Seller debates with home inspector

Q: My home inspector had an edgy debate with the seller of the home I'm buying, and one question nearly stumped the inspector. The house has a forced air furnace below the building, and the inspector reported exhaust being vented into the crawl space. The seller insisted a little exhaust in the building might not be a serious problem. He challenged the inspector by asking why it is OK for the gas range in the kitchen to vent exhaust into the house. How should the inspector have answered this question?

A: At first glance, the seller's question appears to be a perfect challenge: How can it be safe to vent a kitchen range into a house, while exhaust from a furnace must be vented to the outside? Basically, there are two significant variables that affect personal safety when combustion exhaust is vented into a building. The first of these is the relative amount of fuel being burned. The second involves whether or not incomplete combustion is occurring, thereby posing a hazard to occupants.

Regarding the amount of fuel being burned, a kitchen range consumes approximately 12,000 BTUs per burner, whereas a forced air furnace typically burns 60,000 to 100,000 BTUs or more. When range burners are functioning optimally, the products of combustion consist of water vapor and carbon dioxide, both of which are harmless when present in small quantities.

Additionally, a kitchen range has observable burners. When a range burner malfunctions (producing an unusual flame pattern), most users are likely to notice the problem and turn the burner off. A furnace burner, on the other hand, is an automatic appliance, turning on and off literally thousands of times without anyone observing the condition of the flame. Carbon dioxide and vapor from a fixture of that size could be harmful. Moreover, if the burner should ever malfunction while exhaust is venting into the building, the heating system could become a carbon monoxide machine, pumping odorless, toxic gas into the house.

These are the primary reasons why exterior venting of a furnace is essential and is required by code. The same levels of risk do not apply to kitchen range burners.

Q: According to our home inspector, the house we're buying has water in the subarea because of a faulty sump pump. The sellers have agreed to have this corrected, but we're wondering if sump pumps are common under houses with raised foundations. Should we regard the presence of the pump as a warning sign?

A: The presence of a sump pump below a building indicates faulty ground drainage, and this raises two pertinent questions: What is the source and extent of the ground moisture, and does the sump pump adequately address the problem?

Many homes with drainage problems have sump pumps that were installed without the causes for the faulty drainage having been professionally determined. To evaluate drainage conditions adequately, have the site and the sump system reviewed by a licensed geotechnical engineer.

• To write to Barry Stone, visit him on the web at, or write AMG, 1776 Jami Lee Court, Suite 218, San Luis Obispo, CA 94301.

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