Healthy Indoors Magazine
Issue link: https://hi.iaq.net/i/327414
48 June 2014 Spray Poly Foam Continued from previous page the majority of the complaints I respond to are a direct result of inadequate ven- tilation and no method or design consideration be- ing given for the now semi-condi- tioned attic. To help mitigate this problem, we now have very specific guid- ance documents that help both the consumer and the ap- plicator better understand the difference be- tween a traditionally ventilated attic and a SPF unvented attic. "Guidance on Best Practices for the Installation of Spray Polyurethane Foam" established by the Spray Foam Coalition of the American Chemistry Council (ACC) Center for the Polyurethanes Industry states that the contractor and the homeowner should be aware that retrofitting an existing attic by employing an unvented attic assembly technique can result in the existing HVAC system becoming "oversized" in relation to the new demand. This situation is of special concern in southern and coastal climate zones where the HVAC also serves to reduce moisture levels in buildings in order to improve comfort and help prevent buildup of mold and mildew. If an existing HVAC becomes oversized due to the increased thermal efficien- cy of the unvented attic assembly, the HVAC system may begin to short cycle, or to quickly turn on and off, as it works to manage indoor temperatures. This short cycling of the HVAC system may have negative impacts on occupant comfort and efficiency of the building, and po- tentially on the lifespan of the system itself. The guidance document recommends that the ap- plication contractor involve an HVAC consultant to adapt the system to the new, more efficient building envelope associated with the spray foam retrofit. The Spray Polyurethane Foam Alliance (SPFA) Builder's Reference Handbook also lists HVAC and Ventilation as one of its initial Design Considerations and recommends an Initial Evaluation "Test-In" and a Final Evalu- ation "Test-Out" when installing SPF insulation. Unfortunately, less than 10% of the homes I as- sess have had any form of Test-In or Test-Out performance evaluation, and it's rare that the issue of ventilation or the home's HVAC system is discussed at all. The Initial Evaluation (Test-In) serves as a complete evaluation of your home before the installation of the SPF insulation. This includes an assessment of air leakage to establish the air infiltration rate of the home prior to re-insula- tion; evaluation of the type, location, and rec- ommended method of removal of the existing attic insulation; inspection of related systems,