Choosing the right mechanical
equipment for an airtight, energyefficient
house presents a basic problem:
In a tight house, so little air leaks in from
outdoors that it can be difficult for standard,
chimney-vented boilers and furnaces
to get enough combustion air.
More important, powerful exhaust fans
in the kitchen and bathroom may
depressurize the house, overcoming the
ability of the chimney to vent toxic combustion
gases to the outdoors (see "Are
Your Houses Too Tight?" 8/94). The
result can be spillage of these gases back
into the house, with potentially dire consequences
for the occupants.
There are several solutions to the
problem of depressurization in tight
houses. A whole-house ventilation system,
for example, supplies makeup air
and keeps indoor and