How To Improve Indoor Air Quality in Zero Energy Renovations

In Part One of Deadly Indoor Air Pollution, we described how harmful both indoor and outdoor air pollution is to our health, productivity, and well being. We also discussed how building new zero energy and zero energy ready homes and buildings provide a clear path to ensuring excellent indoor air quality (IAQ). In Part Two, we described the IAQ measures commonly used in new zero energy homes and buildings. Now, in Part Three, we move onto existing homes, where creating excellent IAQ can be achieved either in small steps or all at once as part of a major renovation on the path to zero.

The first step, whether renovating step by step or in a major way, is to monitor the air in your home or building to identify and quantify indoor pollutants. It is helpful to monitor the air quality outside as well. You can keep tabs on outdoor air quality by visiting Air Now, where you can view the small particle PM2.5 and ozone levels by zip code, or go to Air Quality Index where you can see both the real time particulate matter (PM2.5 and PM10) and the nitrous oxide, carbon monoxide, and sulphur dioxide levels in the air in many communities, again searching by city. The second step is to track the indoor air quality in your home using a home monitor, such as the FooBot, which measures particulate matter, volatile organic compounds and humidity, as well as estimating CO2. If you have a gas furnace or gas appliances, be sure you have a working carbon monoxide (CO) alarm in your living space as well. A simple hygrometer, or humidity meter, often found in conjunction with digital indoor thermometers, measures indoor moisture levels, another important component of IAQ.

The second step is to identify household cleaning products that are toxic and remove them or replace them with green, non-polluting products. Scented personal products, like deodorants, soaps, shampoos, and perfumes also release VOCs into the indoor air. The EPA has a list of "safer" products for home, school and office. One rule of thumb to apply to both cleaning products and personal products – even if they are "green" products – if you can smell it get rid of it or replace it.

The third step is to hire an energy consultant or home performance contractor to help you determine the most cost effective energy efficiency upgrades that will improve the quality of the air in your home or building. Or, if you are doing a major remodel on the path to zero, along with an energy consultant, you can find a zero energy experienced builder and/or designer.

Another priority step is to evaluate how your current HVAC system affects your air quality, using a home monitor. If you decide to keep your old forced air heating and cooling system, you can take these steps to reduce indoor pollution: seal and clean existing heating ducts, keep the furnace filters clean and add a better filter, up to MERV 13, to your existing system. High-efficiency filters such as the MERV 13 may not be compatible with all furnace blowers because of the resistance they create to air flow. Check with your trusted HVAC technician for your best options.

If you have a combustion furnace, make sure that your heating system is properly vented and that you have a CO alarm in your living space. Sealed combustion furnaces and water heaters are essential in a tight home. If you have baseboard heating make sure to regularly vacuum the pipes and fins to remove dust. If it is time to replace your heating system altogether, consider installing ductless mini-split heat pumps to heat and cool the home. They are very clean, highly efficient, economical, easy to install, and require no ducting. Ducted versions are also available where short duct runs can be installed in the attic under the insulation to serve two or three smaller rooms.

If you have gas appliances, check for gas leaks, be sure they are vented according to code, and be sure you have a CO alarm properly installed. When they need replacing, change out old gas appliances for highly efficient electric ones such as a heat pump water heater, heat pump clothes dryer and an induction stove top. These appliances are less expensive to operate, more user friendly than their gas equivalents, and non-polluting.

Whether you are doing a gradual upgrade or a major remodel, air sealing your home is an important step towards improving indoor air quality, as it will keep outdoor air pollutants out and it will keep radon from migrating into the living space from the ground below. On a cold windy day you can simply find air leaks with the back of you hand or using smoke sticks. Seal any cracks as you find them and double check your work. If you are doing a more extensive remodel, hire a home performance contractor who can set up a blower door to pressurize the home or building, making it even easier to measure and detect air leaks. You can seal most air leaks with non-toxic caulking or use advanced taping systems and low VOC caulk or sealant from your local home center. A new air sealing system, called Aerobarrier, shows great promise for achieving very tight results in existing homes that are undergoing major renovation.

