Chimney Minimum Height - Fireplace Gas insert

[joe Laflaque]

Hello
I had inserted this query in my Introductory Post but now realize that it should have been a separate post with proper technical heading.

I'm about to buy a fireplace natural gas insert. The portion of my masonry chimney extending over the roof needs to be repaired first, as repeated freeze and defreeze in winters (brrr..Canada) have damaged a good number of bricks. And these exact brick colors are no longer available.

One solution would be to reconstruct that portion of the chimney extending over the roof but to reduce its hight from 4 feet to 3 feet in order have enough good bricks.

The insert (Valor) will use the so-called direct venting system for intake and exhaust through the chimney. Is there generally a difference in building code requirements as to chimney height when one switches from wood (solid) to natural gas? If not, could a repaired and reduced 3 ft over-the-roof chimney still be acceptable under the codes?

I've seen some references to the 2-3-10 rules on this site. Shall I assume these apply equally whether I'm using an old fashion wood burning fireplace or a modern natural gas insert with direct venting?

Thanks in advance for your comments.

Joe

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[Jerry Peck]

I'm about to buy a fireplace natural gas insert.

Natural gas does not use the same clearances as a regular chimney does.

A regular chimney would be 3 feet high minimum (the '3' in the 3-2-10 rule), or 2 feet higher than any part of any structure within 10 feet (the '2-10' part of the rule).

Gas vent can be higher, but are typically not required to be as high, and the minimum height of the gas vent depends on both the size of the gas vent and the slope of the roof. The gas vent 'might' be allowed to be as short as 1 foot high above the roof on its high side (the higher side of the sloped roof), or it might have to be several feet high, again, depends on the size of the gas vent and the slope of the roof.

[joe Laflaque]

Natural gas does not use the same clearances as a regular chimney does.

A regular chimney would be 3 feet high minimum (the '3' in the 3-2-10 rule), or 2 feet higher than any part of any structure within 10 feet (the '2-10' part of the rule).

Gas vent can be higher, but are typically not required to be as high, and the minimum height of the gas vent depends on both the size of the gas vent and the slope of the roof. The gas vent 'might' be allowed to be as short as 1 foot high above the roof on its high side (the higher side of the sloped roof), or it might have to be several feet high, again, depends on the size of the gas vent and the slope of the roof.

Thanks Jerry. Here's a couple of pictures showing the chimney. Would you have, or would you know where I could find, the formula that is generally used taking into consideration the slope of the roof?
Joecheminée 5cm-.jpgcheminée 001-5cm.jpg

[Matt Fellman]

Before you sink much money into chimney repair it may be less costly to just remove the chimney and go with a side venting gas fireplace. That could get complicated with installing siding once the chimney is gone but may be an option.

Otherwise, I can't imagine it will save any huge amount of money by lowering the chimney (if it's even an option while still keep the correct clearance). Re-pointing chimneys is usually not as expensive as I would think. I can't tell from your pictures but I'd say an average repair if it's isolated to part above the roof shouldn't run much over $500-$700 but it's hard to say without being there.

[Raymond Wand]

Reducing the chimney height by a foot should not be a problem with that chimney.

[John Kogel]

I have the diagram you need here.

That is a good looking house. La cheminee c'est tres belle. JMO

[joe Laflaque]

I have the diagram you need here.

That is a good looking house. La cheminee c'est tres belle. JMO

Merci.
I've checked at the low end of the roof slope and the pitch appears to be 4.5/12. So, there shouldn't be a problem there. The only other apparent requirement to be checked is the 10-feet. As I don't walk (nor fiddle) on roofs, I shall have someone else next week do that checking. From the ground, the current chimney middle opening (the one in use) appears to be slightly more than 10 feet from the ridge but if we were to shorthen the chimney by one foot, I'm not sure of the result. At any rate, why would these two requirements apply at the same time? Do they both have to do with air displacement (wind) at the top of chimney?

[Jerry Peck]

I've checked at the low end of the roof slope and the pitch appears to be 4.5/12. So, there shouldn't be a problem there. The only other apparent requirement to be checked is the 10-feet. As I don't walk (nor fiddle) on roofs, I shall have someone else next week do that checking. From the ground, the current chimney middle opening (the one in use) appears to be slightly more than 10 feet from the ridge but if we were to shorthen the chimney by one foot, I'm not sure of the result. At any rate, why would these two requirements apply at the same time? Do they both have to do with air displacement (wind) at the top of chimney?

The 10 foot requirement is eliminated with regard to the roof slope, that is what the height of the chart John posted addresses. What does matter would be if there were a vertical surface within 8 feet of the type b gas vent (remember, it would no longer be a chimney is used strictly for a gas insert, but you would need to make sure the existing chimney is suitable for that use). If you are installing a new type b gas vent, then there should not be any problems as the vent is exiting the flat top of the 'brick chimney' and would need to be at least 1 foot high above the top of that 'brick chimney', and the sloping roof would not be an issue to be considered.

