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Basement AC ducting questions...

In the process of finishing my basement after 17 yrs. of ownership and have already roughed in the heat (hot water baseboard) but have questions/concerns about the basement AC.

House was at one time heated & cooled with one forced air unit in the basement. I have since installed a high efficiency hot water boiler w/ baseboard and had two air handlers installed for the AC, one in the basement and one in the attic for the second floor - pretty big undertaking to change the duct work and do it correctly. By correctly I mean that...I'm pretty anal and did not want to see miles & miles of flex, nor did I want duct installed on a skew - square, level & plumb only. Finding the right contractor took some time to say the least.

The contractor changed the duct work in the house from single zone to two knowing eventually I planned to finish the basement and I believe, sized the 1st floor AC equipment accordingly and left some duct (both supply & return air) in the basement rooms.

I know this isn't the best due to stealing from the 1st floor and no controls (t-stats) but due to the design of the finish I believe very little AC will be needed. All exterior walls on the interior side have 2" Styrofoam glued to them and perimeter interior walls will have R-13 or 19 fiberglass in them. There will be 3" fire & sound batts in all the 1st floor joists (basement ceilings). As for humidity it seems to be a very dry basement with no water problems what so ever.

My questions/concerns are...
1. Does individual room supply air duct & return air duct sizes have to match? I may not be able to match the return air ducts, some may be slightly undersized.
2. Most rooms to get sheetrock ceilings. Regardless, is it customary or standard to install small pc. of flex prior to installing the ceiling to register boxes?
3. Do I need to install fitting with adjustable flaps to control air flow, I believe they may be called balancers, on each supply? If so, I'm confused how I'd know where they need to be set prior to sheetrock install.

Comments

  • GWGW Member Posts: 3,789
    Hi John, you'll get differing opinions, here are mine:

    1. Does individual room supply air duct & return air duct sizes have to match? I may not be able to match the return air ducts, some may be slightly undersized. >>>>if you're trying to do this correctly then the answer is yes. And, what do you mean "some may slightly understand"?
    2. Most rooms to get sheetrock ceilings. Regardless, is it customary or standard to install small pc. of flex prior to installing the ceiling to register boxes?>>>>matter of opinion, yes to both methods (flex or no flex)
    3. Do I need to install fitting with adjustable flaps to control air flow, I believe they may be called balancers, on each supply? If so, I'm confused how I'd know where they need to be set prior to sheetrock install. >>>>you shouldn't bury the dampers; seems like you have an idea why .
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    www.wilsonph.com
    [email protected]
  • john p_2john p_2 Member Posts: 359
    GW -
    the ducts are what was left after changing from single zone to two zone, didn't install for the basement - just got very lucky

    due to layout of the ducts I can see no way of installing dampers with access to them. This looks to be a huge problem.

    I hate flex, lol. Will install hard pipe all the way, thanks.
    I may need to find a pro to look at getting this done correctly.
  • GWGW Member Posts: 3,789
    John, yes ok if you MUST bury stuff (dampers), you're just rolling the dice with the whole process. But, sometimes the world isn't perfect :)
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    www.wilsonph.com
    [email protected]
  • john p_2john p_2 Member Posts: 359
    I will take another look, just thinking most of the supply air ducts have to go thru an area where drop ceiling will be installed. Hopefully this is the case.
    What about lack of control? Now you have me thinking I might be better off installing motorized dampers to each room (4)...at least I could shut completely if I had to.
  • JackJack Member Posts: 1,044
    Sheetrock in a basement ceiling is a problem. Not that it shouldn't be used or is inferior in any way, but you make any other modification to the living space a real problem by limiting access to electrical, plumbing and ducting. Every time I think I have something figured out really tightly I am reminded that life is a humbling experience. I would suggest a drop ceiling for future access.
  • GWGW Member Posts: 3,789
    Sure that’s a good idea, motorized dampers, but don’t call on the system with two or three 6” runouts!

    I did a basement once where we had a separate panel for the basement zone. I just wanted then to open and close, not actually call on the heat or ac
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    www.wilsonph.com
    [email protected]
  • john p_2john p_2 Member Posts: 359
    GW -Exactly what I was thinking because essentially I'm stealing the AC from the first floor. So being I cant control when it will be cooling at least I can open/close it when I want. Would love to see the panel you used for that or get a model # if possible.

