Why is there frost inside my house

I had a client upset because when she removed a blanket that was lying against the door. The blanket was frozen to the door and when she pulled it away from the door it removed the paint on the door. What actually happened? The door is a solid core wood door with an R-value of 2.47. This means in the winter with the outside temp of -20°F and 65°F inside. The center of the door is 17.5°F and it’s hard to maintain the temp. of 65°F at the surface of the door even with air moving across it. 5/8″ from the inside surface of the door is the freeze point of the door.

Now lets put a blanket against the door. Next there is no air moving across the door and the blanket is like adding a blanket of insulation on the inside surface of the door.

The new freeze point is now located at 1 1/2″ into the blanket so when the blanket is now removed the moisture in the blanket has frozen to the door. With this under standing let’s look at your windows.

A window with Low E II will have an R-value of 3.5 – 3.75 Now let’s add drapes on the windows and people blame the window that it is bad.

When in fact there are 2 problems 1 no air movement across the surface of the window and the humidity in the house is to high for the exterior temp.

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