If Bob Harper were to read this thread and respond, Bob could provide much better and more detailed information as to what you would need to do, should do.

[joe Laflaque]

The 10 foot requirement is eliminated with regard to the roof slope, that is what the height of the chart John posted addresses. What does matter would be if there were a vertical surface within 8 feet of the type b gas vent (remember, it would no longer be a chimney is used strictly for a gas insert, but you would need to make sure the existing chimney is suitable for that use). If you are installing a new type b gas vent, then there should not be any problems as the vent is exiting the flat top of the 'brick chimney' and would need to be at least 1 foot high above the top of that 'brick chimney', and the sloping roof would not be an issue to be considered.

If Bob Harper were to read this thread and respond, Bob could provide much better and more detailed information as to what you would need to do, should do.

What I plan on purchasing is a Valor Legend G3 Series fireplace insert. It could be used with eiter conventional B-Venting (single 3"liner) or the Direct Vent with co-linear 3" venting. I would use the latter to ensure that warm air from the house isn't used, but air from outside only. Also, I understand this would totally prevent smoke from getting back in the house should there be a problem with the chimney.

[Jerry Peck]

It could be used with eiter conventional B-Venting (single 3"liner) or the Direct Vent with co-linear 3" venting.

Type B gas vents are only for use with gravity draft systems as type be gas vents are not to be pressurized.

With direct venting there is pressurization due to the fan - not sure how a furnace can use either?

Then again, I'm not a 'gas man', maybe someone else who is will reply with more detailed information.

[joe Laflaque]

Type B gas vents are only for use with gravity draft systems as type be gas vents are not to be pressurized.

With direct venting there is pressurization due to the fan - not sure how a furnace can use either?

Then again, I'm not a 'gas man', maybe someone else who is will reply with more detailed information.

It says the system can work fine even if there a power shortage. That's actually an additional reason for me to buy that gas insert. Although I can also buy a fan as an additional feature to improve the efficiency in hot air distribution in the house, that insert is advertized as working with no electricity, and therefore no fan.

[Jerry Peck]

It says the system can work fine even if there a power shortage. That's actually an additional reason for me to buy that gas insert. Although I can also buy a fan as an additional feature to improve the efficiency in hot air distribution in the house, that insert is advertized as working with no electricity, and therefore no fan.

That's not direct vent or even fan-assisted venting - that is referring to the interior air flow being by natural gravity flow (hot air rises) and circulates the air without any mechanical help (no fan).

That is not addressing the venting of combustion gases up and out the vent to the outside.

[joe Laflaque]

It says the system can work fine even if there a power shortage. That's actually an additional reason for me to buy that gas insert. Although I can also buy a fan as an additional feature to improve the efficiency in hot air distribution in the house, that insert is advertized as working with no electricity, and therefore no fan.

To make it easier to understand, the manual can be found at:

http://valorfireplaces.com/media/Gen...-IR-Manual.pdf

See Pages 16 and 19 showing diagrams and relevant venting info.

[H.G. Watson, Sr.]

HelloI had inserted this query in my Introductory Post but now realize that it should have been a separate post with proper technical heading.I'm about to buy a fireplace natural gas insert. The portion of my masonry chimney extending over the roof needs to be repaired first, as repeated freeze and defreeze in winters (brrr..Canada) have damaged a good number of bricks. And these exact brick colors are no longer available.One solution would be to reconstruct that portion of the chimney extending over the roof but to reduce its hight from 4 feet to 3 feet in order have enough good bricks.The insert (Valor) will use the so-called direct venting system for intake and exhaust through the chimney. Is there generally a difference in building code requirements as to chimney height when one switches from wood (solid) to natural gas? If not, could a repaired and reduced 3 ft over-the-roof chimney still be acceptable under the codes?I've seen some references to the 2-3-10 rules on this site. Shall I assume these apply equally whether I'm using an old fashion wood burning fireplace or a modern natural gas insert with direct venting?Thanks in advance for your comments.Joe

Shortening the height of the original masonry chimney (for as I understood the discussion, was for the original wood-burning fireplace **??**also site built masonry...which is in disrepair) would not allow for reversion to its original use when the proposed gas insert **??** and liner may be someday removed.IIRC Canadian requirements and approvals differ significantly. Special gas vent/liner may be required esp. in a masonry chimney. ULC 94X I don't recall the exact standard at the moment.I suspect you may be best serve to acquire a WETT or similarly certified specialist. I don't recall at the moment if the 4-10 rule reads the same nor if the requirements of reversion when stove or insert is removed in Canada as we have in NFPA 211 and related codes in your bylaws. More precise descriptions may be required to gleen the exact specifics regarding requirements. O/S wall mass may negatively affect draft, it depends on a number of factors, including orientation to prevailing winds. Unknown proximity to mechanical air intakes, or if open eaves are present. I noted presence of services immediately adjacent and below. Do not know if lightening a concern for your area.

