Need advice on adding heating/cooling to basement

18 years ago

We finished building our open floor plan new england colonial last year, and we did not catch that our builder did not add HVAC vents/zones for the unfinished basement until it was too late. We plan to finish the basement in the next year or two. We currently have 2 zones in the house--one for each floor of living space. Level 2 just has 3 bedrooms, 2 baths, and a laundry room. Level 1 is the larger space by about 700 square feet. Both zones have identical AC units.

The basement when finished will probably be about 1000 square feet of living area if I exclude the storage closets we'll build.

Can anyone offer any guidance on heating/cooling the basement? Can we just add ceiling vents and tap into zone 2? How elaborate and costly is that? If that's not a viable option, how elaborate and costly is this going to get? Heating is a little more important than cooling since we're in the greater Boston area.

The heating/cooling situation is making us dread the project. :) Thanks for any advice!

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Comments (2)

sniffdog
18 years ago
Did the builder size the HVAC unit currently servicing the main level so that it could accomodate the basement? if so, adding the duct work for the basement is not a big deal. Post some details on what size units you currently have for each level and the sq footage.

In my first home, they did no duct work in the basement but they did size the heater and AC unit to accomodate the basement living space. I acted as my own general contractor when I finished the beasment and I paid an HVAC company $1200 (this was in 1998) to add in ducts & registers in the basement. I did not add a seperate zone down there but could have easily done it for not much more. The basement was mostly below grade and worked fine running off the tstat on the main level.

One thing you should get right now is a humidistat (costs about $20) and measure the humidity in your basement. With tighly sealed and insulated houses, moisture can be a big issue in the basement and lead to musty smells or mould. You might find that a dehumidifier is a worthwile investment when you finish your basemenent. I just added a large dehumidifier made by Sante Fe in my basement (currently mostly unfisished with some HVAC ducts) and it not only controls the humidity in the the basement, but we get the effects of drier air on the main level as well. This fixed a musty smell that my wife detected soon after we moved in, and then mildew spots we found on the basement cement floor when we had temperatures that were in the low 70's but humidity around 80% - very damp.

Best of luck.
phhvac
18 years ago
First consult the HVAC contractor. Find out if the system was sized for the basement, hopefully they still have the heatloss/heatgain on file. I would suggest if they don't have it or it is a major project look into minisplit ductless A/C heat pumps like Fujitsu. They are quick easy install with dehumidification.
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