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Direct vent fireplace venting questions

Posted by athensmomof3 (My Page) on
Wed, Sep 14, 11 at 16:22

We were planning on using the Lennox Montebello direct vent fireplace in our basement family room. We chose it because it has very realistic, wood burning proportions, could be set with a flush hearth and could be vented out to the side of the house.

The fireplace is not on an outside wall so we don't have quite enough room to get it outside when you take into account the required rise needed for the vent pipe - it requires 1' rise for every 2' of run, or close to it I think. The other problem is that the vent pipe is very large (10") so with clearances it would require furring down the ceiling in the adjoining room (guest suite) to 8'6", which I would hate to do.

Does anyone have a recommendation on a fireplace with a lower "rise" requirement, or any other solution? I would prefer something realistic, with a clean face (no louvers) and which can be set flush but at this point I am considering everything!! It needs to be somewhere around 42" wide in the viewing area to make the proportions of the framing (which has steel supports holding up the Isokern directly upstairs) which can't be changed.


Follow-Up Postings:

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RE: Direct vent fireplace venting questions

I don't know much regarding rise vs run

we have a Lennox Symmetry in 40" and like both the look and operation. I think we have smaller tubing as well, but since we're on an outside wall I'm not entirely sure.


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RE: Direct vent fireplace venting questions

I'd suggest you take a step back and reevaluate what you're thinking.

8'6" for a ceiling height in a basement guest room is not going to lose you any friends or visiting relatives. You will look at your fireplace every time you are in that room and only occasionally will the guest room have a guest and NONE of them will notice the ceiling is six inches lower than the adjoining rooms. Many basements start at 8 feet and get boxed down from there.

I agree with you that many direct vent fireplaces just don't look right so get the one you want. The rise/run requirement is basic physics. I doubt you'll find any less unless someone makes some sort of power vent fireplace which is a long shot.


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RE: Direct vent fireplace venting questions

I have sort of ruled out the power vent option because they seem to be problematic. There are a couple other venting options we are exploring . . .

You are right about the basement guest bedroom. In fact, it is not even being fully finished and likely won't be unless everyone gets married and lives out of town. We have a guest bedroom upstairs which will be finished and which we will use for now, but this downstairs guest bedroom is really nice (it mirrors the master and has lots of windows) so I would prefer to keep the ceiling at 9'6" if we can. We just framed it out because we have a full basement and aren't finishing all of it. It will be taken to sheetrock though to avoid the mess of finishing it down the road.

This fireplace is also expensive for a basement. It is the only one I could find that had the traditional proportions I wanted and was the right size.

Ideally, I'd like to find a less expensive option with a smaller vent pipe ;)


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RE: Direct vent fireplace venting questions

So I thought about mine which is a Kozy Heat Minnetonka as they had some nice features like doors to cover the glass and the louver on top was not at all obtrusive like the standard builder ones you see everywhere.

An old pic from back in the day:
Fireplace

Before I figured out I had the Minnetonka I thought I had a Napolean. They make some nice looking direct vent fireplaces. I randomly picked the HDX40 which is almost the width you are looking for. On page 9 of the manual which is attached it says you can go a max of 20 feet horizontally with 8 inch vent and potentially with no slope. I'm not sure I buy that but if you look further down the document there are some formulas and tables for various scenarios.

Good luck!

Here is a link that might be useful: HDX40 Manual


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RE: Direct vent fireplace venting questions

Thanks. Those specs are about what we have - 20' horizontal max (I think they all say this), but we have a 9" pipe. The problem is with the horizontal runs they require 3" clearance above and 1" all around so it is too big to fit through the floor joists. They may all be when you allow for clearances.

We can terminate it outside the side wall but that would be outside our porch and quite visible. . . We do have a 9'6" ceiling in there so furring it down some is no big deal, but I would hate to have to fur it down a foot . . .


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RE: Direct vent fireplace venting questions

I should have checked the website more closely. This one has the look you're going for and is 42 inches.

I quickly checked the manual and it looks like it has similar restrictions to the one I posted previously.

