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Question DetailsAsked on 6/18/2015

I have an attic blanket over my insulation but the blanket is coming loose

Should it be stapled down again over my insulation? I have also heard attic blankets are a fire hazard. Should I have it removed instead?

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3 Answers

0
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As an old house doctor and one with a radiant barrier in my attic here's my take LCD.

1)Radiant barriers should be installed stapled to the roof rafters to prevent dust build up and not lose effectiveness thru conductivity loss by being placed directly in contact with the insulation.

2)In my home radiant barrier was worthless in winter and very effective in summer,, My a/c bill halved.

3) You can purchase it for about 10 cents a square foot online and do not forget to wallpaper all sides of the roof leaving openings for your ridge vent and soffit vent chutes. Attic ventilation is critical to allow moisture (& heat in the summer) to escape.

Jim Casper Gutter Cover and Gutter Contractor

ps for ideas on your gutters and covers & my experience with radiant barriers see my blogs

Source: www.heartlandmastershield.com

Answered 5 years ago by jccasper

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Votes

Following are links to a number of prior responses about insulation blankets and similar products:


https://answers.angieslist.com/Is-sma...


https://answers.angieslist.com/attic-...


https://answers.angieslist.com/E-Shei...


https://answers.angieslist.com/Can-in...


As for the fire hazard - the blanket itself is not a hazard unless there is an ignition source nearby, in which case the non-fireproof plastic ones obviously will burn intensely, but generally (unless you have HVAC equipment up there) attics are not a major fire hazard area. One major exception - putting one right over a recessed or can light (or transformer for those) so it causes overheating of the light, or the light catches plastic-coated blanket on fire.


As for stapling down - as long as there is not free airflow out from under the blanket, whether it is laying on the insulation under it or stapled down likely makes little difference - a small airgap under it actually provides more insulation as long as that trapped air cannot flow out around the edges of the blanket. If the "blanket" is a radiant barrier rather than "insulation", the air gap is actually necessaryu for it to work, and it is best installed with an airgap and abilitiy for airflow under it to prevent condensation issues.

Answered 5 years ago by LCD

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Votes

A comment on Jim Casper's reply - if you put a radiant barrier on the underside of the rafters, especially in cold climates, be sure to start it a foot or so upslope of the eaves, or if you have eave chutes that completley block the eaves, then "uphill" of those, so moist air coming up from the house along or through the outer walls can get ventilated byh the air coming through the eaves. Even more important, leave a gap at the top as wide as the ridge vent slot, so the hot air in the attic under the radiant barrier can escape through the ridge vent (assuming you have one) rather than getting trapped and heating up hotter and hotter under the radiant barrier.


Personally, based on seeing a fair number of these, I don't buy Jim's statement that putting it on the underside of the rafters (which granted is a better place than on the floor insulation) reduces dust accumulation - I have seen a continuous dust layer on rafter underside-mounted radiant barriers in only a year or two same as if it was on the floor - that is one of the major flaws in radiant attic barriers, because once they are covered in dust they are no more longer effective in reflecting the heat back where it came. One of these things that is fine in theory but comes far short of promises in practice.


One of the major problems with over-insulation installation is, like Jim says, it has to have an airgap under it to work so it cannot just lay on the insulation directly. Also, unless it has significant air holes to let underlyhing trapped moist air out, it can act to hold in household moisture coming through into the attic, so unless all household air sources are THOROUGHLY sealed before insulating, you can get free moisture or frost on the radiant barrier, leading eventually to mildew and even rot in true winter areas.

Answered 5 years ago by LCD




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