Can anyone help me out with some ideas/suggestions? I'm not an HVAC professional, but have a mechanicial background and a cursury understanding of the basic operation (at least I think I understand).
This is our second winter in this home. Last winter the home never was warm, we spent over $4000 in oil but never got the chill out of the house. There were time that I could feel a cool breeze in the living area and my repeated attempts to find it were unsuccessful.
This fall we installed a wood burning fireplace insert and that has helped immensely with keeping the house warm, however I'm feeling that breeze again. In the living room there is one main HVAC return vent for the entire first floor. Late one night (2am) the breeze was driving me crazy and I tracked it to cool air coming into the room through the return vent.
I have since taped a small strip of tissue paper to the vent so I can see when air is entering the room. At first I only noticed it after the wood buring insert had been running several hours, so I assumed what was happening was the heated air was rising to the second level of the home and displacing the cool air, thus forcing it down the return ducting. However, this morning the fire place wasn't running and I again noticed cool air entering via the return vent.
I don't think this is outside air, but in all honesty I don't know. It hasn't been below freezing since I noticed this vent issue, but from feeling the air I would say it is not from the outside...maybe the basement, upstairs or even the attic (where the upstairs ducting runs are located). But in all honesty I don't know for certain, so it very well be entering from the outside.
I've had a well respected local HVAC outfit here a few times for different things, and no one has noticed anything unusual about the system.
Does anyone have any suggestion/ideas? Any input is greatly appreciated.