What is the perfect wall assembly?
I plan to build in the spring of 2021 and the intention is to super insulate my solar passive house. Your video on ''build the perfect wall - top tips'' is very inspiring and I shall use many of the tips. As a slight variation to what is presented in the video, I am thinking of using 6 inches of dense-packed cellulose on the inside instead of Rockwool. What are your thoughts on this variation?
Also, I do want to insulate on the outside as in the video, using Rockwool on the outside. The wall shown in the video has two courses of 4'' roxul comfortboard [...but I assume this is the ''cavityrock'' product line as I cannot find 4'' comfortboard in the offering.] I appreciate that 2 courses were used in order to break the thermal bridging effect but as mentioned in the video the labour cost was higher. What would be some alternatives given the narrator's comment that ''there are other ways to do this''?
Cellulose is a fine insulation, we recently used cellulose insulation for the walls and roof of our latest demo house, the S1600 LEED Platinum Prefab kit house.
As for how to mount exterior rigid insulation, there are ways that employ more expensive materials, but save a lot of time so it sort of comes out in the wash we figure after having done it that first way.
Cascadia Clips is one such product, alternatively you could try Larsen trusses. You can read more here –
Larnsen trusses and cellulose insulation on the exterior of a Passive House.
And another that makes a lot of sense is ThermalWall exterior insulation panels from Legalett. They are made from EPS foam, and they have a metal rail in the middle of the panel that is used to attach them. What you do is remove the ‘snap track’ of insulation, fasten the panel to the exterior of the stud wall, the you replace the snap track and install your strapping to the same metal rail. The result is the same with what we did at the Edelweiss House, which is a seamless layer of exterior insulation with no screws that pass through the entire assembly to act as a thermal bridge. This looks like it would be the most affordable of the options.
A far less expensive method to mount rigid insulation is with the Ejot fastener, which we use to mount tens of thousands of sf of rigid insulation (Comfortboard80) onto AAC and sheathing.