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  1. #1
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    Default Flue Gases in attic

    Inspected a ranch home today that had a direct vent fireplace. The exhaust hood on the exterior was up under the eave and was in compliance for distance to the perforated soffit. I turned on the fireplace and let it run the whole time I was there. When I went into the attic the smell about knocked you out from the flue gasses being sucked through the soffit. The builder was there and claims it is a energy star home and the that attic is sealed from habitable areas. He also claims the gases in the attic pose know risk and is allowed. It just doesn't sit well with me and I think it's a risk of leakage into the home.
    Is there any code that says no gases in the attic?

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  2. #2
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    Default Re: Flue Gases in attic

    In answer to your direct question, no, not that I can find. But maybe some of this will help.
    First, it has to meet the requirements of the manufacturer
    AND

    2003 IRC

    G2427.3 Design and construction. A venting system shall be designed and constructed so as to develop a positive flow adequate to remove flue or vent gases to the outdoor atmosphere.
    g2427.8 #3
    10,000 or less at least 6 inches from any air opening into the building
    over 10,000 to 50,000 at least 9 inches
    Over 50,000 at least 12 inch vent termination clearance.
    The bottom of the vent termial and air intake shall be located at least 12 inches above grade.
    Diagram in appendix C

    Jim Luttrall
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  3. #3
    Ted Menelly's Avatar
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    Default Re: Flue Gases in attic

    Dumb da dumb da duuuuuuuuumb


  4. #4
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    Default Re: Flue Gases in attic

    The builder claims he wanted as high as possible to avoid putting a guard around the hood at the patio.

    Jim would attic air be considered outdoor atmosphere.........

    Ted, dumb de?

    The attic area is around that dormer you see. You can walk around the walls of the dormer. It's a bonus room second floor. You can see where the vent hood is.

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    Default Re: Flue Gases in attic

    Quote Originally Posted by Mike Schulz View Post
    The builder claims he wanted as high as possible to avoid putting a guard around the hood at the patio.

    Tell him that the guard for the hood at the patio would be a lot less dangerous than the flue gases in the attic might be.

    Especially since (something I did know previously ) was that there is a second floor abutting that attic. Makes the potential for danger much greater.

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  6. #6
    Ron Bibler's Avatar
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    Default Re: Flue Gases in attic

    You may be OK with the install of the unit. but if you have hi flue gaseslevels in the attic then thats another issue.

    Best

    Ron


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    Default Re: Flue Gases in attic

    Ron as posted before the gases about floored me. No I did not take any readings. Maybe I should of. I had the builder and buyer both go up with me and check it out for themselves. I explained my concerns to both the buyer and the builder and he just tip toed around it. So I guess it's up to the buyer what they want to do about it. I suggest installing solid soffit panels above this area but the builder says it messes up the net free ventilation in the attic. So lets see, possible poisoning or Little less venting, tough call on that one............

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  8. #8
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    Default Re: Flue Gases in attic

    Quote Originally Posted by Jerry Peck View Post
    Tell him that the guard for the hood at the patio would be a lot less dangerous than the flue gases in the attic might be.

    Especially since (something I did know previously ) was that there is a second floor abutting that attic. Makes the potential for danger much greater.
    When I was doing a lot of commercial and apartment drywall work the builders woul light a smoke bomb off on one side of the wall in the attic. Looking at the firewall in the attic with all the joints seeled and the top fire caulked you would be amazed at how much smoke still came thru.


  9. #9
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    Default Re: Flue Gases in attic

    Quote Originally Posted by Mike Schulz View Post
    Ron as posted before the gases about floored me. No I did not take any readings. Maybe I should of. I had the builder and buyer both go up with me and check it out for themselves. I explained my concerns to both the buyer and the builder and he just tip toed around it. So I guess it's up to the buyer what they want to do about it. I suggest installing solid soffit panels above this area but the builder says it messes up the net free ventilation in the attic. So lets see, possible poisoning or Little less venting, tough call on that one............

    I want one Bacharach PCA Portable Combustion Analyzer - Oxygen (O2) / Carbon Monoxide (CO) $ 2K OUCH.

