Anyone familiar with insulation and/or roofing?
>Here is my dillema:
This house is a bit over 100 years old, there is a living space in the attic, however it gets over 100 degrees in the summer, and cold in the winter (California). I've gutted the old Celotex walls and ceiling and haven't found any moisture issues or a drop of water even with all the rain we've been getting so the roofing is in good shape. There is no plywood or any sheathing on the roof or walls, just planks on ceiling with an inch space between them, paper & shingles. And clapboards on outside of house.
I can afford rigid foam, and a bit of canned spray, and plan on cobbling between the rafters and box in the attic.
I want to insulate that attic space and I am going to replace the knob & tube wiring... the issue is, the house breaths very and I feel that insulating that attic space is going to create problems with moisture, leaks etc? (fairly hot, dry climate though)
Hoping someone has experience with this.
The important thing is that you need to have air flow underneath the roof sheathing. If you insulate against the sheathing you end up with a 'hot roof' which shorten the lifetime of your shingles and will void warranty claims on them. The lack of airflow also means you end up with moisture retention problems and even infiltration.
You buy baffles which you fit into the space between the rafters from the soffit up to the ridge. These create a thin column of air that can flow up to the ridge vent, or out through slat sheathing gaps. You can then lay your insulation batts into the rafter space. Do not put rigid insulation across the rafters if you intend to create a finished space since hanging drywall on op of rigid insulation is a HUGE pain in the ass. If you do insist on using rigid insulation, score and break it into pieces and mount in wood slats to attach the drywall to to prevent the foam from compressing and warping the drywall panel. I would still suggest against using it since the added bennefit will be negligible in comparison to what batting and the air columns will do.
Furthermore, remember that you can only put a vapor barrier on one side of the wall, inside or outside. One or the other.
If you have windows up there, then don't bother with the installation of fancy vents, the windows will do just fine.
Not OP but I have a knee wall attic that I would like to finish in the hopes of making it a cleaner storage space. A lot of sources I'm googling say it's very important to keep air flow and to try not to store temperature-sensitive items in those areas, but I'm finding articles that suggest allude to otherwise without anything saying it outright. What am I missing here? Also I assume I need to reinforce the flooring trusses/rafters/not sure what to call them.
this is the best course to take, and if you can insulate the entire space making it a conditioned space- that way any ac/heater units can run more efficiently bc they wont be exposed to such a temp. variance