# Installing duct with inline fan



## kbrown (Nov 27, 2009)

Has anyone ever tried this? I am thinking of running some of that flexible insulated duct through the attic from the room with the wood stove to the opposite end of the house to move the warm air. At one point there would be an 8" inline fan blowing the warm air; I have an old circuit in the attic that can be used and tied to a switch to control the fan. At each end I would be installing returns that can be closed during the off season. I really don't see any problems doing this but figured someone out there has done this and can provide some feedback on the results. Thanks!


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## wellbuilt home (Nov 27, 2009)

I ran 4 ducts,  one in each bed room up stairs with 2 in line blower in the ceiling over the stove . 
  I found that the air was cold when it was blowing  out in to the rooms . 
  The ducts never seemed to work for me . John


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## cre73 (Nov 27, 2009)

Yes I did just that and only use it on the coldest of days and it works great for me. I have 6in insulated duct with an inline fan. I have cathedral ceilings through most of the house except my hallway. The inlet is 10 ft high about 15ft away from the stove. One word of caution that I read about on here. In the event of a fire in your stove room this will feed the other part of the house with carbon monoxide and such. So keep your smoke alarms and your carbon monoxide detectors up to date.


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## LLigetfa (Nov 28, 2009)

You would need as much insulation around the duct as you have in the ceiling to not lose heat to the attic.  The one inch of insulation on insulated duct doesn't do anything for preventing heat loss.  It is only designed to reduce sweating when moving cold air.


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## PapaDave (Nov 28, 2009)

This house had that setup already installed when we bought it. 
Register in the stove room, 10" insulated flex about 20ft, inline fan just before a Y,down to 8" to kitchen, then another 8" 12ft or so to the bathroom. This actually works fairly well, but it does lose some heat. 
Small ranch, and I now (this year) am using the blower on the stove to push warm air. Seems to setup a nice circulation in the house. I use the attic setup once the stove room has gotten pretty warm, for a while, then shut it down. We'll see how things go this winter.

Dave


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## kbrown (Nov 28, 2009)

LLigetfa said:
			
		

> You would need as much insulation around the duct as you have in the ceiling to not lose heat to the attic.  The one inch of insulation on insulated duct doesn't do anything for preventing heat loss.  It is only designed to reduce sweating when moving cold air.



I was wondering about that. We had extra blown in Nu-Wool insulation about 4 years ago. It's been the best spent money next to the stove; was thinking that I need to then bury the duct, letting it just rest on top the rafter and cover it back up with the insulation. Only place I wouldn't do that is where the blower is. Would it be a better idea to just run normal rigid duct instead of the ready to go insulated flex then?


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## mayhem (Nov 28, 2009)

What about using the ducting to move the cool air out of the room and into the stove room.  The drop in air pressure there will pull warm air in from the stove room.  We've seen this worlk well with fans just blowing cool air across the floor...with ducts it might work even bettwe and without the clutter of a fan on your floor.


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## kbrown (Nov 28, 2009)

mayhem said:
			
		

> What about using the ducting to move the cool air out of the room and into the stove room.  The drop in air pressure there will pull warm air in from the stove room.  We've seen this worlk well with fans just blowing cool air across the floor...with ducts it might work even bettwe and without the clutter of a fan on your floor.



We are doing that exact thing right now with the fan method and it does work good. I had wondered about doing that with the duct; just install the inline fan in the opposite direction and see what happens. Worse case, you just turn it around the other way. Gonna have to break out the snow shovel to move the insulation now!


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## Dune (Nov 28, 2009)

mayhem said:
			
		

> What about using the ducting to move the cool air out of the room and into the stove room.  The drop in air pressure there will pull warm air in from the stove room.  We've seen this worlk well with fans just blowing cool air across the floor...with ducts it might work even bettwe and without the clutter of a fan on your floor.



There is no contest here whatsoever. Moving the cold, dense air works far better than moving the heated air, and you don,t have to worry about heat loss through the ductwork.
The thing is though, that you want to draw the cold air from the bottom of the room, not the top. Can you run the ductwork in the basement instead of the attic?


