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#4717200 - 04/05/18 12:31 PM Attic radiant barriers
28oz Offline


Registered: 04/20/17
Posts: 295
Loc: Utah, USA
In anticipation of summer, I've decided to install some radiant barrier film in my attic. My home is multiple levels with the master bedroom being at the very top. It gets quite warm, predictably, as does the entire top half of the house. I'm not expecting miracles, of course, but would like to hear first hand experiences of those who have it and what benefits (if any) they have seen from it.

This is what I've ordered:

https://www.amazon.com/RadiantGUARD-Radi...6691&sr=8-1

Thanks!
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1990 Nissan 300zx - Castrol Edge Euro 0W-40
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#4717215 - 04/05/18 12:48 PM Re: Attic radiant barriers [Re: 28oz]
JohnnyJohnson Offline


Registered: 10/22/09
Posts: 2384
Loc: Wet side WA
What is this going to do to your cellphone reception in the house?
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#4717225 - 04/05/18 01:04 PM Re: Attic radiant barriers [Re: 28oz]
sleddriver Offline


Registered: 02/06/10
Posts: 4442
Loc: Central Texas
I used the spray-on type back in the mid-90's. The roof trusses made stringing a foil barrier far too difficult. Note that a barrier only works on roofs exposed to the sun. Many don't.

Your A/C ductwork may also need balancing to ensure enough air up top to deal with the heat load.
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#4717228 - 04/05/18 01:07 PM Re: Attic radiant barriers [Re: 28oz]
PimTac Offline


Registered: 03/04/17
Posts: 3475
Loc: Soviet State of Washington
How is your attic ventilated? Getting rid of the heat buildup with a small fan could be all you need. If you live in a high solar area then maybe a solar powered fan would be the ticket. The design of your attic is the missing part of the puzzle. For a simple peaked roof design, placing vents on each end near the top with fans to exhaust the hot air out will work. Another method would go through the roof with a vent cap.

In a older house I used to live in, the attic had a small window. We would open that with a screen in place and had a regular table top fan pointed out to exhaust the hot air. It might take several hours for any effect to be noticeable.
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#4717253 - 04/05/18 01:39 PM Re: Attic radiant barriers [Re: 28oz]
maxdustington Offline


Registered: 01/21/17
Posts: 233
Loc: Toronna
Good idea, my house faces east but has a tree that blocks the front side of the roof. The sun bakes the west side of the roof during the afternoon, and stays warm into the night. It gets super hot on the second and stays hot because the thermostat is on the first floor. It was brutal before I put a shade in two centrally located skylights.

I would have went with reflectix insulation, that seems to be a popular choice for IR insulation. The stuff you have is nice and thin, so you will probably be able to get better coverage with less cuts.

If you install IR insulation and increase ventilation in your roof the results will be tangible I imagine. I felt a difference installing the shades and retaping the ducting and plenums in my furnace room. It made it so that it was bearable, whereas before it was unbearable for long periods.


Edited by maxdustington (04/05/18 01:39 PM)
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#4717265 - 04/05/18 02:04 PM Re: Attic radiant barriers [Re: JohnnyJohnson]
28oz Offline


Registered: 04/20/17
Posts: 295
Loc: Utah, USA
Originally Posted By: JohnnyJohnson
What is this going to do to your cellphone reception in the house?


Good question. I don't know. However, cell signal will still be able to come in through the walls, so hopefully it won't affect it too much. I can make and receive calls through the wifi anyways, so I still have that, at least.
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1990 Nissan 300zx - Castrol Edge Euro 0W-40
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#4717267 - 04/05/18 02:08 PM Re: Attic radiant barriers [Re: PimTac]
28oz Offline


Registered: 04/20/17
Posts: 295
Loc: Utah, USA
Originally Posted By: PimTac
How is your attic ventilated? Getting rid of the heat buildup with a small fan could be all you need. If you live in a high solar area then maybe a solar powered fan would be the ticket. The design of your attic is the missing part of the puzzle. For a simple peaked roof design, placing vents on each end near the top with fans to exhaust the hot air out will work. Another method would go through the roof with a vent cap.

In a older house I used to live in, the attic had a small window. We would open that with a screen in place and had a regular table top fan pointed out to exhaust the hot air. It might take several hours for any effect to be noticeable.


