The nippy temperatures we've been having lately have set most of us to casting critical eyes on our homes' insulation. And well we might--heating by gas ain't cheap and by electricity is even more un-cheap.
When we do that, we are usually thinking of what is known as the "R-value" of the insulation. In the case of most houses, site-built or factory-built, that is the determining factor, but in the whole field of housing there is another factor of equal, some say greater, importance that applies to certain types of dwelling.
The R-value measures the resistance of the insulating material to the passage of heat through it. It's a convenient tool; for instance, a certain type of insulation--say a four-inch batt of a certain material--might be rated R-11.
The other factor is known as "thermal mass." Have you ever been in a really old Spanish or Mexican building built of stone or adobe? If you have, you've noticed how it remains cool even on a hot Southern California day because you're surrounded by a foot and a half or two feet of stone or brick.
The masonry walls, cool in the morning, soak up the sun's heat throughout the day and by late evening are "full of heat" (scientists and engineers will wince at that phrase but everyone will understand what's meant). By the time the outside air has cooled, the walls are exuding the heat stored within them into the building; they are pretty well cooled by morning, so the result is a cool interior by day and a warm one by night.
There is another material that does the same thing and is probably better adapted to residential construction, and here we turn to feisty Doris Muir, publisher of the quarterly Log Home Guide, who is not displeased by being called an industry gadfly. She contends the R-value concept is widely misused while there is a sad lack of understanding of thermal mass.
"The American Society of Heating, Refrigerating and Air-conditioning Engineers (ASHRAE) invented R-value to estimate sizes of cooling and heating equipment needed in buildings," she told participants and visitors to the National Assn. of Home Builders' January show in Dallas.
"A steady-state measure of materials, its calculation ignores climatic changes. Thus, fiberglass with a 14 to 15 R-value rates better than an eight-inch-diameter log with an 11 to 12 R-value, even though moisture, dust, saturation, compaction and cold bridges caused by studs can reduce insulation value of fiberglass as much as 50%," she said.
She cited a 28-week test by the National Bureau of Standards of six houses, identically sized but built of different materials. The one log house used significantly less energy throughout the test; as an example, during the summer hot period it used 24% less cooling energy than a conventional wood-frame house with standard insulation. The difference, lay in the stabilizing effect of the logs' thermal mass.
Other advantages Muir claims for log houses include health. Commenting "Conventional homes might be more of a toxic waste dump than Love Canal or the chemical dump nearby," she mentioned that many construction materials commonly used in conventional housing--some plastics, certain types of plywood and others--contain cancer-causing agents.
Also, indoor pollution from carbon monoxide and nitrogen dioxide, both produced by fuel combustion, have been named as possible hazards in tightly insulated houses without adequate ventilation.
She also contends that log houses are "environmentally responsible in a global way" since timber comes from a renewable source--trees, and does not drain the nation's energy and mineral resources.
Muir added, "Buyers often wade through endless red tape and wait months simply to get a building permit for a log home. The Veterans Administration, the Farmers Home Administration and private lenders have refused loans because some officials misguidedly say log homes don't meet federal standards for energy efficiency.
"Log-home manufacturers and their customers have had to spend hundreds, even thousands of dollars to have their plans approved--unchanged--by an architect or engineer to get building permits or financing. This is harassment.
"If government regulations and moss-covered officials can be shamed into 21st-Century realism," she concluded, "log homes will represent 10% of new housing starts by 1990 and 25% by AD 2000."
Information is available from the Log Home Guide Information Center (Muir is founding director) at Exit 447, Interstate 40, Hartford, Tenn. 37753.