Draft coming through vents of wood furnace??? Please help!

[jedi_jackson]

I have a Thermo Pride WC-27 Wood/Coal burning furnace in my basement and I am having a perplexing issue. In my den which is right above the fireplace, I have a vent that is beside my recliner. When the stove is not in use, I can feel cold drafts of air coming through the vent that correlate with the wind blowing outside. I know that air comes back down my chimney and flue but can't figure out how it is coming in to the vents. I thought that all the heat comes from convection and then then blower circulates the heat through the duct work throughout the house and back to the cold air return. Please help me figure out where this cold air is coming in from. Thanks!!

 

[lost in the woods]

not sure about the problem but I might have a solution- when I set up my Englander, the theory was to run the hot air from wood furnace into existing oil burner plenum which then takes hot air into existing ductwork throughout the house. the instructions called for a backflow preventer (installed in the woodfurnace duct work up stream of the oil furnace plenum connection) that way in the event the wood furnace blower motor was running and the oil burner blower was running they wouldn't be 'fighting each other.' maybe you could install one of those and eliminate said issue. no local HVAC places had such a thing so I had to order through the computer. so glad Al Gore invented tha internet thing!

 

[jedi_jackson]

not sure about the problem but I might have a solution- when I set up my Englander, the theory was to run the hot air from wood furnace into existing oil burner plenum which then takes hot air into existing ductwork throughout the house. the instructions called for a backflow preventer (installed in the woodfurnace duct work up stream of the oil furnace plenum connection) that way in the event the wood furnace blower motor was running and the oil burner blower was running they wouldn't be 'fighting each other.' maybe you could install one of those and eliminate said issue. no local HVAC places had such a thing so I had to order through the computer. so glad Al Gore invented tha internet thing!

Thanks! I will try to find one of those and give that a try.

 

[Highbeam]

I suspect your house is breathing. Meaning, Air is being sucked into and out of the vents based on variable pressures in the home related to wind and leaks. The ductwork from the basement to the upper floors can act like a chimney as well. Stack effect.

 

[jedi_jackson]

I suspect your house is breathing. Meaning, Air is being sucked into and out of the vents based on variable pressures in the home related to wind and leaks. The ductwork from the basement to the upper floors can act like a chimney as well. Stack effect.

That makes sense. Thanks!

 

[Fred61]

Depending on when the ducting was installed in your house it's possible there could be a small make up air duct in your ductwork. I guess it's something they did in the forties. I've encountered two of them. The first one I found was in a Sears Roebuck kit house. It was just a small 4x4 duct in the sill open to the outside.

 

[jedi_jackson]

I suspect your house is breathing. Meaning, Air is being sucked into and out of the vents based on variable pressures in the home related to wind and leaks. The ductwork from the basement to the upper floors can act like a chimney as well. Stack effect.

The house was built in 1979. If something like this was put in, where should I look?

 

[3fordasho]

The house was built in 1979. If something like this was put in, where should I look?

Mine was built in 1982 and has a screen covered vent directly outside the furnace room. The rectangular duct extends horizontally along the floor joists about 6ft into the room then just is open at the end of the duct run. There is a spring loaded flapper near the outside vent but as far as I can tell is installed to let air out of the furnace room and not let any in??? not sure what its purpose is because it's not supplying any make up air the way it's installed and I don't see any situation where there would be a need to let positive pressure out. The outside vent is about the same size as a dryer vent.

 

[Highbeam]

The house was built in 1979. If something like this was put in, where should I look?

The house is Swiss cheese. You’ve got air leaks in the ceiling that let air out of your room and you have air leaks in the basement that let air into the home. The ceiling air leaks are usually stronger. All of these leaks cause air to enter your house down low and flow through your house to the upper leaks. Your furnace is acting as a conduit for these flows but is not the cause. Go down and block the cold air return to the furnace and it will stop.

 

[JRHAWK9]

Mine was built in 1982 and has a screen covered vent directly outside the furnace room. The rectangular duct extends horizontally along the floor joists about 6ft into the room then just is open at the end of the duct run. There is a spring loaded flapper near the outside vent but as far as I can tell is installed to let air out of the furnace room and not let any in??? not sure what its purpose is because it's not supplying any make up air the way it's installed and I don't see any situation where there would be a need to let positive pressure out. The outside vent is about the same size as a dryer vent.

Our place was built in 2000 and has a similar setup. Ours is a round 6" insulated flexible duct which leads to some sort of BD connected to the metal cold air duct work. Ours is for makeup air if the house should ever come under enough negative pressure when the LP/AC runs. Don't think it has ever worked the way it was designed though, as the house is not that tight. I have just recently disconnected the one end from the BD/return duct and extended it along the wall plate with more 6" insulated flexible duct in order to get it near the wood furnace. I made a Saskatoon loop with it and am currently using it as my makeup air duct (it drops to the floor, loops back up about 3-4' and then loops back down before it ends about 5-6" from the basement floor). Seems to be working good. Got down to 8° last night and 10° the night before w/o seeing any adverse side effects. Also using this 6" makeup air duct for a top secret experiment of sorts.....