    Not sure what you meant in the first sentence of your last post.
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 7,307
    I think what Gary meant was if you zone the basement and it is only supplied by 2 or 3 6 inch round ducts or= you don't want to bring the cooling on for such a small load...it might freeze up the coil which could damage the compressor.

    zone dampers will close to prevent over cooling the basement but have no control over the cooling unit. You will get cooling in the basement whenever the first floor calls on the cooling and the zone dampers will prevent overcooling the basement
    GW
  • GWGW Member Posts: 3,789
    Yes John so if you have a 3 zone panel (basement, 1floor and 2floir), that’s not good.

    You don’t want the basement to call on the equipment. That’s just my general opinion. I have no idea what you’re actually working with in your application

    Get your zones going for the 1 fl and 2 fl. That’s panel A

    Panel A calls on the heating or cooling

    Panel B is the basement zone. B doesn’t get to call on the furnace. It only allows the basement dampers to open and close

    Any basic panel will work. I like Honeywell and EWC
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    www.wilsonph.com
    [email protected]
  • john p_2john p_2 Member Posts: 359
    Ed - Motorized dampers really sound interesting the more I /we talk about them.

    I fully understand I'm stealing the cooling from the 1st floor cooling and have no ability to "call" for cooling in the basement using the first floor equipment.

    What I'm a little unsure of is what would be used in place of a t-stat in my case to control the motorized dampers.
  • GWGW Member Posts: 3,789
    Same answer. If you’re stealing air from the 1 floor zone that’s fine; do what you gotta do. I myself don’t like to tap into existing duct runs.

    Do you want heating and cooling in the basement? You’re gonna want a basic panel.

    Do you just want heating? Then you don't really need a panel, you can just get a cheap 24v transformer
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    www.wilsonph.com
    [email protected]
  • ratioratio Member Posts: 2,562
    What you want is called (around here, at least) a cutoff damper. You generally want spring OPEN, power CLOSED (important for failure-is-not-gonna-screw-up-your-ac reasons). Viconics is our go-to kit. You probably want a T901D-F, see here. With a supply air sensor, it will know the temperature of the air in the duct, & react correctly. This is what I used in my daughter's room. Works smashingly.
  • JackJack Member Posts: 1,044
    Perhaps you should look at doing a mini-split heat pump for the basement and be done with it. Let your current system operate the living space upstairs. The environment in basements is typically much different than the upstairs, differing primarily in humidity levels. Mini-splits are excellent at humidity control. Zone dampers can be very effective, but as noted, you have to be spot on with balanced air flow for the system to accept the modifications. Also, I think that by the time you add all this hardware to the existing system you will be in the same cost zone as a mshp.
    john p_2
  • mikeg2015mikeg2015 Member Posts: 1,178
    I don’t like flex but the ugly truth is that while less durable it’s quieter, if sized well flows plenty of air, much cheaper to install and typically has less leaks unless you are fanatical about mastic on metal duct.
  • mikeg2015mikeg2015 Member Posts: 1,178
    ... minisplits are probably the best basement solution other than a cooling tower setup or ground loop heat pumps that allow heat recovery. Basements often need heating well into the cooling season, but heat requirements plateau and are not completely linear with OAT.
  • john p_2john p_2 Member Posts: 359
    Will be heating the basement as a separate zone already provided for with existing boiler- baseboard, each room w/individual t-stats, about 800 sq. ft. total.

    The basement has no water dampness issues. Between that and the limited amount of time it will be used I believe it doesn't justify the cost of a mini split that will only be used for cooling.

    I also don't care for the look of them, even with 8' ceilings in my basement. I believe I will have no issues be cool enough, more concerned with over cooling, hence my questions about motorized dampers- thinking leave motorized dampers open and close on desired room temps
  • pecmsgpecmsg Member Posts: 1,508
    Where is this basement.

    Here in the NE basements need Heat and Dehumidification. Very little if any cooling.
  • john p_2john p_2 Member Posts: 359
    NJ... extremely dry basement. I put 2" styrafoam on the interior side of all perimeter exterior walls and will be adding R-13 in all studded interior walls & firec& sound Batts in the ceilings.
  • pecmsgpecmsg Member Posts: 1,508
    You need heat and a dehumidifier long after the main heating system is off for the season. Probably little if any A/C needed.
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