Excessive Window Condensation

luckwudaveit

stuart45 said:

The insulation can settle at the top, causing cold spots. When CWI is installed, unless it's done properly there can be voids. You can check the temperature of walls etc with a surface thermometer. Anything at or below the dew point is where condensation will be forming. Damp walls with be colder as well.

Thanks, I'm going to try and borrow a wall thermometer from someone and will report back. We don't get any condensation on the walls though.

luckwudaveit

RobM99 said:

My initial thought is where the moisture is coming from. Do you dry clothes over a radiator, for example?

Thanks. Clothes are dried downstairs on a rack, but doors are closed to the rooms downstairs overnight. And the condensation happens whether washing is being dried or not.

rob7475

The first thing you need to look at is ventilation as this is the cause of the majority of condensation problems.

Lack of ventilation causes excessive moisture in the air which will condense onto a cold surface (usually you're windows or walls behind furniture etc).

Do you have a good extractor in your bathroom and kitchen with at least an overrun timer or preferably a humidistat? Trickle vents rarely provide enough air circulation to help much so may be worth opening windows a bit more when you're drying clothes, showering etc. Keep lids on pans when you're cooking will also help.

PIV units can be very effective at curing condensation issues but depending on your house layout, may have a negative impact on your heating costs. A good dehumidifier (Meaco, Ebac) won't cost too much to run and should actually reduce how much your central heating runs.

FreeBear

rob7475 said: PIV units can be very effective at curing condensation issues but depending on your house layout, may have a negative impact on your heating costs.

Mechanical Heat Recovery Ventilation systems should be a little lower on running costs at the expense of higher capital expenditure.

ComicGeek

Ventilation without putting heat back into the rooms will just make the issue worse. A lot of people have consciously/unconsciously reduced their heating levels as energy prices increased, and even a small reduction in surface temperatures can result in increased condensation forming. 

The old windows were probably leaky around the frames, which helped provide additional background ventilation. Replacing with new windows, with nice new sealed frames, has made the ventilation worse. Trickle vents are fine for newer properties with really well insulated walls and nice warm internal surfaces - they just don't provide enough ventilation for older properties with colder internal surfaces, and can also concentrate the cold outside air on the wall above the window head, making this more likely to have mould growth.

Decentralised mechanical ventilation units with heat recovery (MVHR) are a good option - installed through an external wall like a bathroom extract, they run for a few minutes in extract mode, capture the waste heat, and then reverse and run in supply mode while putting the heat back in the room. Can provide a much more effective ventilated room, without all of the capital cost of a centralised MVHR but with the extra running savings against a PIV system.

Unfortunately the answer is normally also to heat rooms more, or at least heat rooms more effectively. Making sure that the radiator isn't blocked, that air can flow freely around the room, looking at radiant heaters to target internal surfaces etc. 

ThisIsWeird

Lwai, if the only bedroom ventilation you are relying on is 'trickle', then try a few nights with the windows open to at least 'vent' setting. Door shut. Heating off. Thick duvet and/or leccy overnight blanket.
Yes it'll be cold if you need to get out of bed, but it should be plenty warm under the sheets. I suspect you'll wake to a dramatically-reduced level of cond.
If it's unpleasantly cold, then have the heating set to come on at least a half hour before waking time. One of you jumps out and shuts the windows until the bedroom is vacated.
Once you're out, then crack open the windows again, and leave them like that all day - even open them wide if needed. Close the bedroom door.
Before bedtime, I will assume the windows will be dry, so shut them a half-to-one hour before bed and turn on the rad. That should be welcoming. Then, heating off just before bed, windows on vent (more than one if you can), and jump into bed. LOVE the cold nose sensation - it's GREAT.

Please at least try this, and see if it makes a difference. It could be completely transformative.

That cond currently running down your panes - that's almost all from you

knightstyle

Well all this condensation is water in the air settling on a cold surface.  So as the windows will always be cooler than the rest of the room water will always form there.  So you need to reduce the amount of water in the air, when sleeping your breath will contain water and of course drying clothes, towels etc. will make the air damp.
Do you open the bathroom and bedroom windows for several hours a day?    This will help as will getting a proper dehumidifier.