I am a bit concerned in very cold weather it will contribute to the stack effect and make it easier for even more heated air to leave the roof.

 

[Fred61]

The house was built in 1979. If something like this was put in, where should I look?

I'm pretty sure they Teed into the return ducting.

 

[salecker]

Our place was built in 2000 and has a similar setup. Ours is a round 6" insulated flexible duct which leads to some sort of BD connected to the metal cold air duct work. Ours is for makeup air if the house should ever come under enough negative pressure when the LP/AC runs. Don't think it has ever worked the way it was designed though, as the house is not that tight. I have just recently disconnected the one end from the BD/return duct and extended it along the wall plate with more 6" insulated flexible duct in order to get it near the wood furnace. I made a Saskatoon loop with it and am currently using it as my makeup air duct (it drops to the floor, loops back up about 3-4' and then loops back down before it ends about 5-6" from the basement floor). Seems to be working good. Got down to 8° last night and 10° the night before w/o seeing any adverse side effects. Also using this 6" makeup air duct for a top secret experiment of sorts.....

I am a bit concerned in very cold weather it will contribute to the stack effect and make it easier for even more heated air to leave the roof.

Is your house tall?And do you suspect that you vapor barrier is compromised in your ceiling?
My house is tall,from the main floor to the ridge beam is around 25 ft inside.From the ground outside to the ridge it is around 34 ft on the shallow side.I was anal about the vapor barrier when i built the place.I have minimal stack effect pulling cold air into the house.I know my exhaust fan in the upstairs bathroom will leak some in the winter.Crappy flap in them to seal when not in use.I was concerned about the stack effect with log walls,i hate the look of Perma Chink that people use to seal log walls.The builder that did our house is an awesome craftsman and it would take a critic to find gaps in his work.So my belief is it would be an insult to his craftsmanship to cover all his hard work with ugly caulking.The first couple of winters showed a few leaks through the log walls.Most were cracks in the logs allowing air movement out.Some well place expanding foam seems to take care of them.
We were mandated by building codes to install a HRV unit.Waste of time and money.It was shut off as soon as the required balance test was done.
In short if your ceiling was well built the stack effect should be minimal.Ours is almost zero with a tall house.

 

[JRHAWK9]

Is your house tall?And do you suspect that you vapor barrier is compromised in your ceiling?
My house is tall,from the main floor to the ridge beam is around 25 ft inside.From the ground outside to the ridge it is around 34 ft on the shallow side.I was anal about the vapor barrier when i built the place.I have minimal stack effect pulling cold air into the house.I know my exhaust fan in the upstairs bathroom will leak some in the winter.Crappy flap in them to seal when not in use.I was concerned about the stack effect with log walls,i hate the look of Perma Chink that people use to seal log walls.The builder that did our house is an awesome craftsman and it would take a critic to find gaps in his work.So my belief is it would be an insult to his craftsmanship to cover all his hard work with ugly caulking.The first couple of winters showed a few leaks through the log walls.Most were cracks in the logs allowing air movement out.Some well place expanding foam seems to take care of them.
We were mandated by building codes to install a HRV unit.Waste of time and money.It was shut off as soon as the required balance test was done.
In short if your ceiling was well built the stack effect should be minimal.Ours is almost zero with a tall house.

We are probably very similar in height at the peak. We have a log SIDED cabin of sorts with 12/12 pitch roof w/ loft. 32x42 footprint and ~31,000CF, including the basement. It wasn't built with efficiency in mind, lets put it that way. It gets pretty dry in here during winter....10-15% in the dead of winter. This right there leads me to believe I have warm air leaving and cold air entering. When outside after a snow, the snow at the very peak of the roof won't last long. We do not get any icicles forming anywhere though so that's a good sign. I suspect the peak has some air leakage. We also have air leakage at the knee wall (I believe that's what it's called anyway). It's where the vertical walls meet the roofline.

 

[salecker]

We are probably very similar in height at the peak. We have a log SIDED cabin of sorts with 12/12 pitch roof w/ loft. 32x42 footprint and ~31,000CF, including the basement. It wasn't built with efficiency in mind, lets put it that way. It gets pretty dry in here during winter....10-15% in the dead of winter. This right there leads me to believe I have warm air leaving and cold air entering. When outside after a snow, the snow at the very peak of the roof won't last long. We do not get any icicles forming anywhere though so that's a good sign. I suspect the peak has some air leakage. We also have air leakage at the knee wall (I believe that's what it's called anyway). It's where the vertical walls meet the roofline.

Very similar indeed
Ours is 32x36 with 3/5 loft upstairs which is isolated by insulated floor and walls.We can keep a 3 to4 degree difference in the temp,we keep the loft cold as we sleep up there.
We have cast iron rads for heat with TRV's for control.
We get very dry in the winter too,but we are in a semi arid zone.This winter we have had very little snow.I packed my trail to work between xmas and new years with a snowmachine, and i have been riding my bike all winter, with which i have kept the trail packed.