attic insulation options


Old 10-02-03, 08:13 AM
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attic insulation options

I recently purchased a 1960 ranch with an attic that has about 3-6" of batt insulation with vapor barrier...2x6 rafters where some of the insulation has been compressed to 3+"....furthermore 3/4 of the attic had been and still is covered with 3/4" plywood for question is since fiberglass insulation works to slow heat transfer by the principle of slowing air movement....does it make sense to just plywood the remaining areas and seal the top side (seams) of the plywood???....the batts have a vapor barrier on the warm house side (bottom).....I would be able to get 6" of insulation underneath the plywood...not the depth needed to obtain the recommended R value of 39 (in NJ) but it would stop air flow....or I could tear up all the plywood fill the remaining 3" in spots and run batt perpendicular to the joists at 11" depth to give the R-39....the complicating factor is that I have a whole house fan with two (2) large louvered vents 36"x36" on each gable end and therefore would disrupt any insulation placed close to the 36" fan mounted inside one of these gable louvers. Any suggestions?....the large vents coupled with the fact the fan is mounted to the gable end vent instead of the ceiling vent of the house there are NO soffit vents.
Any ideas or suggestions would greatly be appreciated.
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Old 10-03-03, 06:58 AM
Join Date: Nov 2001
Location: Taylors, SC
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My inclination would be to remove the flooring you don't need and bring the insulation up to standard. My feeling is that compressing the insulation degrades its effects and the sealing effect, if any, of the flooring is not a good trade. If a good seal were the equivalent of insulation, then you could seal the area with plastic.

Whole house fan is generally a term for a fan that pulls air through the house windows and doors into the attic to exhaust to the outside for summer cooling. For winter, I would fabricate a holder or bunting for insulation to cover the fan louvres in the ceiling to stop heat loss there.

Attic venting needs to be maintained in winter to resolve problems with moisture.

The absence of soffit vents may be a design feature of the house with blocked soffits and needs not be resolved. It the house has soffits, then soffit vents usually contribute to more effective ventilation of the attic. However, two 36 inch by 36 inch gable vents may be enough if they are open all the time.

Hope this helps.
Old 10-06-03, 12:28 PM
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insulation/whole house fan


Thanks for the info!...the point about the house fan I knew about...this set-up is a little different than most in that the fan is not in the ceiling vent located in the hallway of the house...I believe it was placed in the attic on the gable vent in order to reduce sound from the fan. Therefore, by its placement in the attic no soffit vents were installed in order to get more airflow from the doors and windows of the house up thru the ceiling vent and out the gable end and avoid any draw thru soffit vents...and believe me what a "pull" it like a charm....when not in use, the ceiling vent is closed and the opposite gable vent can be opened to draw air "across" the entire length of the attic to prevent moisture buildup in the winter or heat buildup in the summer.....Thanks for the other info...I have already desinged a "cap" for the ceiling vent to reduce heat loss in the winter.
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