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Teachers’ Union Office Building slideshow

In 2014, Endeavour’s Sustainable New Construction program built a new office building for the Trillium Lakelands Elementary Teachers’ Local in Lindsay, Ontario. The goal was to combine Passive House energy efficiency with low-impact, local and non-toxic materials.

The photo gallery below shows the entire build from start to finish. Click on a photo to view the slide show in full size:

A PassiveHouse Heating System

Passive House is a building certification program that focuses on dramatically improving the energy efficiency of new and renovated buildings. Overseen in this country by the Canadian Passive House Institute (CanPHI), the standard originated in Germany in the late 1980s and buildings that comply with the standard will have energy use reduced by 80-90% from current Canadian code requirements. Specifically, Passive House buildings must have an annual heating and cooling demand of not more than 15 kilowatt hours per square meter of building (15 kWh/m²) per year, and total primary energy (calculated as source energy, not metered energy at the building) must not exceed 120 kWh/m² per year. In addition, an air tight building enclosure is a requirement, with leakage no greater than 0.6 times the house volume per hour as tested with a blower door (0.6 ACH/hour at 50Pa).

The teachers’ union office is our first building designed to meet the Passive House standard, though we have used the Passive House software as our energy modelling software for the past three years. Although we were not intending to have the building certified, we wanted to meet the standard and achieve the energy reductions using our low-energy, low-impact range of building materials. We worked with Rob Blakeney of Local Impact Design to model the building and advise us on insulation levels, passive solar aspects and to design the heating system.

While the term “passive house” is an attractive one, it is quite misleading as the buildings do not feature passive (ie, non-mechanical) systems. In fact, Passive House buildings typically require a mechanical ventilation system to run 24 hours a day. The leap to Passive House standards means that conventional heating systems can often be left out of the design, and instead buildings can be heated with small amounts of heat input into the ventilation air distribution system or other low-input systems.

At the teachers’s union building, a 1 kilowatt heater is used in each of the three main ventilation air supply ducts to provide heat to the three offices. In general, this is the main source of heat for the building. A ductless mini-split air source heat pump is in place in the large meeting room and can provide additional heat capacity when required (though its inclusion in the system had more to do with meeting peak cooling demands in the summer). Through this year’s very cold February weather, the system had no problem keeping the building warm and comfortable… pretty impressive given that the heat source is the equivalent of running two toasters!

We were keen to build to Passive House standards because the most typical means to reach this level of performance has been to use a lot of foam insulation to achieve the necessary R-values and air tightness. We wanted to bring our low-impact, locally-sourced material palette to the challenge, using straw bales, cellulose, clay plaster and simple air tightness detailing to the highest levels of performance. In this way, we can lower both the energy use of the building, and also the embodied energy. Walking into the building when it is -25C outside and feeling the wash of warm, fresh air and knowing that the heat source is minuscule has been very satisfying!

Net metering PV now functional

The use of photovoltaics (PV) to generate electricity has been a common element on most of our projects. PV is affordable, easy to install, nearly maintenance free and very reliable. Once again, a PV array has been a key part of the energy strategy for an Endeavour project.

In Ontario, we are able to create grid-tied PV systems, allowing owners to sell some or all of their generated power to the utility company, and also to use grid power when necessary. Grid-tied PV can allow for systems that are sized to meet the owner’s needs, while still ensuring that power is available at all times. For PV to be used off-grid, generating capacity and storage capacity (in the form of batteries) must be sized to meet needs at the worst time of the year (mid-winter, when power needs are high and the amount of available sunlight is low), making the system expensive and likely to over-generate in the summer months.

There are two systems for owners to connect PV systems to the grid in Ontario:

  • Under the Micro-FIT program the system owner installs two meters, one for outgoing power being sold to the utility company and one for incoming power to be used in the building. The owner receives a cheque for the full value of power generated (currently 38.4 cents per kilowatt hour), and receives a bill for the full value of power consumed (currently around 11 cents per kilowatt hour). Under Micro-FIT, an owner can generate a financial profit even if production is less than consumption.
  • Under the Net Metering program the owner has a single meter, and that meter spins in two directions, “forward” when power is being consumed from the utility grid and “backward” when generation is greater than consumption. Under Net Metering, the power has the same monetary value in either direction. Should production outweigh consumption, a credit will be carried forward on the utility bill (up to a maximum of 11 months). At best, a Net Metering customer can reduce to zero the usage charges on their bill, but can never earn money.

The teachers’ union did not qualify to apply for a Micro-FIT contract, as the restrictions for the program have been growing ever narrower as it becomes more popular. However, with the cost of PV so low now, the economic argument for a Net Metering system is a reasonable one. Combine drastically lowered utility bills with reasonable pay back period and a desire to be part of a renewable energy solution, and you have the grounds for the union’s investment in this 7.5 kilowatt system.

Sean Flanagan of Flanagan and Sun came by this week to turn the system on. With the array and the outdoor connections already made, it was a simple process to turn on the inverter and make sure all the settings were right. Luckily, it was a fairly sunny day and we were able to see about 5 kilowatts of production head out onto the grid when the system became live.

