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People breathe — houses should too By ISAAC SAVAGE People need to breathe. And people perform best when the air they breathe is clean, high in oxygen and low in carbon dioxide. With the growing awareness of personal health and the role that air quality plays in this equation, combined with the rising interest in creating more efficient houses, what we breathe in our homes has never been more important than it is right now. For years, building codes have required outside-air ventilation in commercial buildings for the benefit of those who occupy the given facility. To ensure this indoor air is “good,” one of the requirements involves diluting the indoor air with outside air, typically introduced through the heating and cooling systems. Thank goodness we’re all being looked after when we’re at the office, out shopping or visiting the doctor’s office. Unfortunately, we go home to our poorly ventilated residences, where we breathe less-desirable air for the remainder of the day, and all night while we sleep. Residential ventilation systems are not required by building code. Therefore, few homes actually have any form of outside-air ventilation at all. The typical heating and cooling system simply recirculates the same air, over and over again. If people didn’t like to bring pollutants into their homes, this wouldn’t be that big of an issue. But most people introduce a variety of things into their homes that off-gas harmful pollutants: paint, carpet, stains, cleaning products, dry-cleaned clothes, fabrics, furniture and, the most telling of all, artificially scented “air-fresheners” used to cover up other pollutants. Most residences rely on gaps and spaces in the walls, floors and ceilings to provide air-exchange. The problem with this scenario, beside the fact that the air is coming from places like attics and crawlspaces, is that sometimes the house doesn’t leak enough, and sometimes it leaks too much. Generally speaking, houses leak too much in the winter, when the extra ventilation creates high energy bills, and don’t leak enough in warmer weather, resulting in poor air quality for much of the year. The only way to have an efficient home that is also properly ventilated is to seal up the leaks you can’t control and install a ventilation system that maintains the right amount of air exchange all year long, regardless of the weather.
kitchens and bathrooms), as well as “whole building” ventilation systems, designed to dilute indoor air with air originating from the outside. The standard covers a few main aspects of ventilation systems: • Quantity of local ventilation • Quantity of whole-building ventilation • Sound-level thresholds of ventilation fans This standard can be used for both new and existing buildings. The new construction requirements are relatively straightforward, while the existing home calculation methods are a little more complex. Local ventilation The purpose of local ventilation is to remove pollutants at the source. The two areas that ASHRAE 62.2 focuses on are kitchens and bathrooms that have a tub
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Whole-building ventilation Whole building ventilation should dilute interior pollutants by creating an air exchange within the home. This can be achieved by one or more of three basic methods: • Exhaust-only: Exhaust fans remove air from the building. As a result of exhausting air, outside air is sucked into the home to replace the air that was just exhausted. Replacement air typically enters through the holes in the building nearest the location of the fan, which may result in poorly distributed ventila-
aSHrae 2.2 LoCaL venTILaTIon aIrFLow reQuIreMenTS BaTHS (FuLL)
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Emerging industry standards Widely accepted and supported by organizations like the Department of Energy, as well as the EPA’s ENERGY STAR program, a residential ventilation standard is finally being embraced. The American Society of Heating, Refrigerating and Air-Conditioning Engineers has published the residential ventilation standard, ASHRAE 62.2. This standard addresses both “local,” or “spot” ventilation (exhaust fans located in
or shower. Moisture is the pollutant in bathrooms, while both moisture and by-products of cooking are the main concern in kitchens. ASHRAE 62.2 allows for these pollutants to be managed using a continuously operating exhaust fan or an intermittent fan, used only when needed. The minimum airflow requirements for local ventilation are listed Figure 1.
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FIGuRE 2 WNC GreeN BuildiNG CouNCil & MouNtaiN Xpress