[Frazier Jeffery]

Gas venting has no relationship to the guidelines of solid fuel burning stoves Look under fuel gas appliances in mechanical codes THe brick chimney with the proper insert vent could easily be reduced to 3 ft above the roof if there are no other issues

- - - Updated - - -

Gas venting has no relationship to the guidelines of solid fuel burning stoves Look under fuel gas appliances in mechanical codes THe brick chimney with the proper insert vent could easily be reduced to 3 ft above the roof if there are no other issues

[Raymond Wand]

H.G.

WETT Technicians only deal with solid fuel burning appliances and fireplaces and not gas fireplaces/inserts. Gas fireplace would come under the purview of TSSA (Technical Safety Standards Assoc) licences HVAC technician.

[joe Laflaque]

H.G.

WETT Technicians only deal with solid fuel burning appliances and fireplaces and not gas fireplaces/inserts. Gas fireplace would come under the purview of TSSA (Technical Safety Standards Assoc) licences HVAC technician.

What I would like to see are the applicable provisions of the Regulations that the technician who will install the gas insert will be required to apply.

I understand the technician has to first apply the manufacturer's requirements. In the manufacturer`s documentation for that particular fireplace insert, it says an unaltered solid-fuel burning fireplace shall be used to start with, in which two 3" flexible metal liners are inserted, with a terminal cap added on top. There is a 10-foot minimum vertical height mentioned for the system to work, but no mention of the portion of the chimney that should stick out of the roof. The manufacturer's instructions simply state "Check local codes for allowable vertical vent termination".

I take it these local codes are those applicable in Canada and, in my case, in the Quebec province. I was given to understand that these construction requirements in the broad sense are contained in standards issued by CSA (Canadian Standards Association). I went on their web site but it appears that one has to pay a substantial amount to get copy of their standards. All I need to see is the paragraph that would be related to our chimney height requirements, if any.

Attached areIMG_0001.jpgIMG_0002.jpg Pages 16 and 19 of the manufacturer's instructions.

[Raymond Wand]

From my own knowledge the termination of the cap top portion can be anywhere from 6" to 12" above the crown (top) of the chimney.

[Bob Harper]

Wow! Responses all over the place!

First of all, you need a Level II inspection since you're changing the fuel or efficiency of the fireplace. That will identify other issues not necessarily relevant to this discussion such as pointing or flashing but need to be addressed in another way. When you read the installation manual of most any gas insert, it will allow installation of their appliance only into a masonry fireplace that meets the code (fill in the blank as to which code). That means an insert is not a repair option. So, a "chimney" must meet 3/2/10 regardless of what you're burning in it. This is measured on the uphill side from the junction with the roof deck to the flue gas outlet. Now, an insert will require its own special termination, which will extend that discharge point about a foot higher. The rules in the gas code are for B-vent. This is a direct vent. No Jerry, a "direct vent" does not have to have mechanical exhaust but rather just air in and fumes out--that's it. A gas direct vent works on a thermosyphon principle of balanced venting. The hotter the flue the stronger the air intake draft. The mfrs. listed instructions will determine the correct vent termination, any height restrictions to prevent overdrafting, or clearances to nearby structures and min. vent height.

since you're having such a problem with freeze-thaw damage to the crown, why not pour a concrete crown on a bond break and be done with it? There are forms to do this that have the drip edge molded in. Use a glass fiber reinforced concrete then treat the entire chimney with ChimneySaver once cured.

[John Kogel]

Hello Bob. What do you mean by "an insert is not a repair option"?

If a full height wood-burning masonry fireplace has a bad liner and the owner wants Gas, are you saying dropping in a metal liner is not a correct repair? I just want to be clear, not questioning your knowledge of the subject.

[Raymond Wand]

I don't believe we have what is termed a level 2 inspection up here. As the manufactures manual indicates it is okay to install a single wall aluminum liner and that is what the insurers want too.

[H.G. Watson, Sr.]

Likely to regret it, but K.I.S.S.'ing

quote: "I understand the technician has to first apply the manufacturer's requirements. In the manufacturer`s documentation for that particular fireplace insert, it says an unaltered solid-fuel burning fireplace shall be used to start with..."

W.E.T.T. or similar up there as to what WE (down here) call a Level II NFPA 211.

The solid-fuel burning fireplace, maintained, fully functioning (inspected, and clean - bylaws) to start with. That includes integrity, structurally, performance-wise, etc. and safe to use, as same.

Either demolish existing and install another, or follow the requirements. The inset is not a panecea or repair to the function or integrity of the solid-fuel site built masonry fireplace and/or its masonry chimney in disrepair.