Today I finally got to put some actual physical labor into the house. With the crew off for the weekend, and a nearly 60 degree day in the Colorado mountains, it was a great moment to experiment with one of the key differences of this house versus nearly every other newly built house out there. Sealing the house air tight is maybe the most significant factor in the level of energy efficiency (90% less energy use compared to a normal house) that we are shooting for.
There are many ways air gets into and out of a house – and in a Passive House, we strive to seal every one of them. The fresh air necessary to keep the house comfortable, fresh, and mold-free comes from the use of the one special appliance this house will have – an Energy Recovery Ventilator. But more on that down the road. Today, we tape!
My experiment comes courtesy of the one room that has it’s plywood skin on – the garage. Now, while the garage is not part of the main, double-walled Passive House envelope, it is still connected to the house and cold will transfer in and out of the common walls. So what better place to learn and experiment with tape than a room that by design will not be as tight as the rest of the house.
Because the wall substrate is Oriented Strand Board (yes, sustainably certified, formaldehyde free…), there is a texture to the walls that might not allow the fancy tape to stick as well as possible. Some of the OSB was correctly oriented with the shiny side out, which the tape WOULD stick to well, but some was not – it was put up rough-side out. The upshot of all that is that I decided to prime the seams with a liquid rubber primer, ensuring maximum tack for the tape.
After a lap around the garage to prime every junction (and being fairly well covered in sticky rubber goop) it was time to tape.
The Siga WigLuv60 tape is a pretty special tape made specifically for air and water sealing joints – it is expensive, but once I got the hang of how it acted, I could see what all the fuss was about. The Swiss-made tape is a stretchy-plastic band, with a grid of fibers embedded in the band, all on a super sticky adhesive. Once stuck to the primed wall, it was not about to move! Getting it to form into and out of cracks and joints took some maneuvering, but as stretchy as it is, you can mush it into the corners pretty easily and get a good, tight seal.
But I ran out of time to get the foundation sealed to the OSB. Maybe tomorrow – forecast is for a nice, clear week ahead for building!
Reducing thermal bridges are one of the key ways this house can achieve a 90% reduction in energy use over a standard house of it’s size. Not fancy, only slightly more expensive (maybe 5% more?) – a 90% reduction.
Then there were two! The guys rocked it out on Friday…
Going vertical happens quickly with an experienced and coordinated crew.