roof rebuild- reflectix for roof insulation?

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Well-known member
Jan 14, 2013
I am rebuilding my 1991 Mallard Sprinter and I am going to have to do some considerable roof repair.  I am a fulltimer and usually traveling in cold temps.  Nothing crazy like -40 F  as I have seen in some posts, but I digress...

I know I will be replacing the plywood and insulation.  I have heard of the magical ability of reflectix and from what I have read, people have had great success insulating the underside of trailors, 5th wheels, etc. with it.  Some use it on windows, but I am wondering about the physics of applying it to the ceiling. 

I understand that it creates a radiant barrier, which is why it keeps cold things cold and warm things warm.  My thought is if heat rises, then applying a layer of reflextix as insulation during my rebuild would improve the MH's ability to retain heat in the winter, and even help keep some of the heat off in the summer as it could also prevent heat from the hot sun from "baking" the vehicle so much.  I haven't heard about anyone using it up top, but I wasn't sure if it is because I'm talking about a rebuild anyway and most people don't go there.

Would it be problematic as it would create a barrier between the actual roof and the reflectix?  Would it be problematic in the winter because the sun wouldn't be able to help heat the vehicle as much (the reflectix preventing ambient heat from coming in)?  or is that not a huge factor and the gain in preventing heat loss would make it work it?  Just wondering what others thought on the matter.  Thanks!

Sounds like a good idea to me, these RV's do not have much insulation.  The extra on the roof should really help in the summer. :)
Reflectix FAQs describe how Reflectix works - basically by reflecting heat back to the source instead of passing it through.

A couple of interesting points - first, you can stack multiple layers for greater effectiveness but they have to be separated by an air gap.  Stacking one layer directly onto another does no good.

The other is you can use it for roof insulation, but it's effectiveness is increased if there's convection airflow between it and the roof.  On a sloped roof this is handled by the ridge vent.  I don't know how you'd do this on a flat roof, though.

Putting it underneath the roof is a neat idea - let us know how it works out.  Do you have an infrared thermometer to record before and after inside ceiling temperatures?
Thanks for replies tvman and Lou,

I was planning on taking advantage of the space between the frame and the actual roof to create the air gap.  Without it, reflectix only indicates an R value of 1.1.  With the air gap, it can be higher.  It won't be a big gap, but Once I have everything torn out I'll know more.  I have been posting videos of my rebuild for feedback etc. and I'll keep adding to it as I get to the roof.  I'll reply with links once they are up.

One possibility is on a flat roof actually attaching it to the top of the ceiling panels so it sits below the roof frame.  This would create a gap between the reflectix and the plywood that sits under the roof material.  That might be enough to help.

Lou- I can look into an infared thermometer to record temps.  I have an indoor/outdoor thermometer but it might be nice to get a read of other areas like "attic" space, "basement" space, etc. 

Thanks again!
My only experience with radiant barriers was on the house I built. We used it as roof sheathing in the main livable area, only - not in the garage. The effect was DRAMATIC, as I walked between the two uninsulated spaces in the heat of the Arizona summer. I was kicking myself for not insisting that the roofer put it in the garage, too.

Harbor Freight has a couple of IR thermometers at good prices.  I use their laser pointer one to track tire and wheel temperatures.
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