Indoor Air Quality - You Are What You Breathe
By Maurice Levitch, AIA
Living and working in existing buildings, we inherit all the beautiful spaces along with the air our builder intended us to breathe. There is evidence that even in the most industrialized cities, the air within our homes and businesses can be more polluted than outdoor air. Since most people spend about 90% of their time indoors, it is obvious that we should pay attention to indoor air quality. Many indoor air pollutants have been shown to have negative effects on our health, especially for children, the elderly and those with respiratory problems.
We face a variety of health risks as we go about our daily activities. Some are unavoidable given the way we choose to lead our lives, and some we might forgo if we had the right information. When remodeling or constructing a new building, we can make decisions that significantly improve and maintain better air quality, which translates into better health.
With homes more tightly sealed for better energy efficiency, it is even more important to choose materials and products that do not offgas harmful chemicals into our buildings. While older homes may have potentially harmful materials, some chemicals, such as formaldehyde (a common binder in insulation and pressed wood products), offgas over a long period of time and may therefore not be an issue today. Asbestos, a product with known health risks, is safe if it is encapsulated and not disturbed. Radon, a naturally occurring gas, could have harmful effects, but mitigation can be planned for during construction. (The EPA website, www.epa.gov, recommends testing homes for radon even in areas where it is present at low levels.) There are also biological pollutants such as mold and mildew.
There are three ways to improve indoor air quality (IAQ): source control, ventilation and filtration.
SOURCE CONTROL
Source control offers the best oppor- tunity for better IAQ. There is a wide range of commonly used construction products that do not offgas: formaldehyde-free insulation, low- or no-VOC paints, as well as a variety of flooring, window coverings and other finishes that are manufactured with environmentally friendly materials. Using nontoxic cleaning products in the completed building also contributes to better indoor air quality.
VENTILATION
There are many ways to ventilate a building (to bring in fresh air and exhaust stale air). While removing stale air is desirable, you may also exhaust conditioned air, thereby using more energy to heat or cool incoming air. An energy recovery ventilation system (ERV) or heat recovery system (HRV) uses a heat exchanger to eliminate or reduce heat loss with this operation. Quiet and energy-efficient point-of-use exhaust fans remove bathroom moisture, which with a timer switch make it more difficult for mold and mildew to grow in these wet areas. Quiet kitchen exhaust hoods (surprisingly not required by code) help remove excess moisture and odors from cooking (don't worry, you can still smell the freshly baked cookies). An exhaust fan in an attached garage is also a good way to keep chemical and exhaust fumes out of the living space.
FILTRATION
OK, so you still have some indoor pollutants, hopefully not from your own smoking. Now is the time to look into filtration. There are many types of filters, with the most effective passing a larger volume of air through them. Investing in a standalone system requires research into various filter media, air volumes and other choices. Don't be fooled into thinking that this is the best way to keep the air clean, as some filtration methods can be combined with a forced air system, eliminating the need for additional equipment.
In a nutshell, you are better off if you can first keep the bad stuff out of the building. The tightest buildings will always require mechanical ventilation, and if you're stuck with what you have, then use a combination of ventilation and filtration. At some point, it will make sense to consult with a mechanical engineer to make sure you are doing the right things to create a healthy, energy- efficient building.
December 2007 Builder Architect Edition Issue