West Coast Passive House tour - A phased Passive House retrofit?
Sunday, October 10, 2010 at 1:28PM 
Photo by Quantum BuildersIn my last installment I mentioned a conversation that Jarrod Denton and I had about how builders and homeowners in Europe tend to think ahead and plan for future maintenance issues a bit more. I then left you with a bit of a cliff hanger – that very circumstance came up 2 projects later. I’ll take the next part of my tour out of order so that we can continue the discussion of future planning.
Bronwyn Barry of Quantum Builders was the next consultant I visited on my West Coast Passive House tour. She had 2 projects to show me, one was new construction and the other was a phased Passive House retrofit (a term I was not familiar with). It is this phased project that we will be exploring today.
In Europe the Passive House community has been building and adapting as communities evolve into more energy efficient communities. Sometimes that change happens quickly, sometimes it happens in phases. They have recognized that some homeowners are unable to do a complete retrofit of an existing building in one remodel, and have devised a system to allow the retrofit in phases. The entire project must be modeled in the Passive House Planning Package software and be shown to meet the Passive House requirements. There is then an opportunity to do part of the project with the ability to come back in the future to complete the project for Passive House Certification.
Bronwyn had an ideal project to test the US waters for this kind of phased certification. Mary James, one of the authors of “Homes for a Changing Climate: Passive Houses in the US” (with a NEW book due soon!) wanted to try retrofitting her existing home into a Passive House home. Because of the upheaval a complete retrofit would entail (extensive work outside AND inside) it was decided that only part of the retrofit would happen in the first phase. Insulation was added to the roof and walls of the building (over the existing siding) and triple pane windows were installed. The foundation was insulated on the outside, but the interior foundation insulating work was left for a future remodel.
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Sustainability was a key consideration on this retrofit. The home had an existing HRV, solar H/W & PV, and the crawlspace was sealed. Building on these features by establishing increased energy efficiency as well as improving indoor comfort took this project to the next level. In addition, by installing the new insulation directly over the old siding less waste needed to be disposed of. Installing external shading devices meant stopping unwanted summer heat gain before it could enter the home.
The efficiency of the building was modeled prior to construction starting. It was shown that with the plans Bronwyn designed, the wall system would go from an average 11.1 R value to a 22.3 R value. The roof would increase incredibly from a 2.2 R value to a 50.2 R value. When the final foundation insulation has been completed the foundation will improve from an R value of 1.4 to one of 10.2. Because the modeling needs to also be verified, the homeowner is monitoring her energy use. At this time she has seen in improvement in the energy use, but the gas usage is higher than anticipated. That could be because of the need to move the gas water heater to the outside for ventilation purposes or perhaps because the foundation is not completely insulated yet. It is this kind of careful modeling after a project that will enable us to build better as we sort out the climate differences that are found in the US.
The final determination on whether we will have phased Passive House projects has yet to be ironed out. With US Passive House pioneers like Bronwyn Barry and homeowners like Mary James I believe we will see more definition of what Passive House is in the US. It was very exciting to be able to visit all the different projects during my tour and this one in particular for the trail blazing that it is doing.
Next up – Bronwyn takes me to Palo Alto to see a new construction Passive House and I see a feature that she used that might help with air tightness in retrofits.
- © 10/10/2010 Linda Whaley,
Reader Comments (1)
Hi Linda - Thanks for this great article but I need to make two corrections: I was not the designer of this project, but simply one of the team that helped in it's PHPP modelling. The architect is Josh Moore, also of Quantum Builders, and the official CPHC was Mary Graham of TipToe Energy. Full credit listing is visible at the end of the ppt presentation you included.
Thanks!
Bronwyn