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Foil wrapped bubble wrap instead of vapor barrier?


Northern Mike's Avatar
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CANADA

04-09-13, 06:50 AM   #1  
Foil wrapped bubble wrap instead of vapor barrier?

I was over at a friend's place and noticed that in his newly built house, he used foil wrapped bubble wrap instead of vapor barrier in his walls.
His outside walls (from outside in) fiberglass bat (6" worth between studs), foil bubble wrap, then drywall.

Has anyone seen this before and would it be a good idea or just wasted money?

From what I could see, it would add a layer of insulation between the studs and the drywall, but I don't know if it would be worth the effort.

 
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04-09-13, 09:43 AM   #2  
Hi Mike, it sounds like any radiant benefits have been lost by not providing an air gap. That leaves the bubbles only for insulation, which is minimal at best. Had he installed the same thickness of a rigid foam product he would have been better off (thousands more bubbles). As a vapor barrier, if properly taped, it will do that, but so would 4 mil plastic at a much lower cost. Most of Canada is in a climate zone (6,7,8, I think) cold enough to still advise using a VB.

If he used standard R-19 fiberglass, then he failed to meet the basic energy codes, as I don't believe the bubble wrap has any approved rating. Not sure what level Canada is requiring, but they are often more strict than this side of the boarder.

From my personal experience, I wonder what those bubbles will look like 20 years from now. If they yield, then the drywall may no longer be held tight and screws will start to pop. That could even be a problem right from the start without a proper compression rating. There's only 1.5" support behind those bubbles.

Bud

 
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04-09-13, 09:53 AM   #3  
I think R-24 to R-29 is required now in my area (since 2012 update). His home was built just before this so he's on the older code (not sure off the top what that was).
You did bring up a very good point about how long that stuff will last over time. I would imaging the plastic bubbles would eventually leak over time.
Attics I believe is now R-50 which will make my up and coming renos expensive if I want to meet or exceed code.

 
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04-09-13, 10:20 AM   #4  
Take a piece of bubble wrap and place it on a flat solid surface. Now place a piece of 2x4 on edge on top and push down. I just tested it, the HVAC guy left me half a roll. It compresses very easily. I would bet a moderate bump into a wall would pop the area around the screws. Any place where the staples were applied would be even softer.

Bud

 
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04-09-13, 10:49 AM   #5  
Take a piece of bubble wrap and place it on a flat solid surface. Now place a piece of 2x4 on edge on top and push down. I just tested it, the HVAC guy left me half a roll. It compresses very easily. I would bet a moderate bump into a wall would pop the area around the screws. Any place where the staples were applied would be even softer.

Bud
I would think that the distribution of the drywall along the length of the 2x4 would keep from popping bubbles.
How long the bubble wrap would last and what happens when it goes soft would be my big concern.
If it goes soft, that's ~1/4" of play behind the drywall. Would be popping screws like the latest designer drug.

 
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04-09-13, 04:12 PM   #6  
http://www.healthyheating.com/Page%2...ubble_foil.pdf

The Foil-Faced Bubble Wrap Sham - Understanding Radiant Barriers

So now he has an air-permeable cavity fill insulation with hundreds of bumps creating an air-space in front of the drywall/ f.g. that traps air to work; Info-501: Installation of Cavity Insulation — Building Science Information just short-circuited the cavity insulation by -------%; figs. 2, 3; https://docs.google.com/viewer?a=v&q..._NGatSVo3wzmAQ

So basically, they are forcing convective looping, with the insulation not in full contact with drywall, especially if an older insulation as R-19 (low density) rather than R-22 (medium density) resistant to convective loops. Of course soon as you install R-19 you lose from compression to R-18. Just so there is no temperature difference to drive the looping.... 45-47; http://www.buildingscienceconsulting...Measure_Up.pdf

Gary

 
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