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Fed up with DV LP fireplace drafts/cold air. Found the problems, need advice.

Post in 'It's a Gas!' started by P38X2, Oct 15, 2012.

  1. P38X2

    P38X2 Minister of Fire

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    Jaffrey, NH
    Hi, folks. I usually poke around the pellet forum but we're talking gas here. Sorry if I come off as angry but I'm quite frustrated with what I've read/heard thus far concerning this issue. If it's posted online, I've probably read it .Also, I apologize in advance for my long winded post. .

    I have a Desa DV LP fireplace and when it's cold outside, its cold near the fireplace. When it's freezing outside, it's freezing near the fireplace. I've poked around the internet for a few years now and found many posts by owners and many posts (usually in the form of FAQ sections) from manufacturers/dealers regarding this issue, with no definitive resolution but plenty of excuses, N/A solutions or "duct tape" repairs.

    I had my home built in 2006 and photo documented it's construction thoroughly but didn't notice the likely #1 problem until now. The fireplace sits in a "doghouse" on the gable end of my house. The doghouse is insulated, sheathed, wrapped with Tyvek and vinyl sided. The LP feed, which comes up from beneath in the basement, is sealed where it passes through the floor and into the firebox. The intake/exhaust pipe is sealed with foil tape where it passes through to the termination cap.

    The fireplace was installed by Builders Insulation (Builders Installed Products Inc) and inspected by my local town authority. I've had it looked at twice since occupying the house by BI/BIP and was told everything is installed correctly and up to code.

    First issue, and my concern from the beginning, is the inherent design flaw with a DV fireplace. When crouching in front of the unit, I can see light coming through the vent pipe. Cold air comes pouring into the firebox where my last line of "insulation" defense is the single pane glass and the paper thin sheet metal firebox itself. With the warm air from the house and the cold outside air, a nice convection current is established to ensure I get the freshest, coldest air possible:mad: I understand if the firebox and glass are insulated and can't radiate heat into the room, then it negates whole point of having a fireplace in the first place. I could've just bought the "Yule Log" DVD and watched that, lol. Anyway, that seems like a ridiculous design to me. Seems to me an idiot proof (read- potential accident free) DAMPER might have been a good idea!? Perhaps some DO come with dampers and my unit is without due to it being a "builders grade" product.

    The next issue, and possibly the biggest issue is the fact NO drywall was placed on the walls inside the doghouse. The only thing stopping cold air infiltration from coming directly into the room is the outer "shell" (not the firebox) of the fireplace unit. Yes, there's Tyvek on the doghouse but without physically stopping the airflow from inside the house, insulation is not particularly effective in this application. To add insult to injury, the walls of the doghouse are 2x4 construction, so R13.

    I'll cut to the chase. Anyone have any ideas on how to remedy this situation?

    I'm not about to remove my beautiful mantle and granite surround to get this fireplace unit out. Why it's buried like that is also baffling and I would have slid it out first thing and drywalled behind there if I could've. I feel so STUPID for not noticing this problem immediately during construction.

    I like to do things the best way possible given what I'm working with. Blankets, tape, magnetic vent covers, etc...are all out. So far, considering I can't remove the unit easily or inexpensively, my ideas are...

    1) Somehow seal off the termination to stop the airflow through the fireplace, shut the LP valve off and disconnect the switch. This would give me a fireplace "ornament" in my living room and still not solve the issue completely.

    2) Remove the siding/Tyvek/insulation on the doghouse and somehow install drywall on interior walls...from the outside, then insulate, re-sheathe, bla bla bla.

    Hopefully someone on the forum can chime in with some experience/suggestions for this likely all too common problem.

    Again, sorry for the long read.
    -Mike

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  2. DAKSY

    DAKSY Patriot Guard Rider Staff Member

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    Yes. You can do this. I have done it on numerous occasions, mostly when replacing old wood burning ZC fireplaces with new DV units...
    Remove the DV cap.
    Remove the siding from the rear of the dog house. If you're gonna do this at this time of year, be extra careful. Vinyl will crack or break in the cold weather. A hair dryer can warm it up enough to safely remove it.
    Remove the sheathing.
    Measure the height of the fire place. If it's less than 4 ft, that's good.
    Cut the studs out of the rear of the dog house at 4 ft.
    Check the insulation in the wall to make sure it's completely stapled.
    If you can, use some packaging tape to seal the seams where they meet.
    Measure & cut the sheet rock for the side walls - all the way to the top.
    Install it with screws where you can. Use roofing nails where you can't get your screw gun in...
    Install sheet rock above the opening you cut all the way to the top.
    Build a framework (rectangular box of 2x4's on all four sides 4" side running vertically, make sure it's level, & secure it to the walls above the fire place.
    Cut a piece of sheet rock that will lay on top of this framework.
    Cut some Kraft-faced insulation to the size of this piece os sheet rock.
    Using silicone caulk, attach the insulation, paper side down, to that sheet rock.
    Carefully fit the sheet rock/insulation assembly up into the dog house & lay it on the framework, with the insulation on top.
    Build a 2x4 knee wall to fit in the opening with insulation installed, seams taped & sheet rock attached.
    You must make sure the vent opening is the correct size & in the correct location.
    Fit the wall in & attach it.
    Re-sheathe & reside & re-install the cap.
    PM me a little later if any of this is unclear...
  3. P38X2

    P38X2 Minister of Fire

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    Jaffrey, NH
    Thanks, DAKSY.

