What’s the cost of a healthy home?
California's residential ventilation requirements in Title 24 (the State energy code for buildings) are designed to balance healthy home ventilation with efficient energy use, but some studies suggest that whole-house ventilation systems don't always meet their expected performance in either category. Commissioning, a systematic evaluation of the installed system to identify deficiencies and offer solutions can help homeowners achieve this balance. However, implementing those solutions is likely to cost money, so how should we determine whether commissioning and the recommended changes are worthwhile?
Using detailed thermal, airflow, and pollutant transport simulation models along with novel costing approaches, Will Turner, Jennifer Logue, and Craig Wray—three Environmental Energy Technologies Division researchers—explored this question. In particular, the models quantified the energy and indoor air quality impacts of malfunctioning ventilation systems on occupant health and building energy use. Two existing approaches were used in combination to monetize the impacts: a Time Dependent Valuation (TDV) approach for energy and a Disability Adjusted Life Year (DALY) approach for air quality. This method allowed a direct, apples-to-apples comparison to be made between the health and energy costs associated with correcting ventilation system deficiencies.
The research team determined that health impacts dominate energy impacts—highlighting the importance of ventilating homes to provide good indoor air quality. They recommended that the metric for commissioning ventilation systems should be the net present value of the combined energy and health benefits to the occupant. Put simply, both energy and air quality should be considered together. In order for commissioning ventilation systems to be worthwhile, the value of the combined benefits should outweigh the cost of commissioning (plus any changes made). An interesting offshoot of the research is that this new method can be used to optimize ventilation rates in homes. With a bit more work, it should be possible to set ventilation rates that maximize health benefits to occupants while using as little energy as possible.
The full article, "A Combined Energy and IAQ Assessment of the Potential Value of Commissioning Residential Mechanical Ventilation Systems," by William J.N. Turner, Jennifer M. Logue, Craig P. Wray, is available to Science Direct subscribers.