In certain climates, buildings containing massive building envelopes-such as concrete, earth, insulating concrete forms (ICFs), and solid wood (log) - can be more energy efficient than similar conventional wood-framed houses. This was well known by Native American Tribes who commonly used adobe structures in the past. Also, European residential buildings have been built for centuries using massive wall technologies. Several research studies performed in the last decade or so have compared energy performance of buildings containing massive walls with similar buildings constructed using lightweight wall technologies [Burch 1984a, b, c, Robertson, Christian -1985, Christian 1983, 84, 85]. These experiments required construction of identical houses having the same floor plane, shape, orientation, HVAC equipment, etc... One of the most difficult conditions for such comparisons was the requirement of identical R-values for all building envelope components in all compared buildings. Many experimental studies did not fulfill this requirement making necessary the deployment of whole building energy simulation models. Investigation of differences in energy consumption between massive and lightweight buildings can help in the analysis for potential benefits of using massive building envelope components. Two examples of energy consumption comparisons are presented below for Minneapolis, Minnesota (heating climate) and Bakersfield, California (cooling climate).
Figure 6. A portion of the whole building energy which can be saved in Minneapolis, Minnesota by replacement of conventional wood framed walls by massive wall technologies.
Annual whole building energy savings, attainable when lightweight walls are replaced by massive walls of the same R-value, were calculated for a 143 m2 (1540-ft2 ) one-story ranch house located in Minneapolis, Minnesota. These energy savings were defined as a difference between energies required to heat and cool the house containing massive walls v.s. the same house constructed with wood frame technology. Energy savings for this house were estimated between 3 and 7 MBtu/year for R-1.8 to 4.4 m2K/W (10 to 25 hft2F/Btu) walls. This is approximately 1900-4400 Btu/year per ft2 of floor area of the residential building.
Figure 6 depicts the percentage annual energy savings for a massive house located in Minneapolis (heating climate). Data presented in Figure 6 shows that it is possible for buildings with high R-value walls to save up to 8% of annual energy consumption when traditional wood stud walls are replaced by massive wall systems. It is interesting to note that low R-value massive walls may actually increase energy consumption in this location.
Figure 7 shows similar energy savings comparisons as shown in Figure 6 but for buildings located in Bakersfield, California (cooling climate). Data presented in Figure 7 demonstrates that during the design process, an architect may save 5 to 18% of future whole building energy use simply by replacing traditional light-weight walls with massive systems.
Figure 7. A portion of the whole building energy which can be saved in Bakersfield, California by replacement of conventional wood framed walls by massive wall technologies.
Insulated Concrete Forms (ICFs) have been gaining acceptance by U. S. builders during the last decade. These massive building envelope technologies are using foam forms which are filled with concrete at the building site. Since most of these systems have a similar configuration of materials, foam/concrete/foam, it was possible to develop a single chart which shows approximate energy savings available when conventional wood framed walls are replaced by ICF walls in residential buildings. Figure 8 depicts the potential energy savings available in ten U. S. locations for ICF wall systems. This figure represents combined data from all three simulated houses. It shows the average whole building energy savings potential in houses with 74 - 279 m2 (800-3000 ft2 ) of floor area. For individual building size and shape, this data may vary within "2%. Assuming that average ICF wall R-value is between R- 2.6 and 3.5 m2K/W (15 and 20 hft2F/Btu), average potential whole building energy savings (ICF house v.s. conventional wood-framed house) for all U.S. locations are between 6 and 8%.
Figure 8. Potential energy savings available in ten U. S. locations for ICF wall systems.
© Oak Ridge National Labs and Polish Academy of Sciences
Updated August 13, 2001 by Diane McKnight