Passive House is a voluntary standard for energy efficiency in buildings. Buildings designed in accordance with Passive House standards typically have an ultra-low rate of energy usage, making them more environmentally-friendly than buildings that rely on active heating and cooling. For a new, domestic ‘Passive House’ in County Mayo, West of Ireland, temperature and relative humidity monitoring with a Tinytag data logger was crucial to understanding how the building performed in real, lived-in conditions.

Construction on a new low-energy build in County Mayo, West of Ireland, was completed in October 2019. Straight-away, Mark Stephens, partner of Mark Stephens Architects, set out to assess the performance of the building with a Post-Occupancy Evaluation.

Post-Occupancy Evaluation (POE) is important for understanding how a building performs while it is in use. It helps architects, designers and builders to understand, in practice, how a building's design impacts on running costs and, crucially, how it impacts on the comfort of those who use the building.

In the case of the County Mayo house, the Post-Occupancy Evaluation was also important for assessing whether the Passive House (or Passivhaus) temperature and over-heating calculations met the actual data 'in-use'.

A key component of the Post Occupancy Evaluation came in the form of a Tinytag Ultra 2 TGU-4500 temperature and relative humidity data logger. Temperature and humidity levels are integral to indoor occupant comfort; measuring these parameters was vital for understanding the 'real' performance of the building.

The data logger was placed next to one of the main rooms, and measured continuously for the year-long period of evaluation from October 2019 to October 2020.

At the end of the monitoring period, the data logger was removed, and the data was downloaded and analysed. At the same time, the occupants were given a questionnaire to assess their perception of the building's performance.

The data from the data logger revealed a number of things:

1. The average indoor temperature for the year was 20.5°C, which matches Passive House requirements.
2. The minimum and maximum humidity levels registered were 28.25% and 69.20% (both slightly outside the recommended level of between 35% and 55%) but the average humidity was a comfortable 47.40%.
3. For most of the year, the building remained within 'comfortable' temperature and humidity levels.

The occupants reported in the survey that the house overheated during the summer, but the data revealed that this only occurred for a smaller percentage of the time.

The data was also cross-referenced with data from a local weather station to aid understanding of how the building responded to outdoor temperature fluctuations.

The data logger has been crucial for understanding how the building works in practice - in real, lived-in conditions, and not just in theory or calculations. "The data that we have achieved with the Tinytag has been excellent," says Mark Stephens. "We are able to see if the performance of the Passive House we designed matched the calculations and whether the relative humidity of the house throughout the year was comfortable. In both cases we are pleased to report success!"

In future projects, Mark comments that he would like to use more data loggers to cover more rooms in a building. This would help to construct a more accurate and detailed picture of conditions across the whole build. He would also utilise an outdoor data logger to more precisely understand the relationship between indoor and outdoor temperatures.

Tinytag data loggers are ideal for indoor monitoring in domestic properties. Unwired and compact design makes Tinytags an easy-to-install and discreet option for monitoring in occupied spaces. Long battery life and large internal memory enables extended monitoring periods without interruption or inconvenience to building occupants.

For more information on the innovative work of Mark Stephens Architects on the County Mayo build, and on the results from the Post-Occupancy Evaluation, check out their blog post.

With thanks to Mark Stephens Architects www.markstephensarchitects.com, Architects & Passive House Consultants.

Images courtesy of Mark Stephens Architects.