6 Reasons to Avoid Oversized HVAC Systems 

Thank you Allison. I share your posts with lots of people, in the trade and out.

I have yet and have never found a properly sized system installed in the house yet. I’m still looking. That’s not even talk about undersized duct work . I think the last time I ever found a properly sized ductwork. Was when the original house that was built in 1940 had a gravity furnace, hard sheet metal ducting that was all wrapped in asbestos still excellent condition. Was designed for 160,000 BTU furnace . Design for a house with no insulation in the ceiling no insulation in the walls old wooden windows with the weights in the window sash. Most of the offshoot duct runs to the floor mount grills were 10 inch in diameter . The old house has had insulation blown into the walls, insulation blown into the attic. All the windows have been replaced with glaze vinyl windows. . And a contractor connected 40,000 BTU furnace directly to the 36“ x 28“ Plenum . Under this condition, it would be the most correct by accident overkill size ductwork that was original . . And 40,000 BTUs in a 1200 square-foot home in San Francisco is still way overkill and MORE than DOUBLE the size needed .