Hello,

I have a 5 year old 24x24 attached garage that has R-13 in the ceiling (ceiling is 12' high), R-13 in the walls and R-17 doors. I'm currently using a Dornback 45,000 BTU hanging vented gas furnace that is 7' off the ground. I also have a ceiling fan to help circulate the heat.

The garage gets moisture from bringing a wet car in but the furnace does not dry it up. I keep the temp at least 52 degrees all of the time (through the winter). The man door window, garage door windows and the insulated side window have a lot of condensation on them. I do plan on adding additional insulation and a radiant barrier in the ceiling.

Is the furnace adequate for the application? Do I need to put an exhaust vent in the garage? If so, what CFM would be a good bet? The thermostat is mounted on the house side wall, would this be giving a warmer reading? Also, would a lower ceiling help to dry the air?

Thanks!

It sounds like the solution to your problem would be to raise the dew point in the garage, by either reducing the amount of moisture (probably impossible) or by raising the temperature in the space.

Try raising the thermostat setting a few degrees at a time, and note the effect it has on the moisture, especially the condensation on your glass. A setting of 52F at the thermostat probably results in a temperature several degrees lower at the glass. Perhaps relocation of the thermostat to an area near the glass would help, but raising the setting a few degrees will accomplish the same thing. Either way, the furnace will be running more than it is now.