Our homes can be comfortable and energy-efficient: Especially if we borrow from the high-performing, effective ideas used around the world in “passive houses.” Developed by the German Passivhaus Institut in 1996, a Passivhaus is defined by core efficiency standards. What does this mean in practice? Homes built to the Passive House standard are extremely comfortable to live in—with natural daylighting, even temperatures throughout and virtually no drafts.
Passive homes require 90 percent less energy to heat because energy losses are minimized with generous amounts of insulation and air sealing. The homes are heated largely by solar heat gains and internal gains from people and electrical equipment. Although fully retrofitting a home to the passive house standard is usually very costly, we can use many of the elements of passive home design to make our homes more efficient. Apply the following concepts to your home to boost comfort and reduce energy bills.
Boost Winter Solar Gain
South-facing windows and, to a lesser extent, east- and west-facing windows help gradually warm our homes with solar energy. Maximizing this free energy source reduces dependence on heating systems, in turn lowering utility bills in cold climates and promoting indoor air quality. Forced air heating, for example, can carry dust with the heat as it passes through duct work, while wood-burning stoves and heating systems that use natural gas or propane can emit carbon monoxide. Wood-burning stoves also can produce breathable pollutants such as smoke and ash.
Clean southern windows and remove screens. When the heating season begins, remove screens on south- and east-facing windows and wash the windows to increase your solar gains by up to 40 percent. Keep screens in the west- and north-facing windows to provide protection from the winter wind.
Avoid shading southern windows in the winter. Evergreen vegetation, carports and porches can shade southern windows, hindering solar gains. In colder climates, plant only deciduous trees and shrubs (which lose their leaves in winter) outside south-facing windows, or space vegetation and structures far enough away from the house to avoid shading southern windows.
Expand with a solar addition. If you are planning an addition on your home, consider adding a sunroom, which can help heat your home. Effective sunrooms face south, include lots of thermal mass, are thoroughly insulated, and include ventilation options with windows, doors and skylights.
Tighten the Building Envelope
The building envelope is the physical separation between the inside of a home and the unconditioned environment, providing a weather, air and thermal barrier. After maximizing solar gains, make sure your home retains warm air in the winter and cooler air in the summer.
Use insulating window treatments. Although they help bring in wanted heat during cold, sunny days, windows also serve as a significant avenue for winter heat loss, especially at night. Prevent this by installing thermal shades, blinds, shutters or curtains. Minimize the space between the curtains and the wall with magnets, shutters or Velcro, and ensure that insulating shades are properly sized for the window. Keep window treatments closed all day on north windows and at night for all windows.
Weatherize existing windows. Plugging air leaks will boost the energy performance of your windows and doors. Adding storm windows and lowering them during the heating season will keep in more warm air. Caulk stationary cracks or joints that are less than a quarter-inch wide, and add weatherstripping around moving components, including windows and doors.
Install smart overhangs. Thanks to the difference in the sun’s position in the sky through the year, well-designed overhangs can both block summer sun, helping keep houses cooler, and admit winter sun, helping heat interiors. Try any of several options: eaves or overhangs; a pergola with deciduous vegetation; or even an awning of strategically placed solar panels.
Minimize winter use of exhaust fans. Although they help expel unwanted cooking vapors and mold-producing moisture, exhaust fans and vented range hoods also allow heat to escape from our homes. Whenever possible (without sacrificing indoor air quality), minimize their use. Installing a timer on exhaust fans can be helpful. Because winter air is often dry, you may be able to get away with simply leaving the bathroom door open after showering or turning on the exhaust fan for only a couple of minutes. In the kitchen, only use the range hood fan during stovetop cooking; turn it off as soon as possible.
Capture Heat with Thermal Mass
Thermal mass helps stabilize indoor temperatures by capturing and storing heat from the winter sun and slowly releasing it at night. This helps avoid large temperature swings, with a room becoming uncomfortably warm during the day and then chilly at night. Thermal mass works most effectively in the direct path of the sun’s rays.
Install tile flooring in sunny southern rooms. Stone or concrete tiles have a high thermal mass. If you have rooms on the south side of your home that receive a lot of sun, install dark- or medium-colored tile where the sun hits the floor and avoid covering it with carpeting. For slab-on-grade construction with insulation underneath and around the edges, consider keeping concrete floors exposed.
Add masonry planters. Placing heavy concrete, tile or stone planters in the direct path of the sun will help capture daytime heat and boost comfort. If they are dark in color, they will absorb more heat during the day for nighttime heat release.
Mitigate Energy Drains
Many homes have rooms that use a disproportionate amount of the home’s overall energy. Identifying these will pay dividends in savings.
