On Sat, 26 May 2007 02:57:43 GMT, aemeijers wrote:
Probably the exhaust for the high-efficency furnace. But there is
usually a second pipe to suck combustion air in.

4" is too big for a furnace. Maybe a water heater - mine is like that.

BTW, I've seen new construction with high efficiency heating that do
exhaust to the outside, but take combustion air from inside - just a
short stub on the furnace intake with a plastic grille on it. I thought
that was wierd.

--
Art Greenberg
artg at eclipse dot net