How to address my humidity issues

knightstyle

I think that the first thing is to identify where exactly the damp coWhat happens to the damp air in the bathroom ank kitchen after showering and cooking?
All these matter plus we all give off "An individual person gives off about 400g (or 0.4 liters) of moisture per day through breathing and transpiration, which is equivalent to roughly 2.8 liters per week."

WIAWSNB

Aloysius1972 said:

I have begun the experiment. Both rooms began at 73% humidity and 17.5 degrees. One room has windows closed and a small/tiny dehumidifier running. The other has window wide open and door shut. The first room is unchanged but the second room now has temperature of 16.4 degrees and 75% humidity.

ChatGPT tells that whilst this has reduced the dew point and there is less moisture in the air, it has also reduced the gap to the dew point (due to the temperature drop) and therefore increased mould risk. 

Keep it going, and use the ultimate result of whether it feels damp, or develops mould. 

Bear in mind that the first room has a dehumidifier running - although small - and the other one relies fully on nature. 

Things may well change overnight, where the wee dehumid cannot cope. 

This is brilliant - you have both temp and humid monitored. A great test! (Either way...)

Vitor

Vent at the sources (kitchen, bathrooms), gently heat the cold rooms and consider a well-installed PIV as a whole-house baseline. 

subjecttocontract

Apart from the kitchen & bathroom what's the source of the moisture ? Do you dry wet clothes in front of heaters ?

Nebbit

You have not mentioned whether the walls are insulated at all. If, like me, you have single skin walls  then you *will* need a dehumidifier because, unless you have no heating at all, mould is inevitable. We had constant black mould in our bedroom until we got an  EcoAir Dessicant  dehumidifier which runs for 2- 4 hours a day in the winter, and pulls out 1-2 litres of water daily. Previously we had a compressor dehumidifier which was far less effective. The benefit of the dessicant type is that it also acts as a heater, thus defraying some of the energy costs. 

Albermarle

Nebbit said:

You have not mentioned whether the walls are insulated at all. If, like me, you have single skin walls  then you *will* need a dehumidifier because, unless you have no heating at all, mould is inevitable. We had constant black mould in our bedroom until we got an  EcoAir Dessicant  dehumidifier which runs for 2- 4 hours a day in the winter, and pulls out 1-2 litres of water daily. Previously we had a compressor dehumidifier which was far less effective. The benefit of the dessicant type is that it also acts as a heater, thus defraying some of the energy costs. 

The original/main part of our house is solid walls, with no insulation and we keep it reasonably warm.
We have never had any problems with damp or mould, or used a dehumidifier. 
Also we commit the cardinal sin of drying clothes on radiators  
I put it down to our house being older and a bit draughty, well ventilated. Plus it is a reasonable size, with high ceilings, wide hallway and stairs, and one open fireplace. So lots of space for air to move around
It seems from many threads on here, that some homes just seem more prone to condensation/damp problems than others.

subjecttocontract

Reading this thread it's obvious to me where your problems are
* Stop drying wet clothes over radiators. Use a tumble drier, hang them outside or on an airer in a spare room.... with some ventillation
* Fit and use an extractor fan in the kitchen when cooking.
* Fit and use an extractor fan in the bathroom. In addition when you have finished showering/bathing open the window and shut the door for 10 minutes.
Good luck.

ComicGeek

Aloysius1972 said:

I have begun the experiment. Both rooms began at 73% humidity and 17.5 degrees. One room has windows closed and a small/tiny dehumidifier running. The other has window wide open and door shut. The first room is unchanged but the second room now has temperature of 16.4 degrees and 75% humidity.

If you take the starting point of 73% RH (relative humidity) and 17.5 degrees for the room, and then heat it to 20 degrees, then the RH drops to below 65% RH. RH is just the percentage of how much moisture the air can hold at that temperature - in isolation it's meaningless.

If the air temperature drops, and no moisture is added or removed, then the RH % increases, as you have found with the second room. 

The outside air is not currently cold enough to provide a 'drying' effect on the room air. When you take 100% RH 10 degree outside air and heat it up to 20 degrees, it will still be above 50% RH. If you take 100% RH 0 degree outside air and heat it up to 20 degrees, it will be below 30% RH and too dry. So the ventilation strategy should change depending on the weather outside.

Ventilation alone is not sufficient to reduce RH - you have to remove the excess moisture (bathrooms & kitchens) at source, and also adequately heat the rooms to manage RH.

Condensation and mould growth is also slightly different in that it's the room surface temperatures that are critical - again, installing insulation by itself is not sufficient, the rooms have to be adequately heated as the room surface temperatures are generally lower than the room air temperature. There can also be large variations in surface temperature around a room, hence mould growth in high level corners, skirting boards, around window frames etc. Short term surface condensation (ie after a shower) with good ventilation may not lead to mould growth, but heating is still vital for circulating air to remove the moisture. 

subjecttocontract

An additional source of moisture in a property would be running a calor gas heater. It's by product is water vapour.

WIAWSNB

Ventilate the room fully, keep the inside door shut, and leave off the heating.
That will work.
You won't have condie on your windows, and you won't have mould on your walls.
I stake my nonexistent repute on it.
If I'm wrong I will leave this forum.
And come back as someone else...