Today as we design remodeling projects for our clients, energy efficiency and comfort are high on their list of wants. The first priority in achieving energy efficiency is to seal the building’s envelope. Air sealing, when taken by its self, tends to reduce the quality of the indoor air by trapping various pollutants in the home. In last month’s article, “Greening a Kitchen Remodel,” the impact of several products on IAQ was mentioned. So, in the process of tightening the building envelope, you need to consider implementing processes that will ensure the home’s air remains of high quality. There are four basic ways to accomplish this.
First, eliminate the offending materials from your projects. This is done by selecting products that have no or very low VOC off-gassing potential. Use low VOC caulks, sealants, flooring and other building materials as a method of eliminating VOC contaminates. When installing gas hot water heaters, furnaces or fuel heaters, use direct vent products to ensure the combustion byproducts are vented outside. If appropriate to your climate, consider using solar water heaters for hot water and even heating.
Second, ventilate as close to the sources of pollutants as possible. In the kitchen you will want to ensure the range hood and fan is adequately sized and vented directly outside. Island cooktops should be hood vented vs. using the lower-efficiency downdraft method. The same consideration should be applied to ventilating the bathroom. By placing the exhaust intake close to the source of moisture it will prevent the mixture, of pollutants with the home’s normal air supply. If an attached garage is present, consider installing an exhaust fan in it. This fan should be connected to the garage door opener to start upon opening and close some minutes after the door is closed. This will reduce the likelihood of auto exhaust gases infiltrating to the home.
Third, provide positive ventilation to the home. The key to a healthy home is to seal it as well as possible and then provide positive, controlled ventilation. The home should be maintained under a slight positive pressure to reduce infiltration of external pollutants including soil gasses. Some type of controlled, mechanical whole-house ventilation system should always be provided.
Fourth, if the home has a central air system, the standard filter system should be augmented with a high-performance filter. HEPA filters are recommended. When installing them as a retrofit, be sure your HVAC contractor takes into account the additional pressure drop across the filter when designing the duct system.
Poor IAQ Contributors
Mold has been in the headlines lately, and many remodelers have had to deal with this problem either as it impacts their projects or after the fact. Mold spores are ever present; however, typically the volume is small enough that they present little effect on the home’s residents, but can become a health hazard in excessive amounts. Generally it can be said that mold growth is caused by too much moisture in some part of the structure, either in the wall system, basement, attic or the home in general. For maximum comfort and to control mold growth, the relative humidity of the home should be maintained between 25 and 60 percent.
Another source of contaminants in the home is old attic insulation. Homes with central air/heating systems typically route the supply and return ducts through the attic. With age, the duct joints fail and the insulation deteriorates, creating a fine dust that finds its way into the duct system. The two problems associated with this are loss of heating/cooling efficiency and introduction of an irritant into the home. The corrective action in this case is to replace the insulation and seal the duct systems.
Attached garages can also be a major source of air contamination. Homeowners typically will use this space to store pesticides, lawn mowers, fuel, caustic cleaners, and the list goes on. If possible, recommend a detached garage as an option during a whole-house remodel, but if it’s not an option, recommend a vented storage space outside of the living space for chemical and lawn tool storage.
Indoor air quality is an important consideration when conducting remodeling projects. Your clients depend on you to make the recommendations that will keep them healthy. The following are references that may be helpful to you.
Green Building Guidelines: Meeting the Demand of Low-Energy, Resource-Efficient Homes by Sustainable Building Industry Council
Green Remodeling Changing the World One Room at a Time by David Johnston and Kim Master