How to measure the moisture in your home

We have lots of requests for the right kind of equipment to measure the moisture content of your house.

Don't forget that moisture is constantly changing, so any measurement is always going to be at a point in time. Constant monitoring is the best way to do it, and will show trends, rather than alarming you with a single reading out of the blue. The cause of moisture is usually human occupation - so monitor kitchens, bathrooms and any sources of moisture that at first you wouldnt recognise - like fridges and freezers (auto-defrost), pets (dogs produce a lot of moisture through panting) and cellars (usually not well ventilated)

These days there is some really good equipment available very cheaply - home automation has come of age. The best gadgets that we have found are these humidity sensors, which are linked to a hub - this links to your home wi fi, and you are then able to monitor not just at home, but on the move. I've added some photos of the graphical output from my iphone - this shows Temperature, Relative Humidity, and most importantly the Absolute and Dew Point. 

Using the monitors:

Ideally you set one up outside, so you can tell if the atmosphere externally is dry or wetter than internally. This helps make decisions about things like opening windows. There's no point in opening a window if the air outside is too wet! You'll just make the house wetter.  This is often the case in summer, less so in winter.  This moisture risk is always higher in hot, thundery weather. It doesnt really matter in summer if the air in the house is a bit wetter, so long as the building fabric is nice and warm. This is where knowing the dew point comes in:

The dew point is the temperature at which you start to get condensation, which leads to damp problems. Generally, houses are warm and above dew point in summer, but towards the end of the year, september / October, walls start to cool down, and thus 'condensation season' starts. The table below helps you understand dew point risk.

This also applies to cellars - as they are always colder, the floors and walls of cellars can be well below dew point in summer - so warm damp air entering the cellar immediately condenses and makes the cellar wet. 

Make sure you monitor kitchen and bathrooms - the little gadgets are cheap and if you buy three or four, you can spread them around the house so see where most of the moisture in your home is coming from, and when!

Although the monitors dont show any read-out, the hub does, so you can always see the temperature and RH as a live readout.

This information is vital to monitoring conditions that give rise to mould.