    Best

    Ron


  10. #10
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    Default Re: Flue Gases in attic

    "Flue Gases in the Attic"...........wasn't that a book by VC Andrews??


  11. #11
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    Default Re: Flue Gases in attic

    IMHO, the attic space cannot be considered "outside", therefore it's a violation of the requirement to vent to the outside.


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    Default Re: Flue Gases in attic

    Quote Originally Posted by Fred Warner View Post
    IMHO, the attic space cannot be considered "outside", therefore it's a violation of the requirement to vent to the outside.

    Fred,

    The attic is not considered to be "outside" (but you know that ), one way to know that is that the attic is required to be vented to "outdoors" (unless using the sealed attic system) ... how can you vent an attic to "outdoors" if it is already considered "outside"?

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  13. #13
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    Default Re: Flue Gases in attic

    Thats an inside joke Trying to get out


  14. #14
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    Default Re: Flue Gases in attic

    Quote Originally Posted by Ron Bibler View Post
    I want one Bacharach PCA Portable Combustion Analyzer - Oxygen (O2) / Carbon Monoxide (CO) $ 2K OUCH.

    Best

    Ron
    The Testo version is "only" $1069. And mine came with a free boroscope! My first use of the Testo, I found a gas stove venting > 300ppm into a kitchen with no exhaust fan

    testo combustion analyzers


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    Default Re: Flue Gases in attic

    Quote Originally Posted by Claire R View Post
    My first use of the Testo, I found a gas stove venting > 300ppm into a kitchen with no exhaust fan

    I'm guessing that most, if not all, gas stove will do that, and no exhaust fan is required.

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  16. #16
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    Default Re: Flue Gases in attic

    Quote Originally Posted by Jerry Peck View Post
    I'm guessing that most, if not all, gas stove will do that, and no exhaust fan is required.
    I am an energy auditor, not a HI. This was my first (and so far only) gas oven. The BPI "Combustion Safety Test action levels" are as follows:

    (measurements of undiluted flue gases at steady state)

    100-400ppm Retrofit action - "stop work: work may not proceed until the system is serviced and the problem is corrected."

    I will be interested to re-test the stove (for my relative) after service, to if the number is lower.


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    Default Re: Flue Gases in attic

    You mentioned only one measurement of proximity.

    From the photograph it is clear that there are a number of proximity issues including a partially enclosed area capturing eddies and preventing effective exhaust to outside atmosphere. Consider "fresh" air for combustion, from another source?

    What are the ruling codes in your jurisdiction? Regarding chimneys, and fuel gas?

    There should also be listed instructions for the firebox itself which will reference exaust/vent requirements usually referencing a specific national code - if the locally adopted code requirement differs in that it is less stringent, usually that local code defers to the equipment, product, etc. be used within its labeled and/or listed and/or referenced limitations-restrictions-instructions. If the manufacturer's labeled/listed instructions/requirements/restrictions for the equipment itself are required to be followed if those are more restrictive, specific, etc.

    I find fault with the pictured proximity to the lower level roof extension, the adjacent roof line of the ell, and the compound overhang and angle/projection of the capturing corner space for vent.

    If required use the beginning of whichever code adoption is in force - products of combustion are to be exacuated effectively, not only noxious gasses but also moisture.

    A locally based certified chimney professional could be upon.

    Last edited by H.G. Watson, Sr.; 02-20-2009 at 10:31 AM.

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    Default Re: Flue Gases in attic

    Did you test it with the oven and the broiler on too?

    Turn on all burners, including the oven and broilers before testing.

    I suspect you will find the results 'go through the roof'.

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    Default Re: Flue Gases in attic

    Quote Originally Posted by Jerry Peck View Post
    I'm guessing that most, if not all, gas stove will do that, and no exhaust fan is required.
    Without an operable window in the room that statement is untrue in many jurisdictions.


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    Default Re: Flue Gases in attic

    Quote Originally Posted by H.G. Watson, Sr. View Post
    I find fault with the pictured proximity to the lower level roof extension, the adjacent roof line of the ell, and the compound overhang and angle/projection of the capturing corner space for vent.

    I suppose you do "find fault with" the location of the vent as it seems that your intent is to "find fault with" everything posted here, so, in the same spirit ...

