House Doc Redux

Pat Dundon
The Insulation Man
Windsor, New York

House Doctor John Tooley responds:

Spray urethane might work to insulate and even seal the ducts. However, the National Fire Protection Association limits duct sealants to class one sealers, and urethane might be outside these limits. The next problem is that the ground temperature in the crawlspace can cause the urethane skin to fall to a temperature below dew point, so that condensation will form on its surfaces. Moisture in the air of the crawlspace must be controlled, and air-transported moisture from outdoors and from the ground and foundation walls must be stopped. This can be accomplished by air sealing and proper installation of a vapor retarder on the ground and foundation walls, and in some cases, by conditioning the crawlspace. Don't forget to ensure proper drainage and get the water from the roof well away from the foundation.

Objections to Gas Retrofits

I object to a number of aspects of the article "Retrofitting Electrically Heated Multifamily Buildings" (Jan/Feb '00, p. 18):

1. The article was ostensibly about "energy savings"--a phrase that was used repeatedly. In fact, it was primarily about cost savings. The annualized gas usages shown in Table 1, when converted to kWh, are 24% higher in each of the housing type examples. Thus, more energy is being used in order to compensate for flue losses, and the term "energy savings" is inappropriate.
2. The author recommends bulk gas metering, to reduce both the installation costs and the ongoing monthly base charges. This goes against the very basic tenet of all demand-side management (DSM) practitioners: namely, that individual metering is necessary to ensure responsible consumption. Bulk metering and/or flat rates encourage waste--ask any water or irrigation district trying to curtail usage without meters.
3. The oversizing of the gas-fired replacement units, due to a lack of smaller sizes, disturbs me. It is poor practice, at best, and endangers the occupants, at worst. In any case, the annualized fuel utilization efficiency (AFUE) ratings of 81% are probably invalidated by the improper application and the inevitable short-cycling.
4. I suspect the annualized gas usage figures shown in Table 1 were converted by calculation and not actually metered after installation. Since the occupants were paying the high electrical rate of 11¢/kWh beforehand, they would have tempered their usage accordingly. Conversely, once the gas-fired heaters were installed, given the much lower gas rate, it would be expected that the occupants would use their space heating more generously. This basic economic law, called "price elasticity", was confirmed by a monitoring study of 200 new homes constructed in the early '90s in British Columbia. After all house sizing, location, and occupancy factors were normalized, it was found that the gas-heated homes used, on average, one-third more energy compared to the all-electric homes. Although the natural gas prices were 40% lower than the electric rates, the average home saved only 15% of the utility costs. Finally, I note that natural gas prices within our province have risen by a total of 29.5% over the past calendar year. Similar increases elsewhere in North America would reduce the cost savings considerably, and no doubt increase the payback period, making these conversions less attractive.

Keith A. Veerman, Engineer
West Kootenay Power Limited
Trail, British Columbia, Canada

Author Ian Shapiro responds:

Regarding the term "energy savings": If you account for the conversion efficiency of electric power plants, the majority of which use fossil fuels, then you are indeed talking about energy savings.

The issue of master versus individual metering has pros and cons on both sides. I know many DSM practitioners who do not believe that the savings from individual metering outweigh the added meter charge. Utilities obviously like individual meters, as they represent an income stream.

Oversizing of the gas unit is not desirable, as I pointed out in the article, but it is substantially mitigated by the modulating capacity of the heaters. Smaller heaters, which modulate down even further, are now available, making this a nonissue.

Finally, Mr. Veerman suspects that the annualized gas usage data were converted by calculations and not actually metered. He is wrong. All of the test calculations were metered, with stand-alone gas meters serving only the heating unit, and so providing an extremely accurate postinstallation measurement of gas consumption.

f Mr. Veerman, electric utilities, and others sound defensive at the prospect of converting space heating from electric to gas, they should be. The widespread installation of electric heat, especially in low-income apartments--given the typically imbalanced cost between electricity and gas--is sad. Our study was intended to be objective, as we clearly tried to lay out both the pros and the cons of these gas heaters. In the face of electric utility public relations attacks, I begin to feel a little less objective.

