0 Helpful?

I have a 1-story dwelling with an attic (cold space) that has approx. R-30 insulation

I have a 1-story dwelling with an attic (cold space) that has approx. R-30 insulation but NO plastic vapor barrier between the sheetrock and the insulation....

I am considering adding a radiant foil barrier on top of the the blown insulation.
What are potential problems could I have, as a result of this installation? Moisture problems? Our home is in Northfield, MN 55057

Asked by gary schutte
Posted Aug 27, 2014 1:52 PM ET
Edited Aug 27, 2014 3:31 PM ET

Tags:

3 Answers

Select your preferred way to display the comments and click "Save settings" to activate your changes.
1.

Don't do it.

Foil is a true vapor barrier, less than 0.05 perms, and if located on the cold side of the assembly even vapor diffusion is enough to create wet/frozen insulation in your climate at the top layers if you trap it.

The thermal benefit of a foil radiant barrier is truly miniscule in a MN climate too- you're far better off spending the money on air sealing & insulation.

Answered by Dana Dorsett
Posted Aug 27, 2014 2:11 PM ET

2.

Gary,
Dana is right on both points.

A radiant barrier on top of your attic insulation will make the top layer of insulation damp.

You'll get much more of a performance improvement by spending the same amount of money on deeper insulation. (Of course, if you haven't sealed the leaks in your ceiling yet, that work always comes first.)

Answered by Martin Holladay, GBA Advisor
Posted Aug 27, 2014 3:26 PM ET

3.

Gary,
For more information on air sealing, see Air Sealing an Attic.

For more information on radiant barriers, see Radiant Barriers: A Solution in Search of a Problem.

Answered by Martin Holladay, GBA Advisor
Posted Aug 27, 2014 3:51 PM ET

Other Questions in General questions

Unvented slanted roof with radiant cooling and NO polyurethane in 4C

In GBA Pro help | Asked by Jan Verschuren | Mar 11, 15

Interior plywood for earthquake areas — can it replace a vapor retarder?

In General questions | Asked by Jan Verschuren | Mar 29, 15

Cold climate (6) standing seam metal roof leak

In Energy efficiency and durability | Asked by David Metzger | Mar 28, 15

Fresh air distribution for hydronically heated house?

In Mechanicals | Asked by John Charlesworth | Mar 26, 15

Basement insulation

In Energy efficiency and durability | Asked by Mike G | Mar 30, 15
Register for a free account and join the conversation


Get a free account and join the conversation!
Become a GBA PRO!