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  1. #1
    Join Date
    Jan 2013
    Location
    West Michigan
    Posts
    17

    Zone or no zone Basement

    We have a 1550 sq ft walkout ranch in West Michigan, currently basement is unfinished, looking to finish in the near future. It would add two bedrooms, bathroom and very good sized lower great room (550 sq ft). Total finished in the basement would be about 1100 sq ft. It has nine foot ceilings, slider, two large picture windows and a couple smaller 30 in windows. Currently it is cold down there, bare concrete floor (believe it is insulated below) concrete walls are mostly insulated, only R-6 and stud walls are insulated R-15. I will insulated any bare concrete that remains, plus add r-11 to the walls when I stud the concrete. There are two HVAC vents currently at the ends of each trunk and it does not get warm. I know two vents wouldn't be able to warm it, just not enough CFM.

    My question: Should I spend the extra money to have a zone in the basement? I haven't had anyone come out and quote yet but I do know some HVAC guys and one says it shouldn't need to be if setup right, and the other says being nine foot ceilings with the windows and slider it should be zoned.

    What are you suggestions from past experiences?

  2. #2
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
    Posts
    2,744
    Are you asking if you need another furnace and A/C or if it can be zoned with automatic dampers? A zoned system, with auto dampers, is the way to go. You could expand it to 3 or 4 zones easily depending on the house lay-out.

  3. #3
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    If it's a walk-out basement and well insulated in a home that's also very well insulated, you mgith find that in winter at least it works well. Summer could give you some issues, but you might be able ot manually adjsut a couple dampers and make it work. In my last home I didn;t have much issues. If you have long run times form properly sized equipment, that makes a HUGE difference.

    In Michigan, it's really, really common to find oversized AC and furnaces, especially in the wwestern part. Why? People assuem tha MI is really really cold, when in fact the extremne cold days are usually tempered by lake effect percipitation and clouds. Design temps are often closer to 5F winter and 88F summer, when most contractors probably thing they need ot design for -5F winter and 95F summer. But those temps represent far less than 1% of the time. You design for 99% and 1% conditions, not 0.1% and 99.9% situations. You let the system just run really long, fall behind jsut a little and enjoy more comfort and effciency the other 99.9% of the time.

    But then again, it's not uncommon to buy a car with a bigger engine in MI (until recent gas price increases) for that 0.01% of the tiem you need that little bit of extra power. We spend probably >95% of our time driving at either constant speeds or slowing down or idling using <20% of the engines capacity.


    Zoning is still always best.

  4. #4
    Join Date
    Jun 2007
    Location
    Minneapolis, MN
    Posts
    766
    No zone, no control. You do not need AC in a basement in MI.

  5. #5
    Join Date
    Aug 2009
    Location
    Beatrice, NE
    Posts
    2,492
    If you are going ot zone it, do it right, which will probably require all new duct system, which you may need if there are only 2 registers in the space now. If you are not willing to spend the cash to do it right, don't do it. All zoning info I have read require the duct to be oversized by 25% for when only one zone is on. Many contractors will try to use the existing duct and a bypass to handle the excess air when only one zone is on. This is not good for the equipment as it recirculates to much air.

  6. #6
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
    Posts
    2,744
    Quote Originally Posted by kls-ccc View Post
    If you are going ot zone it, do it right, which will probably require all new duct system, which you may need if there are only 2 registers in the space now. If you are not willing to spend the cash to do it right, don't do it. All zoning info I have read require the duct to be oversized by 25% for when only one zone is on. Many contractors will try to use the existing duct and a bypass to handle the excess air when only one zone is on. This is not good for the equipment as it recirculates to much air.
    It all depends on the size of the A/C. I think with a 1,500 s.f. ranch he'll have no problem with the existing ductwork. No by-pass will be required if he goes with only 2 zones. Maybe 4 zones would require a by-pass but there are ways around that as well. Modulating by-pass dampers (when needed) are wonderful. If he doesn't have a ECM motor this would be a good time upgrade to that as well (assuming the furnace is not too old).

  7. #7
    Join Date
    Jan 2013
    Location
    West Michigan
    Posts
    17
    Thanks for quick replies, I'm not worried about a/c, heat rises, and the back of the basement where most windows are faces the north.

    I'm an engineer (not HVAC) so naturally I have been doing research and calculating load size and figuring out the system. 78,000 btu, 1040 cfm heat (does that seem low for the size house?) 2.5 ton A/C.

    I'm concerned with the heating, I do not want it to be a large temperature difference, currently it is approx a 5-6 degree difference from main floor. It will have two bedrooms, I do not plan on using unless for guests, and large great room and it will be used. With the nine foot ceilings that got me thinking about zones.

    I am leaning towards the zones because I am the type to do it right the first time. I'm just watching costs because we are only planning on living in this house 5-7 yrs.

  8. #8
    Join Date
    Jan 2013
    Location
    West Michigan
    Posts
    17
    House was finished in November 2012. So system is brand new, but Not the most happiest with the system. It is Single stage system I will be doing more research for the next house.

    As for ductwork, I have it figured out where dampers could go and I can add branches for the basement.

    My question (because I would like to do it myself) can I add a trunk for the basement to an existing trunk? Currently there is the main plenum with two trunks splitting the house, I'm wondering if there is a way to tie another trunk for te basement into an existing? I have calculated the sizes for airflow already.

  9. #9
    Join Date
    Feb 2004
    Location
    Wadsworth, OH
    Posts
    316
    Great application for zoning...if your registers will be in the ceiling be sure that you design for max velocity to push the warm air towards the floor.
    Our system (available to contractors only) allows for dampers in the branch runs eliminating the need to add a trunk for the basement. Regarding the over sized ducts for zoning, this is somewhat beneficial and only economically justifiable if done at the time of construction. Our contractors have been zoning for the past 2 decades using the existing ducts without issues. On about 30% of systems a modulating bypass is required.
    You might want to consider a blower motor upgrade to an EverGreen ECM, that would further reduce the need for a bypass duct.
    "When you perceive zoning not as a bandage but as an enhancement, you truly understand the dynamics and limitations of forced air heating and cooling"

  10. #10
    Join Date
    Jan 2013
    Location
    West Michigan
    Posts
    17
    I have it planned out so vents can be near the floor or ceiling. I figured the main room will have two near the exterior walls in the ceiling and two near the floor in interior walls, Ceiling return. Bedrooms would allow for near flor vents and ceiling returns, bathroom in the ceiling.

  11. #11
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
    Posts
    2,744
    Quote Originally Posted by drewscm View Post
    I have it planned out so vents can be near the floor or ceiling. I figured the main room will have two near the exterior walls in the ceiling and two near the floor in interior walls, Ceiling return. Bedrooms would allow for near flor vents and ceiling returns, bathroom in the ceiling.
    I was going to comment on this but I see that you're planning to do the work yourself. This is not a DIY site. Good luck.

  12. #12
    Join Date
    Jan 2013
    Location
    West Michigan
    Posts
    17
    I said "i want to do it myself" I am an engineer, these are the types of things we like to do... Figure things out. I am planning on having a contractor come in to see what they think still and probably go with whoever seems to be the best setup. I like to know the technical side of it naturally. So your comments would be appreciated.

  13. #13
    Join Date
    Jun 2007
    Location
    Minneapolis, MN
    Posts
    766
    78mtuh. Lets start there. I can't imagine a house south of the Yellow Knife and below Mt. McKinley that has a heat load that high. At 90% efficiency the furnace would deliver 70btuh! This an 18th century number and suspect the cooling could be halved as well.

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