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chimney vent

BarrowBuilds's picture

chimney vent (post #205775)

BarrowBuilds on Fri, 02/10/2012 - 06:37 (updated 02/10/12 - 02:14) 
in

I have a brick chimney that needs to come down. The owner had a gas log installed and would like to keep the lower part of the chimney in tact so he can continue to use it. What we plan to do is remove the chimney down to its shoulders and cap it with slate.The gas logis a "ventless" type but we do want to vent it.The owner always opened his flue when using it.Could we simply remove some bricks on the top course where the new slate cap will sit. ,with some wire mesh to keep birds etc .out?I'm wondering if there are any drafting issues without a full lenght flue.Thanks.

-A +A

If you use the chimney as a (post #205775, reply #1 of 11)

by DanH in reply to BarrowBuilds [original] on Fri, 02/10/2012 - 17:22

If you use the chimney as a flue then you need to maintain its height.


We are like tenant farmers chopping down the fence around our house for fuel when we should be using Nature's inexhaustible sources of energy -- sun, wind and tide. ... I'd put my money on the sun and solar energy. What a source of power! I hope we don't have to wait until oil and coal run out before we tackle that. --Thomas Edison

I would check with your local (post #205775, reply #2 of 11)

by Piffin in reply to BarrowBuilds [original] on Fri, 02/10/2012 - 19:14

I would check with your local AHJ and get it in writing.

 

Personally i don't bwelieve in 'ventless' gas appliances

 

 


or try this site for the whole gang

http://forums.delphiforums.com/breaktimeclass/start

I would check with your local (post #205775, reply #3 of 11)

by Piffin in reply to BarrowBuilds [original] on Fri, 02/10/2012 - 19:14

I would check with your local AHJ and get it in writing.

 

Personally i don't bwelieve in 'ventless' gas appliances

 

 


or try this site for the whole gang

http://forums.delphiforums.com/breaktimeclass/start

There's an echo (post #205775, reply #4 of 11)

by seeyou in reply to Piffin [original] on Sat, 02/11/2012 - 07:31

in here

http://www.grantlogancopper.com/

Naw - That's my alter-ego (post #205775, reply #5 of 11)

by Piffin in reply to seeyou [original] on Sat, 02/11/2012 - 16:51

Naw - That's my alter-ego agreeing with me

 

 


or try this site for the whole gang

http://forums.delphiforums.com/breaktimeclass/start

Naw - That's my alter-ego (post #205775, reply #6 of 11)

by Piffin in reply to seeyou [original] on Sat, 02/11/2012 - 16:51

Naw - That's my alter-ego agreeing with me

 

 


or try this site for the whole gang

http://forums.delphiforums.com/breaktimeclass/start

Reducing the chimney height (post #205775, reply #7 of 11)

by rdesigns in reply to BarrowBuilds [original] on Mon, 02/13/2012 - 08:12

Reducing the chimney height will reduce the venting ability of chimney. How much? Hard to predict.

I am not a fan of ventless gas appliances, but if the existing gas log really is listed and approved to be ventless, there is no code prohibition against doing as you plan, because you could close off the chimney altogether. Having a shorter chimney at least offers a possibilty of venting the flue gases out of the home, or, if the flow reverses and the chimney downdrafts, that would bring in a good supply of fresh air to dilute flue gases. Presumably, the homewowner uses the gas log occasionally for its decorative effect primarily, and approved ventless appliances are equipped with an oxygen depletion sensor.

Your liability in this would be scary to me--anything that goes wrong with the gas log's operation will be your fault, even if it's not your fault, because you were the last pro who modified the installation.

The problems with ventless (post #205775, reply #8 of 11)

by Jigs-n-fixtures in reply to rdesigns [original] on Mon, 02/13/2012 - 14:09

The ventless appliances have two problems:

1.)  The produce a lot of moisture that needs to get vented out somewhere.   We had huge issues in a bunkhouse last winter because a decision was made to use it through the winter.  The ventless heater that was installed for just a bit of morning heat in the summer season, ended up running pretty much constantly.  The vapor from it saturated almost everything in the building.  Iced up all the windows, etc. 

2.)  Even with an oxygen depletion sensor so that people don't die from carbon monoxide poisining, the carbon monoxide levels in the blood and body tissues can build up to the point that people get vague flu like symptoms of headaches, muscle pain and stiffness, and feeling lethargic.  The Doctors at the local clinic, have learned to test people for actual blood levels of carbon monoxide. 

I would never have one in my (post #205775, reply #11 of 11)

by rdesigns in reply to Jigs-n-fixtures [original] on Tue, 02/14/2012 - 07:55

I would never have one in my own house for those and other reasons.

I suppose they have a place, maybe like what you mentioned as the original intent (summertime chill-removal) of that bunkhouse.

The manufacturers, and the fuel gas codes, state that they are not to be the primary source of heat, and that you must open a window or door when they fire, but your example shows how reliable that is. Not.

Thanks for the replies (post #205775, reply #9 of 11)

by BarrowBuilds in reply to BarrowBuilds [original] on Mon, 02/13/2012 - 15:02

Thanks for the replies everyone, wouldn't this be the same principal as a rear vented gas fireplace?I believe they are self venting-meaning there isnt a blower or exhaust fan. Am I wrong about this? 

Vented gas fireplaces that (post #205775, reply #10 of 11)

by rdesigns in reply to BarrowBuilds [original] on Tue, 02/14/2012 - 07:49

Vented gas fireplaces that I'm familiar with all require a metal vent system. And, no, they generally do not have an exhaust blower.

Some use Type B vent and take their combustion air from inside the house. Most that I see, however,  take combustion air from directly outside, either by means of a second metal pipe to the outside, or by means of a direct-vent concentric pipe, such as made by Simpson.

But none that I know of vent by means of the masonry chimney itself; instead, the masonry chimney is simply a chase for the metal vent system.

Using the masonry chimney results in too much condensation being formed inside the chimney, which can eventually result in severe deterioration of the masonry.

Gas logs don't form a lot of condensation inside the masonry chimney because of their gross inefficiency--they allow a lot of drying room air to escape up the chimney.