Heat Source?

Do you ever find that your house is cold? Do you have pets. Well I think that these pets soak up what ever heat source that we may have.

Seriously though, our fat cat Delilah like to sleep on the heater vents, all the time. I wonder how she can stand the heat all the time. Skippy does that too once in awhile, but he completely covers the vent to the point no air can come out. Well I guess the animals have to stay warm somehow.