Sizing Direct Vent Natural Gas Furnace

[robhouston]

I'm trying to determine the correct size for a direct vent gas furnace that I'm intending to have installed for supplemental heat for my finished basement. So far, I've gotten two conflicting opinions from contractors.

I live in New Jersey. The size of the space is about 1000 sq. ft with 7.5 foot ceilings, insulated walls and open air circulation throughout. The space is currently heated by a forced air furnace that provides heat to the main floor of the home and the basement. Even during the coldest weather, the basement is typically maintained around 60 degrees F or higher, so I only need to increase the temperature by about 10 degrees or so.

One contractor told me that since the direct vent furnace will only be used for supplemental heat, I only need one sized for about 15,000 BTU's input. Another told me I should go for 80,000 BTU's. I'd like to keep the size to a minimum to allow for the greatest operating efficiency.

I've found many calculators for determining the size for primary heat, but what's the best size to allow for supplemental heat in my situation?

Thanks, in advance, for your help!

Rob Houston

[key]

I agree with the first contractor, 15 to 22K would do the job. If you go to big, it will short cycle..look into the Rinnai space heaters.

[jeffshvac]

if your basement is open you might want to look into a ductless system theyre efficient and cost effective. thanks

[Carnak]

You should go with the contractor who calculates what the heat required in the basement is in the first place.

80,000 sounds like you could toast the basement and by default you could heat the ground floor by radiant floor in the process. :)

The guy suggesting the small heater is most likely on the right track.

[t527ed]

why not add a zone to existing heater?