Masonry Magazine January 1977 Page. 4
BEFORE WE COULD CLAIM THAT
MASONRY CONSERVES MORE ENERGY THAN
ANY OTHER BUILDING MATERIAL, WE
HAD TO PROVE IT.
The gap between knowledge and documentation had to be closed. And building designers and others had to be provided with a way to easily use the new proof.
Not easy tasks. But critical ones in an era when the energy performance of buildings is a matter of the highest priority.
For thousands of years people have known that buildings with masonry walls were more easily kept warm in winter and remained cooler in the summer. The reason was obvious: masonry walls both stored and slowed down the passage of heat, making interior climates more stable. A simple, observable fact. But no longer sufficient.
Designers and owners needed to know how much better masonry conserved energy than did competitive materials and systems. And they needed a simple way to calculate the differential.
Only then could masonry's superior thermal performance be reliably taken into account in meeting energy conservation goals and requirements. Only then could heating-cooling equipment be more accurately sized to save money on both initial and operating costs.
Disdaining "claims" without documentation, the masonry industry began a broad research project to quantify the relationship of the mass or weight of masonry walls to the transmission of energy. The masonry industry engaged a highly qualified firm of consulting engineers (Hankins & Anderson, Inc.) to conduct the study. Ten different walls ranging in weight or mass from four pounds (19.5kg/m²) to 116 pounds (567.5kg/m²) per square foot were specified for analysis in 10 widely varying climatic conditions. And in eight solar orientations.
Researchers used a special computer program built around the "response factor" method adopted by the National Bureau of Standards Load Program along with other computer programs. They analyzed U.S. Weather Bureau data and considered the effects of many variables, including the weight of walls, on thermal performance. Results of the computer analysis showed:
Traditional "U" value measurements of the thermal performance of walls are inadequate. They are based on the incorrect assumption that energy transmission occurs in a "steady state". Contrarily, the process is dynamic and varies greatly in relation to many factors, one being the weight of walls.
Steady-state "U" value measurements therefore may often result in the over-sizing of heating equipment for buildings with masonry walls (and the undersizing of such equipment for buildings with lightweight walls).
The difference between steady-state and dynamic measurements can be accounted for by the use of a correction factor-the "M" factor-in making heat gain and loss calculations.
The consulting engineers' report and data consisted of 460,800 numbers on 1,200 pages of computer print-out. Important as this proof of the superior thermal performance of masonry walls was, it was not enough.
The task of developing a tool for the easy use of the findings remained. Masonry industry engineers began studying and correlating the data to provide a simple correction factor for dynamic analysis.
The result: An easy-to-use "M" factor graph or curve.
Only two numbers are required in order to use the graph: the number of "degree days" in the locale (obtainable from the U.S. Weather Bureau) and the weight per square foot of the wall. The graph can then indicate the appropriate "M" factor modifier, or correction factor, to be applied to steady-state "U" value measurements. A more accurate measurement of the dynamic thermal performance of walls results.
The graph shows that in all cases, masonry walls perform better than lighter weight walls with the same "U" value rating. The heavier the wall, the greater the differential.
Results of the masonry industry study and the "M" factor graph have been submitted to the Conference of American Building Officials (CABO). And CABO has agreed that the effect of mass should be considered in making heat gain/loss calculations.
The "M" factor study findings are contained in a new Masonry Industry Committee publication, Mass, Masonry, Energy. With the findings are graphs and charts, and an explanation of how to use them. An all-in-one booklet-everything you need to know in order to take advantage of the superior thermal performance of masonry walls.
We're proud of the new proof that masonry walls save more energy than walls of competitive materials with the same "U" values.
We're proud of the fact that the masonry industry decided to produce this proof, rather than simply make a claim.
But our pride isn't important to you. What matters to you is that we've made it possible to design, build and operate buildings that will save energy and money.
We've got the proof. Just write for it at the address below:
IMI INTERNATIONAL MASONRY INSTITUTE
Suite 1001, 823 15th St., N.W, Washington, D.C. 20005, (202)783-3908
The Mason Contractors and Bricklayers Union of the USA & Canala.