Most homes already have "spot ventilation." This comprises the kitchen range hood and small exhaust fans in bathrooms and sometimes a laundry room. If you stick with this ventilation arrangement, make sure all fans vent to the outside. It is alarming how many fans pump moist air into attics or crawl spaces. You can see if all the vents run to the outside by counting the number of fans and then the number of vents on the exterior to be sure there is an outside vent for each fan. Don't forget to look on the roof and high on exterior walls. Use your vent fans to get rid of excess moisture, especially if humidity is over 60%, and to clear out any odors caused by cooking, cleaning, or personal care. Use vent fans for at least 20 minutes when using bathrooms, when using scented cleaning or personal care products, and during and after cooking. If your vent fans are noisy, install silent vent fans, such as the Panasonic Whisper Comfort, as they will more likely be used than noisy fans.

To fully meet ventilation standards, ventilation fans may have to run anywhere from 8 to 24 hours per day. Either of two types of controls can be used to ensure this level of ventilation. First, a general ventilation control ensures that the fan operates long enough to comply with the basic whole house ventilation standard. The hours of operation can be set with a 24-hour clock timer. Another method is to install a dehumidistat control that starts the fan when indoor relative humidity rises to a specified level. Bathrooms and kitchens can especially experience short-term elevations of humidity or odors..A spot ventilation override switch should also be installed. This can be a simple 30-minute timer that is started when needed. It runs for a short time and then turns itself off.

If you have carefully air sealed your home and your air leakage rate is below 6 air changes per hour (ACH50) or if your air quality monitor shows you have significant indoor or outdoor air quality issues, consider a more systematic approach. If you have a clean, well-sealed, ducted heating system, you can have a trained HVAC professional add an HRV or ERV to the existing ductwork to ventilate the building with fresh filtered air. If the ducts are toxic or leaky, instead of using them, you can add spot energy recovery ventilators such as the Panasonic WhisperComfort ERV in key locations.

If you install ducted mini-splits you can use the mini-split ducting with an HRV or ERV added to it in the attic. If you are doing a major remodel towards zero consider adding a new whole house ducted ERV or HRV fresh air system. You can balance your ERV or HRV to have slightly positive indoor air pressure to help ensure fresh air comes through the filter and is not sucked in through the building shell. This strategy can also help keep radon out of the living space. On the other hand, you can balance the system to have a slight negative pressure to prevent moisture laden air from entering building cavities and supporting mold and decay. The approach you choose depends on your climate, seasonal variations in humidity, and personal priorities.

You may want to supplement your ventilation system by purchasing one or two portable ENERGY STAR labeled HEPA portable air filters, such as the air purifier made by Honeywell, to place in the most lived in areas of the home to filter out indoor pollutants. And consider cleaning out and completely sealing that old fireplace. Why not convert it to a new use such as a display area for plants. If windows need replacing, you can select inexpensive double pane windows with a U-value of 0.23 or less and be sure they are well sealed when installed. If you are adding insulation to your home, use rock wool or cellulose for insulation to avoid adding toxic chemicals, often contained in fiberglass and spray foam. During a major renovation, when selecting finishes and furnishings, select green products for carpets, flooring, furniture, and cabinetry, that are certified to be non-toxic, VOC and formaldehyde free. Organizations that certify products include Green Seal, Carpet and Rug Institute and Greenguard.

Since indoor air quality is so important to our health, well being, and functioning, and since global warming, reduction in regulation, use of synthetic chemicals, and population growth are exacerbating air pollution, now is the time to start planning to upgrade your home or business on the path to zero toxic indoor air, either in a step by step manner or as part of a major renovation. When you get on this path, exceptional indoor air quality and the health, high level functioning and well being of your family, students or employees will be one of your many rewards.

Don't miss these great posts on indoor air quality:

Part One: Deadly Indoor Air Pollution — Are Zero Energy Buildings the Answer?

Part Two: Zero Energy Buildings are Much Healthier Than Conventional Homes