Whole-house mechanical ventilation in a mixed-humid climate
MetadataShow full item record
As building codes and green building programs require tighter home construction, the need for outdoor air ventilation to improve indoor air quality increases. Major improvements in building envelopes and duct systems have led to decreases in heating and cooling loads causing fewer HVAC system run-time hours, and increasing the probability for air stagnation within homes with poor outdoor air ventilation. ASHRAE Standard 62.2 quantifies the amount of whole-house ventilation required based on the number of occupants and the square footage of conditioned space, but leaves the design of the ventilation system up to the mechanical engineer or HVAC contractor. In 2010, ASHRAE began requiring flow testing for confirmation of outdoor air ventilation rates, yet few municipalities and green building programs have adopted the new standard. Builders in mixed-humid climates are forced to balance the need for outdoor air ventilation with the upfront costs for mechanical ventilation systems, and the potential for increased humidity loads and energy costs associated with mechanical ventilation strategies. One common solution employed in the southeastern United States involves a central fan integrated supply (CFIS) ventilation system controlled with an air-cycler for minimum run-time to meet ASHRAE Standard 62.2. While this system has been tested and proven to meet design ventilation rates, those tests were often conducted on homes constructed by well trained builders receiving strong oversight from building scientists and the design ventilation rates were not always ASHRAE compliant. The following report analyzes whether the CFIS ventilation system with air-cycler controller provides ventilation meeting ASHRAE Standard 62.2 when employed by builders with minimal training and support.