On Wednesday, December 30, 2015 at 12:19:25 AM UTC-5, Ed Pawlowski wrote:
On 12/29/2015 8:25 PM, wrote:

But isn't the rate of heat transfer higher in an upward
direction than downward? Not that I want to be standing
on a floor in direct contact with a frost table, but, just
saying.

Always to the coldest no matter the direction. The reason hot air rises
it that hot air is less dense than cooler air. Actually, cold air is
sinking and displacing the warm air.


Agree with regard to the first order effects. And if everything was held
constant, it would be 100% true in this situation, but it isn't. With a
cold floor, you wind up with a layer of cold air near the floor that's
going to tend to stay there. With a cold layer of air forming from a cold
ceiling, it's going to move and circulate via convection. So, it would
seem to me that a cold ceiling is worse than a cold floor, because you're
going to have more heat transfer via convection. If you had the
same temp delta with a hot ceiling and a cold floor, then I would expect
the heat transfer to be the same. Or vice-versa, a cold ceiling and a
hot floor.

In poster's case, seems he has enough insulation in the attic.