Radiant Barrier Foil Insulation - Why Is Air Gap or Space Required?

http://AtticFoil.com - Why Is An Air Space Required For Radiant Barrier?

Ed Fritz, the owner of http://AtticFoil.com illustrates why you MUST have an air gap on at least one side of the radiant barrier foil insulation for it to be effective. In fact, without an air gap, heat flow is actually accelerated through conduction or conductive heat flow.

Ed also explains and demonstrates the difference between reflectivity and emissivity.

This video gives tips on adding radiant barrier to walls and why you cannot put radiant barrier directly between the shingles and your roofing felt or deck when you re-roof with new shingles. Radiant Barrier Decking works off of emissivity rather than reflectivity.

Visit http://AtticFoil.com for complete information on Do-It-Yourself Radiant Barrier installations, tips and trricks.

http://AtticFoil.com

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Education

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[ak99372]

Great video (I especially appreciate all marketing BS being excluded). I have a question. I was thinking of using the double sided bubble wrap around duct work. Do you have any recommendations on that? (I checked your website but I guess you focus only on attics)

[AtticFoil]

@ak99372 Bubble foil has an R-Value of about 1 since it's only about 1/4" thick. Any additional r-value you see advertised is in the form of a "dead air space" which is very tricky to achieve on ducts. It's not worth even trying. I'd keep it simple and buy some "duct wrap" - R-4 to R-8 with foil on the outside. It's a standard issue product in the HVAC industry. Before insulating you want to SEAL the ducts with a good quality mastic. Seal then insulate. Need more info? - AtticFoil-dot-com

[AtticFoil]

@ak99372 Bubble foil around ductwork is a lot of work for very small benefit. You must be very careful to maintain an airtight airspace. You are better off using a standard radiant barrier/fiberglass insulation duct wrap. you will get more, r-value, it's cheaper and it's much easier to install.

[thermaldog]

is there a minimum air gap size for it to work...10mm, 20mm..?

[AtticFoil]

@thermaldog Generally, you want at least 1/2" if the air space is "sealed" or "dead". You can go down to a 1/4" if you have a ventilated air space. With a sealed airspace less than 1/2" you tend to loose some of the radiant barrier benefit due to conduction across the air space. If possible go 3/4" to 1" is ideal.

[bumhokim]

I heard there is new fire code for radiant barriers.......if you install radiant barrier that does not meet the new fire code, is it a violation of state or county code?

[AtticFoil]

@bumhokim There is a new testing procedure for flame and smoke. This is called the ASTM E 84 and ASTM E 2599. Nothing changes with the product except it must undergo a different method of testing. Eventually codes like the IRC, IBC, and IECC usually adopt the ASTM Tests. It will be a while before anything happens. Right now nothing has changed.

[KINGJOHN808]

Awesome video! Thanks again for the easy to follow explaination.

[AtticFoil]

@ChrisUTMBA Bubble foil is a decent product. However, it usually works no better than AtticFoil - It's the foil doing all the work to reflect radiant heat. The only airspace is on the outside of the foil since it cannot have an airspace on the side that it is glued to something.

[ChrisUTMBA]

How does your product compare to the bubble wrap type stuff with foil on either side? it would seem like this would give you some built-in airgap.