Reflective insulation

[trimguy]

I found this old thread about Reflectix, I thought I would just add to it. This is the first hands-on experience I've had with it. These pictures are from the same wall in my shop from the same time.

 

  

That's 20* difference. These readings were taken one afternoon. This wall gets sun all day. I realize that this will not make this much difference, if any on a wall that is shaded, but I would say it's money we'll spent. 

[Don P]

That is a good application for it. When I see it being used under a slab, don't do that with any notion of it being more than a vapor barrier. At best, till the bubbles pop, it is R-1 and provides no radiant benefit at all being in direct contact with the concrete. 

This is a good explanation;
Avoiding Home Energy Saving Scams – Part 2 - Reflective Insulation - Sustainable Energy Group

[trimguy]

Interesting, thanks Don.

[Ljohnsaw]

I just bought the aluminum foil on Mylar product about 10 years ago.  I have a tile roof that was put on skip sheeting from the old shake roof.  There is a layer of Cool Roof or something like that to act as a tar paper.  Though it doesn't work that well I found out.  That's another story.  Anyhow, my 10/12 pitch roof gives a lot of attic space and it is HOT up there in the summer and pretty warm in the winter.  I stapled the Mylar product to the rafters and foil taped the seams.  I have a ridge vent, so air comes in the soffit vents and up the heat goes between the rafters now acting as plenums, and out the ridge vent.  It made a huge difference in my attic and more comfortable in the room below the attic - no heat radiating down.

[Raider Bill]

I stapled plain old aluminum foil to the underside of my roof decking in my garage.
Reflects the heat pretty good here in the hot south.
Dropped the underside of the roof 20 degrees

[peakbagger]

More than few independent building authorities do not give this type of insulation a good review 

Here is one 
Stay Away from Foil-Faced Bubble Wrap - GreenBuildingAdvisor 

[trimguy]

I wasn't under the impression that I was getting any R value from this, I want something to reflect the excessive heat back out of my shop. My test convinced me that it was a big help. I put R-19 insulation inside of this to help with the temperature control.