Residential balanced ventilation and its tested impacts on indoor pressure and air quality

This paper presents results from a project on the assessment of the indoor air quality (IAQ) benefits that might accrue from the use of a balanced energy recovery ventilation system. The study compared the whole-building pressure, IAQ and ventilation performance of a balanced energy recovery ventilation (ERV) system with that of an exhaust-only ventilation system (continuous exhaust from master bathroom).  This investigation compared experimentally the impacts of the two ventilation systems in a side-by-side testing configurations using the Canadian Centre for Housing Technology’s (CCHT) twin houses to demonstrate and quantify the potential indoor air quality benefits of balanced ventilation system. The testing approach was a combination of building air leakage and HVAC characterization, envelope differential pressure, perfluorocarbon (PFT) tracer gas tests, sampling of aldehyde and volatile organic compound (VOCs). Two VOCs, toluene and α-pinene, were dosed at a constant rate to mimic indoor sources. The winter testing results have shown that a house operated with an ERV was under low positive pressure (1 to 3 Pa) and the house operated with an exhaust-only system was under negative pressure (-1 to -3 Pa). The effect of positive pressure on the IAQ has shown that relevant IAQ pollutants were significantly reduced in the house operated with a balanced ERV system. Average concentrations of formaldehyde in houses with balanced ventilation were reduced by 10-66% over houses operated with exhaust system. The average concentrations of two VOCs added (aPin and dTol) were respectively significantly reduced by 8-89% and 14-76% with partial mixing and with no mixing, respectively. The house with balanced ERV system had an average weekly space heating and ventilation total energy consumption reduced by 3.9-8.5%. The balanced (ERV) ventilation system was an energy-efficient solution to improve IAQ by generating a positive indoor pressure (1-3 Pa).