Article #1469 - Commercial Air Barrier Requirements for Insulated Ceilings - Code Notes

[2003 IECC, 2006 IECC, 2003 IBC, 2006 IBC, 90.1-1999, 90.1-2001, 90.1-2004]

Insulation installed on top of dropped ceiling. This does not meet code.

Insulation is sometimes proposed to be installed on top of the dropped ceiling tile in commercial buildings in an attempt to meet the provisions of the International Energy Conservation Code. Insulation is also sometimes proposed to be suspended from the bottom cord of a truss with a dropped ceiling suspended below.

Neither of these installations are allowed by the commercial provisions of the 2003 and 2006 IECC or ASHRAE 90.1 as they do not include an approved air barrier to prevent air movement from the conditioned space through the insulation to the unconditioned space. This technique also allows the insulation to be easily disturbed.

Insulation installed with dropped ceiling suspended below. This configuration does not meet code unless an air barrier is properly installed.

The 2003 and 2006 International Energy Conservation Codes require openings in the building envelope to be sealed to prevent air leakage into and out of the space including an air barrier at insulation installations. The building envelope is defined as the building assembly that surrounds the space that is heated or cooled (conditioned space). The building envelope is comprised of insulation and a pressure boundary that prevents the flow of air through the insulation. Air movement through insulation (wind washing) diminishes its rated R-value. It is essential that the barrier be able to prevent air movement across itself when subjected to a pressure differential.

For example, gypsum board with taped joints installed on the bottom cord of the truss is considered to be an effective air barrier. Other approved air barrier systems can be used instead of gypsum board as long as they can be completely sealed and sealed to the wall system. The air barrier must also meet the flame spread and smoke-developed index in the 2003 IBC Section 718.1 and the 2006 IBC Section 719.1.

Another common installation for commercial buildings is to install insulation between wood or metal joists or trusses directly underneath, and in contact with, the roof sheathing, which is allowed by the energy code.

Plan Review:

For insulation installed on top of an insulation support and an air barrier at bottom of attic truss or floor joists:

1. Verify that the insulation installation detail for the roof/ceiling assembly includes an approved air barrier between the insulation and the conditioned building.
2. Verify that tape or appropriate sealing method is specified for all joints of the gypsum board if used as the air barrier.
3. Verify that the air barrier meets the flame spread and smoke-developed index requirements from the IBC if other than gypsum board. Also verify that plan notes call for sealing of all joints and penetrations in the air barrier.

For insulation installed under the roof sheathing between wood or metal truss system:

1. Verify that the plan detail shows the insulation in contact with the roof sheathing.
2. Verify that the method of insulation support is specified in the plan detail.
3. Verify that air sealing and an air barrier are specified for the roof assembly.

Field Inspection:

For insulation installed on top of the insulation support and air barrier at bottom of attic truss or floor joists:

1. Verify that insulation support (such as gypsum board) has been installed under the insulation and that all of the joints and penetrations from plumbing, HVAC and electrical systems are sealed.
2. For air barriers other than gypsum board, verify that the product meets the flame spread and smoke-developed index.
3. Verify that all holes, seams or other penetrations are sealed using products that are designed to adhere to the air barrier to form a permanent seal.
4. Verify that the air barrier is sealed to the exterior walls of the building.

For insulation installed under the roof sheathing between wood or metal truss system:

1. Verify that the insulation is installed in contact with the roof sheathing.
2. Verify that the insulation is properly and securely supported and is allowed to "fluff" to its full thickness.
3. Verify that the insulation fills the truss or rafter cavities horizontally from one member to another.
4. Verify that all holes and penetrations in the roof assembly are sealed.

Code Citations*

*Copyright, 2003, International Code Council , Inc. Falls Church, Virginia. Reproduced with permission. All rights reserved. 2003 International Energy Conservation Code

*Copyright, 2006, International Code Council , Inc. Falls Church, Virginia. All rights reserved. 2006 International Energy Conservation Code .

*Copyright, 2003, International Code Council , Inc. Falls Church, Virginia. Reproduced with permission. All rights reserved. 2003 International Building Code

*Copyright, 2006, International Code Council , Inc. Falls Church, Virginia. All rights reserved. 2006 International Building Code .

Copyright, 1999, American Society of Heating, Refrigerating and Air-Conditioning Engineers , Atlanta, GA. ASHRAE Standard 90.1-1999 . Reproduced with permission. All rights reserved. ; Copyright, 2001, American Society of Heating, Refrigerating and Air-Conditioning Engineers , Atlanta, GA. ASHRAE Standard 90.1-2001 . Reproduced with permission. All rights reserved. ; Copyright, 2004, American Society of Heating, Refrigerating and Air-Conditioning Engineers , Atlanta, GA. ASHRAE Standard 90.1-2004 . Reproduced with permission. All rights reserved. PNNL-SA-48699