I live in a house with older double glazed wooden windows and when the outside temperature falls below 10 or 15 degrees Celsius, the window panes start dripping with water in the mornings (inside temp. i.e. 15 degrees and air moisture between 65 and 70 %).
Is there any way to stop this from happening, short of getting new windows and/or let the heating run all night?
Added info: I do air the place every morning with wide open windows for about a quarter of an hour.
Condensation is caused by warm humid air cooling down. You can affect different parts of this process.
The first thing to do is to reduce the humidity, especially as it sounds like you have very humid air already.
Make sure you do not have any open containers of water evaporating.
After you take a shower or bath, keep the bathroom door shut (and the vent fan on or window open) until it has dried out.
Similarly, vent steam from cooking to the outside if you can.
Having fewer people in the house will also reduce the humidity (exhaled air is warm), but I doubt you want to change that.
Air out in the evening, not the morning: you want to dump the warm humid air before it has a chance to deposit its water on the windows.
Finally, you could use a dehumidifier.
You can also keep the air on the inside warmer:
Fix any air leaks around the windows, so that cold air isn't mixing with the warm air and cooling it.
Do not let air be trapped next to the window glass: if you have curtains/blinds/shades, make sure they are open at least at the bottom of the window, so that air cooled by the glass falls away from the window instead of staying where it is. This will of course mean the inside air loses more heat overall as it is circulating against the windows, but that can't be helped.
Opposite strategy to the previous item: if you are not opening the window then seal it with an airtight cover (kits for this with clear plastic and tape can be found in hardware stores) so the humid air doesn't reach it and it stays cold.
Increase the air temperature, i.e. turn the heat up. Get a programmable thermostat so you can tweak it to be just-warm-enough in the day and night.
Finally, if you've done everything you can and you still have water on the windows, wipe it off regularly so that you don't grow mildew on your windows.
Seal the sill and sash between the windows thoroughly with caulking, leaving just a "weep" hole or two at the bottom so moisture can drain from between the panes.
Seal the window sash pulley holes if it's an older-style window with sash weights.
Cover the windows with a shade at night. It might help to put a bit of self-stick hook-and-loop tape ("Velcro") at the edges of the shade and the window frame. This provides a third layer of insulation and keeps moist air from impinging on the glass.
Get a window insulation kit at most hardware stores.
Keep humidity in the house at a reasonable level. Vent bathroom and cooking areas. (If its too low, the air feels colder and dries the skin.)
The windows definitely need replacing by the sound of it, but using plastic sealed at the edges over the windows will stop the problem, by and large, but obviously means you can't open the windows till spring. The other thing that might help is leaving your bedroom door open all night - breathing and body heaat create moisture, and that condenses on the cold window panes, even if the air isn't too humid already, so leaving the door open may help to disperse that humidity.
I recall as a child (unheated houses other than a central fire in one room, single glazed windows) my parents and grandparents putting newspaper on the inside of the window panes when condensate appeared to soak up moisture, replacing it once it was too wet. Once into proper winter, the condensate on the inside of the windows froze, creating some rather wonderful patterns, not something commonly seen now. Those were the days when you left your clothes for the next day on the end of the bed, and in the morning, pulled them under the covers to warm them and got dressed whilst still in bed... certainly not something I'd want to do as an adult.
