Indoor air problems are unfortunately common even in new buildings. These problems may be a result of poor structural designs or misuse, but more commonly they occur due to mistakes during construction.
Structural engineers are familiar with the problematic designs. Consequently, with active review processes and utilisation of BIM (building information model) these can be handled. But what about the mistakes during construction?
New modular methods are reducing the problems with construction, as more and more construction phases are made inside protected from environmental elements. However, all buildings cannot be built modular and even with modules, some of the work needs to be done on site, for example final assembly. Transporting the modules and panels from the factory to the site is always a risk. Delays in the assembly are another significant risk since this means that the panels are stored temporary on site to wait for their assembly. Consequently, the panels may be exposed to harsh and difficult conditions for extended periods. Modules are typically protected at the factory with a plastic film. However, there is always a risk that the protective plastic film is damaged during the transportation or it is removed too early, as happened in the Wood City case (https://www.rakennuslehti.fi/2017/11/diplomityo-kertoo-miksi-wood-cityn-kosteudenhallinta-petti/).
Incompletely protected panels and panels and modules with damaged protection are at risk to get damp before assembly, which can later lead to Indoor air problems
How new technologies may help in moisture risk management
Utilising IoT-sensors and 3D BIM models makes measuring temperatures and relative humidity in real-time possible. Could the construction related problems be avoided or at least noticed early enough to make it possible to fix them without excessive dismantling of the building if sensors were used? Adding humidity and temperature sensors to modules and panels in the factory and monitoring values in real-time during construction would give a warning in case the structure became damp. This way a drying process could be started before actual microbe damages formed. Adding the sensor data into the 3D -BIM model via API (application programming interface) makes monitoring really easy and possible without visiting a site on daily basis.
In the case of concrete structures, it is crucial that the relative humidity of a concrete slab is low enough before progressing to the finalising phase. In addition to the humidity sensors, the addition of temperature sensors would be beneficial in monitoring the conditions and optimising the temperature and ventilation for the drying of concrete. With this method it might not be possible to replace the current measurements based on test pieces. But at least the sensor measurements would give a possibility to react to unwanted changes in drying conditions and to prevent wasting several weeks of drying time due to poor drying conditions. Consequently, optimal drying process, better quality, and less delays on construction would be achieved.
In 4APIs project demo we have integrated 3D -BIM model and IoT sensor data via APIs. Our case building was Ypsilon Community Centre / School in Yli-Maaria located in Turku, Finland. In this demo case, the sensors were installed onto a finished building and the sensors measured temperatures, relative humidity, and in and out air flow in real-time.
Interestingly, the demo case raised questions and some discussion about whether real-time is actually real-time. Like Teemu Mikkonen wrote in his blog “Real-time data with cloud platform” there were noticeable delays in data from sensor to actual services. However, in the case of moisture risk management during construction, the delay may be several minutes and it still does not cause problems, as the time scale, for example for concrete slab drying, is weeks. Even with delays the benefits are remarkable, since unsuitable changes in drying conditions or moisture in structures can be noticed almost in real-time. This gives possibility for constructors and supervising authorities to react to humidity related problems earlier.
In new buildings sensors may be added in the early phases of construction. In such cases some of the construction time sensors would also be utilisable later in use time monitoring. As a result, a complete measurement history of the building could be collected and utilised in indoor air quality investigations.