Idea for Florida Building Commission Funded Research

Background: In 1995, a report was prepared for the Florida Department of Community Affairs on the topic of building airtightness, titled “Reassessment of Airtightness Practices in the Florida Energy Code”. That report indicated that Florida homes were becoming progressively tighter at a relatively rapid pace and had reached a point where additional tightening would result in natural ventilation that would be sufficiently small as to fall substantially short of levels needed for good indoor air quality. Further tightening might necessitate installation (and of course maintenance) of mechanical ventilation systems to achieve acceptable indoor air quality.

In the past 18 years, residential construction practices have continued to change over time and a number of groups and programs have also begun pushing to make homes much tighter and to require mechanical ventilation. The saying “Build it tight, ventilate right” represents a strongly held view among many within the buildings community. Underlying this issue is the concern that when the house envelope is made very tight and mechanical systems are therefore essential to achieving desired ventilation levels, the question arises, “Who will maintain the ventilation systems and what happens to indoor air quality when the system fails or is turned off?”

For Florida, a special concern relates to humidity in homes. The most widely encouraged and employed method for providing mechanical ventilation in homes across the United States is continuous exhaust. But this approach would create negative pressure and elevated humidity in Florida homes. Combined with other factors beyond the control of the building code, such as homeowner thermostat set point and interior vinyl wall coverings, negative pressure has been found to cause mold growth in Florida homes and buildings. Alternative methods of providing mechanical ventilation are generally more complicated and often much more expensive.

Proposal: Provide an update to the 1995 report, which would include tracking of house airtightness trends since 1995, review of current recommendations and policies regarding house envelope airtightness, an overview of mechanical ventilation options for the Florida climate, and alternative approaches to achieving acceptable levels of ventilation while avoiding the risks associated with super-tight home enclosures and potential mechanical system failures.

One topic that comes to mind is use of foam insulation products in attics and other locations, since there seems to be inconsistencies of code requirements and a mosaic of code enforcement. The topic of unvented attics without foam insulation also comes to mind; I see no reason to vent attics or require foam insulation if venting is to be eliminated. Why not allow unvented attics either without insulation at the roof deck (preferably with a cool roof) or allow other forms of insulation to be applied to the roof deck with attic venting sealed.