When the combustion air duct is connected directly to the return plenum for a furnace, the blower fan on the furnace pulls outdoor air in to the return plenum. To supply this air to the furnace room, ...

Dry indoor air affects comfort, health, and homes during heating season. Knowing how whole-house humidifiers work helps contractors match homeowners with the right solution.

Q: I’m confused about maintenance of my crawlspace, which also serves as a cold-air return plenum for an oil furnace. No cold-air return ducts, just crawlspace. The crawlspace looks quite dirty, and ...