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  1. #1

    New construction two stage verses single

    We are building a new home in the charleston sic area Hot and humid! The home is 4400 sqft with 2850 on first and 1580 on second with 547 worth of 20 foot ceilings.

    I had specs 2 stage 16 seer but am struggling with cost. Original plan was 3 units master suite and study 780sqft, rest of lower level 2000 sqft with high ceilings and the upstairs. Manual j by the builder is about 7 ton

    Quote came in for a 5 and a 3 which puts master suite on 5 ton with all the high ceilings. To had a zone capability is not much less than adding a 1.5 single stage with two speed VAM.

    So at the end question is with SC coastal cooling days will I below the threshold often enough to have 2 stage make sense? Or could I go 3 single stage with two Speed VAM and get near 15 and be in pretty good shape.

    House should be pretty tight foaming attic space and under first floor, also used liquid applied membrane and personally caulked all top and bottom plates,jack studs, windows doors etc foamed all cells, and intrusion points.

    Thanks for reading this far!

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,334
    Are you in an area that reaches 105 outdoor temp? 7 tons sounds big for a spray foamed attic and basement.
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  3. #3
    Quote Originally Posted by beenthere View Post
    Are you in an area that reaches 105 outdoor temp? 7 tons sounds big for a spray foamed attic and basement.
    Yes it can do that easy in the summer. Bases celing will be foamed but is drive under construction so ceiling I'd 8'8" above grade.

  4. #4
    Join Date
    Feb 2006
    Location
    Float'N Vally, MS
    Posts
    1,841
    I may have misses something here?
    Is this an encapsulated home? Attic, walls and floors foamed?

    I am In a coastal area and 5 tons is a little big for an encapsulated home.
    And yes we use 2 speed HP's for comfort.



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  5. #5
    Attic and first floor everything else is batted


    Quote Originally Posted by behappy View Post
    I may have misses something here?
    Is this an encapsulated home? Attic, walls and floors foamed?

    I am In a coastal area and 5 tons is a little big for an encapsulated home.
    And yes we use 2 speed HP's for comfort.



    Sent from my iPad using my fingers.

  6. #6
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,538
    Quote Originally Posted by Dgg View Post
    We are building a new home in the charleston sic area Hot and humid! The home is 4400 sqft with 2850 on first and 1580 on second with 547 worth of 20 foot ceilings.

    I had specs 2 stage 16 seer but am struggling with cost. Original plan was 3 units master suite and study 780sqft, rest of lower level 2000 sqft with high ceilings and the upstairs. Manual j by the builder is about 7 ton

    Quote came in for a 5 and a 3 which puts master suite on 5 ton with all the high ceilings. To had a zone capability is not much less than adding a 1.5 single stage with two speed VAM.

    So at the end question is with SC coastal cooling days will I below the threshold often enough to have 2 stage make sense? Or could I go 3 single stage with two Speed VAM and get near 15 and be in pretty good shape.

    House should be pretty tight foaming attic space and under first floor, also used liquid applied membrane and personally caulked all top and bottom plates,jack studs, windows doors etc foamed all cells, and intrusion points.

    Thanks for reading this far!
    A word of caution, do not live in this space without fresh air ventilation. Most codes are suggesting mechanical fresh air ventilation to purge indoor pollutants and renew oxygen. Also the cooling load is reduced to the point that the a/c will not operate enough to remove the moisture from the occupants and adequate fresh air ventilation. Suggest a small whole house ventilating dehumidifier like an Ultra-Aire XT105H to provide fresh air and humidity control.
    Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  7. #7
    Can you share a little,more detail as it apples to this space?

    Quote Originally Posted by teddy bear View Post
    A word of caution, do not live in this space without fresh air ventilation. Most codes are suggesting mechanical fresh air ventilation to purge indoor pollutants and renew oxygen. Also the cooling load is reduced to the point that the a/c will not operate enough to remove the moisture from the occupants and adequate fresh air ventilation. Suggest a small whole house ventilating dehumidifier like an Ultra-Aire XT105H to provide fresh air and humidity control.
    Regards TB

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