Dear Barry,

My home inspector had an edgy debate with the seller of the home I’m buying, and one particular question nearly stumped the inspector. The house has a forced air furnace below the building, and the inspector reported that exhaust was venting into the crawlspace. The seller, however, insisted that a little exhaust in the building might not be a serious problem. He challenged the inspector by asking why it is OK for the kitchen range to vent exhaust directly into the house. How should the inspector have answered this question? – Debbie

Dear Debbie,

At first glance, this appears to be a perfectly reasonable dilemma: How can it be safe to vent a kitchen range into a house, while exhaust from a furnace or water heater must invariably vent to the outside? Basically, there are two significant variables that affect personal safety when combustion exhaust is vented into a habitable building. The first of these is the relative amount of fuel being burned. The second involves whether a combustion problem is occurring and is likely to be noticed by an occupant.

As to fuel consumption, a kitchen range is a comparatively small appliance, using approximately 12,000 BTUs per burner. Forced air furnaces, on the other hand, typically burn 80,000 to 100,000 BTUs or more. When burners are functioning optimally, the products of combustion consist of water vapor and carbon dioxide, harmless when present in small quantities.

As noted by Michael Casey, past president of the American Society of Home Inspectors (ASHI), a kitchen range “is a human-operated appliance. When it is malfunctioning (producing a strange flame pattern), most users would notice the problem and turn the burner off.” On the other hand, Casey continued, “a 100,000-BTU furnace is an automatic appliance, turning on and off literally thousands of times without anyone noticing the condition of the flame. Carbon dioxide and vapor from a fixture of that size could be harmful. But far worse, if the burner was malfunctioning while exhaust was escaping into the building, the heating system would 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 simply do not apply to kitchen range burners.

Dear Barry,

According to our home inspector, the house we’re buying has water in the sub-area because of a faulty sump pump. The sellers have agreed to have this corrected, but we’re wondering if sump pumps are common in houses with raised foundations, or should we heed the presence of the pump as a warning sign? – Gary

Dear Gary,

The presence of a sump pump below a building indicates faulty ground drainage and 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 by handy homeowners, without the causes of faulty drainage having been professionally determined. To adequately evaluate drainage conditions at the property, have the site and the sump system reviewed by a licensed geotechnical engineer.

To write to Barry Stone, please visit him on the Web at


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