On Dec 22, 9:53*pm, Van Chocstraw
wrote:
On Mon, 22 Dec 2008 18:27:58 -0500, "Percival P. Cassidy"
wrote:

Our front door has an aluminum alloy threshold, and we have just noticed
that ice is forming on the indoor side of it; this, when it melts, will
not be good for our wooden floor.

What must be happening, I am sure, is that, because the outdoor
temperature is now well below freezing, water-vapor from the indoor air
is condensing an freezing on the surface.

Short of (a) replacing the threshold by a wooden one or (b) cutting the
aluminum one lengthwise and interposing a "thermal barrier" between the
two sections, what's a good way of solving this problem?


It's not likely conducting cold the entire 4 or 5 inches of threshold.
There must be air leaking under it to get frost on the inside.

You mean the entire 1.75" - the thickness of the door. The threshold
could be siphoning off heat through conduction for either distance.
If ice is forming on the inside, it certainly is. Other posters have
addressed the remedy.

R