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  1. #1
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    Default When does combustion air requirement for fossil fuel furnaces, etc appear in the code

    I tried an online search for the earliest requirement for combustion air in the IRC, but struck out. I am looking for earliest language like G2407.
    Background: Some years ago, Denver city inspector told me that he thought Denver started requiring considering combustion air whenever a furnace, water heater, and/or boiler were replaced in 1990. Certainly, around here, I never see pre-1990 furnaces with any combustion air source regardless of the room volume.

    But I've seen references to combustion air that indicate that code required it earlier than 1990. I know some of you have a code book library going back to just after the last ice age, so I am hoping that you can give me a good timeline on when code began to require adequate combustion air.

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  2. #2
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    Default Re: When does combustion air requirement for fossil fuel furnaces, etc appear in the

    I don't have any code books any longer, but I'm guessing it was in the CABO and UBC, UMC codes.


  3. #3
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    Default Re: When does combustion air requirement for fossil fuel furnaces, etc appear in the

    I suppose the best answer is a question: when did Denver start using building codes?

    Some states have used building codes for a very long time, while other states still don't use building codes.

    Some states leave it up to each different city to use building codes ... or not.

    From your question, it sounds like Denver may not have used codes very far back, and when Denver started using building codes they likely only applied those codes to "new" construction (which is not uncommon for places to do when they start using building codes).

    It typically isn't until sometime later that they realize "existing buildings" have work done on them too, and that trying to apply a "new construction" code to "existing buildings" isn't very workable, so they adopt 'existing building" codes.

    It has mostly only been since the various model codes joined together and formed ICC codes that adopting an "existing building code" has become more common (which puts it in the same time frame you stated).

    Find out what code(s) Denver adopted and when, only then will you be able to answer your question (and the answer may be that few codes, if any, applied to houses, that they only applied whatever code they were using to larger buildings such as schools, highrises, malls, etc).

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  4. #4
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    Default Re: When does combustion air requirement for fossil fuel furnaces, etc appear in the

    Quote Originally Posted by Jerry Peck View Post
    I suppose the best answer is a question: when did Denver start using building codes?
    Everything you said is true, of course. But when Denver began using code doesn't answer my question. From my many conversations with tradespeople and inspectors from around the country and Canada, few, if any, states, provinces, and localities adopt codes the day they are published. And few, if any, adopt the codes as written.

    But none of that goes to my question. I am wondering when guidelines for combustion air first appear in the code book(s).

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  5. #5
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    Default Re: When does combustion air requirement for fossil fuel furnaces, etc appear in the

    Quote Originally Posted by Lon Henderson View Post
    I am wondering when guidelines for combustion air first appear in the code book(s).
    I have the old Uniform Building Codes on disk, and a link that Gunnar provided us to those codes which are on one of the CA universities servers (and which are easier to use than my disks as the software of the disks is only suitable for use on Windows XP and older systems) - maybe Gunnar will repost the link to those codes before I get to my computer (using my phone for this).

    Jerry Peck
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  6. #6
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    Default Re: When does combustion air requirement for fossil fuel furnaces, etc appear in the

    Finally got back to my office and my computer: https://digitalassets.lib.berkeley.edu/ubc/

    I started with the oldest UBC listed, the 1927 UBC (Uniform Building Code), and started skimming through the code and ... on page 175, last paragraph at the bottom, it says:

    Sec. 3707.
    (skipping to the last paragraph on page 175)
    An air supply shall be provided for every gas furnace. Such supply may be from the outside air into the furnace room, from inside the building into the furnace room or from either source direct to the furnace by means of cold air pipes or ducts constructed of metal or other incombusti-
    (continued on next page)
    ble material. When the air supply is taken from the outside air one or more openings shall be provided into the furnace room and such openings shall have a net area of not less than four hundred (400) square inches. No obstructions of any kind shall be placed over such ducts except a wire netting with openings not less than on-half (1.2) inch square.

    The above is describing combustion air.

    Last edited by Jerry Peck; 01-17-2020 at 01:38 PM. Reason: "fro either source" should have been "from either source"
    Jerry Peck
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  7. #7
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    Default Re: When does combustion air requirement for fossil fuel furnaces, etc appear in the

    Quote Originally Posted by Jerry Peck View Post
    Finally got back to my office and my computer: https://digitalassets.lib.berkeley.edu/ubc/

    I started with the oldest UBC listed, the 1927 UBC (Uniform Building Code),
    The above is describing combustion air.
    Wow! I have to say that I did not expect to find a code for combustion air going all the way back to 1927. Thanks for looking that up. And thanks for posting the link.

    I recently did an inspection for the son of Denver's chief inspector in the mechanical division. He's a guy in his 50's. I had spoke to him on the phone several times over the years but had never met him. He did not know when Denver began inspecting for combustion air (before his time), but agreed with me that it appeared to begin in 1990. He had no idea when combustion air appeared in the code.

    That piece of information really changes the picture for me. I had known that code contained combustion air consideration by the 80's. The story that I stitched together from the many short comments here and there is that combustion air was not a major consideration until the aftermath of the first oil embargo of the 70's. When the price of fuel oil and gas spiked, concern about energy costs spiked in a parallel move. Builders started building more energy efficient homes and home owners started doing things to "tighten" their homes such as replacing old "leaky" windows, sealing and insulating. Air exchange was decreased and concern about adequate combustion air for fossil fuel appliances increased. Circa 1990, around most of the US, AHJs began requiring combustion air to be considered whenever a fossil fuel furnace, water heater, and/or boiler was replaced, regardless of the age of the residence or building.

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  8. #8
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    Default Re: When does combustion air requirement for fossil fuel furnaces, etc appear in the

    Quote Originally Posted by Jerry Peck View Post
    maybe Gunnar will repost the link
    Hi Lon,

    I didn't get it before Jerry managed to post his response - I have had the flu. Included is the link to the U.C. Berkeley archive UBC library.

    https://digitalassets.lib.berkeley.edu/ubc/

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  9. #9
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    Default Re: When does combustion air requirement for fossil fuel furnaces, etc appear in the

    Quote Originally Posted by Lon Henderson View Post
    I tried an online search for the earliest requirement for combustion air in the IRC, but struck out. I am looking for earliest language like G2407.
    Background: Some years ago, Denver city inspector told me that he thought Denver started requiring considering combustion air whenever a furnace, water heater, and/or boiler were replaced in 1990. Certainly, around here, I never see pre-1990 furnaces with any combustion air source regardless of the room volume.

    But I've seen references to combustion air that indicate that code required it earlier than 1990. I know some of you have a code book library going back to just after the last ice age, so I am hoping that you can give me a good timeline on when code began to require adequate combustion air.
    We used 1 sq inch per 1000 btus input so we used to make sure a furnace in a closet utility room had a 6 x 12 inch hole at the top and bottom of the door. The code is in the IFGC and NFGC and is covered under NFPA 54. If my book was in front of me I would cite the code reference and pages. Which I may still do if I get back into my shop bldg. As far as old units there is a section in the NFGC that deals with air infiltration thru joist bays and such and also the size of a room in relation to the input of the unit.

    Last edited by Richard Bushong; 01-29-2020 at 03:34 PM. Reason: add ons

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