Page 1 of 2 12 LastLast
Results 1 to 13 of 16
  1. #1
    Join Date
    Jul 2007
    Posts
    79

    how many btu's do i need for 1400 square feet

    i live in phila pa, on a slab with 1400 square feet,there are 11 supply vents in the home and the attic is well insulated,about 20 inches of blown in fiberglass how many btu's would be the proper amount for my house,im getting 3 quotes,one says 70000,the other 80 and the other 90,would chose a 2 speed variable furnace,thanks,im thinking 70 is too small am i wrong

  2. #2
    Join Date
    Apr 2004
    Location
    MN
    Posts
    1,803
    Not nearly enough info. We need window/door info and orientation. Attic insulation, wall cavity insulation values, how many people, attic info etc. Then, we would plug all of this into a load calc. program and give you your answer after we received payment for our time. Or, you could buy the one time use load calc program listed in the quick links at the top of this page called hvac-calc. and do it yourself for no hourly charge.

    Better still, ask your contractors which one of them performed a load calc and go with that one.
    A Veteran is a person, who at some point in their life, wrote a blank check payable to the United States of America for payment up to and including their life.
    Gene Castagnetti-Director of the National Memorial Cemetery of the Pacific in Hawaii

  3. #3
    Join Date
    Apr 2008
    Location
    Northwest Arkansas via Chicago Area via Straight Up from There on Lake Superior
    Posts
    1,411
    Quote Originally Posted by salv97 View Post
    i live in phila pa, on a slab with 1400 square feet,there are 11 supply vents in the home and the attic is well insulated,about 20 inches of blown in fiberglass how many btu's would be the proper amount for my house,im getting 3 quotes,one says 70000,the other 80 and the other 90,would chose a 2 speed variable furnace,thanks,im thinking 70 is too small am i wrong
    Like Doc says, you need a Manual J calc. But anecdotally, I have a house 2.5 time that big with a 100,000 Btu furnace that I think is too big. It's not a super new green house either. I am guessing that most of the time we are running well below 60,000 Btu. We do get 0-10 F a few times and there is no problem heating with the furnace. Now I'm not in Phila but that number would inspire me to look a lot closer at both the house envelope and the HVAC needs. If you listen to the pros here they tell you that the right sized unit should run a lot when close to design temp outside. I find that the more it runs the evener the temps around the house.

  4. #4
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,095
    A load calc will tell you how many BTUss your house need HVAC Calc.

    Are you supplies in the slab?

    In philly, doubt you need a 70,000, let alone a 80 or 90. Unless the supplies are in the slab.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  5. #5
    Join Date
    Jul 2007
    Posts
    79
    why does it matter if the supplies are in the slab

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,095
    They loss heat to the ground.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  7. #7
    Join Date
    Jul 2007
    Posts
    79
    how much heat 10 percent,20,or 10000 btu's or 20

  8. #8
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,095
    That depends on run length and size. And the temp of the air from the furnace.

    So yours are in the slab then, huh.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  9. #9
    Join Date
    Oct 2003
    Location
    Washington
    Posts
    7,405
    Quote Originally Posted by beenthere View Post
    That depends on run length and size. And the temp of the air from the furnace.

    So yours are in the slab then, huh.

    Wow, this screams of a homeowner trying to purchase their own unit.

  10. #10
    Join Date
    Jul 2007
    Posts
    79
    the house runs 60 feet long and is 24 feet wide,if you had to guess,thanks

  11. #11
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,095
    Quote Originally Posted by seatonheating View Post
    Wow, this screams of a homeowner trying to purchase their own unit.

    Hard to tell.

    Do you remember that other thread. Where the contractor sized furnace is sized right for the house. But, the ducts in the slab are losing too much heat to the ground(guess he forgot to include them in the heat loss).

    That OP should have been here asking these kind of questions.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  12. #12
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,095
    Not sure anymore. But, I think HAVC Calc has allowances for slab duct.
    You might want to use it. I put a link to it in post #4. Its worth the 49 dollar fee. if your contractors won't do a load calc.


    I'd rather pay 49 bucks to do my own load calc. then to get a furnace too small that doesn't heat the house. Or one too big that trips out on its safeties and can't heat my house.

    Newer furnaces NEED to move a lot more air then the older ones did.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  13. #13
    Join Date
    Jul 2007
    Posts
    79
    i have a 114 btu furnace now and thats too big, 60 or 70 btu might be too small,so it could be either 80 or 90 how does that sound,it cant be perfect

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event