Strategy and Practice of Adaptive Thermal Comfort in Low Energy Buildings

Overview

Reducing energy use and providing comfortable indoor environments for occupants are both key objectives of the building sector globally. However, establishing the appropriate balance between these often competing issues is challenging. Is it possible to achieve thermal comfort in buildings without increasing energy use? To answer this, this project focused on:

• creating a scientifically based explanation of the underlying mechanism of adaptive thermal comfort for people in buildings, and
• the application and evaluation of the thermal adaptation concept to reduce building energy consumption through design and control strategies.

The concept of adaptive thermal comfort is not new, but prior to this project there were existing problems to be solved in this field of research:

1. Although the adaptive effect has been recognized by many researchers, the mechanism of the adaptive process is still unclear. How do the physiological, psychological, and behavioural factors work alongside conventional thermal heat balance explanations taking account of clothing, airspeed, and metabolic rate. This cannot be readily explained by the current adaptive model, which is partially due to the inherent limitations of the last generation of thermal comfort field study database.
2. The specific thermal adaptive mechanisms of people in diverse climate regions can differ considerably, which may suggest different building design and operational strategies, and indoor environment standards. At this point, understanding of occupants’ adaptive thermal demands in different climate regions remains limited.
3. While purely free-running buildings and purely mechanically ventilated heated / cooled buildings are common, mixed-mode buildings (cooling / heating together with natural ventilation) are actually the most typical. However, at present there are no specific evaluation criteria for the latter kinds of buildings. Only mechanical cooling / heating standards are used for mixed-mode buildings at the moment, which may represent an unnecessarily conservative barrier to their more widespread adoption. Many clients are unaware of the potential energy savings available from adaptive modes in mixed-mode buildings with indoor thermal conditions departing from conventional HVAC comfort ranges in current standards.

The deliverables from this project are:

• a database with a user interface including information about human thermal reactions, together with occupant behaviour and building energy consumption,
• a model and criteria for the application of adaptive thermal comfort in buildings,
• guidelines for low energy building design based on the adaptive thermal comfort concept, and
• guidelines for personal thermal comfort systems in low energy buildings.

The project beneficiaries are:

• the building research community and associated specialists,
• policy and decision makers involved in developing standards and building performance evaluation,
• architects and design companies, engineering and consulting offices in building physics, HVAC systems, and energy consumption,
• developers and manufacturers for HVAC devices with an interest in high performance as well as energy conservation, and
• educational institutions.