Newbie chimney questions

bri86

Hi all,
The home I purchased recently has a chimney that's in poor condition above the roof line. It's being used to exhaust the gas boiler (recent model LoganoUS/CA GC 144II) and Rheem gas water heater for the house. We're gotten quotes for tuck pointing that range from $ to $. I don't know the condition of the pipes within the chimney.
I'm wondering if it makes sense to use a "power vent" (Tjernlund HS1) to side vent the exhaust instead of going through the chimney? It's appealing to me to be able to seal the roof, and to avoid possible chimney expenses in the future. I have one quote to install a power vent (that would handle both the boiler and water heater) for about $. Here are some questions I have:
a) how reliable are Tjernlund power venters?
b) If there is an electrical outage, that's problematic for a power venter, right?
c) How much more worrisome is it to have the exhaust gasses being exhausted near ground level (as opposed to chimney height)?
d) Does $ to install a power venter seem reasonable?
e) Could I install a separate chimney running alongside the house to 1) avoid using the current chimney and 2) avoid a power venter?
f) Rheem, the company that produced my water heater, said that side venting is not possible. Is it common for companies to claim that side venting is not possible when it actually is possible? Note: HVAC guys who installed the boiler claim it's no problem, and I don't know who do believe.
g) besides tuck pointing, how much maintenance should I expect for this chimney?
All your advice is much appreciated.

STEVEusaPA

Prices really aren't allowed. They vary by region, and the full scope of your project is not detailed.
First, sounds very expensive just to point the chimney, unless it requires a lot of set-up-scaffolding, etc.
Just pointing the chimney doesn't tell anyone about the condition of the entire chimney. Only a Level II inspection by a certified chimney company can tell you that.
The easiest/best solution, depending on entire chimney integrity would be to have the chimney repaired above the roof line, drop a stainless steel liner down there properly sized to handle both appliances.
If you have a basic atmospheric gas water heater, it can't be direct vented. If a manufacturer had a product that could be direct vented, they would definitely let you know. Don't listen to any putz who wants to violate code because they "do it all the time". Manufacturer trumps all and if you drop dead from CO poisoning, that guy will be nowhere to be found.
Both can be power vented, and the price is probably right, depending on what's involved in making the holes, hooking it up, the additional controls, etc.
But I really would only power vent both of them as an absolute last resort.

bri86

Thanks Steve, I value your input.

Sorry, I didn't mean to imply that the HVAC folks said it could be direct vented. They said that it could be power vented.

I don't think that the scaffolding would be especially difficult. The roof is relatively steep though (roughly 12/12). Chimney is roughly 4' or 5' tall above the roof line.

mattmia2

12 in 12 is a bit challenging to work on so that adds some cost.

If you rebuild the chimney then maintain it, keep the cap and mortar in good shape, the future repairs should be minor. Getting in to a condition where it needs to be rebuilt results from neglect or improper repair.

bri86

How common is it to run a new metal chimney up the side of the house? I would expect that the new chimney would need to be sufficiently close to my appliances. The closest exterior wall that could be used is approximately 9' from the boiler (slightly closer to the water heater).
This would be a fair amount of work. It seems like there is an energy efficiency benefit in closing up the chimney.

How crazy is this "new chimney" idea - if it's even possible?

STEVEusaPA

Possible? Yes if done right.
Ugly? Absolutely.
You can vent thru the roof. Take the chimney down below the roof line, patch roof, run liner/piping with proper thru the roof termination.

EdTheHeaterMan

Repairing the chimney = no moving parts for venting
Power venting = maintaining and repairing over the life of the boiler.

My experience with mechanical venting is they last about 5 years before the motor fails or the unit rusts away. I use stainless steel models for both oil and gas venting and in my area, they still corrode away. The longest-lasting one I had installed before repair or replacement was necessary was 8 years. We are surrounded by saltwater (on 3 sides) within 2 miles of every location in my county. You may get better performance if you are away from the coast.

bri86

Ok, I'm getting the message that I should keep the chimney!

Do y'all have opinions on chimney b-vents? I'm considering installing that just below the roofline. What are the pros/cons of that vs a traditional chimney?

JUGHNE

Is the chimney in the center of the roof ridge?
Do you have access in the attic to the chimney ?

On one job I have had the bricks removed from above the roof and below the roof down to about a foot above the ceiling.

Then from the attic able to connect and lower long lengths of B vent down to the basement. There is a great support/fire stop for B vent that would hold the vent up.
Then build upward thru the peak as per code for height.
The roof hole will have to decreased in size, singles and the final flashing would secure the vent vertically.

No mason needed. Just carpenter/roofer and HVAC vent installer.

This limited the time on a steep roof. Easier to assemble the B vent in the attic.

bri86

JUGHNE said:

Is the chimney in the center of the roof ridge?
Do you have access in the attic to the chimney ?
...
Then from the attic able to connect and lower long lengths of B vent down to the basement.

