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joni97 08-08-2011 08:55 AM

Furnace cold air return comes from attic
 
I have a 60 year old house, the attic appears to be dry and free of mold.

Recently while crawling around, I noticed that the cold air return duct had a large hole in it meaning that much of the furnace air is being drawn from the attic. I thought about sealing the hole, then wondered if perhaps it was improving circulation in the attic and if I closed it, I might have circulation problems in the future.

I'd appreciate any input re possible problems leaving the hole open, I've no idea how long it's been there.

Thanks

paul52446m 08-08-2011 06:40 PM

Quote:

Originally Posted by joni97 (Post 59665)
I have a 60 year old house, the attic appears to be dry and free of mold.

Recently while crawling around, I noticed that the cold air return duct had a large hole in it meaning that much of the furnace air is being drawn from the attic. I thought about sealing the hole, then wondered if perhaps it was improving circulation in the attic and if I closed it, I might have circulation problems in the future.

I'd appreciate any input re possible problems leaving the hole open, I've no idea how long it's been there.

Thanks

I would not think you would want to pull air from the attic an put it in the house. In the winter you are bringing cold air from attic, cost a lot more to heat. The same in the summer if you cool with this unit. Paul

nealtw 08-08-2011 09:43 PM

Are you sure this is a cold air return or is it the vent to supply air for the fire?

joni97 08-09-2011 01:09 PM

Quote:

Originally Posted by paul52446m (Post 59692)
I would not think you would want to pull air from the attic an put it in the house. In the winter you are bringing cold air from attic, cost a lot more to heat. The same in the summer if you cool with this unit. Paul

Well I hadn't really thought about that, even from a financial point of view, I should seal it off. Thanks for the input

joni97 08-09-2011 01:19 PM

Quote:

Originally Posted by nealtw (Post 59703)
Are you sure this is a cold air return or is it the vent to supply air for the fire?

By 'fire', did you mean the furnace burners, I guess indirectly the duct does provide combustion air to the burners. Its definitely the furnace cold air return duct, the hole is irregular in shape as though it had been broken out by force or even chewed out by an animal. Anyway, it's on the top of the duct and I decided to close it off (possibly temporarily) with a piece of cement board which I happened to have laying around. I'll make my visits to the attic more frequent from now on to see if anything changes. Thanks for your input.

nealtw 08-09-2011 03:01 PM

I'm having a hard time figuring why the cold air ducts are in the attic, but it should be sealed and insulated. Your cold air for the furnace will be a lot warmer than the attic and you want to keep it that way. In the winter that is!

joni97 08-09-2011 03:39 PM

Quote:

Originally Posted by nealtw (Post 59746)
I'm having a hard time figuring why the cold air ducts are in the attic, but it should be sealed and insulated. Your cold air for the furnace will be a lot warmer than the attic and you want to keep it that way. In the winter that is!

Without going into a long story, we have no basement and originally the heating was just pumped into the crawl space under the floor with no ducting. From there it just floated up through grills in the floor. I guess the cold air return was located in the ceiling to encourage circulation on the assumption hot air rises. Some time in the past, ducts were added under the floor, probably when natural gas came to the area.

nealtw 08-09-2011 04:50 PM

I have seen that type of system before, the people that put in the ducts should also have dealt with cold air, it should be taking cold air from the floor or close to the floor. Perhaps it was designed for airconditioning also.

paul52446m 08-09-2011 06:16 PM

Quote:

Originally Posted by nealtw (Post 59752)
I have seen that type of system before, the people that put in the ducts should also have dealt with cold air, it should be taking cold air from the floor or close to the floor. Perhaps it was designed for airconditioning also.

If the hot air is in the floor, and you put the return air in the floor, you will get cold air drafts across the floor. also when the return air is in the floor, you will have hot stagnant air at the ceiling that never get moved out. Any good engineering firm will say for heating and cooling, take 80% return hi in the side walls or in the ceiling, and 20% from low in side wall or in the floor.
This way you get the air properly mixed . Paul

joni97 08-09-2011 06:49 PM

Quote:

Originally Posted by paul52446m (Post 59755)
If the hot air is in the floor, and you put the return air in the floor, you will get cold air drafts across the floor. also when the return air is in the floor, you will have hot stagnant air at the ceiling that never get moved out. Any good engineering firm will say for heating and cooling, take 80% return hi in the side walls or in the ceiling, and 20% from low in side wall or in the floor.
This way you get the air properly mixed . Paul

Yeah... that's pretty much what I figured since the hot air rises, you would want to draw it off at the top to keep a continuous supply of air warming the room. We have 2 returns in the ceiling, one high on the wall (cathedral ceiling) and none low down.... but in my 16 years in this house it has all worked fairly well. I appreciate everyone's advice.


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