Effect of control strategies on ventilation system performance.

Dynamic computer simulations were used to compare residential ventilation methods to identifyan approach that would improve indoor air quality with minimum energy penalty while maintainingcomfort. Various ventilation methods and control strategies were evaluated to determinethe cost of providing the ASHRAE-recommended minimum ventilation level of 0.35 air changesper hour (ach).Analysis of simple ventilation methods showed that single-direction ventilation partially compensatesfor high natural infiltration levels and saves about half the energy cost of ventilating with atwo-direction method without heat recovery. Of the single-direction ventilation methods considered,the strategy of continuous exhaust fan operation to provide 0.35-ach mechanical ventilationdid not result in the lowest annual energy cost. Other single-direction ventilation methods,such as connecting an outdoor air duct to the return plenum, had relatively low annual energycosts. In tightly constructed homes with few cracks through which a single-direction fan couldforce air, two-direction ventilation may be required. Simulations indicate that a heat recoveryventilator significantly reduces the annual energy cost of two-directional ventilation.Simulations showed that if the amount of natural infiltration is known exactly, a significant energycost savings is possible compared to the constant two-direction ventilation without heat recovery.