Datalogger set-up

These instructions are for the ORIA Wireless Thermometer Hygrometer currently costing £17.49 for two on Amazon (we recommending using two or more dataloggers to differentiate types of damp and to track down the source).

  1. Place one on or near the main damp patch, ideally on the coldest part of the wall.
  2. Place another in the nearest source of vapour often a kitchen or bathroom, ideally on an internal wall out of the way, such as above a door frame.
  • ORIA also sell dataloggers with displays (they are larger and slightly heavier, so harder to place by damp patches or under floors) £13 Brifit Wireless Thermometer Hygrometer, Bluetooth 5.0 with data display and 35M blue tooth range.
  • Smart Hygrometers, with 50M blue tooth range are useful for measuring sub-floor humidity, that is under timber flooring.
  • Landlords should consider using at least one Govee WIFI connected hygrometer. These costs about £42 through Amazon, the benefit is remote monitoring through WIFI (make sure you have WIFI). So the tenant can see the humidity and temperature and the landlord can monitor ambient conditions, and agree changes accordingly, for example proving improved ventilation or requesting the tenant increases nighttime temperature. After all it takes teamwork between tenant and landlord to maintain a property.

Dataloggers for identifying the root cause of damp

Dataloggers are instruments that monitor and log data collected from the environment, such inside a building. They can form part of Internet of Everything (IoE). The datalogger that interests us here is the hygrometer datalogger. It collects relative humidity and temperature, typically logging every 10 minutes.

For the past 5 years we’ve been using ever more data to pursue the root cause of damp. Data-loggers are an important part of that mix.

We ask clients to install one or more dataloggers for some time before the onsite damp survey begins. This helps understand when and where water vapour is being produced, ventilated, heated, insulated and therefore which areas are suffering from low temperature, condensation and mould. They help differentiate rainwater and mains water leaks from ambient vapour.

Setting up your datalogger the first time.

This applies to the Smart Hygrometer (which costs about £16 for two, is light weight, low profile (easy to stick near damp wall) and has a 100 day battery life). However, most dataloggers are designed with similar set-up and functionality.

If you find any of the above stages difficult, please at least pull out the small piece of plastic to initiate the loggers, and place them as below, we can complete the process during the survey.

  1. Place one on or near the main damp patch, ideally on the coldest part of the wall.
  2. Place another in the nearest source of vapour often a kitchen or bathroom, ideally on an internal wall out of the way, such as above a door frame.

Dew point formula

During and after the survey we will help with the next part, processing and understanding the data.

Alternatively download data to an excel or other spreadsheet, to find the Dew point the formula is

Dew point is a proxy for vapour pressure, i.e. amount of vapour in the air (note atmospheric pressure affects the dew point for the same vapour pressure, but if the devices are at the same atmospheric pressure, then vapour pressure correlates directly with dew points). Therefore you can compare the dew point of one device to another to work out where vapour is being produced and when it is being removed.

Screenshot from an excel spread sheet. Note you may have to remove the % and ° symbols. Also, occasionally the datalogger exports % as 0 – 1, in which case remove the two instances of “/100” from the formula. Note you can find the mould point by using “/85” instead of “/100” see, with daily forecasts.

Ex. 1 condensation

See spreadsheet

Sheet shot of complex datalogger graph

In this interesting example, four dataloggers were used in a mouldy top floor modern flat. I attached the eXcel file, with formula for you to copy. I don’t normally make the changes myself for insurance reasons, but in this case I foolishly provided the details of a general builder, who made a mess of the vents and was unwilling or unable to make the necessary improvements.

The issue was the ducting from two extractor fans were combined before exiting the building (as a top floor flat is was difficult to drill out an additional hole). Unfortunately back-flow drafts were not included in the original set-up, so the kitchen was venting into the bathroom and vice versa. On 5th January I installed two back-flow shutters and improved distribution of the loft insulation. 

From the graph, looking at the blue bathroom lines you can see a drop in %RH from nearby 100%RH to an average below 80%RH. The bedroom has similarly dropped. It’s looking considerably better. I have asked for replacement of the thermostat, that I found was unreliable, so as to reduce the temperature fluctuations. Otherwise the issues will disappear over time.

Top floor flat suffering from mould and condensation.

The problem was the extractor fan from the kitchen was venting out into the bathroom and vice-versa.

The data-loggers helped identify the problem, and provide a good comparable of before and after intervention.

The cost of solving the problem was very low, maybe £10 plus 1 hours work, it saved about £1,200 (plus annual maintenance) from an unnecessary PIV (Positive Input Ventilation). PIV are untargeted, expensive to install and run and often suffer from short-circuiting.

Ex. 2 mould

In this second mouldy property the client solved most of the mould problem with a dehumidifier before we surveyed the property – note the improvement from late November. We further improved the property with no need for additional equipment.

This image has an empty alt attribute; its file name is datalogger-dehumdifier.jpg
This mouldy property was solved in part by installing a dehumidifier, in late November

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