Texas Building Code – Attic Insulation

Ask The Expert – Q & ACategory: Building CodesTexas Building Code – Attic Insulation
RIMA Expert Staff asked 6 months ago

The state of Texas has adopted IECC 2015 starting in 2016. A year from that effective date any builder that is seeking ENERGYSTAR certification must adopt version 3.1. As part of that higher standard, the builder will be required to have their ducts in conditioned space. Most of the builders that I have spoken to have be leaning towards foaming their roof decks to solve that problem. (which does not bode well for the radiant barrier people in the world) …. Has RIMA produced any solution alternatives or white papers on this issue on how builders can meet the requirement without jump shifting to foam?

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RIMA Expert Staff answered 6 months ago

RIMA-I has not taken a position or action on this issue – but, the panel industry is very involved. One of our panel experts responded with the following:
Under sheathing foam has had some moisture issues that can and will cause wood rot. Dr. Bill Miller’s research at Oak Ridge National Laboratories confirms our field observations as well. The underlying cause for the wood rot is the moisture that builds up over time by not having a “vented attic”. To obtain attic ventilation in an “unvented” assembly, you must use the mechanical HVAC system to remove the VOC,S/ moisture from the attic while the moisture is in the vapor stage, before it turns back to a liquid. Using the mechanical system requires the attic to be a “conditioned space”. To create a conditioned space, the attic must have a fresh air vent and a return air vent. The root problem behind using the mechanical system to vent the VOC,S is right sizing the mechanical unit. If the Mechanical system is too small it will run all the time thus you get no energy savings, if the unit is too large it does not run enough to pull the VOC,S from the envelope. There is a chapter in the International Code Council’s Residential building codes under R806 that will give you some guidelines on an unvented attic assembly by climate zone, however, R806 does not address the mechanical system’s requirements. In R806 you must be cautious on the type of paint used on the underside of the attic floor (ceiling inn living space), the coating or the ASSEMBLY OF THE CEILING CANNOT CREATE A CLASS VAPOR RETARDER. Some of the OSB and Plywood manufactures void their warranties if an unvented attic assembly is used as R806 cannot be met.
The above is the caution on the structural integrity of the assembly and obviously some health concerns. The other issue that we are dealing with is in the case that a building has gas appliances or gas piping in the attic and the gas leaks. The gas leaks into the open cell of the foam and waits for an ignition source. Some States suggest a mechanical room to house gas appliances that are in the attic with natural ventilation flows.
Another one of our reflective products experts confirmed the comments above agreeing Dr. Miller is not in favor of the foamed attic. There was an FSEC paper 3-5 years ago on the energy savings that were not favorable for foam. Also, bringing up the issue of satisfying the code requirement for attic R tends to suggest the use of closed-cell high R foam – very expensive.
None of this is in a white paper to date. I hope this is helpful to you. Thank you for writing.