The chimney is mid-way up the roof, and I do have access to it in the attic.
It sounds like you're talking b-vent all the way to the basement, which is not what I was imagining. I was imagining having it start in the attic (ie the existing would connect to the b-vent there). But perhaps that's either impossible or unwise?

If it's simple, can anyone share how high the b-vent must rise above the roof line per code? If it's complicated and/or depends on local authorities, I totally understand and will do that homework.

JUGHNE

If you have a clean out door for the chimney in the basement,
if you open it and clean it out then with a mirror do you see blue sky straight up the inside?

If you want B vent it needs to be continuous B vent from the basement to the roof cap. There is probably not any pipe inside your brick chimney. The mirror inspection would tell you that.

An old school rule of thumb was that chimney had to be 24" above anything within 10' radius. That explains why your brick chimney sticks up 5'. Local current codes would dictate that height.

Is there a good corner/closet or wall location that you could get a straight shot from the basement up thru near to the peak of the roof. It could be boxed in and then finished to match the decor.
Then you would have minimum steel pipe showing.

Or take the brick down to almost the attic floor, drop B vent pipe to the basement opening. Then offset with elbows in the attic to get near the peak.

We took an old chimney down. Full 2 story with steep roof line.
On the roof the bricks were dropped down inside the chimney and a helper pulled them out of the clean out a couple at a time.
Coordination and communication between each end to avoid smashed hands.

In your case then the old hole in the roof would allow straight length to be lowered into the basement

Bob Harper

At a 12/12 pitch a chimney would need to be at least 120 inches above the roof plus two feet or 144 inches or 12 feet. If you run a gas vent it would need to be 120 inches. Some B-vent mfrs. list their vent for use using the chimney 'flue' as a 'chase'. You can also line the chimney with ss then extend the chimney using listed factory chimney to the requisite height. I did this on my own house. I had the chimney pipe powder coated grey so it doesn't look like a chrome pagoda.

bri86

Bob Harper said:

At a 12/12 pitch a chimney would need to be at least 120 inches above the roof plus two feet or 144 inches or 12 feet. If you run a gas vent it would need to be 120 inches. Some B-vent mfrs. list their vent for use using the chimney 'flue' as a 'chase'. You can also line the chimney with ss then extend the chimney using listed factory chimney to the requisite height. I did this on my own house. I had the chimney pipe powder coated grey so it doesn't look like a chrome pagoda.

Wow, 12 feet!?! Can you share the formula? I'm asking this because the pitch might be slightly less or more than 12/12...

JUGHNE

Look up install instruction for Hart & Cooley Type B vent or any other brands.
The old form I have is from 2006 and poorly written.....confusion.

There must be something out there that gives clearer info.

You still have to go by local codes though.

bri86

JUGHNE said:

If you have a clean out door for the chimney in the basement,
if you open it and clean it out then with a mirror do you see blue sky straight up the inside?

If you want B vent it needs to be continuous B vent from the basement to the roof cap. There is probably not any pipe inside your brick chimney. The mirror inspection would tell you that.

The chimney is very very straight. from the bottom I can see blue sky. There *is* a 5" or 6" in pipe inside of the chimney. What I'd really *like* to do is to slide b-vent around this pipe, starting in the attic. In the attic, if the seal between the chimney and b-vent was good, then I couldn't see how this would be any problem - especially since most/all of the gasses should be inside the pipe and not between the pipe and chimney. But it sounds like code doesn't allow for this?

JUGHNE

Do you see the 5-6" pipe at the top of the chimney....perhaps a cap on it?

realliveplumber

Bob Harper said:

At a 12/12 pitch a chimney would need to be at least 120 inches above the roof plus two feet or 144 inches or 12 feet. If you run a gas vent it would need to be 120 inches. Some B-vent mfrs. list their vent for use using the chimney 'flue' as a 'chase'. You can also line the chimney with ss then extend the chimney using listed factory chimney to the requisite height. I did this on my own house. I had the chimney pipe powder coated grey so it doesn't look like a chrome pagoda.

Or you could penetrate the roof at the peak and have 24” of pipe exposed.

Or one foot below the peak and have 36” of pipe.

Bob Harper

On a chimney the rule is 3 ft minimum even if a flat roof plus 2 ft. above any point within 10 ft .horizontally. On a 12/12 pitch, 10ft. x 12= 120" + 24=144. B-vent has very low penetration requirements above a roof except it must be 2ft. above any point within 8ft. 8x12= 96+24=120. Anything over 5ft requires a roof brace.

bri86

... Some B-vent mfrs. list their vent for use using the chimney 'flue' as a 'chase'.

Hey Bob, Can you explain this "flue as a chase" idea? I appreciate it.

