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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8769
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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In Portland, Maine, I have a seven year-old Buderus G115/34

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In Portland, Maine, I have a seven year-old Buderus G115/34 with a Riello burner (40 F5 w/ LBT). Due to leakage, I've been told that the chimney must be torn down or replaced. My understanding is that there are five options that all involve significant cost to tear down the chimney, so the chimney tear-down cost seems irrelevant to the decision. First, we could rebuild the brick chimney (estimated cost is $2640). Second, we could install a metal chimney to replace the brick one (cost?). Third, we could replace the LBT burner with a Riello BF5 (or equivalent) and make it a direct vent system. Fourth, we could keep the existing boiler and install a power venter. Fifth, since this area is likely to have natural gas within about two years (the deal is nearly complete between the town council and the gas supplier), we could take out the Buderus and install a combination propane/gas direct vent system.

Generally, have I outlined the available options? And if so, which ones seem most worthy of further investigating? As a homeowner, the one that appeals most to me is to switch out the burner and direct vent the Buderus. But I read bad stories about doing this--like it never seems to work. What other questions should I be asking and what are the best ways to find the answers to them?
Welcome to Just Answer!.

I would simply replace the brick chimney with a double insulated metal one...

.... or if it will fit, put a metal liner up the existing brick chimney.

There are kits made for the purpose, that decision has to be made after the boiler service company looks the job over and sees if a flexible metal liner kit will work. There are many variables. That option should cost less than $800 in many cases... that is if the chimney just leaks but is not structurally unsafe and can be left in place.

I would not spend any money on a different burner for now. When you get natural gas to the area you can change the burner head to one that uses natural gas.

New metalbestos chimney (double insulated metal) costs vary with the wall construction and what length is required to clear the roof. Cost to clear a one story roof, should be under $1,500 as a blind estimate if you wouldn't mind the look of it.

The other options all have their merits, pro's and cons. The approach I have outlined here will most likely be lower cost than the other options... let me know if the chimney is structurally safe enough to be left standing or not please and if you do not mind the look of it.

This are my opening remarks, we can go from there until I understand the chimney issue a bit better, and you have decided on an option.


Customer: replied 4 years ago.



Thank you for your thoughtful reply. Tomorrow afternoon at 4 pm a chimney mason is coming to check if the flue is safe enough to continue to use. Is a chimney mason using mirrors the right person for this type of check? Will he be able to answer both questions: whether the chimney is sound structurally and whether it leaks? My guess is that he says it is structurally sound or he wouldn't be doing the mirror work, right?


We will be getting natural gas service in this area within two years. If there is a way to use the existing chimney for about two years (i.e., it's safe enough), I'm thinking that we might install the metal liner kit if necessary and flash the existing chimney now, finish the current siding job, wait until gas comes and then install a new direct vent gas boiler that is designed for both radiant and floor-panel heat (we have about 1/2 and 1/2 in the house). What do you think of this plan?




Hello, its a good plan.

If the chimney mason says the chimney is strong enough to stand .... ask what the inside dimensions are in that case. He might recommend a $500 're-pointing' job to make it stronger so it will be safe to stand.

.... and ask him if it looks like a flexible vent kit, the same diameter as the vent collar on the boiler will fit. Its probably a 6 inch vent collar. Check that with a tape measure.


There is no need to replace the boiler in most cases when switching to natural gas, you can buy a new burner head in almost all cases for $600 or so installed that burns natural gas. You might want to see what your local buderus dealer has to say about that.

The buderus boiler is one of the best on the market, chance are that a new one of a different brand will not outlast this one if it were replaced.

If you choose to rate my advice so far positively I will hold the question open for unlimited follow up.


Phil and other HVAC Specialists are ready to help you
Customer: replied 4 years ago.



The chimney mason said that the chimney is probably not strong enough to stand in the long term and therefore not worth repointing. He used a light and mirror and looked down the inside for interior damage and found damage only to four tiles at the top of the chimney but the lower part was ok. He said he thought it would be usable for two years if I did the minor repairs he suggested--holding the loose bricks at the top together with mortar and creating (from mortar) an angled slope from the top of the ceramic flues down to the edge of the chimney to better drain rain water away from the chimney bricks (done, see attached photo). This will protect the siding workers from falling bricks. He also suggested putting silicone into the visible cracks alongside the chimney (purchased but not yet done). I offered $100 and he took $50 for coming to look.


Since we'll be getting natural gas in the area in two years, I plan to convert the Buderus to natural gas, change it to direct vent, remove the chimney from the top down to a point that is no higher than the existing roof, and side over the chimney to prevent water from seeping into the house. Do you think it is reasonable to direct vent the Buderus after being adapted to a gas burner?


Alternatively, since about 1/2 of the house is radiant heat and the other 1/2 is baseboard hot water, I've been advised to spend $9000 when gas comes to town to install a high-efficiency direct vent modulating condensing gas boiler with a cost of about $9000. Your thoughts about this? I just dodged a $5000 bullet by not tearing down and rebuilding the existing chimney so maybe that is the best?


Below are photos in very large format, first of the damaged interior of the top of the flue, then of the repaired top of the chimney, and then of the damaged seam between the chimney and the exterior wall without siding (for some reason the last photo lies sideways with the top of the chimney on the left). Your comments about the photos are of course welcome.


Thank you.


Jeff Gramlich

Hello again,

- It is reasonable to direct vent the buderus after you get it on natural gas if the work is done by the local buderus dealer.

- The wonderful new ultra high efficiency boilers last less than half as long as the largely bullet proof older 80% efficient boilers... you can spend as much keeping the high efficiency boilers running as you save in fuel in about half the cases. My preference is lowest legal efficiency in your area, *cast iron heat exchange, and the crudest possible controls.. I would keep the existing boiler and not spend $9,000 replacing it with a high efficiency boiler.

The pics look good, your plan to remove the top section of the chimney sound good to me.