    Do you think the lack of drywall is the main culprit of the cold air? Is there anything that can be done about the firpllace itself being cold?...perhaps some sort of damper system?
  4. P38X2

    P38X2 Minister of Fire

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    Also, I was thinking the same thing regarding the vinyl siding. To boot, it's on the southern exposure and likely even more prone to cracking.

    I also thought of this approach but I'm not sure if the product exists. It would potentially cost more, likely requiring professional installation, but would maintain more of the structure. Fireproof expanding foam insulation is what I'm thinking. It would require only a few access holes be cut in the sheathing in order to rip the fiberglass out then in goes the expanding foam to fill the airspace between the fireplace shell and the sheathing.

    Seems brilliant to me anyway. What's your take?
  5. DAKSY

    DAKSY Patriot Guard Rider Staff Member

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    Your main problem is that when the pilot's off, there is absolutely NO heat in that dog house.
    Whether or not there's an air leak to the outside is one thing, but I will be honest when I tell
    you that even if you seal everything tighter than a crab's a$$, you will still feel cold convection air
    movement in front of the unit. The heat exchanger cavity works in reverse as the warm household
    air hits the cold metal, it gets cooled & drops down the back of the unit, & comes out the bottom,
    creating that "draft" that you feel.
    We actually constructed a doghouse in the middle of a NY winter that was hanging off the side of our
    warehouse, using standard framing practices, in order to see what we could do to mitigate the problem,
    & we insulated & sealed everything with acoustic caulk, except where the DV passes thru the wall thimble.
    We sealed that gap with the tape gasket that is used in woodstove doors to seal the glass...
    We STILL had those convection currents, because the fire box was cold. Only keeping the pilot (or
    the burner) lit, would stop the air flow.
  6. DAKSY

    DAKSY Patriot Guard Rider Staff Member

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    Oops..As far as the expanding insulation, we never tried it...
  7. P38X2

    P38X2 Minister of Fire

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    Well, as you probably figured, my pilot is in fact off. However, only this year did I start turning off the pilot during warmer months. In prior years the amount of cold air near the unit was disturbing, with the pilot on. I'm not disagreeing that it would improve the situation but still brings me back to what I should address next and perhaps more importantly, how much cold air is considered acceptable for these things. I understand without looking at it first hand, you can't answer that.

    I understand that I have areas of heat loss in my home. Windows with their limited R value, dryer vents, range exhaust vents, outlets etc...are all areas of what I would consider "acceptable" heat loss. Again, I have nothing to compare my fireplace with but it feels like there's a window open about 1/4" near it. Maybe that's just the nature of the beast.

    I'm waiting on call-backs from a couple insulation contractors.
  8. P38X2

    P38X2 Minister of Fire

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    Well, I back burnered the insulation issue for this winter. Re-lighting the pilot did help a bit.

    Couple more questions when I do decide to deal with this.

    First, I'm doubtful the vent pipe is sealed properly as it passes through the fireplace shell and out and through the doghouse. I went in through the top vent and sealed the vent where it passed through the shell as much as possible. There was a wicked draft there and since I don't have spaghetti arms, I was only able to seal the top 1/3 of the circumference of the pipe.

    1) Can I easily remove the termination and reach in there and get it from the outside?

    2) the soffit is perforated vinyl. Seeing the area behind the stove doesn't have an air infiltration barrier, should I replace the soffit with something solid? Its the south side of the house and generally gets the most wind. IMO, I won't have a moisture issue because it'll just vent through the unfaced insulation and it's a relatively small area to begin with. It seems highly possible that soffit could be a big culprit in this issue.

    What say you guys?
  9. DAKSY

    DAKSY Patriot Guard Rider Staff Member

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    Remove the cap from the outside. That's the LAST part of the installation process so it should come off easily, unless it's goobed in caulk... When you do, it should have a section of DV pipe attached to it that slips inside/outside the one connected to the back of the unit. Look in there after you remove the cap to see where the gap is between the firestop & the pipe. If the attached section slips OVER the inside pipe, you can measure to where it passes thru the wall firestop & wrap it with tape gasket to get a seal when you reassemble. If the DV pipe off the unit is the outermost, you should be able to wrap THAT with the tape gasket. When you go to buy the gasket, don't short yourself. You may have to go around the DV pipe a couple of times to get the seal...HTH
  10. P38X2

    P38X2 Minister of Fire

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    Thanks, DASKY.

    Gotta feeling it's gooped up pretty good as the service tech addressed that issue twice due to him thinking that was the reason the fireplace was blowing out under certain winds. If its basically glued, then what? Here's a pic. Am I removing the entire termination?....which appears to be flanged and secured under the siding and J channel?


    Any thoughts on the perforated soffit?

    2012-11-16_14-32-46_767.jpg
  11. DAKSY

    DAKSY Patriot Guard Rider Staff Member

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  12. P38X2

    P38X2 Minister of Fire

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    OK, nice. I'll check it out during daylight hours.

    The soffit is about 7' from the sill. Above the FP is approx an 18" air space. Above that is a cubby where my TV is. I'm thinking cold air is coming through the soffit and down the wall between the back of the TV cubby and the insulation. I highly doubt the insulation sits perfectly flat against the back of that area which would leave a nice channel for the air to infiltrate. Perhaps the top plate of the stud wall is serving to block that air. It's hard for me to visualize the situation as I'm not a framer.

    Thanks for the help :)

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