flue caps

[jadm]

I want to put flue caps on my existing flues. I have 2 flues that lead to unused fireplaces. One flue that is used for my insert and it is capped. One flue for my hot water heater and boiler. All are in the same chimney. All are the same height except my install one. All have their own stacks.

I have two concerns - raccoons down the unused chimneys and moisture.

Two options seem to be to place a metal sheet on top of the unused fireplace flues which will keep everything out including combustible air possibly needed by my insert to draft properly or I can put the caps on that look like little metal screen houses than have metal around the side and metal roofs slanted so water runs away from the chimney.

Problem I run into with the little house type caps is that my flues are very close together and there isn't enough room. The 'roofs' hit each other and can't be adjusted due to how they are constructed.

Wondering if anyone here has run into any problems by completely covering up their flues with a metal sheet - or any other type of material - in terms of how their draft is affected on their stoves/inserts. My house is fairly air tight. Built in the 60's but we had new windows put in about 10 years ago that sealed things up a lot more than they were before.

 

[swestall]

I have the same setup. I put stainless cage type caps on the woodstove and furnace flues that are in use. I used a good adhesive caulking and cut two pieces of aluminum to the exact size of the other flues and blocked them off. There was no difference to venting in the house and no more leakage. (when it rained I would get water dripping into the fireplace that is unused). If you ever need to use those flues you can just scrape the aluminum off with a sharp putty knife.
Home Depot and Lowe's have the sheet metal and adhesive caulking.

 

[jadm]

Thank-you for your response. I will wait until it warms up here and get back up on our roof and take measurements and see how it works here on my install. I just hope I don't get a lot of smoke in my house but I guess I won't know until I try it.

Just realized that I can experiment too by blocking off the flues completely but not sealing with caulking until I know what will happen below. I will use the 'cage' on my boiler flue too.

I have the same setup. I put stainless cage type caps on the woodstove and furnace flues that are in use. I used a good adhesive caulking and cut two pieces of aluminum to the exact size of the other flues and blocked them off. There was no difference to venting in the house and no more leakage. (when it rained I would get water dripping into the fireplace that is unused). If you ever need to use those flues you can just scrape the aluminum off with a sharp putty knife.
Home Depot and Lowe's have the sheet metal and adhesive caulking.