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Draft issues due to chimney cap?

Posted: Wed. Feb. 28, 2018 6:27 pm
by brandonh98
I just wanted to get some input on this. I have horrible draft on my chimney when it gets warm out and I've tried just about every trick in the book. Did countless searching on this forum and others. One thing I haven't read much about is the chimney cap causing draft issues. I just took mine off today to do a test it out.

Previous owner had a wood burner and had a 5" SS chimney liner installed. The 8X8 clay tiles look brand new and the manufacture called for at least a 6" chimney liner so I elected to remove the liner altogether and go without one. The cap, however, stayed. Maybe the pictures will speak for themselves.

Let me know if you think removing the cap will improve draft or not, and I'll get back to you with the results of the test.
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Re: Draft issues due to chimney cap?

Posted: Wed. Feb. 28, 2018 6:44 pm
by coaledsweat
How tall is the chimney?

Re: Draft issues due to chimney cap?

Posted: Wed. Feb. 28, 2018 6:50 pm
by Olllotj
That chimney needs a crown on top to protect the blocks!

A proper masons builders supply should have premade crowns that fit the 16x16 block with the 8x8 terra-cotta liner.

I removed my cap in order to stop the roof staining, and it worked great. Not sure how it effects the draft, but I’ve heard it both ways.

Here it is http://www.genestprecast.com/chimney-caps.html or you can pour in place

Re: Draft issues due to chimney cap?

Posted: Wed. Feb. 28, 2018 6:51 pm
by Qtown1835
The cap shouldn't effect draft if anything I would think it would help to reatin some heat and keep the draft. You can try cracking a window, running stove hotter, and make sure dryer and bathroom vents are not running.

Re: Draft issues due to chimney cap?

Posted: Wed. Feb. 28, 2018 6:53 pm
by freetown fred
As in, is the chimney a couple feet taller then the roof peak?

Re: Draft issues due to chimney cap?

Posted: Wed. Feb. 28, 2018 6:54 pm
by lsayre
Weather Vane type chimney caps are reported to enhance chimney draft. I'm not sure of any other types being of draft related benefit.

Re: Draft issues due to chimney cap?

Posted: Wed. Feb. 28, 2018 7:28 pm
by brandonh98
Olllotj wrote:
Wed. Feb. 28, 2018 6:50 pm
That chimney needs a crown on top to protect the blocks!

A proper masons builders supply should have premade crowns that fit the 16x16 block with the 8x8 terra-cotta liner.

I removed my cap in order to stop the roof staining, and it worked great. Not sure how it effects the draft, but I’ve heard it both ways.

Here it is http://www.genestprecast.com/chimney-caps.html or you can pour in place
Never even heard of a chimney crown. Thank you for the link. So I guess the weather will eventually destroy the top of the chimney? That chimney has been covered with that aluminum cap since it was built in 1995.

Re: Draft issues due to chimney cap?

Posted: Wed. Feb. 28, 2018 7:30 pm
by brandonh98
freetown fred wrote:
Wed. Feb. 28, 2018 6:53 pm
As in, is the chimney a couple feet taller then the roof peak?
Chimney would need to be 15 feet taller to be above the peak of the roof. There is nothing within 12' of the top of the chimney though. It's a long gently sloping roof.

Re: Draft issues due to chimney cap?

Posted: Wed. Feb. 28, 2018 7:35 pm
by brandonh98
coaledsweat wrote:
Wed. Feb. 28, 2018 6:44 pm
How tall is the chimney?
27' from thimble to top of chimney. What does that tell you?

Re: Draft issues due to chimney cap?

Posted: Wed. Feb. 28, 2018 7:37 pm
by lsayre
brandonh98 wrote:
Wed. Feb. 28, 2018 7:35 pm
27' from thimble to top of chimney. What does that tell you?
At 27' tall it should draft like a champ.

Re: Draft issues due to chimney cap?

Posted: Wed. Feb. 28, 2018 7:40 pm
by coaledsweat
brandonh98 wrote:
Wed. Feb. 28, 2018 7:35 pm
27' from thimble to top of chimney. What does that tell you?
It tells me "toss the cap."

Re: Draft issues due to chimney cap?

Posted: Wed. Feb. 28, 2018 7:42 pm
by Lightning
Do you have a manometer installed? What are your numbers?

Re: Draft issues due to chimney cap?

Posted: Wed. Feb. 28, 2018 7:47 pm
by CoalJockey
coaledsweat wrote:
Wed. Feb. 28, 2018 7:40 pm
It tells me "toss the cap."
100% agreed with CS Brandon. Back in the Fall, I was in your exact shoes as I tried to run an EFM through a liner and a cap just like that. It would pressurize the firebox and just wouldn’t breath. I later found out the liner was perforated when we pulled it out.

The difference is nothing short of dramatic. There are times it will stand the baro wide open... heaven forbid the Jack Russell dog walks by it, she will be up the pipe like a rocket!

Re: Draft issues due to chimney cap?

Posted: Wed. Feb. 28, 2018 7:52 pm
by freetown fred
You're good with that B.
brandonh98 wrote:
Wed. Feb. 28, 2018 7:30 pm
Chimney would need to be 15 feet taller to be above the peak of the roof. There is nothing within 12' of the top of the chimney though. It's a long gently sloping roof.

Re: Draft issues due to chimney cap?

Posted: Wed. Feb. 28, 2018 8:14 pm
by brandonh98
Lightning wrote:
Wed. Feb. 28, 2018 7:42 pm
Do you have a manometer installed? What are your numbers?
Yes, on a cold day the dampener holds it right at 0.05 with the dampener only open slightly. When it gets above freezing it struggles to stay at 0.04. A warm day in the 40's it'll go down to 0.02 or 0.01. It's at this point I start to smell it and the CO detector starts giving a low reading (not alarming, maybe 10-30ppm).