Any Advantage in Using a Chimney Cap Reducer?

I have a clay square flue liner and the stove dealer south of town tells me I should put a cap on the chimney to reduce the opening to 6 inches to help increase draft. I have a new short chimney, so I'm interested in doing anything that might help insure proper draft. Any thoughts on this?

Yep, add on to the chimney! Why do you have a short chimney????????????

How Well Will This Chimney Work? discuses the original plan. The contractor gave me about 5 feet of chimney and put my thimble about 5' 10" above the floor. So at best we are looking at 8-9 feet of length from the thimble to the top of the flue. I'm going to install a fresh air intake so that will help some, but...

I don't think I have more than that and my draft is huge year round fire or not. And I am not a big fan of caps, nor do I know how that would increase draft since it would restrict flow. Maybe someone else knows more, IDK...

Ah yes, I remember---Again, it should work fine without a cap--hold a match at stove outlet & see what the flame does.

I use a stainless steel cap on my 8 inch square tile chimney just to keep water out. I just think keeping the tile dry saves on corrosion, mainly on the joints, and I even set the first tile in refractory cement so the footing would not be eaten away. 30 plus years ago and everything is still good.
I am not reducing the opening just protecting it.

freetown fred wrote:Ah yes, I remember---Again, it should work fine without a cap--hold a match at stove outlet & see what the flame does.

Fred,

Every time I have checked the chimney I have had outside air flowing into the house through the thimble. The addition is not tied into the central HVAC and at this point it sealed off from the rest of the house, so perhaps it's to tight and there is negative pressure. During the summer should there be draft?

Thanks everyone for the information.

Mine drafts whenever but I'm 3' above my roof ridge with a cap-- like sierra said, to keep the weather & critters/birds out

NorthernIndiana wrote:

freetown fred wrote:Ah yes, I remember---Again, it should work fine without a cap--hold a match at stove outlet & see what the flame does.

Fred,

Every time I have checked the chimney I have had outside air flowing into the house through the thimble. The addition is not tied into the central HVAC and at this point it sealed off from the rest of the house, so perhaps it's to tight and there is negative pressure. During the summer should there be draft?

Thanks everyone for the information.

Yes, There should be draft in the summertime It will not be as strong as the winter. My chimney is on the short side. It is 21 feet but the thimble in about 6 feet off the floor that gives me about 15 feet of chimney to pull draft. When I put a flame in the baro damper it sucks in in to the chimney even if the Hvac is running.

Try opening some windows, doors, etc & try your draft--if it works well, then yes--you got a real tight addition--summer, winter---which-ever in my situation.

Reducing the chimney opening at the top doesn't sound Kosher to me. Ok with the cap but I have no idea how he would believe a restriction would increase flow.

Is there house above the chimney top? Is the chimney on a one story room and the house is two floors elsewhere? If so, the home may be experiencing stack effect where the house itself is a better chimney than the chimney. It would be worse in warmer weather. If this is the case, you probably need more chimney.

Buy it from him and if possible have him install it for you, he needs to make every dollar he can.

Seriously though the only reliable way to make your draft stronger is to add height to the chimney.

Why didn't you have the mason build your new chimney high enough?? It was mentioned in your other thread how to build this stack and not have problems with draft. Reducing the outlet isn't going to do anything for you.