Opinion: Vertical attic insulation

Inquiry: 

97-36

Subject: 

Vertical attic insulation

Code:

1994 Minnesota Energy Code, Section 7670.0470, subpart 6

Submitted By:

MN B. O. Uniformity Committee

Approved By:

Thomas R. Joachim, State Building Official

Issue Date: 

July, 18 1997

Question:  

When fiberglass insulation is installed in wells separating conditioned from unconditioned spaces, are measure required to protect the insulation R-value? (Example: vaulted ceiling walls exposed to the attic area)

Answer:

Yes. The Energy Code state in the charging paragraph, "Building assemblies are required to maintain the thermal performance of required insulation an intrusion or unconditioned air."

Committee comments:

The movement of air through fiberglass insulation will significantly reduce the thermal effectiveness of the insulation. Acceptable exterior air resistive barriers include exterior sheathings or vapor permeable house wrap products. Where vaulted ceiling walls are exposed to attic areas, the barrier product shall be installed to a minimum of horizontal insulation height to provide a baffle for the ceiling insulation at the top of these walls.

Adopted by Committee November 20, 1996 and ratified as amended at the 41st Annual Institute of Building Officials on January 17, 1997.