Condensation

[RichD1]

I don't know if anyone else experienced it, but yesterday our house suffered from a huge amount of condensation. The north facing double glazed windows were running even the uPVC frames and the wood frames were covered and the walls and ceiling in our en-suite was dripping even though the extractor was on and the window open.

I've never seen it anywhere near this bad before. Humidity was about 75% upstairs and 65% downstairs. We have reduced our heating and closed off unused rooms. Today the humidity and temperatures are the same but everywhere is bone dry.

We live in South Dorset.

I can't get my head around what the cause was, any ideas?

 

[fourtytwo]

I have noticed sometimes the humidity is very high outside together with low temperatures so it's possible sometimes opening windows is no good.
We have used a dehumidifier for years in winter as the only way of controlling the problem although you have to move it around rooms. We aim to keep the house generally below 65% that stops condensation whilst not using huge amounts of electricity. House temperature is also an issue as compressor dehumidifiers (cheaper to run) loose efficiency if its too cold, generally we find 11-12C is the lowest we can use the dehumidifier.

 

[Pat ex]

If yesterday, the internal temperature was higher than outside, then warm moist air (75% !) on surfaces in contact with outside can cause such condensation. There will be a temperature difference on such surfaces as windows (even double-glazed ones, etc).
Today, with internal temperature lower, and closer to outside temperatures, the possibility of such condensation is reduced because the inside air contains a smaller amount of moisture, perhaps similar to outside, and the temperature difference is smaller.

If your extractor is near to your open window, it won't be very effective.
The idea is to draw warm air from the rest of the house, it collecting moisture along the way, and expelling warm moist air outside. Hopefully cold, relatively drier air will be drawn in elsewhere in the house, thereby replacing the air inside. This in turn will collect moisture as it warms up.

Ideally, you do want to reduce your RH upstairs, at least below 70%.
Don't be overly concerned at attaining the magic 50%, it's rarely attainable in the average house.
And lowering your internal temperatures is not a good way to avoid condensation, to save energy - yes, but not to reduce condensation.

There are other factors also, such as how hygroscopic are the internal surfaces. Low hygroscopic surfaces (such as tiles, plastics, etc) cannot absorb much moisture. Higher hygroscopic surfaces and furnishings (plaster, wood, towels, curtains, et) can absorb greater amounts of moisture, and they release that moisture naturally as the air RH falls. Although if the RH does not fall, and they retain that moisture, is when mould can occur.

Even outside wind strength and direction can make a difference to the effectiveness of natural house ventilation.

 

[JohnD]

A cold night will start by making the windows cold.

You don't drape wet washing inside the house, do you?

 

[opps]

I was working outdoors in London during the week and was annoyed that my filler was still wet two days later. According to my accuweather app the RH humidity was 89%. We did have slight fog for 2 days though.

 

[Justin Passing]

Could be a temperature inversion. Look em up. Do you live in a depression or valley? Makes them more likely till the wind blows. Can be caused by a warm front coming through too.

 

[Deleted member 18243]

First world problems!

 

[^woody^]

I can't get my head around what the cause was, any ideas

Your house was too cold to keep the moisture in the air.

 

[fillyboy]

Some years back I was halfway through decorating an empty house and I noticed a slight fog, I think a 'sea mist' had rolled in, Next thing I know there was literally water running down the walls and dripping off the ceilings.

Hadn't seen anything like it before or since.

 

[Odds]

Some years back I was halfway through decorating an empty house and I noticed a slight fog, I think a 'sea mist' had rolled in, Next thing I know there was literally water running down the walls and dripping off the ceilings.

Hadn't seen anything like it before or since.

Weird.
The early morning fog last week persisted through the day with a misty drizzle (a mizzle?) and after 20 minutes or so soaked you as much as a fall of rain would. Better that than snow any time. I just wipe away morning condensate from the windows and carry on.

 

[Pat ex]

.

 

[Pat ex]

.

 

[Justin Passing]

I half watched a guy from Autoglass changing a windscreen recently. He took the new screen out of the van where it had been all day, and it immediately had condensation over it. Never seen it before, he said - cross!
I think that was a warm front coming in. You can get the same if the wind changes and comes in off the sea, which is warm in cold weather when the land cools faster. - "sea fog"

 

[jeds]

I'm in the South West - we had thick fog since Tuesday and all over the weekend - only lifted yesterday. Did you not have any fog in Dorset?

 

[RichD1]

Thinking about it, it was foggy last week when I had the condensation problem, but cleared on the Friday.