Written April 23, 2009 by John Hendricks, Architect AIA • Filed Under Energy Efficiency
At Hendricks Architecture, we specialize in the design of mountain style homes and cabins. We try to make these as energy efficient as possible to save homeowners on long term heating and cooling costs. We educate them on the practicalities, costs and benefits of energy efficiency throughout the design process.
According to Residential Design & Build Magazine, 2008′s most asked for feature in a house was energy efficiency. Currently, Americans use approximately 25% of the world’s energy, and roughly 21% of this is consumed in our homes. Whether we knew it or not, energy efficiency has always been at the forefront of the green and sustainable movements, and is an important part of the LEED process. As architects, we are committed to doing our part to promote and implement energy efficiency in the homes we design.
There are numerous ways that energy efficiency measures can be incorporated into a new or existing home, and often these measures will also enhance the appearance, functionality, and resale value of a home. Some of the strategies are listed below. This is not an exhaustive list but an overview of readily available measures that we can use to enhance the energy efficiency of your home. Many people think adding energy saving measures to a home will initially cost more, and in many cases this is true. In some cases, just making the appropriate design decisions can save energy and not cost any more. It is important to measure additional first costs against long term savings in energy costs, and consider that no one is predicting cheaper energy costs in the future.
DESIGN AND EMBODIED ENERGY
Probably the most fundamental step in creating an energy saving home is to design it for space and functional efficiency. Minimizing non usable space (hallways are one example) and creating spaces that can serve more than one function like Guest/ Exercise or Laundry/ Mud rooms can reduce the overall building area that needs to be heated or cooled. Open plans tend to feel bigger than they are, and save space that would have to be taken up by walls, doors, etc. A good reference for these strategies is Sara Susanka’s “The Not So Big House”.
It is also worth considering the energy use that goes into everything used in the construction of a home. Materials require energy to manufacture, package, store, deliver, etc. Almost every decision made during the design process has some impact on the energy use of your home.
SITING, ORIENTATION, & MASSING
A home should be located on its site to allow access to the sun, protection from prevailing winds, minimize site disturbance, and use natural elements to provide shading and shelter. Stacking a building’s spaces whenever possible reduces the footprint and the surface area through which heat can escape. Below grade spaces benefit from the relatively constant 50 degree temperature of the earth, reducing or eliminating cooling cost during the summer.
WINDOW DESIGN AND DAYLIGHTING
Windows serve several functions in a well designed home. Besides framing views and providing a connection with the outdoors, windows allow natural light to enter, provide free ventilation, insulate against heat loss, and help heat indoor spaces when exposed to direct sunlight. Windows are a crucial element in a home’s design and function, and should be carefully sized, located and detailed. Windows are the weak link in a buildings thermal envelope, so it is important to select quality windows with a low U value.
Use clerestory windows to help bring in light
Placing windows to provide ample daylighting will save on lighting costs and the number of fixtures needed. Locating windows to take advantage of solar exposure will reduce heating costs and HVAC equipment required. Direct sunlight does not make for good daylighting, primarily because of glare. The best daylighting utilizes reflected or indirect light from transom, clerestory, or north facing windows. Skylights and solar tubes can be used to provide daylight to interior rooms.
ROOFS, OVERHANGS, AND SHADING
A roof should be designed to shade windows that are exposed to direct sunlight in the summer months. Because the sun is lower in the sky in the winter, roof overhangs should be sized to allow direct sunlight to enter the windows during winter months, maximizing solar heat gain to offset heating costs. On building facades where overhangs are not able to provide shade (gables, etc.), pergolas, awnings, or other shading devices should be considered. Devices that shade lower windows and act as a light shelf for upper windows are particularly effective.
Providing broad overhangs reduces summer heat gain, yet brings in the winter sun.
A house’s roofing material also affects energy consumption. Lighter colored or reflective roofing reduces heat gain, and a well ventilated or cold roof will help keep attic spaces cooler, reducing cooling costs.
INSULATION AND THERMAL MASS
It is well know that the better insulated a house is, the more energy efficient it will be. Building codes dictate minimum insulation values for all new construction. Any insulation value beyond the minimum required will be money well spent, especially in roof/ attic spaces where most heat loss occurs. Several insulation products are available that can provide enhanced R-values and provide a tighter building envelope. It is worth considering spray applied foam insulation, blow in blanket, or rigid sheet insulation rather than conventional fiberglass batts. Snow actually adds insulation as well, though is not recognized by building departments.
Spray applied foam insulation.
SIPS panels are also an energy saving system that can be used in lieu of conventional stud framing. In stud/ cavity wall systems, thermal bridging occurs that allows heat to pass through studs that contact exterior materials. SIPS panels have a solid sheet of rigid insulation sandwiched between plywood sheets, and no thermal bridging occurs. They are commonly used on roofs and for wall systems in post and beam construction.
Thermal mass is the ability of a material to absorb and store heat that is radiated slowly. Materials like concrete, stone, brick, and water all have a high thermal mass. A well placed thermal mass will absorb solar radiation or heat from a fire, and radiate it slowly to keep a space warm overnight or for several days. Concrete or gypcrete floors can be heated by solar or gas fired hydronic systems to provide an even heat that feels warmer than heated air at the same temperature.
Operable windows, ceiling fans, and design that utilizes “stack effect” can all be used to passively cool a space, saving energy that would be required by A/C systems. Ceiling fans can be used in rooms with vaulted ceilings to circulate heated air that collects in the peak of the ceiling. Night venting (operating outside air ventilation systems overnight) can also be used to cool a space without using excess energy. Operable windows in bathrooms will also save energy by eliminating the need for exhaust fans when weather permits.
HVAC EQUIPMENT AND APPLIANCES
Heating and cooling equipment are available in a wide range of efficiencies and types. Choosing high efficiency equipment that is Energy Star certified, using insulated duct systems, programmable thermostats, and creating multiple zones for heating & cooling are simple energy saving strategies.
If you live in an area where gas is not available, heat pumps are much more efficient than electric resistance heating. Radiant heating systems with a high efficiency boiler are generally more comfortable and efficient than forced air systems, but are best used in homes that are regularly occupied and should be supplemented with ventilation systems. If a home is used only occasionally, radiant heat may not be the best choice from a cost standpoint, as it takes much longer to raise the temperature of a home to comfortable levels. If you are considering air conditioning with a radiant system, remember that you will be installing two systems since A/C requires a network of ducts to distribute cooled air.
Appliances (especially refrigerators, freezers, and ice makers) consume significant energy. Buying Energy Star appliances are a good way to increase the energy efficiency of your home at minimal extra cost.
We would love to talk to you about ways to increase the energy efficiency of your current home, or to help you design a new home that utilizes these energy saving strategies.
Tom Russell, LEED AP, Project Manager
Hendricks Architecture, mountain architects in Sandpoint, Idaho.
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