>* Much of the thermal mass in the garage consists of cars, which have recently driven in from the hot surface and are therefore hot.
>...
>* The cars generate a lot of waste heat as they drive around within the garage.
Cars remain exceptionally hot long after they've been parked. That has little to do with their carrying heat from the surface, and much to do with the fact that they run on a constant stream of controlled gasoline explosions. Once parked, they will radiate that heat into the garage. I think this is the most likely explanation for why garages tend to be hot.
Also, for weak evidence: I have never paid that close attention to it, but I'm pretty sure that I've been cold in a parking garage when I came back to my car very late at night.
Exactly. I often used to ponder how effective a heater a PC is with decent graphics card running under load. I could heat my room in winter with just myself and the computer. With the computer off, I was cold. So I suspect that a 2ish litre car is somewhat better a heater, even long after its been turned off. The neighbourhood cats sure seem to love my car after I've been parked up for a while!
I think the PC as heater question is easy to solve. Just add up all the watts and assume that it all becomes heat. A cpu and graphics card can easily be over 100 watts each, and a 100 watt light bulb gets pretty hot. (I had this conversation with another computer guy at one time, and he didn't think all of the watts became heat. I'm not an engineer or physicist, but -- where else could it go?)
You're right that it basically will all go to heat. The only real exception is if light from the display goes out the window, or if sound from the speakers escapes the room.
>...
>* The cars generate a lot of waste heat as they drive around within the garage.
Cars remain exceptionally hot long after they've been parked. That has little to do with their carrying heat from the surface, and much to do with the fact that they run on a constant stream of controlled gasoline explosions. Once parked, they will radiate that heat into the garage. I think this is the most likely explanation for why garages tend to be hot.
Also, for weak evidence: I have never paid that close attention to it, but I'm pretty sure that I've been cold in a parking garage when I came back to my car very late at night.