# Vacuum Insulated Panels



## Bud9051 (Nov 11, 2015)

Not well versed in LEED requirements but suspect they would need those specifications to consider that product.

"to face over the rafters under my roof deck" Trying to be sure I understand. You want these on top of your trusses with the roof deck above. Guess I need to see how those panels are constructed. What r-values are they claiming?

Bud


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## jazzop89 (Apr 28, 2017)

By "face over", I mean attached to the bottom of the rafters, leaving a 4" gap between the backside of the VIP and the roof deck (the trusses are old, full-sized 2x4s). I could fill that void with batts or perhaps just leave it as an air gap allowing airflow from soffit to ridge vent. I would still need to address thermal bridging of the 2x4s that extend from the rafters to the lower truss members.

My existing plan has been to encapsulate the whole interior side of the roof with closed-cell foam, but the VIPs blow that out of the water when it comes to R-value. Most VIPs claim R-50 per 1" thickness.


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## Bud9051 (Nov 11, 2015)

There are a lot of independent energy minded smart people out there that would die for an affordable r-50 per inch insulation material, but I see nothing being discussed on the high level forums. Request some samples and insist on independent testing data. They wouldn't be the first company to stretch the performance in the name of profits.

Bud


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## jazzop89 (Apr 28, 2017)

The R-50/1" figure is pretty standard across every manufacturer I have found (about 6 or 7 so far). I found a nice case study report from the Oak Ridge National Laboratory on a test case they did fitting them to a federal building renovation. They assessed the final installation with IR spectroscopy. The only drawback is that it was a northern project in winter, whereas I am in FL and only concerned with avoiding heat gain.

The fragility of the panels is a major concern because I don't want them to pop a seal and lose vacuum if there is excessive structural flexing during a hurricane. That's why they aren't really suitable for use in the walls, lest someone drive a screw through them. Without vacuum, they are equivalent to plain-old foam panels <R-10. They also can't be cut or trimmed, so you have to order them exactly to fit or use them over an uninterrupted rectangular area.


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## NotyeruncleBob (Mar 9, 2017)

You could also throw stacks of hundred dollar bills into the hopper of a cellulose sprayer and use that for insulation. 
The vacuum panels are pretty good as far as stated R value, but totally impractical in a typical residential build. There are simply too many opportunities to damage the panels vacuum rendering them useless and residential construction involves so many irregularities that vacuum panels just don't fit well. Then there's the cost. You could build the fanciest double stud wall imaginable with a couple extra layers of exterior foam for that kind of money. 
Spend your money on air sealing and good enough insulation. Then plant some trees where they'll shade your house from the harsher exposure of the sun.


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