Here’s an interesting statistic, in 2014 buildings in Toronto were responsible for 53% percent of green house gas emissions while transportation made up 35%. An interesting revelation if we want to start addressing climate change. This is the reason so much building science has begun to focus on efficiency, using less energy to heat and cool our homes. However, there is also the waste stream and human health impacts of construction that are often ignored. This past summer I was involved in building a Zero House. This term has been used before to mean a house requiring net zero energy to run but this project went a step further and built a house that was zero construction waste, zero toxic chemicals, net zero energy use, and zero carbon footprint.
The project was done through the Endeavour Centre in collaboration with Ryerson University. Every summer the Endeavour Centre runs a program about Sustainable New Construction. Their latest project was a single unit of what could be a multistory complex, essentially, an apartment building with a new twist. We pre-fabricated the roof, walls and floors inside a large tent. The main floor walls were insulated with straw bales and the second floor and larger walls, were insulated with cellulose. Plywood contains toxic glues so its use was minimized and no plywood was allowed inside the building unless coated with a sealant to prevent off gassing into the interior. Instead, we used Sonoclimate Eco4 fiberboard on the exterior of the walls. It is made from 81% recycled wood fiber and provides insulation as well as serving the purpose of structural sheathing. ReWall, which resembles dry wall but is made from recycled tetra packs, was used on the interior walls and roof. Imagine boxes that are on average 8ft by 8ft and about a foot deep. That is what the individual pieces of the house looked like, although some were smaller and some larger. It took two days with a crane to put all the pieces together to assemble the building.
The interior was wrapped in an air barrier called Intello that is sort of like Gore-Tex for your house. The exterior was wrapped in Mento 1000, which allows moisture to escape should it manage to find its way into the walls but prevents moisture from entering from the outside. This is a wall system that can breathe and dry out if needed, resulting in nicer indoor air quality and is very effective at preventing mold. The finished exterior was metal siding, which does have a fairly large carbon footprint but its durability reduces that footprint over the lifetime of the house. The interior was finished with natural oil hardwood floors and maple walls. The walls were actually plywood often used in cabinetry. This type of plywood laminate is made with an adhesive that does not contain formaldehyde. Begging the question why isn’t all plywood made that way? The plywood was installed onto strapping which gave us a cavity to run all the electrical without puncturing our air barrier. Wood was used a lot in this building because it sequesters carbon and, if we would manage our forests better, which is slowly starting to happen, is a truly renewable and sustainable product.
Most of the products were sourced from Ontario including the hardwood and insulation. Some items, such a ReWall, had to come from the states and our adhesive solar panels that stuck directly to the roof came from the UK. No one is producing these products closer to home but if we start asking for them someone will see an opportunity.
The entire process took a class of 10 first time builders 3 months to complete. We then took the whole thing apart and reassembled it in Toronto for the EDITdx Expo. We had the building up in 7 days. There was a lot of interest in the building and the concept. One thing that really struck me was how under informed we are about the buildings we live in. There is also a lot of misdirection and partial truths out there in building marketing. For example did you know that “No VOC (Volatile Organic Compound)” paint doesn’t mean that it is safe? The VOC test is designed to reduce outdoor smog but has nothing to do with the air quality you are breathing inside your home. Many commercial paints contain Red Listed Chemicals but can still claim to be “No VOC”. Spray foam is another one that has a huge carbon footprint and contains many toxins but is put in most buildings with very little thought. There are many alternatives but you need to do your research and be wary of people who discredit based on opinion instead of fact. I have heard many skeptics on the topic of straw bales as insulation but when you dig a little deeper they have a very shallow knowledge base. Building with straw bales, like any material, requires that you understand the strengths and weaknesses of that material and design you structure accordingly. Straw bale does not perform to its potential if you simply substitute it into a conventional build. It functions best in an air permeable wall design, which is not how most conventional construction is done.
At the end of the construction process we had only 2 large black garbage bags to take to the dump. All other materials where recyclable and we were very careful to sort appropriately. The house is designed to be grid-tied with 32 solar panels glued directly to the roof. In the summer it will feed excess energy into the grid and if needed it can draw from the grid on credit resulting in a, mostly green, net zero running cost. The heating will be done with mini-splits (air source heat pump), small units that mount on the wall. These can also provide cooling but it is unlikely the house will need it. Ventilation is provided by small ductless units called the Lunos e2 . The estimated cost to build this house is $185 000- $225 000 which does not include the foundation as there are many variations of foundations out there. The amount of carbon sequestered in the materials used is actually greater than the amount expended in their production resulting in a negative carbon footprint.
What an incredible example of how easy it would be to do things differently. We, as a society, just need to start demanding it because it isn’t hard but it does require change and we all know how slow the wheel turns when it comes to change.
More information on this house, the materials and photos can be found on the Endeavour website, endeavourcentre.org/blog/ or type Zero House into the search.
Are you planning a renovation or build and wondering about more eco-friendly alternatives or have you done one already? Please share it.
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