Readers may be interested in an update following our yearlong investigation, now that our results are all in. A survey of tenants found that comfort with the new heaters is generally perceived to be good. Five out of six tenants surveyed found that "the new gas heaters provide good comfort." The one person who answered "no" to the question about comfort stated, "The living room gets rather chilled prior to the heater kicking on during particularly cold days." All six tenants found the new gas heaters to be quiet. The building owner proceeded to install more than 400 heaters in the entire complex, including a high-rise building. Installation costs for the high-rise building were found to be higher than those for the low-rise building. This was due to the need for core drilling of concrete floors and a lift to install vents on upper floors, as well as other factors. For high-rise buildings, the installation cost per heater is in the $2,400-$2,800 range.

It was found that gas leak detection during construction is important, in order to avoid finding gas leaks after gas piping has been covered. In the installation of more than 400 heaters, five gas leaks were identified by a gas detector during construction.

Finally, on the upper stories of the high-rise building, which is subject to high winds off Lake Erie, there were occasional instances of the heaters tripping on a vent safety switch. The heaters could be manually reset right at the unit.

These and other final results will be available in the project report, expected to be published by the New York State Energy Research & Development Authority (NYSERDA) this spring.

Carpeting a CO Hazard

I recently received a cry for help from a couple whose carbon monoxide (CO) alarm was going off continuously. They told me the fire department had come twice and assured them no problem existed. The first question I asked was "Have you remodeled or installed new flooring?" The answer was Yes--new carpeting had been laid.

As discussed in your March/April 2000 House Doctor column ("Is Carpeting Safe?" p. 6), new carpeting is indeed a hazard to health. Among countless other chemicals, it contains methylene chloride, which also sets off home CO detectors and is converted to CO in the liver.

Fire departments use devices that detect only CO emissions, which is why they said there was no problem. Please don't give the same advice. You are correct that the risk diminishes with time, but occupants with small or damaged lungs, and pregnant women, should not expose themselves even briefly.

Finally: Never use a study commissioned by the manufacturer as a source of advice. If you trust them, then you would have believed the Tobacco Institute when it said that cigarettes were not harmful!

Rick Barrett, Owner/Chief Inspector
Sherlock's Home Inspection
Denver, Colorado

House Doctor Joe Laquatra responds:

Carpeting is not a source of methylene chloride, although some water-based adhesives are a source of it. These adhesives are used with some carpeting, but a CO detector would not react to them. However, it is correct that when the body breaks methylene chloride down to carbon monoxide, CO is not exhaled, but binds with hemoglobin in the blood.

The study I referred to was not commissioned by the Carpet & Rug Institute (CRI). It was commissioned by the authors, and CRI contributed partial funding to it. The report was subsequently published in a peer-reviewed journal, Critical Reviews in Toxicology 26, no. 6 (1996): 633-707. Cornell University has a policy in place that does not allow faculty, through the Office of Sponsored Programs, to accept funds for research support from any source, unless that source agrees that no restrictions will be placed on research methods or dissemination of results. This is the case with most universities, but it may not be with many foundations or independent researchers.

Additional commentary from CO expert Thomas Greiner:

Sets off a CO detector?

First, as you have noted, methylene chloride is converted in the body to CO. Quoting from Matthew J. Ellenhorn and Donald G. Barceloux, Medical Toxicology: Diagnosis and Treatment of Human Poisoning (New York: Elsevier Publishing, 1988), 820-21: "Methylene chloride (CH₂Cl), a constituent of paint and vanish removers, is converted in vivo [in the body] to carbon monoxide. Use of these removers for three hours leads to COHb levels ranging from 5%-10%. The use of a paint remover in a poorly ventilated space resulted in myocardial infarction and death in a patient with preexisting cardiovascular disease.... Carboxyhemoglobin levels up to 50% have been reported after methylene chloride exposure, but symptoms are not as serious as the carboxyhemoglobin level would tend to indicate."

I don't know how much, if any methylene chloride, is in carpets. The release is commonly associated with paint and varnish removers. Some factors that I think would affect the amount breathed would be

• the volatility of the remover;

• the surface area covered with remover;

• the volume of the space;

• the ventilation rate in the room;

• the effectiveness of the ventilation in relationship to the person exposed;

• the time exposed; and

• the physiology of the individual (breathing rate, lung capacity, and so on).