The two Rumford fireplaces in Belvedere, CA both smoke. The 48" living room fireplace "burns and draws well during a hot fire" reported architect, David Kotzebue, but as the fire cools down it begins to smoke. The 36" Rumford in the bedroom smokes worse, probably because of the short chimney.
Angelo Gonzales and Jim Buckley met with the owner, owner's representative, architect and current builder's representative at 9:00 am on March 20, 2007*
Planning to follow the guidelines suggested in the "Smoky Fireplace Checklist" Angelo and I arrived armed with incense, lighter, measuring tape and camera.
First we noticed that the "tall" metal chimney was barely as tall as the roof even with what looked like a temporary pipe extension. The chimney venting the bedroom fireplace was not visible from the front of the house and turned out to be ten feet or so below the ridge of the roof.
Because of the information we had that the fireplaces worked okay with vigorous fires, we were inclined to think the problem would be inadequate ventilation, resulting in excessively negative indoor air pressure causing a downdraft in the chimneys. But we wanted to be careful to take measurements and be sure the fireplaces were built correctly and there were no restrictions in the chimney.
In fact the fireplaces were built to specifications and the craftsmanship was excellent. The one problem we saw was that the metal chimneys didn't fit well at the top of the smoke chambers. It could have been a smoother connection. Maybe even the metal chimneys were too small. They should be 16" id for the 48" Rumford and 12" id for the 36" Rumford but we had no way to measure it. But, again, with the fireplaces working well with vigorous fires, we didn't suspect the chimney connection was the reason these fireplaces smoked. Improving the connection - even replacing the chimneys if they turn out to be too small - would not change the fact that the primary problem is the downdraft.
With the incense, we determined that there was little or no draft in the living room fireplace, but at least there wasn't a significant downdraft.
However, in the bedroom fireplace there was very noticeable downdraft - so noticeable that if felt like a window was open when we walked into the room. The owner commented that the draft kept him awake at night and that room was always cold.
We opened the bedroom door and a lot of air came in there too and didn't mitigate the downdraft in the chimney. We opened more doors and windows downstairs and outside air came in them all.
We decided to see where all that air was going. Following the smoking incense we found a little drift into the guest room and laundry room. We cracked open doors to concentrate the flow so we could see about how much air was going where. We found small losses almost everywhere - into the air-cooled media closet and into the various downstairs rooms but the main losses were upstairs.
Maybe we should have started upstairs because, to our surprize, we found all the windows wide open in all four rooms. It was almost as though the house was set up, with all the downstairs windows closed and all the upstairs windows open, to guarantee the fireplaces would smoke. Maybe it was set up to see if we could make the fireplace work under the worst conditions or more likely with the expectation that, if we built fires, the fireplaces would smoke up the house.
That, by the way would be the worst thing to do if the house did suddenly fill up with smoke. You'd want to close all the upstairs windows and open up all the downstairs doors and windows to drive the smoke up the chimney - not drag more smoke down the chimneys, through the house and out the upstairs windows.
So, we closed all the upstairs windows and looked for other leaks upstairs that were not even noticeable with the windows all open. We found that all the recessed lights leaked and there were a lot of them. We also found leaks into the upstairs play room where a fan had been installed to vent paint and carpet odors.
With as much closed upstairs as possible, we went downstairs to see how our downdraft was doing. With the downstairs doors and windows open it was no surprise that we now had an updraft even in the bedroom fireplace.
At this point the owner was pretty upset with the prospect of having to have a detailed checklist of which windows had to be open or closed to make the fireplaces work. We had just been testing to see what the problem was and hadn't decided what to do yet to balance the ventilation system. It seemed to be time to come up with solutions.
It was clear that under "normal conditions" the house was losing a lot of air upstairs and was way too negatively pressurized for the chimneys to draft naturally. We talked about raising the height of the chimneys, installing chimney top fans, plugging the leaks in the recessed lights and eliminating or reversing the flow in the ventilation fans in the playroom and media closet. But the quickest, most automatic fix, I said, would be to install a makeup ventilation air system similar to the one on line at http://www.rumford.com/store/vent.html#mua
So, here is what we decided to do:
1) Greg Wilkins will find a competent HVAC contractor to figure out where and install a pressure regulating auto-adjusting make-up air ventilation system. His charge will be to balance the ventilation system so that there is upward draft in both chimneys when they are cold and to make sure there is adequate capacity even when both fireplaces are burning and exhausting 200 to 300 cfm each.
2) Build the chimneys taller than the house. (In the process, make sure the metal chimneys are the correct size - 16" id for the 48" Rumford and 12" id for the 36" Rumford.) Installation of the make-up air system will insure draft when the house is fairly well closed up with only a few windows open but, if a lot of windows are open, especially upstairs, the house, being taller than the bedroom chimney, will draw better than the chimney, overwhelming the makeup air system and there may still be a downdraft in the short chimney. Building the chimneys taller than the house will insure positive draft in the chimneys even if all the windows are open.
3) Once the ventilation system is under control, the chimneys built taller and we are sure the metal chimneys are the correct size, Angelo will build fires in both fireplaces to prove that they work. If they appear to be temperamental with vigorous fires and a balanced ventilation system, we will take a closer look at the metal chimley-smoke chamber connections.
4) Other recommendations that will improve the efficiency and reduce the amount of make-up air needed are to turn off or reverse the ventilation fans and fix the leaks in the recessed lights. Greg Wilkins said he would check that the correct lights were used.
More Smoky Fireplaces
Buckley Rumford Fireplaces
Copyright 1995 - 2012 Jim Buckley
All rights reserved.