Chimney not drawing? New home with Open cell
I have completed a new home in which the chimney, which is at the proper height, does not draw until an 8’ tall door is opened 8”. We are going to add 4’ to 5.5’ to the total chimney height. We have already added a 5” round vent in the side of the fireplace with fresh air from outside. The house has mostly fixed windows. The house has open cell in the walls & ceiling. The house is located in Sewanee, TN (1 hr north of Chattanooga). Would an ERV or HRV help the chimney draw by bringing more fresh air in? What brand do you recommend? Probably need to do one that is just thru the wall, not add ducts. We though of vents in the floor to draw air from an encapsulated crawl space, which I don’t think is a good option. Or add another side vent or ash clean out in the fireplace. Or homeowner suggestion, “some very simple fresh air vents spaced strategically around the main living space…from which the return air draws? Maybe 6 vents that are maybe 4 by 10” or 240 sqin total…about equal to the door opening required to create the air necessary for the fire place to work.” The main living space with fireplace is 720 sq ft with vaulted ceiling and 10’ walls.
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Replies
jmanmozee,
Fireplaces simply don't need the volume of combustion air you are proposing to function. If it won't draw, the house must be under negative pressure. Balanced ventilation should solve that, but I wonder why that is presently the case?
On a related note: How is the house ventilated now?
The house is not ventilated now. We have bathroom vents to the exterior & range hood vent to exterior.
In what way do one ventilate the house?
Could the hvac system that only draws air from inside be causing the negative pressure?
How do I go about getting balanced ventilation? I’m unfamiliar
You have a 5" fresh air supply for the fireplace? Does it work? Have you tested it to see if air is coming in when you light a fire?
There's a formula for chimney height relative to the distance away from the roof peak and roof peak height. Sounds like a chimney height problem to me.
We are 12’ from the nearest roof. They all confirm the height is good. We are going to add 3’ more to the chimney height. The homeowner requested this for looks.
The vent pipe in chimney didn’t seem to work when a fire was lite. I was not there when the chimney mason & homeowner tested it.
The vent cover blocks the flow of air quite a lot. I may remove it and try again.
Is the chimney’s draw affected by the operation of the HVAC blower?
Walta
Could be. Good point. We can also try without it on.
When it’s been on and the window or door cracked open 2-3” it draws fine.