Balancing Trade-offs between Deep Energy Retrofits and Heritage Conservation: A Methodology and Case Study

ABSTRACT

Drastic reductions in energy consumption within existing buildings are required to achieve climate change mitigation targets. However, a portion of existing buildings have important historic values that need to be conserved. The goal of this paper is to present a methodology and decision-framework for deep energy retrofit analyses that balances trade-offs between conservation and sustainability. This methodology includes historic recording, documentation, a detailed energy model, and calibration to monthly data. An historic house in Ottawa, Canada is studied to demonstrate the use of the methodology. The energy retrofit analysis suggests 67% energy savings are achievable by increasing envelope thermal resistance to 4.1 m²-K/W, reducing air infiltration by 70% to 4.2 ACH at 50 Pa through air sealing and an air-vapour barrier, rehabilitating windows to be triple-pane low-E assemblies, using an air-source heat pump to supplement the existing gas boiler, daylight sensors and controls, and solar PV panels.

KEYWORDS:

• Building envelope
• building simulation
• calibration
• cultural heritage
• decision analysis
• deep energy retrofits
• historic building
• rehabilitation
• residential buildings
• sustainability

Acknowledgments

This work was funded through the NSERC CREATE Heritage program at Carleton University (NSERC grant number: 465459-2015). The author would also like to acknowledge that the owner of the studied house was very accommodating of the research conducted.

Disclosure statement

The authors declare no conflicts of interest.

Notes

¹ An historic building in this paper defines a building that is 40 years or older and has retained most of its original building fabric.

² Note: The power generated by the existing PVs on site is not included in the baseline EUI of the house since PV calculations are done outside of the detailed energy model to be calibrated. There is no air conditioning or mechanical ventilation in this house.

³ See (Meng and Mourshed 2017) for details on heating degree day analyses.

⁴ Deep energy retrofits are defined as “a major building renovation project in which site energy use intensity (including plug loads) has been reduced by at least 50% from the pre-renovation baseline with a corresponding improvement in indoor environmental quality and comfort” (IEA Annex 61 Business and Technical Concepts for Deep Energy Retrofits of Public Buildings 2017).

⁵ The carbon intensity depends on region; in Ontario, Canada, the annual marginal emission factor of electricity is about 0.134 kgCO₂/kWh (Sotes 2019) and 0.525 kgCO₂/kWh for natural gas (Intrinsik Corp., 2016).

Additional information

Funding

This work was supported by the NSERC CREATE Heritage [465459-2015].