Photo: Kindra Clineff
TOH general contractor Tom Silva says that adding weatherstripping to an entry door is one way to prevent condensation from collecting inside a storm door in winter.
Q: I replaced a entryway storm door that had rusted because ice formed frequently on the inside of the glass panel. The following winter, ice formed on the inside of the new door. In fact, the ice builds up to about ½ inch thick. What can I do to stop this from happening?

— Anthony Vallone, Howel, N.J.

A: Tom Silva replies: You need two things to make ice: cold temperatures and a source of moisture. Moisture vapor leaking into the space between the door and the storm door might cause some icing, so make sure that the main door is weatherstripped around its entire perimeter. If the weatherstripping is in good shape, it might be that the storm door is actually too tight and not allowing trapped moisture a way to get out. The solution in that case is to drill four 3/16-inch-diameter holes, two about a half inch from the top of the door and two about a half inch from the bottom. This will allow air to circulate without reducing the effectiveness of the storm door.

But a coating of ice as thick as what you describe makes me think that water is somehow leaking in from above and freezing on the glass. To stop such a leak, first check the door for missing weatherstripping, particularly at the top. Also, see if there's metal flashing on top of the door casing, and caulk the joint between the side casings and the siding. Speaking of caulk, there should be some sandwiched between the storm door frame and the door casing it's mounted to. If there isn't any, remove the frame and run a line of butyl caulk behind it before putting the door back. I prefer butyl caulk in this situation because it stays soft and pliable against metal.

Finally, check the siding and windows above the door to make sure they're weather tight. If water is getting in through an open joint around a window or at a crack in the siding, it's sneaky enough to work down to the door and leak in just where you wouldn't expect it.

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