Passive House Certification

I had planned to have the house certified by both PHI and PHIUS. For PHI, we’ve already done a lot of the work using the PHPP spreadsheet, and for PHIUS, we could use the simplified prescriptive path for certification. A lot of the necessary documentation, blower door test, etc., would be shared, and the PHIUS certification would help us qualify for some tax rebates.

However, while our house is simple enough for the PHIUS prescriptive path, it has too many windows. Especially after the smaller redesign, the window-to-wall and especially the window-to-floor-area ratios were not within the limits for the prescriptive path. (Corrected May 6: Adequate Exposure Diversity would pass as an alternate to the window-to-floor-area.) We would have to use the performance path for certification, and that would involve hiring somebody to calculate the WUFI model for the house. It would have been great to compare the PHI and PHIUS results, but we’ve decided that the extra cost is not worth it. So we’re proceeding with PHI certification only.

Update: In a recent post, I discussed that we were getting close to the limits on electricity use, and were wondering how best to address that. We’ve decided to (1) add a heat-pump water heater in the mechanical room, (2) add ventilation to that room so that there’s enough air to draw heat from, and (3) add sound dampening to the ventilation to avoid noise issues.

In that post, I was worried that we would not gain the benefit of the heat pump in the winter, as the cold air produced by heating the water is not helpful. However, it’s still more effective to have one heat pump draw heat from the inside air (to heat the water) and another heat pump draw extra heat from the outside air (to heat the inside air) than to heat the water with direct electricity. It’s not perfect in the winter, but it’s not a total loss. And in the summer the extra cool air is a win.

In other news, foundation work is supposed to start by the end of this week. Yeah!