1918 built house, 2.5 stories, brick foundation but the main body is vinyl siding. chimney has the following penetrations: clean out, an abandoned flue, a shared flue for natural gas water heater 40k btu and natural gas furnace that is 90k btu 80% efficiency, and then we found out our microwave exhaust above the stove was also routed into the chimney erroneously.   The chimney exposed in the basement is cmu block. Only brick that i know of is above the 2nd story it’s brick inside the attic then brick where you see in the roof picture. Unsure if it’s brick inside 1st or 2nd floor anywhere.   
    
im going to reroute the microwave exhaust  

  

I had reached out for an evaluation of the chimney to see if it was in good shape or could be leaking outside air and/or the appliance exhaust fumes into the walls of the house. 

    
here is a synopsis of one chimney guy’s findings from my phone call with him.  Sorry some of it may not make the most sense.   


No clay liner  
Yes metal liner  
Flexible aluminum been in there for some time

  

recommendations : another place for kitchen exhaust.  A lot of holes in the masonry stack above the rooflines .  Rec take down to 2nd roof line and rebuild with new brick or frame in and side it 

    
The chimney itself is “literally falling apart”. Liner is aluminum and you can have multiple cat 1 appliances in the chimney but no other appliances. Poor venting because of range going into the chimney. Needs stainless steel due to acidic exhaust. The b vent bypasses any chimney furthering deterioration of the existing chimney made worse with the previous coal soot and boiler soot. 

  

so I asked more questions and here are his answers:

1) does the existing aluminum liner get completely removed or is it abandoned in place? 

Yes the liner would be removed so the new B vent would fit properly.

  
2) could we arrange a time for you to look at the attic portion to determine if the degradation extends into there as well? 

Absolutely, however, since the chimney above the lower roof line will either be rebuilt or enclosed, the condition of the bricks in the attic most likely wouldn’t affect the project.  That being said.  If the bricks are in a high level of deterioration, it might be best to apply a surface bonding cement to strengthen that portion of the chimney.

3) your quote is to replace your the green line on my attached picture? 

The chimney above the red line would be eliminated and the section between the green and red lines would either be rebuilt with bricks or enclosed so it can be sided.  Siding is not included with that.

4) the current range vent is a standard rectangular solid metal vent into the side of the chimney. Access is through a kitchen cabinet. Would you be able to repair the penetration through the chimney and can have a carpenter repair the hole in the cabinet interior? 

Yes, once the range vent is disconnected, we can repair the opening in the chimney.  I would contact a well respected finish carpenter to repair the cabinet.

5)  what diameter class B vent?

I would put in a 5 inch B vent to handle both appliances.

6) what manufacturer/model of class B vent?

We generally install Metal Vent products.

7) furnace and water heater will both vent into the same class B vent? As currently is I believe. 

Yes, both appliances will vent into the same stack via a manifold in the basement.

8) current furnace is 90k BTU 80% efficiency and water heater is 40k BTU. Might need to increase BTU on the furnace. Is there plenty of wiggle room for additional BTU and a possible increase to high efficiency in your proposed class B vent? 

If you are planning to install a new furnace, in the near future, I would recommend installing a high efficiency furnace and water heater now and put the money for this project toward the new system.  That way the chimney could be abandon altogether, removed and the opening roofed over.  High efficiency furnaces and water heaters are side vented and cannot use vertical B vent systems.  Fan assist and natural draft only for B vent.

For the overall height of your chimney a 5” system will vent 183K BTU input for 2 combined appliances, 1 fan assist and 1 natural draft.

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**I guess I’m kind of at a loss - if I side vented new high efficiency appliances do I even worry about any sort of repairs to the existing chimney? could it still be leaking in unconditioned outside air to the house if the masonry has holes in it?** 

Help me with proposed repair