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.
• It’s the first step in creating an airtight layer around the whole house.

In essence, the base plate consists of two support beams with insulation in-between. Underneath, a waterproof layer separates the wood from the concrete. Here’s an image of the base plate under construction:

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.

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.

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. For some reason, I had always imagined the overhangs to be 2 feet, and that’s what the spreadsheet contained. It would have been clear to see in the plans, but I didn’t check. The reality didn’t dawn on me until I saw water dripping from the roof.

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. Given the volume of the house, you can calculate the number of air changes per hour (ACH) under those conditions. (The 50 pascals pressure corresponds roughly to a 20 mph wind blowing from all directions.)