Can I tap into existing ductwork for basement heat?

18 years ago

We just finished roughing in our basement. Everything is DIY. This is our third basement. In our first house we installed electric baseboard heat. In our next one we used the existing heat pump and just added additional duct work. That house was 1800 sq ft and the basement increase it to 2700, all on one heat pump. We didn't have any problems doing this. All three floors were comfortable and our electric bill was not astronomical. This house is 3000 sq ft and each floor (1500 sq ft) has it's own heat pump. The basement will add another 1500 sq ft and we would like to do the same thing. Used the furnace that's currently down there and just add additional duct work. The basement is a walkout on one side with the three other sides below grade. We also plan to use the radiant floor heating pads under the flooring in several rooms down there.

Is this okay? Do you think 3000 sq ft will be too much for one furnace to handle? Will it reduce the amount of heat that gets to the main level requiring the furnace to run longer and harder?

I plan to ask the building inspector these questions when he comes on Monday to do our roughin inspection. I considered calling a hvac company but figured they would just try to sell me another furnace whether I need one or not.

Your thoughts would be greatly appreciated. DH is on vacation next week and we hope to drywall then.

Comments (6)

blue_fastback
18 years ago
Depends on the rating of the furnace. An honest hvac company would be the one to ask,
rumble_s
18 years ago
Heating systems are designed to replace heat lost to the outside under normal operating conditions. Will the heat pump run lnger and harder if you pipe the heat to te basement? Of course it will. Will this be catastrophic? Probably not. Basements are not a major heat loss, provided they are insulated. Make sure you have cold air return as well as heat inputs in the basement area.

Normaly you will not see much of a problem when it's not real cold. The bigger the heat pump (tons), the more likely it will be able to handle the full heating needs at sub-freezing temperatures. If it cannot keep up in heat-pump mode it will use resistance heat to supplement. (That is the same as baseboard).
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sierraeast
18 years ago
If your heating system was properly calc'd and designed for your layout, you could jeapordize the system rendering it less efficient. I would go the hvac route and get a professional opinion.Ask around for someone who is reputable, and you might want to get more than one opinion on this.Same as estimates, should be free of charge.Building inspector should be good to advise as well, but i would still get more than one opinion.
woodinvirginia
17 years ago
Where do you live ? Climate & conditions will most likely provide you with an answer. Most HVAc guys are looking to SELL you another system; not tell you how to save $$$ on your existing unit by bypassing them. Check with Housing Inpector to see if it is NOT a code violation to tap in first.Then check to see how many BTU your furnace produces.
Most sytems are OVERSIZED when they put them in. But they try to bamboozle most homeowners saying they have to do a LOAD CALCULATION to tell you whther you can do this and that. Most College 1st year engineering students can tell you that answer in 10 minutes w/o involving the HVAC guy.Plus you get an answer from some one NOT trying to sell you something.
funnycide
17 years ago
How well does your heat pump heat your house in the winter? If it does fine then you probably will be okay. What flooring are you using over the electric radiant pads? ceramic tile? You probably need very little heat. The problem with using the heat pump is typically a heat pump does not put out very warm air. You are then blowing it from the ceiling so the temp at the floor might be pretty cold. Putting a low return will help this.
legardhome
Original Author
17 years ago
Thanks for taking the time to answer. We actually are in the final stages of our basement. Carpet ordered today. We did end up checking with several hvac companies because my builder said he didn't think the unit was large enough to handle the additional space since it was broken into several rooms. Had it been one large space we would have been okay, but we put in a bedroom, bath, media room, gym and playroom all opening off a cental hall. So the basement now has it's own 1 1/2 ton 12 seer heat pump at a cost of $3500. We are in central VA. Just thought I'd post this info for anyone out there who might be in a similar situation. We also paid a drywall guy to mud/tape the drywall. Everything else has been diy. Will post pictures soon.