    According to many (this particular one is unknown) installation instructions showing clearances around such terminations, the minimum clearance from the top of the termination to the overhang, deck, balcony, etc., is 18 inches (the clearance shown in the photo *OBVIOUSLY* exceeds that minimum clearance requirement).

    Additionally, the clearance to the sidewall in an alcove as shown is 6 inches to non-vinyl sidewalls and 12 inches to vinyl sidewalls (the clearance shown in the photo *OBVIOUSLY* exceeds that minimum clearance requirement).

    Obviously you are incorrect in your statements herein. Cheers.

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    Default Re: Flue Gases in attic

    What is the make and model of the fireplace?

    What levels of CO did you measure in the attic?

    What is the measurement from the exhaust point on that termination to the soffit?

    Is that vinyl soffit?

    TIA,
    Bob

    Keep the fire in the fireplace.

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    Default Re: Flue Gases in attic

    Sorry Bob for the late reply.

    It is a Heat and Glo SL-750-tr-IDI-E
    http://www.fireside.com/downloads/in...s/2119_900.pdf

    The cap is 2' from the soffit. It is perforated soffit and vinyl. The roof overhang is 18"

    I did not measure the co.

    Thanks.

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    Default Re: Flue Gases in attic

    Quote Originally Posted by Mike Schulz View Post
    It is a Heat and Glo SL-750-tr-IDI-E http://www.fireside.com/downloads/in...s/2119_900.pdf


    Mike,

    That looks like the wrong installation instructions.

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    Default Re: Flue Gases in attic

    Opps, http://www.fireside.com/downloads/in...s/2118_900.pdf

    It looks like it needs 30" clearance.

    Do you think 6" will make a diffrence?

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    Default Re: Flue Gases in attic

    Quote Originally Posted by Mike Schulz View Post
    Opps, http://www.fireside.com/downloads/in...s/2118_900.pdf

    It looks like it needs 30" clearance.

    Do you think 6" will make a diffrence?
    On page 24 is the chart for clearances, item 'O' is shown as from the top of the terminal to the bottom of the soffit/overhang.

    Item 'O' shows two clearances:
    - 18 inches for non-vinyl soffit and overhang
    - 42 inches for vinyl soffit and overhang

    Thus, only 18 inches is needed for the flue gases, but 42 inches is needed for the heat aspect from vinyl soffit and overhang.

    I suspect that all manufacturers use that same drawing, it is the same one I've seen on all the ones (all the few) which I've looked at.

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    Default Re: Flue Gases in attic

    Jerry,

    I read things wrong all the time but the boxed in area with the "o" in it says at the top for alcoves. On the left column under "C" shows under the eave does it not?

    It should be 4' and not 18" or 30" that the directions show.
    After reading the 30" rule I see it says "vinyl clad" soffit. Never seen that before just vinyl so I guesss 18" would be allowed.

    Thanks for your time

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    Default Re: Flue Gases in attic

    Quote Originally Posted by Mike Schulz View Post
    but the boxed in area with the "o" in it says at the top for alcoves. On the left column under "C" shows under the eave does it not?
    Question for you: Is that under an overhang along an open side, or is it under an overhang in a one-open-side alcove?

    Either way it is 18 inches if not vinyl. It only matters if it is vinyl, then it would be either 30 inches or 42 inches.

    See Note 2.

    Hmmm ... what dimension makes it a one-open-side alcove and what dimension makes it just along an open side?

    The only thing in there I see which helps with that question is dimension 'Q'. *IF* 'Q' is taken as the width of the two-sided alcove, and 1/2Q is to either wall, and Q = 3 feet for one cap, then 1/2Q = 18 inches. Thus, could it be said (maybe, maybe not) that if the side wall is greater than 1/2Q that it is no longer considered a one-sided alcove?

    I'd have to read more of it to see, or simply write the manufacturer and ask them.

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    Default Re: Flue Gases in attic

    Quote Originally Posted by Jerry Peck View Post
    I'm guessing that most, if not all, gas stove will do that, and no exhaust fan is required.
    Jerry,

    "2006 NJ IRC M1507 Table M1507.3 Minimum required exhaust rates for one and two family dwellings- Kitchens 100 cfm intermittent or 25 cfm continuous"

    What say yee?

