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Loading ...In response to an e-mail, you were kind enough to explain how to best insulate our old house attic. We are now seriously considering finishing the attic. I’m guessing this would change how to insulate. Would we just put the insulation between the roof rafters, or am I missing something? If you have time, I would really appreciate some guidance.
Finishing an attic seems straight forward and simple, but there are some things to consider. Planning ahead, research, and correctly installing materials can help make an attic into comfortable extra living space.
Attic spaces are typically very hot in the summer and very cold through the winter. Without properly insulating, your finished attic room will also be cold in the winter. Without properly ventilating the roof, your finished space can be just as unpleasant as an unfinished attic. Since parts of a finished attic are usually very close to the roof, insulation often blocks proper ventilation that is needed under a roof structure.
Ventilation
The best method for ventilating any roof is to have some type of venting up high on the roof that allows for rising hot air or warm/damp air to escape. For this to be fully effective, low vents should be installed to replace the air that is escaping. Continuous ridge vents and soffit vents are often the most effective, but it’s best to have an experienced professional evaluate to determine the best method.
Insulation
I suggest designing the walls and ceilings to minimize the area where insulation behind these surfaces is near the roof as this can restrict air movement.
- The area near where the roof rafters meet the floor doesn’t have much clearance so “knee walls” are often constructed. The area behind these walls is often used for storage of seasonal items and luggage.
- Instead of the ceiling following the slope of the roof all the way to the peak, a flat ceiling can be easily installed by attaching joists horizontally across pairs of rafters.
Both of the above creates some spaces where a good amount of insulation can be installed and areas are created for ventilating under the roof. These spaces aren’t really useable in a room anyway.
Where insulation will have to be installed between the roof rafters, “baffles” should be installed first. Baffles hold the insulation away from the underside of the roof decking, creating a channel for air movement.
Finished Attic
11 Responses to “How to Insulate a Finished Attic”
Thanks for your article.
Would the same advise apply to the tin roof with no ridge vent?
Hi Kit,
Old metal roofs typically didn’t have any ventilation and have held up quite well. Ventilation could reduce moisture condensing under the roof though.
If you’re finishing an attic space under a metal roof, the living area can be quite uncomfortable on hot, sunny days. The ventilation and insulation I’ve described above would likely make it more comfortable.
please tell me if you have to insulate the walls in the attic,when you have insulation on floors, we have 4 vents in attic.
We have a big problem in our finished attic bedroom . The roof is facing north and we were having leaking problem. We took off the plywood and insulation and installed flo-thro(strofoam)vents, installed insulation again and plastic vapour barrier. We thought this would solve our problem until we had a mild spell following very cold weather and water started running down the ceiling inside the vapour barrier. Does anyone have any other suggestions? How much venting is required in the eaves and on the roof? We have vents at each end of the attic at the peak of the roof.
I’m finishing the second floor of a pre-fab home.There is a knee wall about 4′-9″ tall then the rafters (@4′-6″) upto the ceiling which is @ 8′ tall. Because the home is manufactured w/ 2×6 studs including roof rafters, there’s not a lot of space for batt insulation after installing the rafter baffle up above the ceiling height. Is this enough space for exterior wall rated insulation, or do I need to pad out this area to allow for more room for insulation/ refter baffle? Thanks
I have an attic in 150yr old home that is large enough to be used as third floor. How do I insulate and vent this? It has large beam work that I’d like to keep. Can I insulate from the exterior instead? And how would I ventilate? There is knee wall all the way around but ceiling goes to roof peak.
I want to insulate the roof rafters of an unfinished attic with intention of finishing the room eventually. The floor is not insulated. How do I vent using ventilation channels? What type of insulation foiled or not? Vapor barrier or not?
Thank you for that good post. I enjoy your website very much.
I have a cape cod style house (built in 1949) with no soffit vents, it does have gable and ridge vents. This home is NH. The finished attic area seems to be very hot and very cold during the year…The knee wall areas are insulated on the roof and possible the floor (we believe the floor area is insulated). What R rating insulation should we use if we decide to rip all of it out and start over? We also experience ice build up around the edges of our roof. No leaking yet. Any advice would be appreciated. Thanks.
We’re thinking about finishing our bonus room in the attic and need some help. We live in GA and my main question is after putting up the raffles, what type of insulation we put behind, or should we even put any. Our main concern is also that neighbors that had their bonus room done around here are having problems with temperature not staying very stable. Most of them are having very warm rooms and having to run the air almost all the time. Is there a way for me to better prevent that? Will the insulation behind the raffles help? Should I use insulation with vapor barrier or not behind the raffles?
Thanks in advance for any help!!