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Energy Efficiency: Inside and Out


Many homebuilders - and an increasing number of homeowners - have come to view the whole house as an integrated system. The Partnership for Advancing Technology in Housing (PATH) applies this concept to home design, construction, and retrofitting by supplying research-based guidance organized around five action principles:

  • Resource and waste management;
  • Energy system integration;
  • Resource-efficient plumbing;
  • Good indoor air quality; and
  • Low-impact development.

On their own, many of the available technologies consistent with these principles improve home energy efficiency. How these technologies can best work together to achieve ultimate cost savings will require continued research and refinement, even as they are implemented. Below, you'll find some of the methods, procedures, and equipment that enable the whole-house approach while maximizing energy and resource efficiency.

Managing Resources and Waste

Resource and waste management involves using durable building materials and construction methods that withstand the elements, minimize labor requirements, and reduce the amount of unused materials. Energy-efficient technologies that advance this principle with demonstrated results include insulating concrete forms (ICFs) and structural insulated panels (SIPS).


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ICFs are foam forms for concrete that remain in place after the concrete is poured, providing a highly insulated wall that possesses great strength. The completed ICF wall consists of a 4- to 6-inch reinforced concrete core with about 2 inches of foam insulation on each side. The result is a solid concrete exterior wall that resists energy loss, drafts, and noise. Use of such wall systems may also enable reductions in the capacity of the heating and air conditioning systems because the homes are more heavily insulated and air tight.




SIPs are engineered panels that offer structural framing, insulation, and exterior sheathing in a solid, one-piece component. The SIP, used for walls and roofs, commonly sandwiches a thick layer of foam between two layers of oriented strand board, plywood, or fiber-cement board. SIPS are precisely cut in standard sizes or to measure in the factory, thus reducing manufacturing waste. PATH field evaluations of SIPs document increased energy efficiency achieved through optimized thermal performance; indeed, utility bills were cut in half at one development in Dallas, Texas and reduced to $48 per month in a home in Minneapolis, Minnesota. In both evaluations, Home Energy Rating System scores were strikingly better than comparable light frame homes.

Integrating Energy Systems

Well-designed buildings are correctly oriented relative to the sun's path, insulated, day- and electrically lit, and have properly sized HVAC systems. All of these factors help reduce overall energy demand while improving comfort and durability. Among the technologies that are consistent with these principles, PATH suggests high-efficiency equipment and tight ductwork installed within conditioned space, passive and active solar design to maximize the sun's energy, solar water heaters, photovoltaic roofing panels, ENERGY STAR-qualified lighting, high-performance windows, and programmable thermostats. Three of these approaches are discussed below.


High-performance windows


Many high-performance window features improve home energy efficiency. Low-e (emissivity) coatings reduce energy loss, saving $103 in energy costs for a test home in Boston, Massachusetts. Solar control windows allow more natural light to enter the home, reducing the need for artificial lighting, and helping to reduce heating and cooling costs - up to $65 a year in one test conducted in Tucson, Arizona.


Programmable thermostats


Programmable thermostats allow the homeowner to set HVAC systems to turn on and off automatically, and to adjust temperature settings to suit the user's schedule. According to ENERGY STAR, these devices can save as much as $180 a year. A 2001 PATH field evaluation conducted in an energy-retrofitted home in Nevada demonstrated that simply adjusting the temperature setting for an automatic winter nighttime setback saved $67 annually.


Compact fluorescent lights (CFLs)


The U.S. Department of Energy (DOE) says that lighting accounts for nearly 15 percent of a household's electricity consumption. CFLs use 50 to 80 percent less energy than traditional incandescent bulbs and last much longer. A CFL lasts from 6,000 to 10,000 hours, compared with 750 to 2,500 hours for an average incandescent bulb. An 18-watt CFL used in place of a 75-watt incandescent bulb saves about 570 kilowatthours (kWh) over its lifetime; at 8 cents per kWh, that's equivalent to a $45 lifetime savings from one bulb.

Incorporating Resource-Efficient Plumbing

Resource-efficient plumbing technologies are easy to implement, meet current usage expectations, and reduce water consumption, which conserves both energy and resources. PATH-identified technologies that demonstrate this principle are cross-linked polyethylene (PEX) piping and tankless water heaters.


PEX piping


Traditional copper piping can be expensive, corrodes over time, and, because it's metallic, loses heat. An alternative to copper piping is cross-linked polyethylene or PEX - a high-temperature, flexible plastic pipe with a control center (manifold) requiring minimal fittings and no tees or elbows. In field evaluations, PEX has cost less to implement than copper piping, mainly because of reduced labor costs. Additionally, in a field evaluation in Lincoln, Nebraska, a PEX system delivered 100°F water to the furthest fixture in 15 seconds (compared with 32 seconds for a copper system), significantly reducing both water and energy consumption.


Tankless water heaters


Water heating accounts for approximately 14 percent of a household's average energy budget. Tankless water heaters eliminate the loss of energy from warmed water sitting in a tank. PATH field evaluations show that tankless heaters, which supply hot water on demand, shrink the energy consumption of a home's water heater by 10 to 20 percent. Builders and homeowners considering adoption of this technology should check to ensure compatibility of products with the existing power supply.

Ensuring Good Indoor Air Quality

Careful selection of materials and proper ventilation are essential to healthy interior environments. With the increased focus on energy efficiency over the past decade, less fresh air and fewer pollutants enter the typical home and fewer air contaminants leave, resulting in poor air quality. Properly sized HVAC systems and whole-house strategies are needed to ensure that adequate filtration, ventilation, and air exchange exist inside the home. To be efficient, the HVAC system's design must fit the home, for which factors of heat loss, air infiltration through building openings, and heat gain are considered.


PATH explains that, in this case, efficiency refers to longer operating periods that reduce both the number of on and off cycles and the demand on energy and equipment. PATH finds that ENERGY STAR-qualified HVAC equipment will further increase energy efficiency by 20 percent.

Minimizing the Impact of Development

Low-impact development reduces erosion and disturbance on the building site and preserves natural habitats as much as possible. Homeowners can advance the principles of low-impact development while reducing energy consumption by using trees and shrubs to provide shade and windbreaks for the home. According to DOE, shade trees can lower air temperatures by 9°F and improve the efficiency of air conditioners by as much as 10 percent. Trees and shrubbery also serve as windbreaks, lower wind chill, and create insulating air space near the home.


ToolBase Services says that the typical household spends $1,000 to $1,500 each year on utilities. When the principles and technologies described above are effectively applied in conjunction with other energy conservation practices, the result will not be additive savings. However, the whole-house approach can make a significant difference in what consumers get for their energy dollar and can help builders sell more homes in sluggish or otherwise competitive housing markets. ENERGY STAR-qualified new homes are already 20 to 30 percent more efficient than other homes, and since January 3, 2007, federally built residential buildings have a 30-percent energy consumption reduction standard that needs to be met.


Information about these principles and technologies is derived from PATH Guide to Green Building, ToolBase Services, DOE, and ENERGY STAR.


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Energy Efficiency: Inside and Out:  Created on October 12th, 2008.  Last Modified on May 15th, 2013


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