The combination of the PV array and a contract with Bullfrog Power (which we strongly recommend to all our clients) means that 100% of the energy produced and used by this building is from renewable sources.

Goodbye to the class of 2014

The students of the Sustainable New Construction 2014 class said a belated goodbye to Endeavour and the teachers’ union office project.

Their departure was one month later than expected, as five of the seven stayed on through October to make up for time lost during permitting issues earlier in the summer.

The last week was about adding some fun finishing details to the building, including the cordwood entryway to the meeting room and some great bottle and hempcrete transom details in the doorways.

This was an amazing group of builders, and we wish them all the best as they move onto their new lives in the sustainable building world!

Finishing the straw-cell wall system

Our office building project for the Trillium Lakelands Teachers’ Union features a straw bale wall system that combines conventional wood stud framing with an interior straw bale wall.

Recently, we finished the exterior side of this wall system. This involved placing dense-packed cellulose insulation in the frame wall, filling the cavity so the insulation is blown tightly against the straw bales. With the cavities insulated, we add approximately R-21.5 to the R-30 of the straw bales. Our contractor for the dense-packed cellulose was Morgan Fiene at New Energy Consulting in Hastings, Ontario (705-313-2004), whose care and concern for doing a thorough job was very refreshing.

We then covered the framing with an insulative wood fibre sheathing. This 1/2 inch wood fibre sheathing has an R-value of 4 per inch, and is made from 100% recycled wood fibre and a non-toxic binder. Made by Western Louisville Fiberboard in Quebec, this product is the cleanest sheathing product we could find. Most exterior wood fibre products use an asphalt emulsion coating, but the SONOclimat product uses a proprietary coating that is water based, non-offgassing and meets stringent environmental standards.

As a means to blend conventional wood framing with straw bale walls to achieve very high insulation values, we have been very pleased with the straw-cell system. It marries low impact materials throughout (earthen plaster, straw bales, cellulose insulation, FSC framing and recycled fibre board) with high insulation value and a straightforward construction process. It’s a great way to marry the more unconventional approaches to sustainable building with mainstream approaches.

 

Air tightness details for straw bale walls

Straw bale wall systems have been touted for 20+ years now as a way to achieve higher insulation values with lower environmental impacts. And, having built many straw bale homes and commercial buildings now, we know this is true. However, we have also seen that without attention to air sealing details, many straw bale buildings are quite leaky and fall short of their potential level of energy efficient performance because of this.

Along with many straw bale compadres world-wide, we’ve worked to come up with details that address these issues of air tightness in straw bale buildings. Our latest project for the Trillium Lakelands Elementary Teachers’ Local offices have good examples of easy ways in which a bale wall can be built to be air tight without reliance on whole-wall vapour barriers or other sheet membranes.

Plastered straw bale walls have a naturally air tight nature thanks to the continuous plaster coating. Any crack-free layer of plaster does an excellent job of stopping air movement through a wall. However, where plaster meets other materials (at the top and bottom of each wall, at each door and window opening and around through-wall vents and pipes), just plastering up to these seams does not create an air-tight barrier. All plaster types share the characteristic of shrinking as they dry or cure. Every edge of a plaster wall will pull away and leave a gap as the plaster shrinks. It may not seem like much, but even a 1/16 inch gap at the top of 100 feet of wall area is the equivalent of 75 square inches of “hole” in the wall! Add that same gap around every window and door and at the bottom of each wall and you may have a hole in your wall of up to 1.5 square feet! That’s like leaving an average sized window open full time!

Most homeowners understand that having a window open all winter long would have a negative affect on the amount of energy used to heat the home. But many people do not put the time and effort into “closing the window” around the perimeter of their straw bale walls.

For some, there is a reluctance to build air-tight because of a notion that it is unhealthy to seal a house “too tightly.” However, it is also unhealthy to be drawing outside air into your home through cracks and leaks in your walls. That infiltrating air picks up dust, spores, and anything else that is in the walls on its way into the house. Seal the house properly, and deal with the ventilation that is required in an intentional, clean way.

It’s not difficult to make an air tight bale wall. We will report on our blower door test results for this building as soon as we have performed the test!

Stop motion straw bale and earth plastering

Sustainable New Construction 2014 student Ben Bowman set up his camera and took some great sequences of the construction process at our teachers’ union office project.

Here are the two sequences of straw bale installation and earthen plastering. In many ways, these stop motion videos give a better sense of the process than an actual video, plus it makes it all look so fast and easy!

Ben also captured sequences of our earthbag foundation construction and roof craning process:

 

 

High-straw earthen plaster recipe

It’s no secret that we love clay plasters at Endeavour, and the best case scenario is being able to use a clay soil right from the building site. It just so happens that we lucked into this for the teachers’ union office project!

After digging some test holes on the site early in the spring, we discovered that there was a strata in the site soil that was quite clay-rich and appeared to have almost no stone in it (which is very rare in this part of the world). We made some plaster samples from this soil and found that a wide range of recipes seemed to be viable. We left the samples face up into the elements for the whole summer, and one in particular held up really well so we knew we had a workable site plaster.

