In an Endeavour post about a year ago, I examined the concept of embodied energy in buildings. You can see that post here. To quote the summary of that article:
“Choosing high EE materials is willfully neglectful, and in my experience the choice is often due to sheer laziness or an unwillingness to alter choices simply because that’s what has always been done. A builder doesn’t need to dabble on the fringes of the natural building world to drastically reduce EE. Many mainstream choices offer vastly lower EE than others. It’s just a matter of putting the effort into knowing what the EE impacts will be.”
While building our Canada’s Greenest Home project, we made conscious decisions to choose low embodied energy materials, but only recently have we taken the time to do a full embodied energy analysis on the shell of the house. While doing this, we also did the same analysis for a conventional home built to the same dimensions and specifications.
The results of this study (using the Inventory of Carbon and Energy (ICE) 2.0 and the book Making Better Buildings) showed that our home used 138,052 megajoules (MJ) of energy embodied in its construction materials, while a similar conventional build would have used 277,544 MJ. That means that our home used just less than 50% of the embodied energy of a conventional home!
What does this mean? Let’s look at the difference in terms of energy use in the house. In a recent post, we discovered that after one year in the home, our annual energy consumption was 31.92 gigajoules (GJ). The embodied energy difference of 139,492 MJ (converted to gigajoules is 139.5 GJ) is enough to completely heat and power our home for 4.37 years. This means that even if the conventional home had the same level of energy performance, it would always carry a 4+ year deficit compared to our home.
In reality, the comparison is even more dramatic. The majority (68%) of the energy being used in Canada’s Greenest Home is renewably generated on site. The remainder is renewably generated via a Bullfrog Power contract. Whereas the energy embodied in the materials is almost certainly not renewably generated, and comes with carbon emissions and environmental impacts far higher than our home energy use.
The point I made in my embodied energy article is: Why not pay attention to this? The choices we made are easy ones to make, and there are equally easy choices within conventional options that also dramatically lower embodied energy. If it’s possible to cut overall energy use by the construction materials sector by 50%, why aren’t we making that choice? Seen as a choice made by one builder, it’s a small impact, but extended over the entire sector, it is a vast and radical change.