SMT Sensors aid in Forensic Investigation in New Zealand
SMT's sensors and systems were a key component in a forensic investigation in New Zealand, to look into a systematic cladding failure that allowed water to ingress within the building envelope, which damaged schools across the country. The building science specialists that conducted the research and expert testimony published a case study on their findings, (Hubbs, B., Finch, G. "Forensic Engineering Practice Lessons - A Case Study of Cladding Failures in New Zealand" 2022)
The investigation was conducted in response to schools across New Zealand leaking extensively, causing mass amounts of building enclosure damage, remediation construction and disruption to classes. The study took place over 7 years, and from this study, they "investigated and documented the performance of the cladding; set up and performed hygrothermal monitoring and façade testing of four schools and a test hut; performed laboratory testing of hygrothermal material properties; developed a mould sensitivity index for the cladding; used calibrated hygrothermal models to extrapolate the findings; analyzed all of the field, lab, and simulated data; and synthesized all the data into expert reports and rebuttals" (Hubbs, 2022 pg. 2)
While conducting an investigation it's important to identify all mechanism failures and what their contributions are to the overall problem. Investigating a building failure is no easy task, it often involves many years of experience building and restoring façades matched with testing and conducting research to determine the cause of the problem. This also isn't an easy task either, as there are a lot of variables to consider while testing.
In order to gather the data necessary to investigate the cause of these leaks, Hubbs and Finch work with Jason Teetaert (SMT's cofounder and president) to install and compile data using SMT's product suite.
The in-situ school and test hut monitoring program was developed and the following SMT sensors were installed; Relative Humidity and Temperature sensor
Moisture Content Sensors - Brass Nail Sensors
Embedded Moisture sensor (custom for siding studies)
Point Moisture monitoring sensor
Condensation moisture sensor
Moisture detection tape
Solar Radiation Sensors
Exterior wall Driving Rain Gauges
External weather stations
After monitoring the data from all of the sensors in the constructed occupied schools, sensors were installed in a purpose built test hut using ideal construction details with internal occupant controls. From there, data was logged wirelessly and was viewed and studied remotely by the building science specialists. After testing, modeling and lab studies the experts were able to determine the causes of the damage, which were;
Driving rain exposure is the biggest influence of moisture performance and mould/decay risk
The plywood cladding on schools in wetter coastal and colder climatic regions of NZ are more likely to experience wetting and mould growth than those in sheltered walls and those in drier communities.
Walls facing north (facing the sun in the southern hemisphere) tend to be drier than those facing south, especially as the wind-driven rain is from the south
Paint properties, including water repellency, colour, and solar absorptivity, strongly influence moisture uptake, wetting, and drying.
Cladding installed over a drained and ventilated cavity (i.e., rainscreen) significantly reduces the risk of mould growth and decay to the cladding and backup wall. (Hubbs, B., Finch, G. 2022, pg 12)
From their findings, a court ordered that the New Zealand Ministry of Education system to receive compensation to remodel and repair the damaged schools. As part of this court order - the research methods, data and related information are to be dissimulated to enable others to use this body of knowledge.
SMT's products were essential in these findings, and we were more than willing to aid in the investigation. SMT has been involved in many forensic investigations outside of this one, if you're investigating moisture ingress in your building envelope, consider reaching out to our team to see how our sensors can help.
A link to the paper can be found here
Photos of our sensors as used by Hubbs, Finch, and Teetaert.