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The impact of different retrofit technologies on energy consumption, CO2 emissions and indoor climate were analyzed through building level simulations in SUREFIT project. The simulations were implemented in a dynamic simulation tool IDA ICE with an hourly timescale to obtain hourly energy demand and indoor climate profiles. The properties of demo building models were defined based on input data sheet from building owners or online database TABULA WebTool. The demo building models were simulated under the intermittent or continuous heating schedule, and then used as the reference cases for retrofit technology simulations.

The simulated retrofit technologies were divided into different retrofit packages including passive package, including bio-aerogel insulation, PV vacuum window, and phase change material; ventilation package, including insulating breath membrane and room specific air handling unit with heat recovery (RAHU); generation package, including Photovoltaic/Thermal (PV/T) system and solar assisted heat pump (SAHP). As shown in Figure 1, they were integrated into the reference case models with intermittent or continuous heating and simulated separately by following the rule of starting from a single technology to all technologies in each package. Finally, the final combinations, which contain all the technologies in passive and ventilation package and either of the technologies included in generation package, were simulated to present maximum energy saving and emission reduction potential in different demo buildings.

The simulation results show that different SUREFIT retrofit technologies have varying degrees of impact on building energy consumption, CO2 emissions and indoor climate in the demo buildings. Among technologies in passive packages, renovating the external walls and roof with bio-aerogel insulation conserved the largest energy-saving potential, reducing the purchased energy by up to 63%, while PV vacuum windows or PCM only has a slighter impact on energy consumption (up to 10% reduction). In ventilation package, installing breath membrane over the building envelopes resulted in a similar energy consumption reduction (up to 59%) to that brought by bio-aerogel insulation and a negative impact on indoor air quality due to the improved airtightness. Thus, installing RAHU guaranteed the indoor CO2 concentration under 1200 ppm almost year-round after renovating with breath membrane, but increased the space heat demand slightly. Regarding the generation measures, PV/T system and SAHP all conserved a good energy-saving potential under Southern European climate conditions. As for the maximum energy-saving and emission reduction potential, all final combination scenarios could reduce building energy consumption and CO2 emissions by over 60% when the demo buildings were continuously heated.

The impact of the same technology was significantly affected by heating schedules. The energy conservation potential of thermal insulating technologies (e.g., bio-aerogel insulation, breath membrane etc.) under intermittent heating schedule was much lower than that under continuous heating schedule. The indoor temperature was kept at a similar level before and after thermal insulation improvement in the continuously heated building, while thermal insulation improvement led to a significant indoor temperature increase when the building turned into intermittently heating.

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Figure 1. Simulation of retrofit packages in IDA ICE.

Author: AALTO University