Here’s more on Continuous Insulation mentioned a couple of posts ago.
The building codes are driving towards the use of CI or Continuous Insulation due to the large amount of thermal breaks that occur in standard construction. In a wood framed house we assume that cavity insulation occurs in 75% of the wall and 25% of the wall is taken up with the frame. Having a quarter of the perimeter as a hole in the insulation is a pretty big hole. So the idea with Continuous Insulation is to provide a decent, but not full, amount of insulation on the outside of the frame. At the Brackett Road home in Rye, New Hampshire that is under construction now, we are using one inch of foam laminated to the wall sheathing with the Zip R Sheathing Boards.
At the roof plane we are using 3 inches of foam with an Atlas Panel system. With the Atlas Insulated Roof Panels, one puts down a layer of sheathing to start with over the rafters like in standard construction. Then a sheet of vapor retarding material recommended by Atlas goes down. Then the Atlas Panel with foam, a one inch air space, and another layer of plywood is screwed to the first layer of sheathing with 32 or so screws per panel. The air space allows for ventilation in all directions and for keeping the roof shingles from overheating and resultant voiding of their warranties. Getting full ventilation in rafter cavities has always been tricky and sometimes impossible with valleys, skylights, and dormers interrupting the flow.
We are filling the cavities between stud and rafter with cellulose in a dense pack arrangement to keep from any settling. I recommend non ammonium sulfate treated cellulose with a density of 3.7 pounds per cubic foot in the rafter spaces and 3.5 pounds per cubic foot in the stud cavities. National Fiber is a good manufacturer.
One other thing with this is that we are insulating the full perimeter of the home in section. The insulation goes under the Basement slab, up the basement wall to the wood framed walls, and then follows the roof plane. We are used to doing the full perimeter in plan view. Insulating the full perimeter of house in section view allows for Heating and Air Conditioning equipment and ducts to all be in conditioned space. We can get condensation in the ducts sometimes when ducts and units are in non-conditioned space with nominal insulation draped over them. Insulating the full perimeter in section view also helps lessen the incidence of mold and mildew which are a great thing to avoid.
Continuous Insulation and Full Perimeter Insulation in Section have many benefits. Insulation and Structure are things that typically last the life of the building. Many other things last about 20 years. It is good to do the long lasting items right to start with.