This research is based on results of building envelope and energy performance of thirteen dwellings. The dwellings, located in Dunfermline, Scotland, were part of the Housing Innovation Showcase (HIS) developed by Kingdom Housing Association to explore the efficiency and benefits of ten methods of construction.
The study focused on five key areas: 1) The longitudinal correlation between the building envelope and space heating energy demand, 2) Methods of assessing building envelope decline over time, 3) Estimated time stamps at which dwellings fail to achieve targets, 4) Explore retrofit intervention methods and 5) understand the impact climate change has on dwelling performance over time.
The research undergoes in-situ U-value and air permeability testing to measure the decline of the building envelope and how it affects energy demand over time. The use of steady-state calculation methods in combination with dynamic thermal modelling enabled a longitudinal approach of dwelling performance. The models estimated energy demand using a factor of dilapidation by calculating heat loss coefficient values as dwelling performance factors (DPF). Probabilistic climate change weather files were incorporated into calibrated models to simulate the effects of weather shifts on energy and CO2 emissions. This led to a longitudinal trajectory analysis to estimate the effects of climate change and DPF scenarios linked to specific time stamps and tipping points above design standards and targets.
The results and analysis show that a conventional dwelling type (SD.6.17) reached its first tipping point by 2032 (100% DPF) followed by 2035 and 2042 considering medium (50%) and low (10%) DPF’s. A Passivhaus built dwelling (SD.6.18) first reaches a tipping point in 2028 (100% DPF), followed by 2031 and 2037 with a medium and low DPF respectively. Dwelling T.7.19 reached tipping points as late as 2065, by using electricity as its main heating fuel; expected to be decarbonised during the 2050’s. This analysis concluded that airtightness dilapidation deteriorated faster than U-value and that the interventions to remediate airtightness could be easier applied. Also, the sensitivity of the DPF’s on dwelling environmental performance is critical; maintenance of dwellings and material deterioration can determine the intensity of dilapidation.