inverted insulation - InspectionNews

Jerome W. Young · #1 (**permalink**) 05-07-2008, 04:20 PM

this is upside down , but is just flipping it over a problem? There is properly installed insulation under it so is the double layer of paper a problem? Should they just remove the old insulation and install the new or is doubling one on top of the other ok?

Victor DaGraca · #2 (**permalink**) 05-07-2008, 04:29 PM

From the Owens Corning FAQ page;

My home has about six inches of fiber glass insulation in the attic, and I'm planning to add more. Should I use faced insulation?

No. Use only unfaced fiber glass insulation with no vapor retarder. A facing acts as a vapor retarder, which helps reduce the amount of moisture entering a wall, ceiling, or floor. In heating climates, your original layer of insulation should already have a vapor retarder facing the "warm-in-winter" side (living area) of your home.
If you add a second vapor retarder with another layer of faced insulation, any moisture that does get through the first layer may condense on the second. This might cause water stains on the ceiling and could lead to severe structural damage.
Install the second layer of unfaced insulation perpendicular to the first, covering the wood ceiling joists to reduce heat loss through the wood. (NOTE: Apply the second layer of insulation perpendicular to the first layer only when the joist cavity is full. Otherwise, apply the second layer right on top of the first layer, between the joists.)

Frequently asked questions

Jerry Peck · #3 (**permalink**) 05-07-2008, 04:35 PM

Remove all of the exposed paper as it is a fire hazard (says so on each paper in that red box below the Owens Corning logo and above where it says R-13.

Zoom in on it and you will see it say something like the attached photo.

Also, it acts as a second moisture retarder barrier on top of the insulation, which is not good.

David Wood · #4 (**permalink**) 05-08-2008, 02:49 PM

Isn't that usually the warm side in Florida?

Even in a cold climate (where the VB would definetly be on the wrong side), there are so many large gaps in the vapour barrier that I doubt it would cause a problem. The gaps will allow air movement which will move orders of magnitude more moisture than vapour diffusion. But you are correct to call it out because it could potentially be an issue.

Jerry Peck · #5 (**permalink**) 05-08-2008, 03:55 PM

Quote:

Originally Posted by David Wood

Isn't that usually the warm side in Florida?

David,

From the IRC: (underlining is mine)

- SECTION R318
- - MOISTURE VAPOR RETARDERS
- - - R318.1 Moisture control. In all framed walls, floors and roof/ceilings comprising elements of the building thermal envelope, a vapor retarder shall be installed on the warm in winter side of the insulation.
- - - - Exceptions:
- - - - - 1. In construction where moisture or freezing will not damage the materials.
- - - - - 2. Where the framed cavity or space is ventilated to allow moisture to escape.
- - - - - 3. In counties identified as in climate zones 1 through 4 in Table N1101.2.

The easy way to remember which side the vapor retarder should be on is: 'the heated side of the insulation' (even in South Florida, when you put the heat on - which is rarely done - the heat is turned on to heat the inside

).