Bob Harper

A 'chase' is a non-fire rated passageway up through a building. If you get above 4 stories it must be fire rated, such as 2 hours using noncombustible materials and insulation in the walls, floors and specially listed firestop methods.
A chase looks kinda' like a closet or elevator enclosure when framed in. However, it can also be made of masonry, pipes, ducting- almost anything that has a flame spread rating of 500 or less and is fully enclosed. It's a conduit for a mechanical system.

You can take a masonry chimney's flue, install a listed venting system in it such as B-vent and the brick flue becomes a chase- a housing. It's like eating lettuce- nothing to it.
HTH

EdTheHeaterMan

The instructions for what is being suggested starts at the bottom on page 10 of this instruction sheet
https://www.hartandcooley.com/assets/files/o4/150952-typebgasvent-130116.pdf

bri86

EdTheHeaterMan said:

The instructions for what is being suggested starts at the bottom on page 10 of this instruction sheet
https://www.hartandcooley.com/assets/files/o4/150952-typebgasvent-130116.pdf

thanks @EdTheHeaterMan , that's useful!

bri86

Bob Harper said:

On a chimney the rule is 3 ft minimum even if a flat roof plus 2 ft. above any point within 10 ft .horizontally. On a 12/12 pitch, 10ft. x 12= 120" + 24=144. B-vent has very low penetration requirements above a roof except it must be 2ft. above any point within 8ft. 8x12= 96+24=120. Anything over 5ft requires a roof brace.

@Bob Harper do you mean a brace somewhat like this? Over 5' above the roofline, right?

JUGHNE

You see the reason to relocate the roof penetration near the peak.
The expense and grief of the supports would be more than offsetting with 45 degree elbows in the attic.....then you need only the 3' or less pipe showing.

IMO, the 10-12' pipe is necessary only if you are within 10 of the slope of the roof.....such as your brick chimney is now.

bri86

JUGHNE said:

You see the reason to relocate the roof penetration near the peak.
The expense and grief of the supports would be more than offsetting with 45 degree elbows in the attic.....then you need only the 3' or less pipe showing.

IMO, the 10-12' pipe is necessary only if you are within 10 of the slope of the roof.....such as your brick chimney is now.

Yeah ... I do see that reason.

Yesterday I learned that there's a flexible b-vent (previously I thought it was always rigid). Furthermore, many companies make kits. For example, Menards has this "Amerivent® 5" x 35' B-Vent Flexible Chimney Re-Liner Kit".

Could something like this work? Does anyone have experience with these sorts of kits? I would need rigid b-vent above the roofline, so I'm not sure if this flexible version could be connected directly to a rigid version in my attic. All thoughts very appreciated!

JUGHNE

The re-liner kit is designed to drop down an existing chimney that is in good physical condition. The condition of bricks and mortar is a concern to keep the chase for the liner in place.

If you repaired your bricks structurally above the roof then the liner would be an option. As the picture shows there is a plate to cover the chimney and then a B vent type cap for the top.
This system is such that it needs to be continuous from basement to roof cap, just like solid B vent.

Solid B vent is a double walled assembly that has aluminum for the inside pipe, this conducts heat well and induces a draft up the pipe. Then the outside pipe is galvanized steel for strength and weather resistance. There is a 1/4" air gap between the pipes that keeps the outer pipe from getting too hot. It still needs 1" clearance from combustibles. Once you start with the B vent in the basement it needs to be continuous thru the roof.

The flex liner relies upon the brick chimney for the fire resistance to protect the structure.

If you go to a box store and look at B vent of any brand you can see the construction.

Bob Harper

Flexible aluminum liner is listed for use with CAT I gas venting. That doesn't make it a good idea or a good value. It does not hold up and should be considered a temporary liner at best. It only has to pass a 100lb dead vertical load test. No test on torsion or compression. You have to stretch most of them out to their final length. They are not tested with tees, which is a big reason they're unsuitable for 80% furnaces. Most have short warranties. They easily separate or crush during installation. Nesting birds and squirrels can easily rip them apart including their fragile rain caps. You cannot install aluminum into a chimney that has ever served oil or coal. It will eat it up. This is not a DIY project. Just because you can buy stuff online doesn't make it a good idea. Many things, especially in the hearth industry, do NOT honor their warranties on items bought online so check with the mfr. Some mfrs of ss liner do list their liner with a transition piece to class A chimney at a special top plate that gets Tapconned down. You then stack sections of chimney such as in the pics above with the braces. However, some brands do list their rigid vent inside a chimney even protruding out for height. Regardless, transitioning from flex to rigid requires two point stability- one above and below the top plate at min. plus if > 5ft above the roof. Too much exposed pipe will cool the stack gases, kill the draft and suffer from excessive condensation. This is one reason to use insulated class A. Otherwise, get a mason to extend the chimney for the proper height liner so the chimney protects the liner. Still, you will probably need to derate the liner if much is sticking exposed.