Temperature Data

Now that winter weather has arrived, my office can be a bit chilly. While the wood stove is nearby (in the next room), it is difficult to move the warm air from the stove to my desk. A former homeowner's solution was to install a duct in the attic with an intake vent above the stove and an outflow vent above my desk. In the middle of the duct-work is a small fan, positioned to move air from the warm side to the cool side. What a good idea. I mean, that is virtually free heat.

When we moved in, the fan didn't work. I fiddled with it this fall, and even took it to my father-in-law for some maintenance. I finally got it working and felt pretty good about this new way of heating the office. The only problem was that my self-satisfaction seemed to be the only warm glow associated with the project. After a day or two, even I had to admit that it didn't feel much warmer at the desk than it had before. So, I decided to collected some data to see how well it was working.

For 90 minutes on Wednesday, from 8a to 9:30a, I kept the door to the wood stove closed while I ran the fan. The temperature went from 52.6F to 52.2F and back again. (See above.) At 9:30a, I opened the door and shut off the fan. The temperature went from 52.6F to 59.8F over the next 90 minutes. Now, I ain't too good at statistics, so I don't know if my data are significant, but it looks to me like the fan is making things worse. How can this be?

The only thing I can think of is that the air is traveling slowly through an unheated attic and cooling as it moves. The length of the duct is about 30 feet, the attic is cold, and all the heat is gone before it arrives. It is hard for me to believe this, since the ducting is insulated, the air above the stove is super-hot, and 30 feet isn't all that far, but I can't think of anything else. The fan is an old, slow, and probably ineffective squirrel cage, so perhaps it just can't move the air fast enough.