A green home should be a healthy home. It shouldn’t grow mold, mildew, and dust mites. It shouldn’t introduce significant quantities of volatile organic compounds (VOCs) or other hazardous chemicals into the indoor environment. It should have plenty of fresh air for its occupants.
Beyond keeping homeowners healthy, a well-designed green home can go even further with measures to ease stress and enhance a sense of wellbeing.
A few specific strategies for ensuring a healthy indoor environment are described below:
Deal with moisture
Moisture getting into homes—or not being able to get out—is probably the number-one cause of health problems in homes today. Standing water, dampness, and high humidity result in mold and mildew growth, dust mites, and other problems. Strategies for keeping water out include deep roof overhangs, surface grade sloping away from the house, and proper flashing around windows, doors, and other penetrations.
Strategies to get rid of moisture include installation of quiet bath fans that will actually get used (automated controls for bath fans are even better), kitchen range-hood fans that exhaust to the outdoors, rainscreen detailing on walls to allow trapped moisture to escape, and soffit and ridge vents in the attic (unvented “hot” roofs can also work, as long as the roof system is extremely well-sealed).
Various “operation and maintenance” measures are also very important in dealing with moisture: fixing roof leaks that are found, fixing plumbing leaks, never drying firewood in the basement, always operating fans when showering, and avoiding too many indoor plants (especially in the summer when relative humidity levels are high).
Keep pollutants out
One of the easiest ways to cut down on pollutants and moisture being tracked into a building is to install track-off mats for entryways. In commercial buildings, track-off mats are often designed with grates and drainage outside, then a coarse mat to remove soil and particles, and finally a softer mat that dries shoes as you scuff across it. In homes, a place to remove shoes and a no-shoes policy is a great way to keep pollutants out and reduce cleaning needs.
Specify zero-VOC or low-VOC paints, sealants, and other materials with chemical constituents. With recent advances in finishes and adhesives, for most applications there is no longer a compromise in performance or durability when selecting low-VOC products.
Avoid hazardous chemicals and components
A wide range of chemicals are introduced into our homes through building materials, furnishings, and other products. Hazards we should try to avoid include brominated or chlorinated flame retardants, bisphenol-A or BPA (used in epoxies and polycarbonate plastics), phthalate plasticizers (used mostly in flexible vinyl or PVC), and formaldehyde. It’s a good idea to invest in learning about these hazards and working to select products that are free of them. Try to avoid insulation materials that include brominated flame retardants, for example, and cabinets made with particleboard or medium-density fiberboard (MDF) that contains urea-formaldehyde binders.
Provide fresh air
Mechanical ventilation is needed to deliver fresh air throughout a house. The old argument that we shouldn’t tighten up our homes too much, because we won’t get enough fresh air doesn’t make sense. When we depend on air leakage for fresh air, we only get fresh air when there’s a pressure difference driving air exchange in a house: that could be wind or very cold temperatures that create a stack effect. In the swing seasons (spring and fall) and in milder climates air leakage doesn’t cut it. With mechanical ventilation, we can control how much air we introduce, where it comes from, where it is delivered, and from where we exhaust the stale indoor air.
The best ventilation system is a “balanced” system with separate fans for exhaust and supply with ducting. In cold climates, it makes sense to run these air streams past each other using a air-to-air heat exchanger or heat-recovery ventilator, so that most of the heat from the outgoing indoor air is transferred to the incoming fresh air.
Provide for psychological health
Delivering daylighting and connections to the outdoors can help to maintain psychological health. A growing body of research is showing that in offices, these features boost worker productivity, in hospitals they speed recovery from illness or operations, and in schools they improve learning. The idea of design features that connect us with nature is referred to as “biophilic design” (biophilia is the innate affinity humans have for nature). This is a way to make an ordinary home a great home.
My top-10 list of green building priorities so far:
#3. Ensure a healthy indoor environment
In addition to this Energy Solutions blog, Alex writes the weekly blog Alex’s Cool Product of the Week on BuildingGreen.com, which profiles an interesting new green building product each week. You can sign up to receive notices of these blogs by e-mail—enter your e-mail address in the upper right corner of any blog page.