Here is a link that might be useful: Napoleon BGD42CF Clean Face Direct Vent Fireplace


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RE: Direct vent fireplace venting questions

The usual solution for a direct vent gas fireplace too far from an exterior wall is to run the vent to the roof.

The total vertical "rise" required for a Montebello gas fireplace that is 20 ft from an exterior wall discharge is 10 ft in order for the gas to have sufficient draft to rise upward. Elements are often horizontal but they should have no dips and to avoid them the recommendation is to rise upward and away from the fireplace at 1/4" per foot but lower slopes are acceptable all the way down to true level. It is common for such a system to be made up only of vertical and horizontal elements with no sloping elements other than the slight pitch to avoid dips.

The clearance of the 11" pipe is 3" on top and 1" on the sides and bottom so it takes up at least 15 inches in a ceiling space plus the total pitch if there is any. It is bot necessary to drop the entire ceiling since it is possible to disguise the enclosure as a false beam but it would be pretty large.


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RE: Direct vent fireplace venting questions

Thanks for your input, Renovator8. That fireplace has been through a few transitions. It was first an Isokern masonry like fireplace but to save some money we changed it to a b-vent on the plans. Once we placed the house on the lot, it became apparent that the b-vent pipe would be viewable from the street, and would have to be fairly high due to the slope of the roof. The initial hope was to hide the b/vent pipe from view behind the upstairs Isokern chimney, but the house is oriented in a way that it is viewable on approach, even though not seen in the front or back yard.

We then changed to an direct vent. The whole reason for the direct vent was to not vent to the roof, so I would like to avoid that.

We have a couple of options with the Montebello like running them behind a bookshelf in the dead space and then over a boxed bay bumpout, but the pipe is so big it may make it not feasible.

I don't think we have enough rise available to run it over the master bedroom tray ceiling above, unfortunately, because that will vent out the side of a house above the a/c in a very inconspicuous place.


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RE: Direct vent fireplace venting questions

The pipe does not have to rise much until it gets to the outside wall where it can rise vertically to the discharge device. Or it could rise vertically and them run horizontally at a very slight slope. The slight slope of the horizontal pipe is for condensation drainage and the is for condensation and the vertical pipe provides the necessary draft for the hot gasses.

Have you downloaded the installation instructions?


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RE: Direct vent fireplace venting questions

I have and sent them to my builder too. The technical guy from the fireplace shop went out there too and they couldn't find a place to vent it that would work. . . but you bring up a good question. When looking at these specs, can the vertical height be broken up? I.e., if it must have a vertical height of 10 to get the full 20' of horizontal run, can it rise vertically 6', go horizontal 20' and then rise another 4' vertically, or does the vertical have to be before the horizontal, if that makes sense?

The complicating factor is that the pipe on the Montebello is so large that it gets huge when you add the 4" clearance required for horizontal runs. . . a smaller pipe would help but I haven't found one yet with a clean face and traditional proportions in the size we need (about 40" wide viewing area)


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RE: Direct vent fireplace venting questions

You need to check your local codes.

Under the national codes the line is required to have a 1/4" per foot rise. (1" rise on 4' run).

If you use single wall vent pipe the horizontal section may not exceed 75% of the vertical rise.

If you use double wall vent pipe the horizontal section my not exceed 100% of the vertical rise.

However your local codes could be dramatically different.


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RE: Direct vent fireplace venting questions

For gas fireplace appliances the building code usually defers to the requirements that the manufacturer used in order get a UL or other agency rating. Also, this particular kind of vent pipe has a double wall so that fresh air can be drawn into the firebox through the outer sleeve and that is what makes the pipe so large.

Other state and local codes might dictate the design of a vent from a gas appliance with a small air draft requirement like a gas water heater or furnace and usually allows them to draw air from the room and can therefore use a single-walled B-vent pipe.


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RE: Direct vent fireplace venting questions

"The other problem is that the vent pipe is very large (10") so with clearances it would require furring down the ceiling in the adjoining room (guest suite) to 8'6", which I would hate to do. "

You could always raise the height of the whole house.

Maybe you are reaching a little higher than you need.

Are your friends going to talk if the ceiling is only 8'6"?


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