Our approach to earthen plasters has changed over the years, with the addition of more and more chopped straw over the years so that we have reached a point where we have a very high-straw content in the plaster. We have found that the high-straw recipe allows us to build up the entire thickness of the plaster in a single application. The volume of chopped straw supplies a huge amount of tensile support for the clay, and means that we don’t need to add nearly as much sand as we used to do when our plasters used less chopped straw.

The result is a mix that is very sticky thanks to the high clay content, and has a huge amount of “inner cohesion” that allows it to be applied at almost any thickness (4-5 inches is not unreasonable, if necessary!) with no cracking.

Rather than applying a very runny slip coat via sprayer or dipping the bales, we’ve found that a layer of the same mix minus the straw works well as a “primer”. We apply the primer to the bales, and then follow it immediately with the high-straw “body coat.” It’s sort of a two-part, one-coat system. It’s great to be able to apply the full desired amount of plaster and achieve the final look we want in a single application. Less time, and much less concern for de-lamination between successive coats.

The mix stays moist for a day or two, so it allows a lot of time to get the walls looking how we want, and the mix is very intuitive for those just starting to learn to plaster, while being fast to apply for those with more experience.

Our recipe (by volume) for this plaster is:

  • One part high-clay content soil
  • One part chopped straw (1/4 – 1 inch)
  • 3/4 part rough sand

There’s nothing like playing in the mud and making a viable building at the same time!

New system for straw bale walls

Over 20 years of building with straw bales, I have constantly experimented with new ways to integrate bale walls into buildings that are simple, cost-effective and energy/resource efficient. From load bearing to prefab panels to a variety of framing systems, I thought I’d tried them all.

But we were introduced to a new idea by the excellent builders at New Frameworks Natural Building, and we liked the idea so much we decided to try it ourselves.

Their “StrawCell” approach involves building a conventional stud frame wall for the building which acts as the exterior frame and main load bearing element. One immediate advantage is that this system fits into the regular code structure and should not require special engineering or design considerations, which can really ease the permitting process and help to lower costs. The straw bale wall is then built to the inside of the frame wall, with the bales pressed against the framing. The stud wall cavities are then insulated with dense packed cellulose, and sheathed with a permeable board material. Any kind of siding/rainscreen can be created as the final finish on the exterior.

On the interior the bales are very easy to install. The only framing that interrupts the straw is for window and door openings – very similar to the easy installation for load-bearing designs. At the top of the wall there is no beam or framing to notch around, just a plywood plate on the underside of the roof. We tied each bale through to the framing, so the wall was very straight and solid right away.

While the amount of lumber used in this system was initially a red flag for me, an actual calculation showed that we were using no more lumber than any of the other bale wall systems that use a frame of some sort. A conventional frame wall is actually a very effective and efficient way to use lumber, and only some load bearing systems actually use less lumber than this frame wall approach.

One major difference between this system and other straw bale approaches is the lack of exterior plaster. This can be seen as both a plus or a minus. We have been shying away from exterior plaster finishes for clients, especially commercial clients like the teachers’ union. While we love plaster, it is both a high maintenance finish and one that is susceptible to moisture issues unless well detailed, well protected and well maintained. While we definitely have not sworn off using exterior plaster, we are certainly glad to use siding when the client and/or conditions make it appropriate. On the plus side, this system reduces the amount of plastering material and labour required by half (actually, more than half since the interior plastering is always easier). Interior plastering can happen at any time of year, while exterior requires the right weather conditions.

The addition of the cellulose in the exterior wall brings this wall system into the super-insulated category, capable of reaching PassiveHouse standards even in our cold climate (something a single, two-string bale wall cannot do). The cost of the cellulose and siding together are quite similar to the cost of the material and labour for exterior plastering.

All in all, we like this system so far. We’ll continue to report as we finish preparing the walls for plastering and complete the remainder of the system.

Craning a Finished Roof

Building a roof can be intimidating, and statistically the most dangerous element of making a building. The heights involved add risk, time and a lot of effort.

Whenever we have the opportunity, we build our roof structures – including all sheathing and as much finishing as possible – on the ground, and then use a crane to lift the roof and place it on the building. In this way, we reduce the risks associated with working at heights, lower the amount of physical labour involved in carrying materials to roof height and bring protection to our building faster.

For the teachers’ union office, we once again had enough room on the building site to do just this. We set up two rows of beams on the ground at the back of the property and fully erected the entire roof, including trusses, bracing, strapping, membrane, steel sheathing, light tubes and the full PV array. All of this was accomplished with the fascia less than two feet from the ground!

As we’ve found to be typical, the craning is a relatively quick process. We were slowed somewhat this year by wet conditions on site that made placing the crane in the right position difficult, but we still put all three sections of the roof on the building in a single day.

A quick look at the math makes a pretty good financial case for building roofs in this way. The cost of a day’s rental of a crane and operator is easily paid back by the efficiency and reduced labour time of building on the ground.

It’s not a carbon free practice, but when the site and conditions are appropriate – and particularly when working with student builders – it’s one place that we’re willing to let fossil fuels and mechanical advantage help us out!

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