We’re slowly wrapping up the rough framing and getting ready for insulation. I met with our EnergyStar rater and insulation contractor this week to do a walk through of the house. It’s best to know what we need to do before the insulation and drywall start going on. On the exterior the windows are being installed and the rigid insulation is going up.
There is some concern regarding the HVAC ducts being on exterior walls. These days most if not all the ductwork should be on interior walls to insulation them from the exterior. Otherwise it’s difficult to get enough insulation in those wall bays. At least I’ll have 4″ of rigid insulation on the exterior to mitigate the issue as best we can. Flexible ducts have been installed in many of the kneewall attic areas of our Cape Cod style home. This means that in reality we will have to treat all these areas as conditioned space. This will mean insulating the roof and exterior walls just like the main house, but also using some paper material to prevent air movement. The paper material will act like drywall in terms of controlling air flow, but will be less expensive to install. Another concern with the flexible ducts is they were installed with too many tight turns or corners. Flexible ducts need to have gentle radius turns to keep air and debris from piling up in the corners.
A bit more on insulation. We’ll be using blown in cellulose insulation made from recycled newspaper. Fairly green although it is treated to be fireproof. For air tightness we’ll be caulking the drywall seams so that should minimize any perceived ill effects of the fireproof insulation. As far as I know it’s a safe product. Part of the insulation job will include extensive caulking and sealing of the entire house, including around light fixtures, outlets and any wall or floor penetrations. One place to pay attention to is between the OSB sheets. Technically the framers should space the sheets 1/8″ apart for expansion. They usually don’t but regardless, any visible gaps in the OSB should be sealed with spray foam from the inside. On our house there are a couple of areas where you can see daylight shining through the green Raindrop housewrap, between the OSB wall sheathing.
We’ll be having a blower test and filling out three sets of survey forms to establish our home’s HERS rating and ultimately our EnergyStar qualification. It’s critical that the house essentially be air tight. I Googled it and it looks like Ohio has about 1,300 EnergyStar homes so we’ll be in the vast minority. Hopefully in a few years this will be the norm.
On the exterior we continue to pick away at sealing everything and installing the blue rigid insulation. Windows are starting to go in. We seat the aluminum nailing flanges of each window in a bead of silicone sealant / caulk and level / nail the windows in place. Over the top of the flanges, just like our REMOTE wall article says to do, we cover with Grace Vycor Plus membrane flashing. The insulation contractor will seal everything up from the inside with spray foam and caulk where necessary.
The windows show up with a breather tube and mylar expansion bag. Serious windows do this because all the windows are gas-filled. Without the tubes the windows would explode when they’re driven over the Rocky Mountains. Without the mylar balloon the gas would escape. One of the balloons did get cut so I suspect we’ll have to have a tech come out and refill that window. On all the other windows, I’ve been crimping the tube in two places and will cut off the mylar balloon. I then hit the end of the tube with silicone caulk and then tuck it into the window frame. The gas should stay in the windows for 100 years. Definitely not my problem then.
On the exterior we’re installing aluminum termite shield to protect the bottom of the rigid from ant / bug infestation. We simply bought some white aluminum sheet metal and bent it up to form an “L” with a little lip for water run off. The termite shield gets tacked up behind the housewrap at the bottom of the exterior walls. It overlaps the foundation by about 2-3 inches. Resting on top of the termite shield and housewrap are our 2×8 foot x 4 inch thick sheets of Dow blue rigid insulation. The rigid is installed by tacking the panel with a couple of screws. We then come back through and put 1×3 firring strips over the vertical seams. The horizontal seams get a one foot strip of Raindrop; it’s zig zagged with 4″ stapled above the panel against the existing housewrap, then 4″ runs across the top of the insulation panel, and finally the last 4″ flaps down over the top of the panel. If our panels weren’t so dirty we’d just tape all the seams. The firring strips will help give us a decent seal as will the housewrap strips. We use 8″ screws to secure the firring strips to the wall (passing through the rigid insulation). Try to hit studs with every screw. Otherwise the screw will act as a conduit for cold or heat. We missed a ton and technically should back out the screws and try again, but it’s painfully slow already so we’ll snip the exposes screws and I’ll kit them with some foam insulation. Should be alright, even for Ohio.
One interesting thing I came up with this week, the loft window is showing up late but we need to get the blue board in place ahead of time. Once the blueboard is in I won’t be able to get the membrane flashing in place. So I took strips of it and left the backer paper on and stuck the rest to the window buck perimeter. After the window is in they can remove the paper and stick it over the flanges.
Here are some new pics from the last few days.