Advice on humidity/ moisture content of new build house please?

[Barrattnewbuild]

Been in a new build house for almost 3 months. It was built during a wet winter. I understand it could take at least a year for the house to dry out.

Our bathroom (upstairs) has no window. We have been doing everything possible to keep the moisture content of the house low - wiping up excess water, drying clothes outside etc. We keep a humidity gauge in the bathroom to monitor it. It usually reads 80-90% immediately after a shower in the bathroom then gradually decreases to around 40-45% with the extractor fan on.

All of a sudden the other day, the bathroom fan has started automatically turning itself on randomly even at times we haven't had a shower, and staying on. The humidity is not dropping below 60% no matter what. Haven't even had a shower today because I'm concerned about the moisture, and the extractor fan is still on so senses it is too humid.

This has prompted me to move the humidity gauge around the house to compare it. It is around 60-65% everywhere in the house now.

I've just placed it on the floor at the front of the house in the lounge (south facing), as this is where I have always been concerned about possibility of damp occurring. It's reading over 70% today on a sunny, dry day on the floor in that area, but 60% everywhere else.

Should I be concerned or is this part of the normal drying out process? Even if it is normal for a new build house to be have higher levels, don't understand how it has suddenly risen.

 

[Notch7]

What sort of construction?

Brick and block walls, timber frame....

Plasterwork - is it plasterboard dot n dab or two coat plaster

Relative humidity is usually around 40% - 60% in a house, higher in summer because windows are open.

 

[jacko555]

What's the ambient humidity? I mean outside the house. It's 60% where I am outside, and probably inside as all the windows are open!

 

[Barrattnewbuild]

What sort of construction?

Brick and block walls, timber frame....

Plasterwork - is it plasterboard dot n dab or two coat plaster

Relative humidity is usually around 40% - 60% in a house, higher in summer because windows are open.

It's timber frame. Sorry I don't know what type of plasterwork it is.

 

[Barrattnewbuild]

What's the ambient humidity? I mean outside the house. It's 60% where I am outside, and probably inside as all the windows are open!

It's reading 51% when I put it outside.

 

[Scarlet Pimpernel]

If it's warm outside, that means that the air outside can and will support more humidity/moisture than usual.
If that air then travels inside, taking the moisture with it, and the air when inside, cools down, the relative humidity inside will rise.
The readings that you are taking are Relative Humidity (RH) readings.
As the temperature goes down, the RH goes up if the air contains the same amount of moisture.

So don't consider it as ambient humidity, it's ambient relative humidity. Relative to the amount of moisture the air can support at that temperature.
If you think about condensation on a glass of cold beer, that moisture has 'materialised' out of the air, as the air has cooled down when the air comes into contact with the cold glass.