Hygrotrac Project Case Study

Arboreal are nearing completion of construction works for the thermal upgrade of a Grade II listed townhouse in London which is designed to the AECB Silver Standard, though not yet certified.  In  May 2013 we installed 15 Hygrotrac sensors into the building with the aim of monitoring the hygrothermal performance of the walls after the application of internal wall insulation.  Four sensors measure ambient conditions on the inside, outside, cold loft space and chimney flue while the remaining eleven sensors have been built into the masonry structure of the building, mainly located at the junction of the inner face of the masonry and the newly applied insulation.  Each sensor is wireless and has a 10-15 year battery life.  The sensors transmit data to a gateway connected to the internet and information is stored on the GEC Hygrotrac website.  The system was straightforward to set up and install though much consideration was given to the location of each sensor and the detail of how they were installed into the walls.

The moisture probes of each Hygrotrac sensor have been mounted onto a block of timber (in this case Douglas Fir) which will equilibrate to the moisture content of the masonry. Each sensor will therefore provide valuable information about the likely moisture content of the various timber joists, sills and wall plates bedded into the masonry structure. The sensors will also record the temperature and relative humidity at each location – thus providing data on the hygrothermal gradients in each wall.

So far, the data collection (May to September 2013) has recorded the construction phase of the project.  When the sensors were installed into the masonry and covered with a layer of 15mm lime plaster the recorded data revealed high levels of WME (sometimes up to 30%) as expected but these have shown a consistent pattern of drying out over the last 5 months.  When the house is occupied by our client and the wetter winter months set in we will be able to monitor the hygrothermal performance of each sensor and hopefully make observations about the effectiveness of each insulation type (aerogel, woodfibre and calsitherm) with u-values ranging from 0.16 to 0.6 W/m2K.