Comments on: Perforated vs. Solid Radiant Barrier Products. What is a vapor barrier and why does it matter?

By: Ed

Ed — Thu, 24 Mar 2011 18:33:22 +0000

Uninformed,

No worries. A simple solution to this problem would be to cut some holes in the bubble foil or to make some slits – your goal is going to be to make sure that air can flow freely on both sides of the bubble foil.

By: joe

joe — Fri, 18 Mar 2011 03:54:15 +0000

Ed-

I obviously made the mistake of installing bubble wrap in my attic to the bottom of my rafters. My friend told me to get it not because it was more effective but because it has less chance of it ripping. I am not too hep on ripping it out and starting over. What should I do to try to eliminate water vapor from being trapped and constantly evaporating, condensing etc until it breaks down my sheathing? I have a pretty tight install and I now know it wasn’t needed or preferable. Please give advice on any action that I should take.

Signed,

uninformed consumer….

By: Ed Fritz

Ed Fritz — Tue, 10 Aug 2010 17:06:32 +0000

The perforated and non-perforated radiant barriers work exactly the same. The holes are tiny pinholes about 1/2″ apart. The difference in effectiveness of the two products – (reflectivity and emissivity) is so small it’s not even measurable. Vapor barriers should be used with caution regardless of location. The general theory is that you NEVER use a vapor barrier unless you are SPECIFICALLY trying to stop/trap moisture in it’s vapor form. In an attic, you WANT air and moisture to flow freely from from maximize the drying process. Therefore, it is NEVER suggested to use a vapor barrier in a vented attic application. If the effectiveness is the same, why risk introducing something that can slow/stop moisture flow out of the attic?

Also, you CAN get condensation on ANY surface if the temperature is below dew-point and you have a source of warm-moist air. Ventilation helps, but you REALLY want to eliminate the source of warm-moist air.

By: jalal

jalal — Mon, 12 Jul 2010 03:48:57 +0000

I live in Michigan, I want to use your Radiant Barrier in my attic. I want to staple to the bottom of the roof rafters. I am going to leave 3 inch space on the bottom and three inches on top. I like to use non-perforated barrier, I think it does a better job. Since both sides will be ventilated and the same temperature, do I have to worry about condensation, or can I use it?