Improving Indoor Air Quality During the Well-Sealed Winter Months
After decades of neglect by the homebuilding industry, indoor air quality is finally getting some much-deserved airtime. It even has its own nickname: IAQ. Building scientists and progressive architects and builders now focus on air quality as a standard design factor, planning for things like all-season ventilation, reduction of pollutants and safe use of combustion appliances. The same measures can help keep your IAQ in good shape in the winter and throughout the year.
Winter is Worst for Air Quality
If you have one of those smart-aleck dads who upon finding a door left open in winter, would comment, "What're you trying to do, heat the outdoors?" you already have an idea of why air quality suffers most in the winter. Most homes are built with no means for bringing in fresh air apart from open doors and windows. In older homes, window leaks and other openings supply a small but constant air exchange with the outdoors—perhaps the only advantage of a poorly weather-sealed home. In newer, more airtight, homes, bathroom and kitchen vent fans routinely send air out of the house, while nothing is letting fresh air in. This not only reduces the effectiveness of the fans, it also means that moisture and pollutants (not to mention odors) are trapped inside the house in higher concentrations during the winter. Compounding the problem is the fact that we seldom go outside during the wintertime.
"Eliminate, Isolate and Ventilate"
This phrase is commonly used by building pros to summarize the steps for improving IAQ. An expanded version goes something like this: Eliminate unnecessary chemicals and other pollutants in and around the home; Isolate any pollutants that you can't eliminate to keep them out of your living space; Ventilate the home effectively to rid the living space of pollutants and excess moisture, and to bring fresh air inside. (Too much moisture is bad for you and your home because it promotes mold growth, among other problems.)
How to Eliminate...
Chemical pollutants are everywhere in the modern home, from our paint to the carpet to cleaning supplies. There are far too many to list (or even categorize) here. But as a general rule, paying closer attention to product labels and spending a little more time seeking "healthier" products is one of the easiest ways to reduce air pollution in your home. For example, choose low- or no-VOC paint (and other finishes) when appropriate for the application. Carpeting, textiles and furniture can also be found with materials that contain little or no known pollutants, such as formaldehyde and various chemical treatments. Conventional cleaning products are another common source of household pollutants that affect our air quality. And as obvious as it seems, it's worth mentioning the worst pollutant people often bring into their homes: cigarettes.
How to Isolate...
Practically speaking, some pollutants must be diverted rather than avoided altogether. Two biggies in this group are radon and exhaust from gas-burning appliances. Radon is a naturally occurring radioactive gas that emanates from the ground at varying rates all over the world. By building a house over the ground, you're effectively trapping radon and forcing it to stay for dinner. The US EPA considers radon the no. 2 cause of lung cancer (after cigarettes) in the country. Fortunately, it's easy to deal with radon; the basic remedy involves a lining of plastic covering the crawlspace or dirt basement floor, under which a series of pipes hooked up to an outdoor fan continuously sucks out the air and sends it above your house. This is not, however, a do-it-yourself project.
Furnaces and hot water heaters that use natural gas emit poisonous exhaust that must be properly vented from the home. It’s no big deal, really. Just make sure your appliances are properly vented and not leaking exhaust into your living space (you can have exhaust flues checked out by an HVAC pro or qualified plumber). That said, even properly vented appliances can pose a health risk if your home has a serious imbalance of indoor air: too much air going out (through vent fans and the like) with not enough coming in causes negative pressure that can act like a vacuum and can suck appliance exhaust back into the house (see below). If you're in the market for a new hot-water heater, boiler or furnace, one way to avoid both exhaust dangers is with a sealed-combustion unit, which is sealed from the indoor air and draws its intake air from outdoors.
How to Ventilate...
Mechanical ventilation — using electric fans to pull in, circulate and exhaust air for our living spaces — is much more complicated than opening a window, but energy efficiency demands it. There are a few different ways to ventilate a house mechanically, but all involve an energy-efficient electric fan (or two) running most or all of the time. If your home is relatively airtight (a very good thing in winter, in terms of energy use), you probably can improve your IAQ significantly with a well-balanced ventilation system designed for your home and heating system. Consult with an HVAC contractor and/or an energy auditor to learn about your best options.
Improving IAQ Year-Round
All of the measures discussed here can help keep your air quality good throughout the year. In the warm months, simply opening the doors and windows as much as possible will help more than anything. Of course, if you run the A/C a lot in summer, your house is buttoned up as much as it is in the winter and the need for mechanical ventilation and other measures essentially remains the same.