I have a mid nat gas forced air furnace and gas hot water tank. The hot water tank directly exhausts outside, while the furnace has a fan to push the exhaust up a chimney (no draft hood) i also have a natural gas fireplace that has b-vent. I have been fighing trying to keep my utility room warmer as my kids bedroom is directly above. The only cold source i found is the fresh air intake. It is currently a 4" insulated pipe that goes down to the floor then back up 3' like a p trap. It originally just hung in the air, and i thoght the p-trap would help but it doesn't. It has cold air coming from it even when everything is off. I am too nervous to damper it anymore casue there is the chance that all appliances could run at the same time. Should i worry about doing this, or is there any other suggestions on what to do? Oh ya i have a venmar HRV. it has a single motor so whatever it oushes out it draws in so i assume its balanced. I even shut it off and still have the cold air issue. All new windows in the house. I had it tested and its a pretty tight house.