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## Gooserider (Nov 29, 2009)

Agreed, you are much better moving cold air towards the stove, rather than warm air away from it.  Another factor is that it's a code violation to have any kind of air INTAKE within 10 feet of the stove, but outlets are OK...

It is also MUCH better to use rigid duct work than it is to use flex...  Flex causes huge amounts of turbulence and airflow resistance, especially if it is not fully extended, run straight, and cut to length when it's installed... It's a labor saving hack, that will give you a lot less airflow than rigid, unless you compensate by using a bigger, more expensive, higher operating cost blower...  Whatever form of ducting you use, make sure you seal it well, and insulate it to the same value as the ceiling.  If not, while you are going to lose less heat than you would if moving heated air (heat loss is a  ΔT function) you are still moving heated house air through a radiating surface in a cold attic...

That said there are as many, if not more, failure stories of this sort of effort to move heat as there are success stories...  There are so many variables, it is hard to predict whether or not it will work in advance, especially for those of us in places far away that have never seen your setup.

Gooserider


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## Squiner (Nov 29, 2009)

heatit said:
			
		

> Has anyone ever tried this? I am thinking of running some of that flexible insulated duct through the attic from the room with the wood stove to the opposite end of the house to move the warm air. At one point there would be an 8" inline fan blowing the warm air; I have an old circuit in the attic that can be used and tied to a switch to control the fan. At each end I would be installing returns that can be closed during the off season. I really don't see any problems doing this but figured someone out there has done this and can provide some feedback on the results. Thanks!



Check out my thread that discusses exactly what you are thinking about doing.  

https://www.hearth.com/econtent/index.php/forums/viewthread/40728/P0/

To give an additional update from my last post in that thread; I get a very significant difference in temperature when the blower is running compared to natural convection.  No question it's beneficial for my house layout.

Hope this helps


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## westkywood (Dec 1, 2009)

Gooserider said:
			
		

> Agreed, you are much better moving cold air towards the stove, rather than warm air away from it.  Another factor is that it's a code violation to have any kind of air INTAKE within 10 feet of the stove, but outlets are OK...
> 
> It is also MUCH better to use rigid duct work than it is to use flex...  Flex causes huge amounts of turbulence and airflow resistance, especially if it is not fully extended, run straight, and cut to length when it's installed... It's a labor saving hack, that will give you a lot less airflow than rigid, unless you compensate by using a bigger, more expensive, higher operating cost blower...  Whatever form of ducting you use, make sure you seal it well, and insulate it to the same value as the ceiling.  If not, while you are going to lose less heat than you would if moving heated air (heat loss is a  ΔT function) you are still moving heated house air through a radiating surface in a cold attic...
> 
> ...



I just called my fire codes inspector and he said he never heard of it being against codes to have the vent near the stove drawing heat from it. I'm sure I could call another inspector and they'd tell me something else. I have to talk to my insurance agent this week , I'll ask her.


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## Gooserider (Dec 1, 2009)

The person I got it from was one of our former members, and a Mass. building inspector - who knew the codes inside and out, it was something he posted about fairly often.  When I put in our current VC, replacing the stove that was in the same place, the inspector was checking the distance between the HVAC return on the wall, but didn't care about the vent that was much closer...

I think I've also seen something about it in some of the VC stove install manuals - whatever one might say about VC stoves, their manuals tend to be above average in mentioning the code requirements for an install...

The basic idea makes some level of sense - if you have a smoke / CO issue at the stove, they don't want to be sucking up the fumes and spreading them around the house...

Gooserider


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## Hurricane (Dec 2, 2009)

It would make sense that installing a vent sucking air too close to the stove may cause a draft issue or draw smoke from the stove when cooling off. 
I have installed a vent about 20 ft and down the hall from the stove with a fan to blow the warm air down to the basement and it works great for me. I also asked the building inspector and he did not seem to think it was an issue. Although when the stove and my other fireplace was installed he wanted the manual before hand and then knew what to look for. 
Moving cold air is more efficient but not always the best solution depending on the layout.


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