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lazidazi

@frontiernet.net
reply to Draiman

Re: Insulating Attic

Okay, now - please don't anyone get fussy with me for asking an ignorant question.

RE Xcal's pictures, insulating attic with rigid foam board on the bottom edge of roof rafters: When one does this, is insulation at/between the ceiling joists then not needed? Is the rigid insulation at the rafters all that's needed for the attic? [including, of course, what he's done on the gable ends, et al]


Critsmcgee

join:2011-12-02
Reviews:
·Verizon FiOS

said by lazidazi :

Okay, now - please don't anyone get fussy with me for asking an ignorant question.

RE Xcal's pictures, insulating attic with rigid foam board on the bottom edge of roof rafters: When one does this, is insulation at/between the ceiling joists then not needed? Is the rigid insulation at the rafters all that's needed for the attic? [including, of course, what he's done on the gable ends, et al]

You use fiberglass insulation under the rigid board to create a higher r-value insulation while moving the thermal envelope. R-19 fiberglass is the most common under the rigid board which is R-13 for a 2" thickness for a total of R-32. If you can get more then R-19 under the rigid board that's great. Some people use foam instead of fiberglass.

robbin
Premium,MVM
join:2000-09-21
Leander, TX
kudos:1
reply to lazidazi

said by lazidazi :

Okay, now - please don't anyone get fussy with me for asking an ignorant question.

RE Xcal's pictures, insulating attic with rigid foam board on the bottom edge of roof rafters: When one does this, is insulation at/between the ceiling joists then not needed? Is the rigid insulation at the rafters all that's needed for the attic? [including, of course, what he's done on the gable ends, et al]

This type of discussion should probably have a thread of it's own but in the meantime I will quote what I posted to another member earlier in this thread.

said by robbin:

You should research conditioned or unventilated attics. It has become more popular in recent years.



lazidazi

@frontiernet.net
reply to Critsmcgee

You use fiberglass insulation under the rigid board to create a higher r-value insulation while moving the thermal envelope.

Appreciate your reply!

To be sure I understand, one would put (at least) R-19 fiberglass bats, between roof rafters, then put rigid board along bottom edge of rafters. Correct?

I currently have blown-in insulation between [8"] ceiling joists. If I attend the rafters, as per above, will that then suffice [assuming all other air gaps between living space & attic are stopped] as far as insulating the attic?

Attending the rafters w/insulation is going to be quite expensive!


garys_2k
Premium
join:2004-05-07
Farmington, MI
Reviews:
·Callcentric
·callwithus
reply to robbin

Yeah, it allows you to NOT have a ventilated attic, where the goal would be to keep the attic space as cold as possible. All of the insulaiton is against the roof's inner surface, with the vapor retarder (in this case, the rigid foam boards' foil sheet) facing the attic. Spray foam like Icynene can be used for this as well as unfaced fiberglass (the spray foam has more R/inch but either can work).



AVD
Respice, Adspice, Prospice
Premium
join:2003-02-06
Onion, NJ
kudos:1
reply to lazidazi

said by lazidazi :

Attending the rafters w/insulation is going to be quite expensive!

check your ROI when looking at costs and finance accordingly.
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