Windows are a balancing act between light, views, insulation, heat gain, and of course cost. Passive house windows need to be triple-pane, their frames need to insulate well, and they need to seal tightly, so they will necessarily cost more than regular windows.

Detailed quotes

We got quotes from multiple vendors, and made a lot of changes in response to those quotes, optimizing number, size, and type of windows. To do that, we needed detailed quotes listing the cost for each window, instead of just giving us one (very large) number. Without that, you’re limited in knowing what you can do to keep costs down.

The original plans put the house at the minimum setback from the front (25 ft). We needed to do that because the house was bigger and we had limited space in the northwest corner of the lot.

With the smaller design, we gained a lot more flexibility on where to place the house. We decided to move it 5 ft back from the setback line (30 ft instead of the minimum 25 ft). The backyard is still more than big enough, and this makes the driveway a bit longer, and thus less steep.

Yesterday, we went shopping for appliances. Found some we liked, all with good Energy Star ratings, so we thought they would be fine. Today, I looked at the energy use of the fridge, and now everything is in question, as we re-evaluate water heater and solar panels.

Let me back up a bit.

Solar panels

Solar panels are great, and we had planned to add them. However, the electricity in Kanab is too cheap, and the cost of solar is still dropping, so when we ran the numbers, it makes more sense to add those in a few years.

Our house is making progress: the architectural committee of the HOA has accepted the design, Kanab has granted us a building permit, and the walls are in the container.

You read that right. We’re using load-bearing straw panels by EcoCocon: the compressed straw and load-bearing wood frames provide excellent insulation with no thermal bridges. The 100 panels are custom made for our house:

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.

Remember back when I discussed the lot and mentioned that clay soil was a common problem in Kanab? We were glad to know that our lot had already been over-excavated and prepared such that we didn’t have to worry about clay.

Well, while digging the trenches for the stem walls, they found clay in one corner.

Not good. Clearly, something went wrong while preparing the lot, and the company who did that work will be back to fix their mistake. All on their dime, so at least we’re only out time, not money. But it means a delay of about two weeks, so the walls will arrive before the foundation is ready, and thus need to be stored for a bit, complicating the logistics.

All houses need a strong foundation, but that’s not enough for a passive house. The whole envelope of the house needs to be insulated, and the foundation needs to do its part in keeping the heat in (or out).

Here’s a basic diagram of a slab foundation, with footings under the outside walls as well as the interior load-bearing walls. Without any insulation, heat will escape through the concrete slab.

Finally – our lot now has something other than dirt and a porta-potty: the concrete footings around the house have been poured!

It took some steps to get there. After the clay had been removed, that big hole had to be filled with good dirt, compacting it along the way. And some of the trenches had to be dug again.

The foundation has made significant progress. The rough plumbing was put in.

Then those trenches were covered back up.

New trenches were dug for the interior footings.

The forms for pouring the stem wall were completed.

The insulated foundation looks clean and simple on paper: 4 inches of insulation everywhere around the slab, making sure there’s no way for heat to escape from the concrete slab to either ground or stem wall without going through at least 4 inches of insulation. (That amount of insulation provides an R-value of about 20; 4 inches of concrete has an R-value of less than 1.)

When I arrived to check on the work in progress, the reality was not quite as simple, and would definitely not insulate as required. The stem wall is where the temperature differences are biggest, so that’s where the insulation matters most.