Ignition Barriersforthe Spray Polyurethane Foam Industry
8, as well as the
manufacturer’s product literature or the ICC-ES Evaluation Service Report
regarding use of intumescent coatings for alternative thermal and ignition
barrier assemblies. In addition, depending on climate zone, moisture-
permeable low-density SPF may need a Class II or Class III vapor retarder at
the inside surface of the foam to avoid moisture condensation at the roof
Finally, it is extremely important that the finished project be measured
for air leakage and carbon monoxide by a trained professional weatherization
contractor (e.g., BPI Building Analysis or HERS Inspector). While the newly
unvented attic minimize air leakage and energy losses, it has changed the
ventilation dynamics of the building – likely lowering the natural ventilation
rate of the building below recommended levels, or creating a potential
backdraft condition for combustion appliances like gas-fired ranges and
hot-water heaters or heating systems fueled with gas, oil, coal or wood.
Backdrafting of these appliances can bring combustion by-products back into
the building in certain situations that result in high carbon monoxide levels
that can be lethal to the occupants.
In the case of creating an unvented attic in an existing home, the
R-value of the additional roofline insulation does not always add up when
you treat the house as a system. As a contractor, you may need to inform
the homeowner that you need to remove perfectly-good insulation from the
attic floor, and replace it with SPF under the roofline to be
( 1) compliant with the model building code, ( 2) to reduce
the chances of moisture condensation and ( 3) minimize the
potential of odors from the existing attic insulation. It may
not make sense to the homeowner, and they may even feel
that you are overselling the job. In warmer climates, or in
homes with very little attic floor insulation, removal of the
existing insulation may not be necessary, but more building
science research is needed to confirm this. Remember,
removing the attic floor insulation is necessary to not only
meet the current code, but more importantly, it can greatly
reduce your liability for condensation and odor problems
when converting to an unvented attic design.
Rick Duncan is the Technical Director
2012 Come learn everything you want o know about Sprayfoam! SPF Industry Training, Technical & Breakout Sessions, SPF Exhibit Hall, Contractor Awards Session. The industry’s value chain ALL IN ONE PLACE! January 30 – Febru
for the Spray Polyurethane Foam
1. Parker, D.S., ”Literature Review of the Impact and Need for Attic Ventilation in Florida
Homes” FSEC-CR-1496-05, Florida Solar Energy Center, May 2005.
2. Dejarlais, Andre, 2004. ”Comparison of Cathedralized Attics to Conventional Attics:
Where and When Do Cathedralized Attics Save Energy and Operating Costs?”
Proceedings of the Performance Envelopes of Whole Buildings IX International
Conference, December 5-10, 2004, Clearwater Beach, FL.
3. International Residential Code 2007 Supplement – International Code Council, August
4. ”Spray Polyurethane Foam in Unvented Cathedral Ceilings and Cathedralized Attics:
Recommended Design Considerations”, SPFA AY-141, Spray Polyurethane Foam
Alliance, December 2008. www.sprayfoam.org/index.php?page_id=242.
5. Morrison, R. M., ” To Vent or Not to Vent: That is the Question”, Spray Foam Magazine,
June 2010. http://sf.sprayfoam-mag.com/link/spfm/2010/jun/10.
6. 2009 International Residential Code, International Code Council.
7. Conversation with Mac Sheldon of Demilec, May 2011.
8. ” Thermal Barriers and Ignition Barriers for the Spray Polyurethane Foam Industry”,
SPFA AY-126, Spray Polyurethane Foam Alliance, March 2011. www.sprayfoam.org/
9. ”Building America Best Practices Series: Retrofit Techniques & Technologies: Air Sealing
A Guide for Contractors to Share with Homeowners”, Pacific Northwest National
Laboratory & Oak Ridge National Laboratory April 12, 2010. http://apps1.eere.energy.