The neglected 'V' in residential HVAC
Bathroom and range hood fans can help increase indoor air quality.
Our industry talks a lot about indoor air quality, and whenever engineers design a commercial, institutional or industrial building, great care is usually taken to ensure proper air movement and ventilation.
No one wants to be responsible for “sick building syndrome” and the resulting lawsuits. In fact, you’ll find many abandoned (usually government) buildings, because the air quality became so poor that many people claimed it made them ill.
On the other hand, residential HVAC designs usually offer only a token consideration to such concerns. In fact, in new-home construction, the only consideration given to proper ventilation is usually the installation of bathroom fans and a range hood, which may operate for less than an hour per day. And as for air movement, the HVAC circulating fan usually only operates when the thermostat calls for heating or cooling. Yet, when it comes to air quality, homes often have all the air-quality problems of stores, offices and institutions -- sometimes even more!
Whole-house ventilatorsSeveral manufacturers have come up with whole-house ventilators, and I see several of them on display at each year’s AHR Expo. These are wonderful devices because they take in outdoor air, filter it and then perform a heat-exchange operation to reclaim the cooling or heating from the exhausted air, while providing proper ventilation and leaving the home in neither a vacuum nor under pressure.
Unfortunately (probably because of price and installation costs), whole-house ventilators haven’t become very popular, and are considered a specialty indoor-air-quality item for just those with serious allergies. And I don’t know what else we can do to improve this situation, other than to try to educate the public.
Bathroom and kitchen fansYet, something more can be done to improve indoor air quality and ventilation if we can help contractors and their customers understand more about the true function and design of bathroom fans. If they are properly selected and designed, their function is far more valuable than just carrying out odors and making a little noise. The most important function of these ventilators - air-quality-wise - is to remove excess moisture and to help dry out wet surfaces. And this, in turn, reduces the propagation of hazardous bacteria and mold. But to effectively accomplish this, they must be properly sized for the room and operated from timer switches, which force the fans to run for several minutes after they are turned off.
Also, recognize that range hood fans serve a far more important function than just carrying off a little extra heat, smoke and odors. Along with accumulated dander and the released aldehydes of carpeting and furniture, the other largest contributors to poor residential indoor air quality are humidity (from hot or boiling water and gas combustion) and high concentrations of CO2 (from gas combustion). And obviously, the larger the kitchen and stove, and the more cooking and dish washing that is being done, the larger that vent hood should be. Also, recognize hoods not venting to the outdoors don’t meet these air-quality requirements.