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    Default Re: Flue Gases in attic

    Quote Originally Posted by Darren Miller View Post
    Jerry,

    "2006 NJ IRC M1507 Table M1507.3 Minimum required exhaust rates for one and two family dwellings- Kitchens 100 cfm intermittent or 25 cfm continuous"

    What say yee?
    Darren,

    That is one of the sections of the code in which one much pay close attention (closer than most section of the code) as to what is stated to be able to figure out what is required.

    (I'm referencing the 2006 IRC without having a link to the NJ IRC here.)
    You will note in M1506.2 that recirculation of exhaust air is prohibited in "bathrooms and toilet rooms". (underlining is mine)
    - M1506.2 Recirculation of air.
    Exhaust air from bathrooms and toilet rooms shall not be recirculated within a residence or to another dwelling unit and shall be exhausted directly to the outdoors. Exhaust air from bathrooms and toilet rooms shall not discharge into an attic, crawl space or other areas inside the building.

    You will note in M1507.3 that it addresses "Ventilation" rate, and in Table M1507.3 it addresses "ventilation" of kitchens and bathrooms, but also "mechanical exhaust" for bathrooms. Note that "exhaust" and "mechanical exhaust" are not require or specified for "kitchens".
    - M1507.3 Ventilation rate.
    Ventilation systems shall be designed to have the capacity to exhaust the minimum air flow rate determined in accordance with Table M1507.3.
    2006_IRC_Table_M1507.3_ventilation_1-and2-family.jpg

    The Commentary states:
    - Regarding M1506.2 Recirculation of air.
    - - This section prohibits the recirculation of exhaust air
    from toilet rooms and bathrooms within a dwelling or to another dwelling. Recirculating (ductless) exhaust fans are not allowed if mechanical ventilation of a space is required, but such fans are allowed in naturally ventilated spaces.
    - - - Recirculation to other dwelling units is prohibited because odors, disease causing organisms, and excess moisture could be transported from one dwelling unit to another.

    - Regarding M1507.3 Ventilation rate.
    - - The ventilation rates for kitchens, toilet rooms, and bathrooms are specified in Table M1506.3.
    - - The exhaust rates specified in this table are identical to those in Table 403.3 of the International Mechanical Code. The continuous rates are lower than the intermittent rates, reflecting the fact that an exhaust fan that runs continuously will provide some degree of over-ventilation during periods in which contaminants are not being produced. An intermittent exhaust fan will run for short periods of time only, requiring a higher exhaust rate to effectively control odors, cooking effluent, and moisture.

    Being as the kitchen is an allowed "naturally ventilated area" (see M1506.2), recirculation of the air is allowed.

    If there is no other means of "ventilation", i.e., recirculating the air with the air in the house, then one would apply that section to require a range hood, which could be of the recirculating type.

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    Exclamation alcove definition

    The chart in the listed instructions shows you what they call an alcove. Based upon the photo provided, I would say no, this is just a vinyl soffit that requires a 30" clearance per the listed instructions. However, if you're getting recirculation of flue gases into the attic, that needs to be corrected irregardless. My usual recommendation in this case is to remove the ventilated soffit for 3' of centerline and replace it with caulked in alum. coil stock, then re-test in the attic.

    Listed instructions and codes are not a guaranttee---only min. std. Due to field conditions, you may have to exceed the listing.
    Bob

    Keep the fire in the fireplace.

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    Default Re: Flue Gases in attic

    Bob,

    I was hoping you would reply, do you know what distance to a side wall would cause the one-sided "alcove" requirements to kick in?

    The drawing shows a two-sided alcove, but mentions a one-sided alcove as well.

    What distance would cause the two-sided alcove to kick in? The distances shown for 'Q'?

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    Default Re: Flue Gases in attic

    Seemed clear from the get-go that was vinyl. Distracted by the dormer references, and unfortunately I hadn't yet realized to zoom enough for these old eyes to make out details when on the tiny laptop I needed to download pic and open in a viewer to make bigger (originally I was looking at vent cover above 2nd level to L of dormer windows oops). Thanks for confirming not co-linear venting, once I blew the pic up after figuring out how to d/l it I .

