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  1. #1
    Join Date
    Oct 2007
    Location
    Washington, DC Metro Area
    Posts
    25

    Average Heat Loss from Fireplace

    What's the average heat loss in BTUH for a masonry fireplace in a new home?

    Similarly, what's the average heat loss in BTUH for gas fireplace?

    Thanks.

  2. #2
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    It would depend on a number of factors, such as how much air from inside the house is escaping up the chimney, which is then replaced by outside air leaking into the house in other areas, the conditions of the air leaking into the house, etc..

    I don't think you will find anything like an "average" btuh loss.

    With a wood fireplace, you will always loose more heat from the house than is radiated into the room by the fire.
    With a gas fireplace, it would depend on the design, but if it draws its air from inside the house, it's pretty much going to behave just like a wood burning fireplace in regards to heat loss from the home.
    If more government is the answer, then it's a really stupid question.

  3. #3
    Join Date
    Feb 2008
    Location
    Waffleville
    Posts
    10,339
    in NC its a heat gain during the summer causing subsatnce to grow in a home what good is a fireplace anyways?? it really depends on if you have the damper open or closed. and if your home is under positive or negative pressure. then you can start to decide if its a loss, or a gain
    If Guns Kill People, Do Pencils Misspell Words?

    http://www.youtube.com/watch?v=An2a1...eature=related

    Before we work on artificial intelligence why don't we do something about natural stupidity?

  4. #4
    Join Date
    Feb 2003
    Location
    Huntsville,AL
    Posts
    4,125
    is chimney exposed on 3 sides to outside = B I G heat loss

    is the gap closed off at the top of the ceiling rafters -- rafter to chimney -- with galvanized metal = Z

    figure 20% extra to heat room with fire going --
    unless there is a HEAVY metal insert
    & outside air source
    & circulating fans at chimney

    may get more answers at that forum --
    harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!

  5. #5
    Join Date
    May 2006
    Location
    Rochester, NY
    Posts
    22
    As a personal note...

    I recently installed a 90% furnace in my home. The day it was installed, I was being lazy and only put in an exhaust pipe, no intake. Furnace is located in the basement.

    When the combustion air blower ran on the furnace, it would pull a VERY noticeable negative draft down the masonry chimney... even with the damper closed.

    SOOOoooo...

    I stopped being lazy, revisited the venting tables, and installed the intake pipe.

    No more draft. Lesson learned.

  6. #6
    Join Date
    Oct 2007
    Location
    Washington, DC Metro Area
    Posts
    25

    Where should I post?

    Thanks for the replies.

    -Fireplace is exposed on three sides

    -Metal flashing at roof. But unable to get answer regarding galvanized metal where chimney meets rafters.

    Not sure HVAC contractor was aware fireplace was being installed.

    I pose questions to builder who then asks and awaits answers from the contractor and then replies back to me with said answer. Some things get lost in the translation.

    My questions are really more so aimed at the HVAC because I am not sure they are sizing the system properly.


    Will ask question in fireplace forum if that is the more appropriate place.

    Again, thanks.

  7. #7
    Join Date
    Jan 2008
    Posts
    85
    Quote Originally Posted by snookered View Post
    As a personal note...

    I recently installed a 90% furnace in my home. The day it was installed, I was being lazy and only put in an exhaust pipe, no intake. Furnace is located in the basement.

    When the combustion air blower ran on the furnace, it would pull a VERY noticeable negative draft down the masonry chimney... even with the damper closed.

    SOOOoooo...

    I stopped being lazy, revisited the venting tables, and installed the intake pipe.

    No more draft. Lesson learned.
    Bet you'll feel a draft when running a bath exhaust fan or clothes dryer too.

    Even with the intake and chimney dampers closed mine would always leak
    cold air into the room. I finally got fed up with it and built a special frame
    that sits in front of the fireplace doors to seal it off completely when not in use. Works well and one can't really tell it's there unless you look at it closely.

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