The polyiso insulation boards have been going up on the ceiling! We purchased a “bunk” of recycled boards from Repurposed Materials. Or it may have been two bunks–or about 60 4×8 sheets. This is the same recycling business that sold us the blue XPS 2 x 8 ft. panels for the foundation perimeter. They have been growing by leaps and bounds and now have expanded to Chicago and soon to Atlanta! I’m glad to see that there is growing interest in reuse and repurposing as well as recycling.
We chose the 1 1/2″ 4 x8 sheets of plain paper backed board. We didn’t need foil backed stuff because that functions as an air barrier and we will have an air barrier inside this layer. In the background you can see the boards ready for application. This may be the first photo of Dave working on the house on the blog. He is putting up the polyiso after working all summer on mostly outside projects. He uses a long bladed utility knife to cut the boards.
The 1.5 inch boards will add about R-10 or so to the R-46 rockwool insulation as well as form a thermal barrier at the joists so the wood does not conduct cold through to the ceiling. This is an infrared photo of the thermal bridging at the cathedral ceiling from our initial energy audit. The wooden rafters transmit cold from the outside to the inside enough to see the temperature difference in the photo. The polyiso layer should eliminate thermal bridging.
The walls already have a thermal barrier because there is 1″ foil covered polyiso used as outside sheathing. So the wall near the window does not show colder studs than the insulated walls.
Once all the polyiso is installed this will be true for the ceiling too. When we have walls, this will be the family room ceiling. Dave is spraying Great Stuff foam into any cracks between the boards. There is a skylight in this ceiling and allows for updraft cooling in the house on hot days. Skylights are considered energy wasters though. Energy saving is a trade off.
Just for the heck of it, I aimed a temperature differential meter at the ceiling where there is partial coverage of polyiso. The temp at the ceiling without insulation was about 58, the temp at the insulation was 70.1 and the temp at the polyise was 74.6.