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Home : News : News
NEWS | Sept. 8, 2011

Tight envelope improves energy efficiency of buildings

By Robert Goetz 502nd Air Base Wing OL-B Public Affairs

Homeowners see investments in energy-efficient heating and air-conditioning systems as ways to lower their utility bills and reduce their carbon footprint, but they often overlook improvements - some of them inexpensive - that can maximize those costly expenditures, Randolph energy experts say.

Efficiency all starts with the envelope, or shell, of the building.

Bruce Dschuden, 902nd Civil Engineer Squadron resource efficiency manager, said people invest in air-conditioning units with a high seasonal energy efficiency ratio and other high-efficiency equipment, "but if the building leaks, you're defeating the purpose of the process."

"What does it matter if you put in a 15-SEER air-conditioning system in your house if a portion of that efficiently produced cool or heat escapes through the walls, around doors or windows?" Dschuden said.

Newly constructed homes typically have airtight envelopes, but the efficiency of homes built before 1980 typically offer "opportunities," he said.

Dschuden said four categories of improvements can be made to the typical home - sealing leaks and cracks, which is the lowest-cost item; adding additional insulation to attic space and exterior walls and installing a thermal barrier; replacing or upgrading windows; and creating a "cool" roof using reflective materials or coatings.

He said sealing leaks and cracks can be achieved by caulking around windows and doors, applying foam gaskets to all electric outlets and wall switches on exterior walls, using expandable foam to seal the openings where pipes and vents penetrate exterior walls and applying weather stripping to all exterior doors.

Adding insulation is more costly than sealing leaks and cracks, but utility companies often offer rebates, "which will help you buy down the cost of your efficiency improvements," Dschuden said.

Ruben Ramos, 902nd CES utilities manager, said windows can be adjusted in a variety of ways, from replacement to tinting and the use of insulating panels that fit on the inside of existing windows to create thermal barriers.

Replacing single-pane windows with high-performance low-emissivity models, which reduce the amount of heat that enters during the summer and escapes during the winter, can be costly, but rebates and tax credits are available.

"If you are planning to stay in your house and do not plan to move, this may be a good investment in efficiency to consider," Ramos said.

Thermal barriers offer a lower-cost alternative, he said. Insulating curtains and blinds are even less expensive.

Dschuden said "cool" roofs, which reflect the sun's rays, keeping the attic cooler, are possible because of technological improvements in roofing materials and the availability of ceramic and other types of coatings.

Ramos said one of the big advantages of an efficient building shell is that it's more likely to keep out the cold in the winter and heat in the summer.

"By having a tight envelope, you might be able to use a smaller-size air-conditioning unit," he said.

Dschuden said the challenges for Randolph in making its buildings more airtight are the historic nature of many of its structures and low utility rates paid by the installation, but the recent remodeling of Bldg. 901, Headquarters Air Education and Training Command Civil Engineering, provides a template.

"Improvements in the wall insulation were made by making the wall thicker on the inside of the building," he said. "This allowed for adding a layer of insulation between the existing inside wall and the newly constructed interior wall. The leaky window issue was addressed by storm-type windows on the inside, which provided about a 10-inch air gap between the two windows for insulation purposes."

Other ways Randolph buildings can be made more efficient are by weather-stripping and caulking around windows and doors and installing thermal barriers on windows, a technology that was employed in Bldg. 144, Dschuden said.

Reflective roofing products are also being evaluated, he added.

Ramos said a base energy-reduction competition during Air Force Energy Awareness Month in October will give personnel an incentive to make their buildings more efficient.

"It is anticipated that many of the leaks around windows and doors will be addressed by eager participants wanting to claim their building to be the most energy-efficient at Randolph," he said.