The roof is multi-level as well, so I'm not sure. I do know there are vents at the peak of the top roof as well as on the north side under the peak (sorry, not too familiar with roofing and building terminology). *I think* I have ventilated soffits at least on the west side of the house where there is a porch surrounding the front door.

In the attic, there are trusses with varying levels of headspace............from about a foot to being able to stand up straight in spots. A solar powered fan would probably be a great idea. Just have to figure out what type and where to put it.
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1990 Nissan 300zx - Castrol Edge Euro 0W-40
2004 Nissan Quest - Pennzoil Platinum Euro 0W-40
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#4717269 - 04/05/18 02:11 PM Re: Attic radiant barriers [Re: 28oz]
86cutlass307 Offline


Registered: 03/02/10
Posts: 168
Loc: Wichita Falls, TX
We used a very similar material about 7 - 8 years ago in conjunction with additional attic insulation. We also wrapped exposed ductwork (insulated flex-duct) and added ridge vents to our ranch style here in N. Texas and you will notice a difference. Not a large financial load up front but do it now while it is cool.
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#4717285 - 04/05/18 02:38 PM Re: Attic radiant barriers [Re: 86cutlass307]
28oz Offline


Registered: 04/20/17
Posts: 295
Loc: Utah, USA
Originally Posted By: 86cutlass307
We used a very similar material about 7 - 8 years ago in conjunction with additional attic insulation. We also wrapped exposed ductwork (insulated flex-duct) and added ridge vents to our ranch style here in N. Texas and you will notice a difference. Not a large financial load up front but do it now while it is cool.


Good to hear it made a difference. Yeah, it's not expensive and definitely want to get it done before it heats up! Wrapping more insulation around the ductwork is a great idea as well. I'll have a look at it while I'm up there.
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1990 Nissan 300zx - Castrol Edge Euro 0W-40
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#4717336 - 04/05/18 03:39 PM Re: Attic radiant barriers [Re: 28oz]
Kawiguy454 Offline


Registered: 06/01/15
Posts: 567
Loc: Arizona
Keep in mind that the reflected heat does go somewhere and that is back out under the shingles possibly shortening their life.

If you use this stuff you need to make sure each rafter has a soffit and peak vent. Hot air needs to be able to escape from the peak and draw cool air in thru the soffits to keep the roof cool. Without this air flow heat will build up in the roofing and that is not good for them. So yes your bldg is cooler but you need to re-shingle considerably sooner. Additionally in damp areas the lack of ventilation is perfect place for mold to develop.

In Arizona we put a shyt-ton of insulation on the attic floor and heavy insulation on ducts and leave the rafters roof open to freely ventilate. A rafter pink insulation glass side down and stapled to the attic floor has aluminum reflective backing facing the roof that does the same thing. Keeps the cold inside the house and lets the attic breathe.

IMO this is a quick/cheap fix that should be done a different way.

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#4717365 - 04/05/18 04:13 PM Re: Attic radiant barriers [Re: Kawiguy454]
28oz Offline


Registered: 04/20/17
Posts: 295
Loc: Utah, USA
Originally Posted By: Kawiguy454
Keep in mind that the reflected heat does go somewhere and that is back out under the shingles possibly shortening their life.

If you use this stuff you need to make sure each rafter has a soffit and peak vent. Hot air needs to be able to escape from the peak and draw cool air in thru the soffits to keep the roof cool. Without this air flow heat will build up in the roofing and that is not good for them. So yes your bldg is cooler but you need to re-shingle considerably sooner. Additionally in damp areas the lack of ventilation is perfect place for mold to develop.

In Arizona we put a shyt-ton of insulation on the attic floor and heavy insulation on ducts and leave the rafters roof open to freely ventilate. A rafter pink insulation glass side down and stapled to the attic floor has aluminum reflective backing facing the roof that does the same thing. Keeps the cold inside the house and lets the attic breathe.

IMO this is a quick/cheap fix that should be done a different way.


Good points. I'm reading it is a good idea to stop the barrier at least 6 inches from the top so the heat has somewhere to go. The barrier is supposed to be breathable so not too worried about moisture buildup. Our air is pretty dry here for the most part too. I'll definitely make sure there is ventilation between the barrier and the roof as I wondered about that as well. I appreciate the input.
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-----------------
1990 Nissan 300zx - Castrol Edge Euro 0W-40
2004 Nissan Quest - Pennzoil Platinum Euro 0W-40
2003 Ford Excursion 7.3 PSD - Mobil 1 TDT 5w-40

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