Abstract
Thermal zoning is a commonly adopted building energy efficiency initiative, since thermally segregating conditioned spaces is generally expected to minimise energy losses when conditioning unoccupied spaces. When comparing a partitioned building with widely differing heat gains between zones to an equivalent non-partitioned building, ‘zoning’ might not always beneficial. This paper analyses the fundamental thermal processes involved in these scenarios by firstly undertaking a number of steady state analyses, demonstrating that there are scenarios where the thermal energy required to maintain comfort conditions is less for an open-plan arrangement than for a more highly partitioned building. We then performed dynamical simulations of a simple building, confirming the steady state analyses and showing that, for space heating, connecting the spaces can significantly reduce the energy demand. It was concluded that whenever two zones are both conditioned to the same set-points, thermally connecting zones always leads to an energy demand lower or equal to thermally isolated zones. We then conducted simulations of an archetypal residential building with intermittent conditioning of spaces. The results showed that thermally connecting the spaces can be beneficial in climates from cool to warm temperate, with a decrease in energy demand from 2.2 to 9.9%, while this was not beneficial in a hot and humid climate, with an energy demand increase of 0.2 to 2.3% for the thermally connected scenario.
Highlights
Efforts to improve the thermal comfort of building occupants over many decades has led to increasing overall energy demand for heating, ventilation and air conditioning (HVAC) in the global building stock
These results confirm the expectations presented in the steady-state scenarios of Section 3.1, showing that in any scenario with high enough internal gains (Scenarios 2, 3 and 4) there is a reduction in the total energy demand, and this reduction is greater as the internal heat gains in Room 1 increase
While thermal zoning is perceived as an effective energy efficiency solution for buildings, the results presented in this study showed that thermally connecting spaces provides a more effective solution than zoning in some cases; in particular when the spaces ventilation mode and closed when it is mechanically heated or cooled) and the other one with the doors always fully opened
Summary
Efforts to improve the thermal comfort of building occupants over many decades has led to increasing overall energy demand for heating, ventilation and air conditioning (HVAC) in the global building stock. To mitigate this increased energy consumption, many energy efficiency initiatives have been developed and implemented over the years. According to Bembook [2], for example, a thermal zone should approximately correlate to the spatial subdivision, or partitioning of a building, and there are guidelines indicating that a BPS user should choose the number of zones so that they match the number of heating and cooling systems serving the building [2,3,4,5]. Bembook [2] and CIBSE AM11 [4] suggest that two adjacent spaces can be considered as one thermal zone in some circumstances, but they need to have similar heating and cooling set-points, internal gains, solar gains, spatial location and the same thermal behaviour without the heating or cooling system operating and similar requirements are specified in ASHRAE 90.1 [3]
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