    Side wall or not its an overhang, the material is vinyl above the vent. That's your 30" so it must be at least 6" lower.

    M or O, it must be 18" lower than the 24" it is now since you have vinyl overhang above (minimum clearance is 42" below according to your linked instructions).

    Your question about side wall is your dimmension N - if vinyl that's 12" minimum clearance. There is no maximum listed in your instructions to consider its presence. The sidewall would be to the left the ell.
    Might help to follow to the end of the notes in the box at the end below note 5 it says:

    " Vent system termination is permitted in porch areas with two or more sides open. You must follow all side walls, overhang and ground clearances as stated in the instructions."

    As you know, the "tighter" the house the more critical even minor defects can be when it comes to fuel fired appliances/systems vents being sealed, installed properly, not blocked, to assure combustion air and proper evacuation of the products of combustion.

    Attic is part of structure. Must exhaust to outside the structure effectively otherwise it doesn't meet the definition of direct vented fireplace (Nat. Fuel Gas Code). Fuel Gas Code also requires 10' from any mechanical ventilation inlet of the structure. IIRC that does not except mechanical attic ventillation inlets (sofit vents), electric fan, heat pump in attic, or wind driven turbine type ventillators. Of course since the T.I.A.s I don't always recall correctly and I'm too drained after listening to the Prez to-nite to double check it (the last 3 editions changed so much esp. the chapter numbers) let alone cross reference its applicability to your instructions and your jurisdiction.

    CO in the attic means trouble as you know. The clearance from vinyl overhang is deficient.

    Perhaps you might note your attic experience - if you're sure that wasn't just break-in burn-off (was a window open?). If you have exhaust temperature readings, thermal photography, CO alarm or reading are you allowed to include them? The clearance from vinyl overhang deficiency or just generalize the concern/deficiency of the function/definition of the direct vented gas fireplace and cite the vinyl overhang clearance example?

    Last edited by H.G. Watson, Sr.; 02-24-2009 at 09:35 PM.

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    Default Re: Flue Gases in attic

    At the time of the inspection with the builder and the client I explained to them I believe the soffit should be solid in this area. I'm sure some of it may have been burn off but if the attic is filled with that it will also have co.
    I did not take readings because both where there and experienced the same thing. All was noted in the report. I sent a side note by email to my client about my concerns as well. I included Jerry's Post from his site. (Thanks Jerry)

    Reason for not taking readings is with different weather patterns, prevailing winds etc. it may change from time to time and I don't want to put a specific number on it. In my opinion taking a reading is not necessary because no exhaust period should be returning into the attic.

    The hood is 24" so it is 6" off but I don't believe 6" will change that much. I believe it should be 42". The manufacture should change there instructions. Maybe Jerry and Bob who have great credentials could lobby for this.

    Anyway if one of you guys get a home that a cap is under a vented soffit run the unit for a half hour or more and check the attic. This is the third time it has happened for me.

    Thanks

    Mike Schulz License 393
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    Cool Re: Flue Gases in attic

    Mike there is no "lobbying" to change the clearance. It is based upon testing. As long as it passes the 30" in the test model, they will leave it as is or unless litigation forces a change, which is why it was increased from 18-30" in the first place. Understand, after 30 inches, you should not have a heat issue but the exhaust fumes will always be a question mark. We discussed putting it into the manuals requiring the solid soffit 3ft bilateral of center line. What about 41 or 43 inches? How was this distance determined?

    Jerry, if there is not clear info. in the manual stated then you would have to defer to the mfrs. technical services dept. In the case of a "one sided alcove", you would actually be looking for two sides such as a corner with an overhang. They left this open with the intent to discourgage the practice. Alcoves trap heat and gases. The more frequent application is where a porch is enclosed over and around a vent termination. You cannot screen that porch as it restricts airflow too much, trust me. You, as a HI, can always flag it as a possible problem then send a sketch to the mfr. for a ruling, which, quite frankly, is what we did all the time when I was a Regional Field Operations Manager. Get an engineer's eyes on it and let them put it in writing. That usually draws out a more conservative recommendation.

    BTW, I've seen terminations 6ft below a soffit inhale fumes---attic/ whole house fans. That's not the fault of the fireplace mfr.

