Building heat transfer in a changing climate

Abstract

Anthropogenic climate change due to greenhouse gas emissions caused global surface temperature in 2011-2020 to be 1.1 °C above pre-industrial levels. By 2100, this increase is predicted to be between 1.4 °C and 4.4 °C under low (SSP1-1.9) and high (SSP5-85) emission scenarios respectively. In response to this and the need to reduce energy usage and fuel poverty levels, buildings are being retrofitted for energy efficiency. UK retrofit guidance considers building thermal performance in the context of steady-state heat transfer through the building envelope. This simplification describes heat flow when external and internal environmental temperatures are constant in time, which greatly reduces computational complexity. However, the steady-state approach neglects the thermal inertia of the building envelope, i.e., its ability to store and delay transmission of thermal energy. This can result in significantly inaccurate calculations of indoor temperatures and the energy required for space conditioning. It is currently unknown how climate change affects the problematicality of using steady-state analysis for walls of different thermal properties. This research investigates this problem through a novel analysis of the dynamic nature of the interaction between a building and its environment. Air temperatures obtained from historical data and SSP5-85 projections are used to calculate sol-air temperatures at 100 km² resolution for 1951-1980, 2011-2040 and 2071-2100. The deviation from steady-state heat transfer is characterised through analysis of the temperature field inside the building wall when excited by the air and sol-air temperatures. The dynamic nature of the heat transfer is examined for different building envelopes and environments across the three time periods. This information indicates when, or if, it is problematic to use steady-state thermal analysis in retrofit decision-making for buildings of a given location, orientation and envelope construction.