Insulation, Radiant and Vapor Barriers - Insulating attic/roof
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pato1681
03-05-05, 05:20 PM
I just purchased an older misison style home, 2.5 stories w/ a partially finished attic. I've heard mixed messages regarding whether or not you should insulate your roof, and I'd like to hear some opinions from people who either know or have done this themselves.
I know a little from reading books and things on the internet. I know the insulation cannot be placed directly against the planks (I have 1x6 planks for a roof), and baffling needs to be placed first to allow air to flow and prevent condensation and ice dams here in MI. I know that soffits or other vents need to be placed somewhere (I'm not sure where) to help with ventilation too. I know the R-rating I need, but I'm not sure if I should use rolled insulation or foam board or both. After the insulation, I'll be re-hanging drywall that was installed a few months prior to my purchase.
What I don't know is if this is something that should be done, and whether or not it will help lower my heating bills. I also do not know the speciifics, as everything I've read regarding attic insulation concentrates on the flooring, and never mentions the roof.
Is this because this is really not neccesary, and could potentially lead to more problems than it is worth? Or is it just because most people do not have a finished attic?
This is something I'd like to do as part of a whole package of insulating changes designed to make my house much more energy efficient, but if it doesnt make sense, I'll move elsewhere.
Thanks for your help!
I know a little from reading books and things on the internet. I know the insulation cannot be placed directly against the planks (I have 1x6 planks for a roof), and baffling needs to be placed first to allow air to flow and prevent condensation and ice dams here in MI. I know that soffits or other vents need to be placed somewhere (I'm not sure where) to help with ventilation too. I know the R-rating I need, but I'm not sure if I should use rolled insulation or foam board or both. After the insulation, I'll be re-hanging drywall that was installed a few months prior to my purchase.
What I don't know is if this is something that should be done, and whether or not it will help lower my heating bills. I also do not know the speciifics, as everything I've read regarding attic insulation concentrates on the flooring, and never mentions the roof.
Is this because this is really not neccesary, and could potentially lead to more problems than it is worth? Or is it just because most people do not have a finished attic?
This is something I'd like to do as part of a whole package of insulating changes designed to make my house much more energy efficient, but if it doesnt make sense, I'll move elsewhere.
Thanks for your help!
michiganguy
03-05-05, 09:00 PM
A lot of newer homes have cathedral or similar designed roofs/ceilings, which
are more suitable for insulating, mostly due to the dimension of the rafters.
The typical rafter dimension I see in houses like yours is the old full dimension
2 by 4's. There is not enough space in 4'' to adequately insulate, much less
provide space for ventilation. While the average house only has 3 1/2'' ext.
walls to insulate, far more heat is lost through the attic than the walls, hence
a requirement for much more insul. up there. In most conventional attics, it
is possible, with certain provisions for ventilation, to install adequate depths
of insul. on the '' floor'', that wouldn't be possible between the rafters.
The biggest problem I've seen with sheets of foam between framing members
is the fact that they are very difficult to cut to size evenly. With gaps and
''ragged'' edges abounding, the ability to actually do the job of insulating is
greatly reduced.
are more suitable for insulating, mostly due to the dimension of the rafters.
The typical rafter dimension I see in houses like yours is the old full dimension
2 by 4's. There is not enough space in 4'' to adequately insulate, much less
provide space for ventilation. While the average house only has 3 1/2'' ext.
walls to insulate, far more heat is lost through the attic than the walls, hence
a requirement for much more insul. up there. In most conventional attics, it
is possible, with certain provisions for ventilation, to install adequate depths
of insul. on the '' floor'', that wouldn't be possible between the rafters.
The biggest problem I've seen with sheets of foam between framing members
is the fact that they are very difficult to cut to size evenly. With gaps and
''ragged'' edges abounding, the ability to actually do the job of insulating is
greatly reduced.