    Mike, I appreciate your concerns about not testing and there's some validity. Until you are trained and qualified--don't. In that case, I would recommend a qualified technician inspect and test the fireplace to determine that it was installed to the listed instructions and operating within specs. then have them sample in the attic while burning as a spot test but noting the results can vary with conditions.

    I would recommend low level CO monitors outside the bedrooms.
    Bob

    Keep the fire in the fireplace.

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    Default Re: Flue Gases in attic

    Bob,

    In his photo above, which I've annotated and attached, how close would that wall be to be considered affecting the exhaust termination and to be considered a one-sided alcove?

    Any "rule of thumb" or, as I did, look at the drawing, the dimensions, and where 'Q' equals their distance for a two-sided alcove, 1/2Q would equal the distance to a one-sided alcove?

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  36. #36
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    Wink alcove definition

    Jerry, think there is a little confusion. The Note 2 in the listed instructions reference to "one side open" means the front--not a side. Otherwise, you would simply use the side clearance and soffit clearances stated. I've seen a corner in a bldg next to a bay window where it formed an "alcove" because it formed a sconce of sorts trapping heat and gases. The mfrs. cannot anticipate every installation iteration so as I say, when in doubt, send them a few pics or sketches with dimensions. In the case with HHT products, you would measure from the trapezoid termination itself and not the square base pan flashing.
    Bob

    Keep the fire in the fireplace.

  37. #37
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    Default Re: alcove definition

    Quote Originally Posted by Bob Harper View Post
    Jerry, think there is a little confusion. The Note 2 in the listed instructions reference to "one side open" means the front--not a side.
    (slaps forehead)

    Okay, got it.

    Thanks, that one went right over my head (or through it without meeting any resistance) - whoosh!

    Otherwise, you would simply use the side clearance and soffit clearances stated.
    Which, in that installation instruction drawing, would be 'E' which only requires a 6 inch clearance to an inside corner (not shown on drawing, just in key to the drawing).

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  38. #38
    Ed Voytovich's Avatar
    Ed Voytovich Guest

    Default Re: Flue Gases in attic

    If the direct vent fireplace introduces combustion gases into the unconditioned attic, and if the appliance is run very often, and if the climate where the house is located is cool enough to get people to run the fireplace, then the flue gases will most likely condense on the underside of the roof and enable the growth of mold and possibly damage the roof sheathing. The attic ventilation so dear to the heart of the builder won't help, because the moisture in the combustion gas will change state from vapor to liquid on the first condensing surface, and that's going to be the roof sheathing between the soffit vents and the vents at or near the ridge.

    The builder's argument that reducing the supply ventilation by sealing the soffit above the vent is not very persuasive. It's like an Emergency Room physician saying that the arriving patient's hang nail needs immediate attention when, in fact, the patient has a sucking chest wound.

    If this is an Energy Star Labeled Home, the question could be referred to the Rater Provider of the third party rater who certified the Energy Star Label. It's possible that the Rater missed this issue.

    On the other hand, this problem most likely falls outside the specifications for Energy Star, and the builder just doesn't understand that the existing condition compromises the durability of the home.

    The condition should be corrected not because of some code or rating issue, but because it is poor building practice. If some Home Inspectors don't insist on addressing problems like this, the value of all inspections is compromised.

    My hat's off to the inspector who caught it. Good catch. Please find the guts to follow through.


  39. #39
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    Default Re: Flue Gases in attic

    If some Home Inspectors don't insist on addressing problems like this, the value of all inspections is compromised.

    My hat's off to the inspector who caught it. Good catch. Please find the guts to follow through.
    Ed, maybe I am misreading your intent but I can't drag and beat the people. Guts to follow through?
    As I stated above in the other post I have informed the client and builder while on site. I have it in my report. I also sent personal emails to my client on the subject.
    How would you do it? Call the fire Dept., the health dept. ........Please explain

    As far as energy star I believe there concern is the interior envelope air leakage. I don't think air quality in the attic is there concern for meeting there rating. Maybe I wrong correct me if I am.

    Mike Schulz License 393
    Affordable Home Inspections
    www.houseinspections.com

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