What is this duct going directly outside?

I've owned my house for about two years, and I've started preliminary planning to finish the basement. This house was built in the 70's, and the basement was previously finished at one time.

Next to the furnace area, there is an insulated duct which goes directly to a vent on the outside of the house. Does anyone have any idea what purpose this serves? Once sheetrock is placed back up on the frames, this duct will be enclosed within the same space as the furnace. Did this have something to do with air flow for the furnace? I've plugged it with insulation for the time being, because a cold draft was coming out of it.

 

Does it have any sort if fan on it? A radon fan maybe?

 

I suspect the cold draft is exactly what it is supposed to do. There are two possibilities, fresh air for the house or combustion air for the furnace. Either of those needs is determined after some testing and calculating. Typically a 1970 home would not have included either in an unfinished basement. Renovations at a later date might have introduced that duct but we would need to know more to advise what to do.

Certainly enclosing that furnace will affect its supply of combustion air. Are those studs new or were they already in place when you bought the home.

Bud

 

There is no fan on it.

The framing was in place when I bought the house. What I was told is that the basement was completely finished at one time, then an in-ground pool in the backyard (long since removed) caused flooding the basement around the year 2000 which resulted in them tearing everything but the framing out.

 

I suspect that duct was installed to meet the combustion air needs for the furnace. 1970 homes were not usually sealed tight enough to need additional fresh air.

There are guidelines for how large of an opening you need based upon the size of your furnace, assuming you are going to enclose it with drywall again. Current framing I see in the pictures may have issues, one is the need for a pressure treated bottom plate. Other code requirements may have kicked in so discuss that with your local building department when you pull your permits, there will be several and don't skip them.

Bud

 

That was probably run for the water heater and the furnace. It looks like the furnace may not be vented to the chimney any more. If that's true.... you may be able to decrease that duct size.... if it's even needed for just the water heater.