Achieve Energy Efficiency and Maintain Indoor Air Quality

Willem Maas is the Founder and Publisher of GreenHomeGuide.  Thanks to David Bearg and Dean Sherwin for their edits and advice.

Energy efficiency and indoor air quality (IAQ) are both high-priority goals of greening the home, but achieving them during winter and summer months when the home is sealed tight can seem like a puzzle.

The Environmental Protection Agency recommends three strategies for improving indoor air quality: source control, improved ventilation, and air cleaning. Source control—eliminating sources of pollution or reducing their emissions—is the most effective and should be the first step you take. Many source control options are easy and inexpensive.

Improved ventilation will improve indoor air quality by increasing the amount of outdoor air coming into your home. However, most ventilation improvements are likely to increase energy costs unless you make design changes to your home. The third strategy, using mechanical air cleaners to remove pollutants, is a good adjunct to source control and ventilation but is not recommended as the sole solution.

Below is a range of energy-efficient IAQ tips—from easy to better to transformative—for the winter and summer months, when your home is likely to be sealed tight and reliant on heating or cooling systems.

EASY STEPS TO CLEANER AIR
These easy, inexpensive source control measures will eliminate pollution or reduce emissions from cleaning products, gas appliances, building materials, and furniture.

1. Clean with the least toxic nonaerosol product that will do the job.

The powerful chemicals in many conventional cleaning products can have a toxic effect on human skin and lungs. In addition, the propellants in aerosol products can be inhaled, so it’s prudent to use pump products instead. Find out how to make nontoxic cleaners from common household ingredients here.

2. Air out dry-cleaned clothing before bringing it inside.

Perchloroethylene (PERC) is the most commonly used dry-cleaning solvent and a potential carcinogen. In a report titled Hung Out To Dry the Coalition for Clean Air recommends allowing the cleaning solvents to offgas by removing clothes from the plastic bag and placing them outside for four to five days.

3. Dispose of unused paint, solvents, pesticides, and other household chemicals promptly, and tightly close the containers of products still in use.

Buy household chemicals in smaller sizes that you can use right away. These products can emit harmful gases that can pollute the air and may cause health problems. Earth 911 offers an easy-to-use national directory of safe disposal sites for toxic household wastes.

4. Use the exhaust fan over your stove to remove gases like carbon monoxide and nitrogen dioxide, and fans in your bathrooms to remove water vapor.

Make sure your gas range has a hood fan that exhausts to the outside—some exhaust systems are ductless hoods that exhaust air pulled from the stove right back into the home. Bathroom fans are also important since poor moisture management in a home leads to localized elevated moisture levels, allowing molds to grow.

5. If your home’s walls, doors, and windows are tightly sealed and energy efficient, open a window slightly to avoid creating negative pressure when running an exhaust fan or when you’re using a fireplace.

Without another way for outside air to replace the air leaving through the exhaust fan or chimney, air may be drawn through the exhaust pipes for your furnace or hot water heater.

6. Replace the air filter in your furnace and air conditioner at the start of the heating or cooling season, or as recommended by the manufacturer.

Filters actually become more effective in capturing and removing particulate air contaminants as they get dirtier and build up a dust cake. This increased effectiveness comes with a cost, however, as the pressure drop increases and less air gets through. It is a good idea to change the filter for the furnace at the start of the heating season, as the dust cake from the previous year has been sitting in the cold, dark basement throughout the summer and may have started to grow molds. You don’t want to disperse the metabolic products of mold growth into your home.

7. Room-size air cleaners can be effective tools for removing pollutants in one or more rooms.

If you are concerned about pollution in a particular room and it’s not possible to remove the pollution source, consider buying a room-size air cleaner. Sources like Consumer Reports and the American Lung Association recommend air cleaners for improving air quality in one or several rooms, but not for the whole house. See this GreenHomeGuide Tips article for advice on selecting an air cleaner.

BETTER STEPS TO CLEANER AIR
These better steps to improved indoor air quality are modestly priced, but do require advance planning.

1. Remodel in temperate months of the year, when you can open outside doors and windows to naturally ventilate construction areas without reducing energy efficiency.

During the winter and summer months, when heating or cooling systems are in use, opening doors and windows to vent construction dust and gases will reduce your home’s energy efficiency.

2. Use low-emitting, low-maintenance building materials to achieve improved indoor air quality year round.

By reducing the amount of pollution released into the indoor air, low-emitting, low-maintenance products can help you avoid more drastic steps necessary to clean dirty air. See GreenHomeGuide’s Know-How series for advice on selecting healthy flooring, furniture, and paints & coatings.

3. Add a fresh air intake to your forced-air heating/cooling system’s ducting.

A fresh air intake will allow fresh replacement air to enter the house when you’re using exhaust fans or the fireplace. If you already have a ducted air system, you can add a dedicated outdoor air opening by extending the return-air ductwork to the outside. You may also want to install a filter in this outdoor air source to capture air contaminants such as pollen and prevent them from entering your house. 

TRANSFORMATIVE STEPS TO CLEANER AIR
Most homes will always contain significant sources of indoor air pollution. These three ventilation strategies are recommended as transformative steps because they offer long-term improvements in both energy efficiency and air quality.

1. Install an energy recovery ventilator (ERV) to provide a continuous supply of fresh air while minimizing loss of heat and water vapor.

This ventilation system is connected to the existing forced-air heating/cooling system and uses fans to exchange stale indoor air with fresh outdoor air. Note that these systems cost several thousand dollars and are unlikely to pay for themselves in a timely fashion. This article from the University of Minnesota answers common questions about ERVs.

2. Use a heat pump water heater to increase energy efficiency and improve indoor air quality.

Heat pumps achieve energy efficiency by moving heat around as opposed to liberating it—the heat for the next batch of water to be heated is reclaimed from the warm, humid air being exhausted. Heat energy comes both from cooling the air being exhausted from about 72F to 42F (sensible heat reclamation) and from the condensation of the water vapor back into a liquid (latent heat reclamation). Heat pump water heaters use 30 to 50 percent of the electricity consumed by conventional electric water heaters.

The improved IAQ stems from the moisture management aspect of this approach. The amount of mechanical ventilation provided directly matches the amount of hot water consumed. Also, because the hot water use reflects the level of human occupancy (with more people in the home, more washing occurs), the result is mechanical ventilation with heat recovery that corresponds to occupancy levels.

3. In temperate climates, use natural ventilation to cool your home.

Natural ventilation can reduce total energy consumed by 10 to 30 percent compared with a home using a forced-air cooling system. A natural ventilation strategy relies on the buoyancy of hot air (the stack effect) and wind (cross ventilation) to increase the amount of outdoor air coming into your home.

While natural ventilation is best incorporated into the building’s overall design, there are simple ways to apply natural ventilation in any home: open both the top and bottom sashes of double-hung windows, and open windows on opposite sides of the same room. Opening windows at night during the summer will bring cool, fresh air inside and the thermal mass of the house will help the interior stay cool for part of the next day. The greater difference in temperature between inside and outside air at night also will cause more rapid air exchanges and vent air pollution from inside more thoroughly. In addition, outside air may be cleaner at night due to fewer cars on the road.