If you remember one of our early solar posts when building the house, we initially assumed that solar was going to be too expensive for us. Then we ran the numbers and found that the rate of return was actually quite attractive over the log run.
Our contractor used our house as an opportunity to apply for status as an Energy Star builder. It worked. He’s now an Energy Star approved builder, and we have a 5+ star Energy Star home. In the process we discovered a big difference in the projected energy usage by our Energy Star certified rater using REM/Rate and our certified PassivHaus consultants who used the PassivHaus spreadsheet.
To get to net zero energy use, we must produce enough energy to offset our energy usage over a year. We originally planned to live in the house a few years before installing photovoltaic (PV) panels on the roof, but after we ran the numbers we decided it made sense to do it now rather than wait.
There are several ways to approximate the cost of a leaky house. Before I proceed, however, I just want to mention there are other much larger longterm monetary benefits to building a tight house, like a longer lifecycle and less maintenance due to keeping critters and moisture out of the building enclosure. I’m sure there’s a way to calculate the value of these additional benefits, but it’s beyond my abilities (and you’d have to use a lot of assumptions to get there).
Having gone through the numbers, there is some value to understanding the factors that are used to estimate the cost of infiltration, as well as the proportion of infiltration cost to the overall energy costs required to heat a house.
As the snow piles up outside, I have turned my thoughts to Spring. Not only because it’s warmer and nature is waking from it’s long slumber, but also because I hope we will be conducting our first blower door test by then. Specifically I’ve been considering what type of results I should be expecting from the blower door tests, and how to interpret them.
We made the decision early on to build an air tight house. This guided our choice of building materials, Zip system and tape for the exterior sheathing, gaskets and acoustical sealant to seal all other connections, and foam to seal gaps at the rims, windows and doors. The blower door test will help us seal any gaps we missed. But what target should we aim for? How do we know when the house it tight enough?
Lots of updates this week. We have updated house plans. We received window estimates. We hired energy consultants and a land surveyor. We have estimates for the driveway and getting electric service to the site. It has been a very busy two weeks.