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An Evaluation of Fabric Insulation and Exposed Thermal Mass to Maximise Adaptive Thermal Comfort

Lookup NU author(s): Dr Mohammad Royapoor, Professor Tony Roskilly



This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0).


In Northern European climates, passive decarbonisation of building design has predominantly been concerned with limiting fabric U-values. Within a well-insulated fabric however the contribution of internal thermal mass and the dynamics of fabric to air heat exchange become more instrumental in achieving thermal equilibrium. Where high internal gains can also lead to overheating, energy intensive cooling retrofits can become necessary in well-insulated buildings originally designed for natural ventilation. Therefore adequate fabric insulation and internal mass are critical and if more flexible climate controls such as adaptive comfort bands are used, it is be possible to maintain thermal comfort with minimal heating and cooling duties. This work offers a set of indices on the level of insulation and internal mass that can counteract high internal gains (average and maximum aggregated gains of 29.6 W/m2 and 46.4 W/m2) in a well-insulated 5-storey office (designed to 2006 UK part L guides) under a mixed mode ventilation regime. Actual summer time surface temperatures collected of the exposed internal concrete in the case study office are on average 3.1°C cooler than concurrent indoor air and are more closely coupled to the running mean of weekly external air temperatures than external daily peaks, allowing the internal exposed concrete to act as a heat sink. Using a calibrated building energy model, the existing static zone target temperatures are replaced with EN 15251 adaptive comfort categories II and III and night purge ventilation to assess the actual building’s performance as well as a Passivhaus version under current and future UK Climate Impact Programme (UKCP09) weather data scenarios. Examined in ‘freefloat’ mode, the actual office building (with overall fabric thermal resistance of 0.61 W/m2/K and an internal thermal capacity of 167 kJ/k/m2) achieves adaptive thermal comfort 32% to 52% of occupied hours, whereas a Passivhaus fabric (with overall fabric thermal resistance of 0.27 W/m2/K and internal thermal capacity of 167 kJ/k/m2) achieves adaptive comfort 100% of occupied hours across all weather files, with no overheating in either fabric types. Against a static 22°C heating setpoint, adaptive comfort bands II and III can offer heating load reductions of 31% to 69% over current and future weather files.

Publication metadata

Author(s): Royapoor M, Roskilly T

Publication type: Conference Proceedings (inc. Abstract)

Publication status: Published

Conference Name: 4th Sustainable Thermal Energy Management International Conference (SusTEM2017)

Year of Conference: 2017

Pages: 381-389

Print publication date: 28/06/2017

Acceptance date: 27/03/2017

Date deposited: 23/08/2017