Indoor-air quality is important for buildings
By Cindy Meehan-Patton on 03/16/2006
The air we breathe is a blessing to humanity. Living and working in clean indoor air is important for the body’s restoration. We were not given a plethora of manipulated and compound chemicals when the universe was created; this has been mankind’s doing. Therefore, it is our job as stewards of the earth to restore damage.
This is hard for humans to do. Our lives have become overwhelmed by complexity and the deception that we need the complexity. To add to the complexity, building with clean indoor air as the end result can mean different things to different people. It does not necessarily mean we should build a home out of straw if it means the home will be bombarded by humid air that results in mold and mildew. It does not necessarily mean that one should always keep windows closed to completely control indoor air through mechanical means. The balanced strategy between these two extremes seems to vary with each person’s needs.
Mold is the most common indoor-air pollutant that is making many people sick. Strategies must be built into the design plan to prevent mold in any building. According to the Mayo Clinic, the number of asthma-related diseases from mold has increased by 300 percent in the past five years.
Experience tells me that if we live or work in an environment burdened by mold, then illness enters the body because mold suppresses the immune system. The universal opposites of dark and light, positive and negative, good and evil begin to shift in our lives when illness creeps in, resulting in imbalances in all facets of our lives. This interferes with our intention to live an abundant life.
How can we make our homes and other buildings healthier? First, we must understand that our climate in Western North Carolina is a mixed-humid (bordering on extreme) climate zone, according to the Environmental Protection Agency and the Energy and Environment Building Association. For more than 200 days a year, our outdoor humidity level is 75 percent to 100 percent. High humidity traveling through open windows, leaky walls, floors and roofs quickly can result in toxic mold indoors.
The first step to clean indoor air, therefore, is to keep the home dry inside and out. The best way to create a healthy home requires design strategies with a “built tight and ventilated right” result. The other step is to use nontoxic materials inside the home. Hundreds of nontoxic materials are available today compared with 1991, when I started my business.
For indoor-air quality, the main system in the home is the HVACD (heating, ventilation, air-conditioning and dehumidifying) system because it is the lungs and heart of the home regardless of the age of the house. Let’s look at the heating and cooling component. With current resource depletions, we will all require the most energy-efficient system possible. Passive-solar designs for heating are best because they use the sun. However, pillaging trees from our forest to harness the sun is not ideal. We have an abundance of trees, some of them unique deciduous tree forms. This can present a challenge in creating a passive-solar structure.
Radiant floor heating can be healthy and comfortable but expensive to install. Its efficiency depends on the tightness of the home’s envelope, or exterior shell, and the type of flooring used to transmit the warmth. A high SEER electric heat pump is a common healthy option for a tightly constructed home but has the major drawback of dependency on the electrical companies that pollute and are not as reliable as we once thought they were. And the monthly bill can be expensive, depending on the home’s energy efficiency.
Reliance on oil, natural gas and propane is not only shaky in terms of these ever-decreasing resources but in terms of their toxicity. Propane and natural gas have an added chemical to detect leakage. The putrid smell produced is actually a pesticide. Combustible fuels inside the home are a dangerous and toxic choice to heat and cool. Several good “on demand” furnaces can be installed outside the home and are ideal because they are efficient and do not allow open pilot lights in the home. Last but not least for heating is perhaps the most practical option: wood, masonry or pellet stoves. The industry is creating more resource-efficient, cleaner-burning models all the time.
Cooling strategy options are numerous as well. If radiant floor heating is used, then Energy Star-rated portable cooling units can be effective in keeping the humidity down and creating comfort inside the home. These can be effective in a tighter built home as well. Some units can be placed above doors and between rooms inside the home, which can be particularly efficient in a passive-solar situation because they target the areas challenged with the most heat gain.
Let’s look at ventilation and dehumidification. Reliance on natural ventilation (open windows) in a mixed to extreme climate such as WNC can be detrimental to your health and the health of your home and must be done in a monitored and balanced way. The use of strategically-placed dampers on mechanical and heat-pump systems along with zoned thermostats can help. There are many mechanical ventilation systems on the market now, including ERVs (Energy Recovery Units) and HRVs (Heat Recovery Units). Both types exhaust stale air and bring controlled amounts of fresh and filtered air in. But they don’t have the dehumidification capacity required in a mixed humid-extreme climate.
The best system for our area brings a controlled amount of fresh air in, filters it and acts as a whole-house dehumidifier but leaves out the exhaust part of the equation. This seems to work well because it results in a positive pressure in your home at all times. According to Building Science Corporation, even the tightest home has weep holes, so when a house has a constant positive pressure in it, the stale (or negative) air will find its way out. From my experience, this is true. This system addresses ventilation and dehumidification.
If your building is older and leaky then mechanical ventilation is not needed as much as cooling and dehumidification. Whole-house or basement-size dehumidifiers are the most efficient sources.
These Web sites can provide more information:
The periodical Environmental Building News is also a resource, in addition to the following books:
- Builders Guide to Mixed Humid Climates (Joseph Lstiburek)
- Moisture Control Handbook (Joseph Lstiburek and John Carmody)
- The Solar House (Dan Chiras)
- The Sick House Survival Guide (Angela Hobbs)
[Cindy Meehan-Patton is a founder of the WNCGBC. She is president of her residential-design practice, which has a healthy-buildings consultation division and a green materials store called Shelter Ecology Inc. She can be reached at 225-2829, or consult her Web site atwww.shelterecology.com.]