Climate Adaptation and “Outsulation”
The following post was written in a collaborative format with Lara McKendrick Architecture.
Awareness of the impacts of climate change have been part of my education and in the curriculum that I have been teaching for the past few decades. It has been long established that our built environment contributes greatly to the issues of climate change, and once my family had settled on a neighborhood and purchased a home, we were soon impacted by the effects of massive weather events regularly.
According to the U.S. Green Building Council, “buildings account for approximately 40 percent of the total energy used today… and 38 percent of total carbon dioxide emissions in the United States,” which amounts to higher energy use than in the entire transportation industry. These statistics are similar in Canada.
It became clear that our house had minimal insulation, let in a lot of uncontrolled outside air (cold or warm) through gaps and the windows, combined with terrible heat distribution. We were cold in the winter, and summers without air conditioning became hot enough that we have spent nights outside in the garden. Attempts to use our fireplace in the winter clarified that as pretty as it was- it didn't provide heat. However, the main motivation for us to address the sustainability of our home were the frequent power cuts in our neighborhood due to tornado events and severe storms. While my husband and I were doing our best to tolerate it, having a senior member of the family move in combined with greater awareness of my own health issues in relation to heat waves, prompted a serious look at addressing the heat issues which we could see increasing with climate change. We had been relatively lucky in colder months but knowing that Ottawa has a history of ice storms, it became a question of 'when' rather than 'if' it would be an issue. Once a baby came into the picture it became even more pressing.
In 2020, the climate change projection for Ottawa report was published. Having some actionable data allowed us to clarify what our priorities were. You can read it here.
At this point, most people ask why we didn't just buy a new house, and while we considered it, the cost of housing had increased dramatically since we first purchased our home, and secondly there was nothing on the market that addressed both sustainability and accessibility. I would have to modify any other home we purchased, and more space was not necessarily the solution, just a better use of the space we already had. Additionally, I was researching minimal maintenance solutions as we were looking at such a big renovation, to sustain my physical health for as long as possible. As someone in my 30's, I must approach my home as an aging-in-place renovation as some days my limitations are worse than most of the seniors I know. I believe adaptation for climate change should be part of any aging-in-place plan.
The rest of this journal will explain how we have addressed the interior of the home, but getting the shell of the building right led us to looking at the passive house standard. This is a strenuous standard to build to, especially in a renovation environment, but it served as the inspiration for the cohesive approach to air distribution within the house, insulating all the various components, and changing the way the house breathes. It was crucial to hire an architect to help us with this, as I discussed here.
Prior to any demolition, we had an energy audit done, and I knew we had minimal insulation, but I was quite shocked at how many air gaps the negative air pressure test found. I talked about some of these in this post here.
Daylight coming through the side of the exterior outlet. Also note the dark patches on the plywood around it, indicating the build up of mould from moisture.
Our architect, Lara from Lara McKendrick Architecture (LMA) advised that one of the most effective solutions is to use “outsulation”, which is essentially creating a 'cozy new sweater all around the building'. And when she said all around, she meant ALL Around. I was surprised at how much overlap there should be to create this continuous insulation. The other benefit of using only exterior insulation is that the stud space can be easily used for electrical, hvac and plumbing runs without holes in the vapour barrier and our small house was not made smaller by making the walls thicker towards the inside.
Continuous insulation, also known as outsulation, is defined in American Society of Heating, Refrigerating and Air-conditioning Engineers 90.1 (ASHRAE 90.1), as:
“Insulation that is continuous across all structural members without thermal bridges other than fasteners and service openings.”
Above shows thermal bridging with only cavity insulation. Bottom image shows continuous insulation that prevents heat flow through continuous framing.
The benefit of thick continuous exterior insulation installed as we did (using wood strapping and stainless steel screws) is that there is very minimal thermal bridging (fasteners only) and by virtue of it being uninterrupted, you get more bang for your buck (so to speak). to illustrate... two walls - Case 1 - A basic house wall made of 2x6 wood studs at 16" on centre and nominal R24 batt insulation between the studs and no exterior insulation has an effective R value of only 17.9 because 13.4% of the wall is not R24 insulation but rather R6.825 wood studs. Test results actually vary from effective R17.02 - R18.44 depending on cladding. Case 2 - Whereas 6" of continuous exterior insulation attached using wood strapping and stainless steel screws to the same 2x6 at 16" wall has an effective R value of 28.61 which is higher than the nominal R value of 25.2 for the 6" of mineral wool insulation because the wall structure is warm and contributing to the overall R value rather than lessening it. So in the first case you got less Rs than you paid for and in the second case you got more Rs than you paid for :) gotta like that math!
Almost everyone who has visited our site has been confused by the location of the vapour/air control membrane (outside) because now all the insulation is outside. During our demolition phase we had also discovered some mould building around the areas that had air gaps to the outside. One of the issues with patching up older building types with modern, efficient insulation is not being continuous. Mold is prevented by the combination of proper continuous insulation, air tightness and breathability. Got to have all three!
Figuring out what our climate location is, and what our R-value should be was daunting to me. There were so many variables. As homeowners, we committed to installing an electric cold climate heat pump air handling system and the outsulation plan. LMA works with a mechanical design consultant who properly sized the cold climate heat pump, and distribution system for LMA's building envelope design with an effective minimum R value of R28 for walls, R50 roof, high performance windows, and airtight building envelope. This meant we bought a smaller sized heat pump than what would have been required for a less insulated, less airtight house (means $$$ savings on both initial purchase cost and most importantly ongoing operation of heating system!) This is why you consult with experts!
Our final design solution, simplified, was 2 layers of 3 inch thick semi-rigid mineral wool insulation installed with staggered seams to eliminate uninsulated "gaps" between the panels, and creating a total of 6 inches of insulation outside our house sheathing and framing. The house was originally built with brick and wood siding, alternating on different walls. I have since learned that brick, although wind resistant, has 0 insulation value, and the wood was minimal. While it was sad to lose that component of the original building, we found someone willing to re-use the brick. All painted wood on our building had to be disposed as it was lead contaminated.
