Passive Homes: Leaders in Energy Efficiency
Energy efficiency has continued to grow in importance in home design and renovation in recent years. As energy bills climb and awareness of eco-responsibility grows, finding eco-friendly options for the home has become a priority. The U.S. Department of Energy (DOE) reports that the heating and cooling of a home will cost more — and use more energy — than any other system in a home, averaging almost 54 percent of a homeowner’s utility bill. Just replacing old heating and cooling equipment with equipment that has earned an ENERGY STAR® rating can lower a homeowner’s annual energy bill by more than $115. Those simple steps can have an immediate impact, however, one design movement takes energy efficiency to an entirely different level: passive solar design. Passive houses minimize energy loss and use strategically placed natural elements, including the sun, to heat and cool the house so that minimal heating is required. This type of design can save up to 90 percent of space heating costs, according to Passive House Institute US.
What is Passive Solar Design?
Passive solar design relies on insulation, solar energy and minimal electrical equipment to decrease energy loss. The DOE defines a passive solar home as “a comfortable home that gets at least part of its heating, cooling, and lighting energy from the sun.” This approach is effective because it first reduces heating and cooling loads through energy-efficiency strategies and then meets those reduced loads in whole or part with solar energy,” according to the DOE.
It is passive because it avoids active energy consumption, instead drawing upon natural sources that are already within the home. Passive homes have several key features that make the system possible.
Windows in the living area must face as close to true south as possible — within 30 degrees. During the winter, they cannot be shaded by trees, overhangs or blinds from the hours of 9 a.m. to 3 p.m. so that daylight can enter the windows and heat the home. Bedroom windows should be oriented toward true north. Extreme climates — both hot and cold — have slightly different specifications.
The key is ensuring the south side of your house will have an unobstructed “view” of the sun. “Consider possible future uses of the land to the south of your site — small trees become tall trees, and a future multi-story building can block your home’s access to the sun. In some areas, zoning or other land use regulations protect landowners’ solar access. If solar access isn’t protected in your region, look for a lot that is deep from north to south and place the house on the north end of the lot,” cautions the DOE.
An overhang — or control — must jut out over the windows. The sun is positioned high in the summer, and the overhang will block the light from entering the window during peak hours, keeping the home cool. The sun hangs low in the winter, and will not be blocked by the overhang so that the house will get as much heat as possible. Controls can also be blinds or awnings. Click here for an graphic example from the DOE.
Thermal Mass and Absorbers
Thermal mass refers to materials that absorb energy from the sun, including stone, brick, concrete and tile. When these materials are not exterior, they are referred to as thermal mass. Exterior products are considered absorbers. They soak up the energy from the sun, retain it and distribute it within the home.
“Knowing about thermal storage capacity of certain materials and their ‘passive’ effects on the indoor temperature of a home, the architect/designer can plan for enough thermal storage mass in a house by specifying tile floors, finished concrete slabs, concrete or granite countertops, stone fireplace surrounds, adobe walls or earthen plaster,” reports Passive House Institute US.
The energy collected from thermal mass and absorbers is stored and distributed throughout the house via conduction, convection, and radiation.
Conduction: Conduction occurs when heat moves between objects that are in direct contact. For example, you experience conduction when you touch the handle on a pan and feel warmth.
Convection: Heat is moved through the air or in water. The warmth rises, cools in the air, and sinks back down to the heat source, where it warms again to continue the cycle. Some passive homes use fans and ducts to promote convection.
Radiation: In-floor heating systems such as those sold by WarmlyYours Radiant Heating use this principle. Heat is transferred off of objects within the home. You feel this when you stand next to a hot stove or by a window where sun is streaming in. With the WarmlyYours LAVA® radiant heating panels, nearly 100 percent of the panel’s heat is transferred into the room with minimal loss.
Minimal Electricity Consumption
Between the windows and energy collectors, passive homes don't require much extra heat. People inside the house also generate warmth. However, some homes still require some extra heating in cold weather. Radiant heating panels are a good option to quickly improve the comfort level in individual rooms. Because radiant panels have the quickest response time of any heating technology and offer individual control for each room, they allow homeowners to adjust temperature settings and be comfortable very quickly in a room compared to other methods, according the DOE.
Slab heating is another option for additional heat. It uses the thermal mass of a concrete floor to absorb the heat generated by the cable, enabling it to gently distribute heat and maintain warmth in the room even after the system is turned off.
There are many contractors and designers that specialize in creating passive houses. You can start your search here.
At WarmlyYours, we are proud to offer a heating technology that can support passive homes and help homeowners find ways to reduce their energy use. If you are using WarmlyYours products in any special energy efficient installation, we’d love to hear about it. Share your ideas with us on the WarmlyYours Facebook page or tweet us at @WarmlyYours.
Whether you are adding passive design and energy-efficient appliances to your home, reusing and recycling items, or participating in a local Earth Day cleanup event, you can do your part to help the environment. WarmlyYours is always looking for new ways to go green and do our part to care for the world we live in. Take some time today to discover changes you can make--large or small--to do your part to make the world a better place.
Happy Earth Day!