Technical Info

Following is the technical information for the energy efficiency testing done by the Log Homes Council of the National Association of Home Builders:


Description of Test Buildings

Six 20' wide and 20' long one room test buildings with a 7-1/2" high ceiling were constructed outdoors at the National Bureau of Standards facility located in Gaithersburg, Maryland (20 miles north of Washington, DC).

Construction Details of Walls

Building #1:  An insulated wood frame home, nominal R-12 (without mass) with 5/8" exterior wood siding, 2×4" stud wall, 3-1/2" fiberglass insulation, plastic vapor barrier, and 1/2" gypsum drywall.

Building #2:  An un-insulated wood frame home, nominal R-4 (without mass) with same detail as above, but without the fiberglass insulation.

Building #3:  An insulated masonry home, nominal R-14 (with exterior mass) with 4" brick, 4" block, 2" polystyrene insulation, plastic vapor barrier, furring strips and 1/2" gypsum drywall.

Building #4:  An un-insulated masonry home, nominal R-5 (with exterior mass) with 8" block, furring strips, vapor barrier, 1/2" gypsum drywall, and no polystyrene insulation.

Building #5:  A log home, nominal R-10 (with inherent mass) with 7" solid square wood logs with tongue and groove mating system, no additional insulation, no vapor barrier, and no interior drywall.

Building #6:  An insulated masonry home, nominal R-12 (with interior mass) with 4" brick, 3-1/2" loose fill perlite insulation, 8" block and 1/2" interior plaster walls.

Interior/Exterior Surfaces

Interior surfaces were painted off-white. Exterior surfaces of buildings 1,2 and 4 were painted approximately the same color as the exterior face brick of buildings 3 and 6.


Four double-hung, insulating glass (double pane) windows, with exterior storm windows, two in south facing wall, two in north facing wall. Total window area was 43.8 sq. ft. or 11% floor area.


One insulated metal door on east wall. Total door area was 19.5 sq. ft.

Ceiling & Roof System

Each test building contained a pitched roof with an attic space ventilated with soffit and gable vents. The ventilation opening was consistent with the HUD Minimum Property Standards. Eleven inches of fiberglass blanket insulation (R-34) was installed over the ceiling of each test building.

Floor System

The edges of the Concrete slab-on-grade floors were insulated with 1" thick polystyrene insulation at both the inner and outer surfaces of the footing.

Heating/Cooling Equipment

Each test building was equipped with a centrally located 4.1 kW electric forced air heating plant equipped with a 13,000 Btu/h split vapor-compression air conditioning system.

Technical Report Available

A complete technical presentation of this study was prepared by D.M. Burch, W.E. Remmert, D.F. Krintz, and C.S. Barnes of the National Bureau of Standards, Washington, DC, in June, 1982, and is entitled "A Field Study of the Effect on Wall Mass on the Heating and Cooling Loads of Residential Buildings." This study was presented before the "Thermal Mass Effects in Buildings" seminar held in Knoxville, Tennessee, on June 2-3, 1982, Oakridge National Laboratory, Oakridge, Tennessee.

Copies of this report and other studies are available by writing to: U.S. Department of Commerce, National Bureau of Standards, Center for Building Technology, Building 226, Room B114, Gaithersburg, MD 20899.

BSC's Participation

The log building used by the National Bureau of Standards for this energy conservation study was donated and erected by members of the Log Home Council. Since the inception of the Log Homes Council in 1977, well over a quarter of a million dollars have been spent on research and testing projects related to the log home industry.

Members of the Council have voluntarily contributed tens of thousands of hours of their time to accomplish these tasks for the benefit of the industry and the builders and owners of log homes. On January 1, 1982, the Log Homes Council affiliated with the National Association of Home Builders as part of the Building Systems Councils. In July, 1985, the Council membership expanded due to a merger with the North American Log Builders Association. All members of the Council are also individual members of the National Association of Home Builders and through their dues support the many worthwhile activities of the NAHB. The Log Homes Council is a non-profit, voluntary membership organization representing some sixty manufacturers of log homes.

A research report published by:
Log Homes Council of the National Association of Home Builders
1201 15th Street NW
Washington, DC 20005
(800) 368-5242 ext. 576
Barbara K. Martin, Executive Director

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