc)

Silicate dispersion paints are unique in that they don’t coat a surface, they mineralize onto the mineral surface and become an integral part of the surface. This makes them extremely durable. We use them a lot as a finish for exterior plasters, where they have the Goretex-like effect of protecting walls from bulk water penetration, but maintain the permeability of the plaster. They can be used indoors or outdoors on any surface that is mineral-based, including clay & lime plasters, concrete, brick, stucco and stone. They come in a wide range of colours, and colour matching is available.

Eco-House Silicate Dispersion Paint, available in Canada from Perma-Tint

Non-toxic Clean-up
One of the unsung benefits of using any of these paints is that they are all biodegradable. Even the “cleanest” conventional paints have a petrochemical base that ends up in waterways or in soil during cleanup, with an aggregate of thousands of gallons entering the ecosystem annually. Natural paints clean easily and the wash water can safely go into septic systems or onto the ground.

So Many Viable Options
All of the paints listed here are products that we have used with excellent results. Each type of paint has specific uses and surfaces, meaning there is no surface in or on a home that cannot be treated with a natural paint. Costs tend to be slightly higher than mid-range conventional paints, and in line with higher-end conventional options. None of these paints are unaffordable, and the slight extra cost is a small price to pay to be surrounded by non-toxic surfaces that are not off-gassing into your home, and did not have a deep impact on the environment. A worthy investment for any home!

Want to Try These Paints?
Endeavour’s Eco-Paints workshop is a day long opportunity to learn all about natural paints, and to actually use all of the paints mentioned above.

The Art and Science of Natural Plaster DVD Now Available

The Art and Science of Natural Plaster is a 140-minute DVD created to help homeowners figure out how to use natural plasters on their own projects, created and narrated by Chris Magwood of Endeavour Centre. The
DVD is now available for purchase through PlasterScience.com in hard copy or online streaming formats.

Produced by Bart Glumineau, a graduate of Endeavour’s Sustainable New Construction program in 2013, and co-founder of PossibleMedia.org, creating original video content to share the stories of individuals and groups of people who are actively engaged in creating a better, more sustainable future.

The DVD covers base coat and finish coat mixes and applications that are suitable for a wide range of sustainable and conventional wall surfaces, from cob and straw bale to drywall. Chapters include:

  • Introduction to Plaster
  • Types of Plaster
  • Substrates and Substrate Preparation
  • Mixing
  • Tools and Trowels
  • Body Coat Application
  • Finish Coat Application
  • Paints, Washes and Sealants
  • Repair and Maintenance of Plasters

Much of the hands-on footage for the DVD was filmed at Endeavour’s 2014 project, a straw bale office building for the local teachers’ union.

We are excited to have some of our teaching and methodology presented in an accessible video format, and hope that the DVD inspires more people to take up natural plastering on new builds and renovation projects!

Thatch roof update

In 2009, we undertook the first permitted thatch roof in Ontario as part of the Camp Kawartha Environment Centre on the nature preserve grounds at Trent University. This roof sits atop a timber framed entryway for the building and greets all those arriving at this busy public building. The roof is nearing the end of its fifth winter, and a hike along the nature trails near the building gave us a chance to inspect the thatch under a blanket of snow and find that it is still water-tight and holding up very well.

Thatching is a roof system that has ancient origins and is still widely used in a modern context… just not in North America. Only a small handful of buildings on this continent have thatched roofs, and the skill set is extremely limited. This despite the fact that the material for thatching roofs is a widely available invasive reed known as phragmites (or elephant grass). An abundant supply of these reeds grows along many highway medians and ditches.

Thatched roofs exist in a wide range of climates world-wide, with the northern European roofs in countries like Denmark and Germany most closely representing Canadian conditions. In these places, thatching typically lasts 40-70 years, an impressive improvement over the commonly used 25 year asphalt shingles.

The actual process of thatching a roof is a bit more labour intensive than conventional shingling, though experienced crews in Europe move a rate that is not far off conventional practice here. For our project, the manual harvesting and preparation of the reeds was the most labour-intensive aspect. This would be quite easy to mechanize (as has been done elsewhere in the world), which would make thatching a much more viable proposition in this part of the world.

Given that the material for thatching grows annually, for free, along our highways, and that the environmental impact and working lifespan of this type of roof are far better than conventional options, it would be great to see more thatching happening in this part of the world.

Building bottle wall features

Many natural buildings feature bottles incorporated into walls. Bottle walls add colourful light and whimsy to a wall and open up all kinds of great design possibilities.

Here’s a little “how-to” guide to building your own bottle wall. It’s quite an easy process, and is applicable to interior walls and renovations as new buildings. Your own creativity is the only limit when it comes to using bottles in your building!

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