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old window condensation problem

I recently purchased a 2 story home built in the mid- to late-1800's. During the colder winter months, the upstairs windows (2nd floor) have been collecting an excess amount of condensation on the inside. They are the single pane original windows. There are storm windows on the outside. We've done some caulking, around the sides and top of storm windows (not the bottom), and around the window trim. Is it possible we've made them too airtight or even that our attic isn't venting properly?

Thanks and any advice helps :)

Re: old window condensation problem

New windows are double pane with gas in between. Naturally, they provide better insulation than old single pane windows.

Try to improve air flow in the upper bedrooms.

How warm is your house and how cold is it outside?

Re: old window condensation problem

The house is generally 55* F during the day, and 62*F during the evening (inside). The outside temperature is around 30-40* F right now. Any suggestions on how to increase air circulation on the second floor?

Re: old window condensation problem

Do you have forced air heating? very unlikely, but if you do, run it to get the air to flow.

Ceiling fans running in reverse are effective ways to get the hot air flowing.

Regular fans or small protable heaters with fans could give you some air movement too.

All of the above will reduce the humidity in the rooms.

MLB Construction
Re: old window condensation problem

a simple test which should work. obviously the air trapped between the strom window and the regular window is causing hte problem. warm inside, cold outside and in between it's a different temp. pick one window that normally fogs up, lower the upper storm window down one notch so that the air temp can equalize between the storm window and interior window. i bet it won't fog up.

storm windows are not designed to be a thermal barrier, they are designed to keep wind and rain from hitting the interior window. there should be air circulation between the two windows, at least enough to stabalize the temperature.

Re: old window condensation problem

dj1, I don't have forced air heating, but I can try a small heater or fan.
MLB, I will definitely try that!

Thank you both for the helpful tips!

Re: old window condensation problem

There seems to be some confusion here. My interpretation of the original post is that there is condensation on the inside of the primary glass, not between the primary window and the storm window.

The storm window should not be caulked at all. It is there to block wind and rain from the primary window, thus reducing drafts. It also provides a small thermal barrier, not very much but a small one none the less. The air between the panes is almost dead air, it does warm up slightly from the radiation of heat from the primary window.

Cold air does enter the void between the panes of glass and is warmed up by the radiation of heat from the primary glass. This reduces the relative humidity (RH) of this air so any warm air that leaks from the inside of the house, through the weatherstripping around the window, will have its moisture absorbed in the cooler drier air. This keeps the outside of the primary glass and the inside of the storm window dry.

The problem is that the inside surface temperature of the primary window is below the dew point of the room air. To prevent condensation on the window, you must either increase the surface temperature of the glass or reduce the dew point of the air in the room. Neither warming up the room air or circulating it is going to do this. The air needs to be dehumidified or the inside surface of he glass needs to be raised.

Something that MIGHT work would be to put a reflective film on the outside surface of the primary glass. This will help warm up the glass a few degrees. If you do this, also make sure the window weatherstripping is in very good shape or you will cause an outside condensation problem.

You could also build interior storm windows.

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