This article was originally published in the May/June 1999 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.
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Home Energy Magazine Online May/June 1999
Hot Topics Covered at Thermal VII Conference
Thermal Performance of the Exterior Envelopes of Buildings is unique in that it gives equal recognition to the principles and the practical applications of building science research. All of the presentations at this conference, in fact, are assigned to one of two parallel tracks--Principles or Practices.
The conference is sponsored by the Department of Energy and has been held on a regular basis since 1978. This year, the seventh meeting of the conference (Thermal VII) was attended by a broad range of researchers and practitioners alike. Five special-topic workshops were held at the beginning and end of the conference, which took place in Clearwater Beach, Florida. The opening workshops included demonstrations of software tools for simulation, digital hardware tools for diagnostics, a discussion of probable R-values for a variety of alternative wall construction materials, and a discussion of ventilation techniques. The closing workshop asked us to suggest where future research and practice should lead. The complete papers are published by the American Society of Heating, Refrigeration, and Air conditioning Engineers (ASHRAE).Presentation Pick Selecting just one paper as a representation of the conference does injustice to the other presentations. But there was one paper in particular that I feel everyone will want to know about--not only because it could affect our health, but also because it provides evidence that we should rethink the way we build the part of the house envelope that is in common with attached garages. Carbon Monoxide Exposure from a Vehicle in a Garage, written by Tom Greiner and Charles V. Schwab, was presented by Greiner at the conference. It demonstrates how incorrect our assumptions about safe practices can be. It also illustrates the interrelationship of practices with principles.
In this case, on a cold winter day in the Midwest, a homeowner opened the door of his attached garage and started his car. The car, facing inward, was allowed to warm up for a few minutes before being driven. The owner backed out, closed the garage door, and drove away. Several minutes later, carbon monoxide detectors throughout the house went off. Although technicians from the utility company and the heating contractor verified that the house had high concentrations of CO, they could not identify the cause. The natural-gas furnace and water heater were not backdrafting, and there was greater pressure in the mechanical area than in the chimney.
Greiner and Schwab discovered that stack effect in the house was causing enough negative pressure in the basement to draw air in from the garage through the adjacent or common wall/floor joints. The forced-air furnace then circulated the contaminated air throughout the house.
Even though the catalytic converter was working properly, Greiner and Schwab measured the car's tailpipe CO concentration at more than 87,000 parts per million (ppm) on cold start-up. This amount dropped to half within five minutes, and when the car was fully warmed up, the CO level was measured at only 100 ppm. They also discovered that even a fully open garage door does not guarantee adequate ventilation of the garage.
Greiner and Schwab's observations prompt several questions. On the practical side: What steps should we take to ensure adequate ventilation in attached garages? Should we treat house/garage common walls as if they were outside walls, and build them with the same--or even more--care, in order to keep harmful gases out of our homes? Should we depressurize attached garages with respect to the home?
There are also questions with regard to principles: What kind of ventilation does occur in a room with one open side? Does suddenly removing the air/thermal barrier on one wall in cold weather (as would be done by opening the garage door) start a powerful convective loop, with cold air washing across the floor toward the interior?Talk of Tools Another topic in wide discussion at the conference was the development and use of tools, which are becoming ever more sophisticated.
For example, blower doors were only an idea two decades ago. Today they are not just basic to performance testing, but are reconfigured to determine duct tightness, and are being refined to compensate instantaneously for fluctuating wind pressures. Infrared (IR) thermography is not just showing us where areas are colder, but is telling us how cold. Sophisticated software decreases the time it takes to convert IR data collection and analysis into information transfer. Golfball-sized data loggers accumulate information in our absence, while house-sized test chambers give data on whole wall performance in exact detail. Simulation programs are relentlessly refined to address and integrate more and more variables.
Such tools have become indispensable to building scientists and practitioners alike; virtually every paper presented in both the Principles and Practices tracks depended on using at least one of the tools mentioned.Scientists Can Learn Sharing newly discovered scientific information allows us to begin putting principles into practice. But what can scientists learn from practitioners? Many things.
For instance, How do insulation materials work in real life? How do they work in windy conditions? Can you easily incorporate the principle and make it affordable? The ultimate filter of an idea is the consumer. If the consumer does not think it's worth the cost, the idea goes nowhere.
The cyclical nature of principles and practices learning from each other was one of the key points of Thermal VII. It'll be hard to wait for Thermal VIII to continue this examination.
--Don OttoDon Otto is owner of DPO Construction in Iowa City, Iowa, and has been building energy-efficient homes for more than 20 years.
For a copy of Conference Proceedings, Thermal Performance of the Exterior Envelopes of Buildings VII, contact:
American Society of Heating, Refrigeration, and Air-conditioning Engineers, 1791 Tullie Circle NE, Atlanta, GA 30329. Tel:(800)527-4723; Web site: www.ashrae.org.
For information on the next conference, contact: Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6070. Web site: www.ornl.gov.
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