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Installing Rockwool Insulation: Rigid Boards in the Walls and Batts in the Attic

September 22, 2018

Insulating the shell after blower door and IR camera-assisted air sealing

In the last episode of the Model Remodel Show, we spent a fair bit of time sitting on the roof while Ben spent a fair bit of time bending panels ...

"We spent a fair bit of our time prepping roof panels and getting our roof coming together. Getting our large runs and working our way into our valleys. I was really impressed with the quality of these panels, as far as the finish goes. Some panels that we've used in the past will scratch if you look at them wrong. This is a really durable finish. Installs nicely, and stands up to the abuse of being installed, no matter how ginger you try to be on them.

—Ben Bogie, remodeler

And after all of that, we’ve Gingerly smacked down the roof on Professional Remodeler’s 2017 Model Remodel.

This week we had a push to work on our interior air sealing and insulation. And the push is because we've got drywall coming on Friday, at the end of this week, so we have to have the interior insulated, wrapped, inspected, and ready for drywall, so they can start hanging board Monday morning.

Before Installing the ceiling drywall, Ben decided to try an interior air barrier membrane which ought to help the attic insulation do its job.

Roxul is one of my favorite insulations and kind of my go-to for a couple of reasons. first and foremost, for its performance and really good moisture management ability. Add on top of that that it is inorganic, so we don't end up with any mold issues, or biological growth. And the fact that it is a strong fire retardant, so it makes for a safe building enclosure.

For smaller projects and projects where I'm really trying to make a robust hygric shell, Roxul's my go-to."

With the membrane in place, we climb into the attic to fill the space between the raised-heel trusses, and around the ductwork that will provide fresh air. Ten more inches of insulation is added to this first layer, too. To completely enclose and bury the ducts.

Before insulating the walls, they look for big and easy to fix leaks.

"Blower door-assisted, IR-guided air sealing—finding some of the weak spots in our envelope and taking the chance before we stuff our walls full of insulation to knock those out."

Another piece of prep is cleaning the cavities of junk before sealing them up. This is part OCD, part concern for IAQ in the future.

The hard spots in stud walls are the teeny cavities, which require cutting insulation down to size.

These are Swedish-made Bahco Insulation knife and saw. For years I've used a cheap bread knife to cut Rockwool insulation. It works really well; it was the best thing that I had found. But I heard some guys talk about these, and took a stab at it, and they work really, really, really well.

The saw works really well for the rigid board; it cuts like a laser through that stuff.

Those teeny cavities mentioned earlier can come in all shapes and sizes. This one is two inches deep, so the 2-inch Rockwool comfort board tucks in nicely.

Ben cuts them in place with the insulation knife.

Full-size batts can slip into the standard stud cavities with a friction fit.

He cuts around outlet boxes and tucks the batts cleanly around them. One tip is to have the electrician run the wire at 47 inches, which is the height of the batts.

Headers are padded with 1-inch Rockwool Comfort board, and the basement ceiling gets Safe, and Sound batts tucked between the joists. These batts rest on the flanges of the I-joists providing fire resistance and insulation.

Next week, Monday, we'll have our sheet rockers in starting to hang board, at the same time, we've got our helical pier crew coming out to set our piers for our deck ledgers and girders. So Monday, we'll set helical piers, and start into the framing process and start banging out a couple of decks here on the project. Really excited for that, just plugging along and moving our way toward finishes here.

—The Model Remodel Show is a production of the SGC Horizon Media Network and was shot on location at the 2017 Model Remodel project in southern Connecticut.

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