Is Your Cold Air Return Vent Chilling You Out?

We have been having a stretch of below freezing temperatures here in western NC for a number of days now. Our home has a main level of about 1500 sq. ft. where our Jotul F600 is located in the living room. The lower level of the house is another 1200 sq. ft. where a Woodstock Classic is located. There is an open staircase between the two levels. For the most part we spend most of our time upstairs in the winter and do not heat the lower level where it will stay around 55 F while the upstairs will be around 72 F.

Last night my wife mentioned to me that she was covering up the floor register in her bathroom because she felt a cold draft coming in through it. We have a propane forced air heating system, but we don't use it; we heat exclusively with wood. The cold air return in the lower level is sealed off, but the large cold air return in the living room floor is open. After my wife made her comment I took my IR thermometer and did a check on our heating/AC registers. I recorded temperatures about 3 degrees cooler over the registers than the surrounding laminate floor. However, when I took a reading over the large cold air return in the living room floor it read 53 F! I put my hand over the vent and was surprised to feel a cold draft blowing up through the vent.

I had never bothered sealing this cold air return because I wrongly assumed any air flow would be going from upstairs where it is warm to the downstairs where it is cold. Since cold air sinks and hot air rises I figured the air current would be from warm to cold. However, the air was flowing in the opposite direction and the cold downstairs air was rising up into the heated part of the house. I covered the vent with some books for the time being until I can make a more elegant cover for the vent. So, if you have similarly open cold air return vents you might want to do a temperature check and see if you are getting cold air coming through them.

No, the furnace is completely shut down. I turned the power off to the unit so I can't turn on the air circulating fan without going down to the furnace and turning the juice back on. One hypothesis might be that the wood stove is sucking air (no OAK) out of the living room and the slight vacuum is pulling air up through the path of least resistance, which would be the cold air return vent, which measures about 16" x 12".

Yes, all the duct work is sealed and insulated, but I don't think that makes much of a difference since the ducts are all running along the ceiling of the unheated lower level (floor of the upper level of the house), so they are sitting in 55 F temperatures 24/7. I was just a bit surprised at how noticeable the cold air draft was that was rising from the floor return. A stream of 53 F air coming through such a large vent had to be doing a lot of cooling to the living room.

I think my intention for this post has been misunderstood. I know the cold air coming up through my cold air return is coming from my unheated lower level. My intention was to alert other members that they too could have cold air infiltrating their heated space if they have a similar set up to mine so that they could check and then close off the cold air return if cold air was coming through it, as is my situation. Thanks for the brainstorming.