# Can the HVAC system support a newly finished basement?



## kcremodeling (Nov 8, 2009)

I always have my HVAC tech come in to run the duct work for our basements. The only reason I have him come in is to determine whether or not the system can support the added square footage. He has never came back and said we need additional unit's. I'm not sure he is checking the units properly. I think he just wants to come in get it done and go home. Maybe i'm wrong, but I would like to be able to check the units myself. Does anybody have any tips for this?

http://www.kcbasementfinishing.com


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## bert0168 (Jan 28, 2008)

Im not an HVAC guy but on all the finished basements and additions I've done with forced air or hot water, your guy needs to be doing a heat load study of the house to determine if the furnace is big enough. I usually get a packet to submit with the permit as they require it.

I'm sure others will chime in here but it basically entails figuring the cubic footage of the existing heated space and taking into account windows, insulation, etc and then adding the demands of the new space.

If he's just looking at the unit and eyeballing the house and new space, I hope you didn't pay him much (if at all) because he didn't do you any favors (or what he was suppose to have done)


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## AtlRemodeling (Jan 23, 2008)

I will start by saying I am not an HVAC guy but have done a fairly large number of basements (and I did sleep in a Holiday Inn Express last night). From my understanding, a quality HVAC contractor will not install a system large enough to handle future expansion unless the ductwork is also run at the time of original installation.

The reasoning as it has been explained to me is, if you install a 5 ton system but only 3 tons of ductwork (assuming you need 3 tons for the main level and an additional 2 tons for the future basement) the system will be under strain from the start and it will shorten the life of the system. We always have HVAC subs review the load requirements for our basements and we have never had a basement where a new system was NOT installed. 95% of the time we install a new heat pump for the basement.

If my understanding of this is incorrect, HVAC guys please let me know.


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## beenthere (Mar 5, 2009)

Load calc to determine what size unit is needed to heat and cool the house, and the basement. And then check what size equipment is installed.

Some guys just rely on the equipment already being oversized. And the fact that below grade basements don't need much to heat or cool them.

Someday, your guy will get burnt on one that was sized to the existing load/unfinnished unconditioned basement load.


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