Identify inefficiencies with an energy audit. Many homes have significant leaks and thermal bridges, where heat is drawn out of the home by discontinuities in a thermal barrier (for example, from gaps in insulation). Energy auditors use infrared cameras or a blower door test to identify inefficiencies and make recommendations for corrective action.
Prioritize uncomfortable rooms. Many homes have one or two rooms that are less comfortable than the rest, causing the heating or air conditioning to work overtime to compensate. Finished basements, poorly insulated spaces, north-facing rooms, and spaces that have malfunctioning ducts or that are far from the HVAC system all have this tendency. Enhancing the thermal performance of these rooms can have a significant impact on household comfort and energy use. Targeting such rooms with improved insulation, air sealing, upgraded windows and thermal window treatments, as well as balancing or cleaning the HVAC system, can impact the comfort of the entire house.
Purchase energy-efficient appliances. Major appliances, including the refrigerator, washing machine, clothes dryer (if electric) and dishwasher, can account for a large portion of a home’s energy usage. Appliances more than 15 years old are far less efficient than current models. Use a Kill A Watt electricity usage monitor (available on Amazon for under $30 or sometimes from the library) to measure the energy usage of your appliances and electronics. When purchasing appliances, look for the Energy Star label and use the EnergyGuide label to compare the energy use of different models. Ensure that any appliance is the right size for your needs, as oversized air conditioners, water heaters and refrigerators waste energy.
Upgrade Your Windows
If your windows are single-pane or are one of the leakiest places in your home, consider replacing them with high-efficiency Energy Star-qualified windows. Check with your local utility companies about rebates or incentives.
For colder climates, some window manufacturers fill the space between the panes with an inert gas that is more resistant to heat flow. Low-emissivity (low-E) coatings are a transparent, insulating glazing that can reduce heat loss by 30 to 50 percent by reflecting heat inside during the winter and reflecting back some of the summer sun.
For warmer climates, select windows that reduce solar heat gain. Choose windows with spectrally selective coatings that block infrared light while admitting visible light. Windows with a low solar heat gain coefficient (SHGC) help reduce solar radiation through the window.
Balance Efficiency with Air Quality
Although we all want efficient, warm and affordable homes, we also want to make sure the air inside our homes is healthy to breathe. As we improve the tightness of our homes, we also reduce ventilation, meaning what goes into the air inside our homes stays there. Use these tips for keeping your indoor air healthy as you improve your home’s energy efficiency.
Use only nontoxic, natural cleaners. The EPA lists cleansers, disinfectants, moth repellents, air fresheners and dry-cleaned clothes as potent sources of indoor air pollution. Find an array of homemade cleaning recipes in our Guide to Homemade Cleaners, or visit ePantry to get nontoxic cleaning products delivered to your home via subscription service.
Perk up with plants. Houseplants can help purify stagnant indoor air. For example, the areca palm is adept at removing airborne toxins, especially formaldehyde. To learn more about plants that help reduce indoor pollution, read Reduce Indoor Air Pollution with Houseplants.
Rely on the oven in winter. Stovetop cooking produces more than indoor aromas. Using gas burners can spike levels of nitrogen dioxide and carbon monoxide, and cooking on any type of stovetop fills the air with fine particles. Range hoods help eliminate cooking particles, yet they also can suck warm air out of the house. Instead rely more on baked dishes in winter; after baking, crack the oven door to allow heat from the oven to help warm your home.
Fortify furniture. Polybrominated diphenyl ethers (PDBEs) are flame-retardant chemicals that were commonly used on upholstered furniture, carpets and rugs prior to 2005. They are suspected to disrupt the thyroid, the liver and brain development. PDBEs are no longer manufactured in the U.S., but products that contain them were not labeled. To reduce exposure to these and other types of flame retardants, keep furniture coverings intact to avoid loose foam. Read more about avoiding flame retardants in 3 Toxic Chemicals to Avoid in Your Home.
Be wary of wood. Inexpensive wood furniture and cabinetry often contains plywood, particleboard, fiberboard or pressed wood, all known to emit an array of volatile organic compounds. You can avoid these chemicals in a few ways: Opt for solid wood furnishings; choose antique or secondhand wood furnishings, which are likely to have offgassed most of their toxins; or seal these items with AFM Safecoat’s Safe Seal, effective at sealing in formaldehyde and preventing emissions. Learn more about keeping formaldehyde out of your home in A Healthier Home: Furnishings and Décor to Reduce Indoor Air Pollution.
Sarah Lozanova is a freelance health and environmental journalist with an MBA in sustainable management. She resides with her family at Belfast Cohousing & Ecovillage in Midcoast Maine.