Woodstove vs Attic Fan

[31 bertram]

I hope someone can help me with this problem, I have a two speed attic fan with thermostat in my house and when the temps rise in the summer the high speed attic fan kicks in and pulls a strong creosote smell throughout my house. Smells like the inside of the woodstove. No problems when fan is operating in low speed mode. My wood stove is about 10 ft. in distance from the attic fan. I would like to get this thing figured out because my attic is very hot in the summer. Any advice would be greatly appreciated.

 

[DuaeGuttae]

Just for clarification: by “attic fan” I assume that you’re not referring to a whole house fan (what I always called an attic fan growing up) but rather to a powered attic ventilator. Correct me if I’m wrong.

If it’s a powered attic ventilator, it seems that the high speed on the fan removes more cfm of attic air than can be made up through vents, and it’s pulling air from your house. My guess is that your house is closed up and air conditioned (or at least closed up just to keep the heat out and delay turning on that expensive air conditioner), and the chimney is one of the paths for least resistance for pulling in make-up air. If that’s what’s going on, you might consider if there’s something blocking the vents in your attic, or if there is even sufficient natural ventilation up there. You really don’t want your attic ventilator pulling conditioned air from your house all summer. Do you have a radiant barrier to help keep heat out?

If it’s a whole house fan, it’s much easier. Open more windows for make-up air.

 

[31 bertram]

Yes sir, it's an attic ventilator not a whole house fan. I finally got the search right and found some information on this. Seems that the high speed is drawing the air down thru the flue and out in the house from the woodstove. I'm thinking about disconnecting the high speed on the motor control switch to where only the "low speed" will turn on.

 

[begreen]

Sounds like high negative pressure created by the attic fan on high speed is pulling air through the stove flue. Is there an attic window or vent that can be opened so that there is cross ventilation in the attic and not as strong a draw from the house?

 

[31 bertram]

Sounds like high negative pressure created by the attic fan on high speed is pulling air through the stove flue. Is there an attic window or vent that can be opened so that there is cross ventilation in the attic and not as strong a draw from the house?

I added some extra vents(not for sure what you call them) at each end of the house but must not be enough to compete with the negative pressure drawing from the flue. At least I now have an idea of what's going on.

 

[Andyman]

I added some extra vents(not for sure what you call them) at each end of the house but must not be enough to compete with the negative pressure drawing from the flue. At least I now have an idea of what's going on.

Gable vents?

(broken link removed)

 

[snaple4]

Your problem it two fold. First, you do not have enough fresh air available to your attic from outside the house. This should come from clear gable vents and/or vents on the side of your house depending on design.
Second, you have some massive air loss from your house into your attic. Climb up there, seal up all the holes, caulk all the seams, box in all the can lights and enjoy a more comfortable/healthy home.

If you are unfamiliar with air loss into the attic just do a search on "air sealing attic". Our terrible quality control when building a house leaves all kinds of ways for air to move from inside the house into the attic. This is done by all the holes the plumber, electrician, framers, cable guy, HVAC tech, and every other numb-scull with a drill put into your studs, sheet rock, seal plate, top plate, and sub-floor. They usually do not seal up the hole with sealant. Then to top all this off you have to look at insulation. If you have fiberglass, and most people do, then all that air just flows right through it.

I was at a house last week that was having an addition done. You could see light under the seal plate!

 

[bholler]

Your problem it two fold. First, you do not have enough fresh air available to your attic from outside the house. This should come from clear gable vents and/or vents on the side of your house depending on design.
Second, you have some massive air loss from your house into your attic. Climb up there, seal up all the holes, caulk all the seams, box in all the can lights and enjoy a more comfortable/healthy home.

If you are unfamiliar with air loss into the attic just do a search on "air sealing attic". Our terrible quality control when building a house leaves all kinds of ways for air to move from inside the house into the attic. This is done by all the holes the plumber, electrician, framers, cable guy, HVAC tech, and every other numb-scull with a drill put into your studs, sheet rock, seal plate, top plate, and sub-floor. They usually do not seal up the hole with sealant. Then to top all this off you have to look at insulation. If you have fiberglass, and most people do, then all that air just flows right through it.

I was at a house last week that was having an addition done. You could see light under the seal plate!

It is a sill plate not a seal plate. If you are going to bash builders for not knowing what they are doing atleast get the terminology right.

 

[31 bertram]

I realize now that years ago when they changed the siding on our house we had huge triangle gable vents and they replaced them with smaller ones. I just added another vent yesterday and will see if this feeds enough air with the attic fan on. I think I'm on the right track now.

 

[maple1]

Soffits should be vented also. Air should come into the attic thru (low) soffit venting and leave thru ridge or (high) gable vents. If done properly there should be no need for a fan. Also agreed with the above about the needed air sealing, that's also killing your ability to heat and have adequate humidity levels in winter.

 

[snaple4]

It is a sill plate not a seal plate. If you are going to bash builders for not knowing what they are doing atleast get the terminology right.

You are correct, I should double check the spelling regardless if I am bashing the trades or not. Using a phone to type a response between job locations isn't an excuse and I should know better.

Also, just an fyi, I am one of those guys who drill holes throughout the building.

 

[bholler]

You are correct, I should double check the spelling regardless if I am bashing the trades or not. Using a phone to type a response between job locations isn't an excuse and I should know better.

Also, just an fyi, I am one of those guys who drill holes throughout the building.

Lol no problem i didnt mean any offence by it. My spelling is horrible