Work

Measured performance of cooling systems in nearly zero-energy office buildings during extreme summers and optimal cooling sizing

Year: 2025

Type: article

Abstract: This study used measured data from four NZE office buildings in Tallinn under sizing or in more severe climate conditions to find risk levels for cooling sizing to avoid oversizing. Studied building`s measured cooling peaks over full operation period were compared to the designed ones, simulated with a design day and standard use input data for occupancy, appliances, room temperature set-points and air handling units’ operation time. While recorded ambient dry-bulb temperature and enthalpy were significantly higher than the design day outdoor conditions, all buildings' measured cooling peaks were significantly lower than the designed loads and measured indoor temperatures did not exceed EN16798-1:2019 II category upper limit. Cooling systems were oversized, and the design cooling loads of the studied buildings varied more than measured loads, referring to different safety margins used in the designs. A calibrated case study simulation model was used to find optimal risk levels for supply air and space cooling design based on measured ambient climate, electricity use data and actual controls of HVAC systems. Outdoor enthalpy 92nd percentile revealed an optimum, reducing total cooling capacity to ~86% and zones cooling to 35% of the initial design loads. Thermal comfort long-term assessment under the strictest outdoor conditions showed that the design temperature was not exceeded for 95% of the occupied hours. In conclusion, this study demonstrated that considerably higher risk levels than commonly applied can be adopted in space and supply air cooling design while still relying on well-established methods.

Source: Energy and Buildings

DOI: 10.1016/j.enbuild.2025.116829

Authors: Jevgeni Lukaštšuk, Jarek Kurnitski, Martin Thalfeldt

Institutions: Tallinn University of Technology, Aalto University

Language: English

Topic: Building Energy and Comfort Optimization

Subfield: Building and Construction

Field: Engineering

Domain: Physical Sciences

SDGs: Affordable and clean energy, Climate action, Sustainable cities and communities

Open Access status: hybrid

Estimated APC paid: $4,260