I live in MA and I want to insulate. I need some advice as to the best approach to insulating the roof. Currently there is no ceiling - it is open to the roof above. So I was thinking I could put fiberglass batts of insulation between the roof rafters. The only problem might be moisture buildup between the roof and insulation which might cause a problem. The only ventalation is a gable vent - there is no ridge vent. Do I need a ridge vent if I go this way or is the gable vent enough? Would I also be required to drywall over it?

Another option I guess is to put up a ceiling using drywall and then insulate between the ceiling joists. This might be easier and cheaper. However, I would lose this "attic" space which would be nice for storage. I'd also have to frame in a hatch or possibly attic stairs so I could get to this space.


I also thought about hiring a company to spray on the foam insulation. Would this be best? Would I still need to drywall over it? It sounds expensive, but I don't know.

You want to keep the roof itself COLD, which is why an air space is ALWAYS required when insulating between rafters. The air space should be vented by soffit vents plus a ridge vent. The gable vent will do nothing.

Any foam insulation must, by code, be covered with a thermal barrier, usually gypsum board. If the garage is attached to the house, you may need to use Type X gypsum board. Foam insulation sprayed between the rafters will again not produce a cold roof. and this could lead to ice dams and leaks.

To the best of my knowledge there is no insulation which requires no venting in a rafter application.

Personally I would like to see you supply enough gable ventilation to prevent condensation on the underside of the roof if you install fiberglass.It'd work, but you wouldn't be able to stay warm.

Especially if you used kerosene heaters.

If you want to go with insulation on the underside of the roof, you could go with vent chutes.

To the best of my knowledge there are insulation systems out there that require no ventilation, but the amount of expertise required to get them reliable makes them better to reserve for applications where nothing else will work.

It's like translucent concrete: I need to get light through this loadbearing wall, but I can't cut any openings in it. What do I do? I'll use loadbearing translucent concrete.

But could a normal homeowner afford a translucent concrete wall? Probably not.

Thanks. This is good advice. I guess I'll put up a ceiling using drywall and then insulate between the ceiling joists. This sounds like the cheapest and best option.

quote:

Originally posted by Richard Hetzel:
You want to keep the roof itself COLD, which is why an air space is ALWAYS required when insulating between rafters. The air space should be vented by soffit vents plus a ridge vent. The gable vent will do nothing.

Any foam insulation must, by code, be covered with a thermal barrier, usually gypsum board. If the garage is attached to the house, you may need to use Type X gypsum board. Foam insulation sprayed between the rafters will again not produce a cold roof. and this could lead to ice dams and leaks.

To the best of my knowledge there is no insulation which requires no venting in a rafter application.