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: The panels are 40 cm (15"3/4) thick, providing an R value of 39.

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.

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 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. Road base was added in the trenches, then compacted, to give a solid base for the footings.

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. And now stem wall and interior footings have been poured. Note the cutouts in the stem wall where the doors are going to be, leaving room to add insulation below the doors (using purenit or equivalent).

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 slab was poured on Monday July 15, starting at 7 am. The whole operation went very smoothly. They were careful to push the insulation into place as the concrete was poured, to avoid the concrete flowing into cracks. Moving the house a few feet westward paid off: the ready mix truck could get through on the east side and deliver concrete from the back, eliminating the extra cost of pumping the concrete.

The wall panels need a base plate to stand on. The base plate goes around the perimeter of the house – the red ring in the following image: The base plate fulfills several functions: It moves the straw panels a few inches off the ground to protect them from any future water mishap. It’s firmly tied down to the concrete, and in turn gives a solid base to screw the panels into.

After a long trip from Lithuania, the EcoCocon wall panels finally arrived at the site. The panels consist of a load-bearing wood frame densely packed with straw (110 kg/m3, about 7 lb/ft3). The panels are light enough to be moved by two (strong) people. However, a mechanical loader helps a lot. EcoCocon recommends starting with a corner and building out from there. The panels have dowels to align them, and get screwed together, but not anchored in the base plate yet.

It’s amazing when you’ve been carrying a design around in your head for so long, and it finally gets realized. With the walls almost completed, I’m very happy to see the plans come to life. Here’s the last beam being placed in the front. The current state as seen from the hill. And here it is as seen when you’re coming up the street. A few panels are still missing.

Lots of progress in the last week. The walls are now complete; the last panel was a very tight fit. Interior walls Meanwhile, the interior walls are being built: first assembled on the floor, then raised to vertical. And the roof trusses have arrived. Airtight membrane The airtight membrane on the outside gets taped to the waterproof layer that went underneath the base plate. The membrane continues underneath the ring beam to be added on top of the walls, and then taped to the membrane underneath the roof, making the whole house as airtight as possible.

I was on a family trip to Norway and Portugal for two weeks. We got updates and handled some house questions while traveling, but it’s good to be back and see the progress with my own eyes. A lot has happened. Roof We have a roof! As the roof is at a low angle (4°), TPO works really well. We looked into a standing seam metal roof, but it would have been twice the cost, which was not worth it for a roof that’s mostly hidden.

Roof overhangs are an important component of the whole passive house strategy: keep the sun from hitting the facade during summer, let the sun help heat the house during winter. In the Passive House Planning Package (PHPP) spreadsheet, each window not only includes size and orientation, but also overhang depth and position. This allows the heat gains to be calculated accurately throughout the year. However, this only works if the value entered in the spreadsheet is correct.

Things are happening – significant progress this last month. First, they installed the glass in the huge windows in the living area. The view from the planned couch location remains amazing. Here you can see those windows in the context of the kitchen and living area. Doors to backyard and patio still need to be installed, but you can already feel that the temperature inside is more comfortable and even than in regular constructions.

The front door (from Neuffer in Germany) is now installed, very happy with how it looks. The builder also installed the doors to the patio and backyard (matching the windows by Alpen in Colorado). They are large and heavy – check out those hinges. Each hinge can be adjusted in all three dimensions. Some more adjustments are still needed to make sure they close as tightly as required (more on that in the next blog post).

As explained in a previous post, making the house airtight is crucial to passive house: air lost is energy lost. As well as a loss in comfort, air quality, and confidence that the house will perform as calculated. A blower door test is used to determine how airtight the house is. After a fan is mounted in a doorway, the house is depressurized by 50 pascals, and the airflow is measured.

We ran a second blower door test after sealing up a bunch of leaks. The result was a lot better: we got down to 1.1 ACH50 (air changes per hour at 50 pascals): a big improvement from 1.6, but not up to the passive house standard of 0.6. Before the test We sealed off all the drains with plastic sheeting and duct tape. The front door was much better adjusted, and also got taped on the outside.

After our last blower door test, the builder found and fixed a significant leak hidden behind one of the beams. Hopefully, that was the last one, as the airtight membrane is now inaccessible behind the drywall (gypsum board, sheetrock) in the ceiling. Before mounting the drywall on the straw panels, the wood beams are furred out a bit so that any straw sticking out doesn’t cause the boards to warp. We’re also using 5/8" drywall everywhere to keep it as straight as possible (also improves sound proofing).