This is one of the winning articles in the Ingenious Writers Contest organized by SARA and Substance ÉTS. It summaries an article co-written by Claudiane Ouellet-Plamondon, Professor in the Department of Construction at the École de technologie supérieure (ÉTS), entitled: The Impact of Future Scenarios on Building Refurbishment Strategies towards Plus Energy Buildings.
Homes, lighting, air conditioning and heating account for more than 40 % of Europe’s energy consumption. Studies show that the human race is achieving record greenhouse gas emissions and that climate change affects both humans and natural ecosystems. Forecasting models predict that inaction on our over-consumption of energy will have dramatic and irreversible consequences for all of our planet’s inhabitants.
The goal of the International Energy Agency is an 80% reduction of emissions by 2050. Since 2010, the European Commission has been encouraging European Union member states to take measures to promote the transformation of existing buildings, to increase their energy efficiency and to encourage the construction of positive energy buildings.
Non-renovated buildings built between 1950 and 1980 are prime targets for renovators. Indeed, their deplorable wall and roof insulation results in huge spending on heating, and they are particularly vulnerable to stress caused by increasingly violent weather.
The goal of the renovation campaign is to reduce heating and cooling demand for these buildings, to install low-energy or energy-efficient equipment and technologies based on renewable energy sources, and to raise public awareness of good practices.
The challenge is this: will the renovations undertaken today be appropriate for future climate and potential changes in our consumption or energy supply?
The objective of this study is to assess different renovation strategies in consideration of climate forecasts and possible energy combinations. The winning strategy will be the one with the least environmental impact. An analysis of the model’s sensitivity will be undertaken to confirm the robustness of the scenarios with respect to contingencies.
The study is based on the renovation of Austrian buildings built during the 1960s. The proposed renovation strategies are:
- The first model (I) is the control: the building is renovated just enough to ensure the safety and well-being of the inhabitants.
- The second scenario (II) follows the standards of the Austrian Institute of Construction: in order to improve thermal efficiency with regard to insulation and energy efficiency, the building is covered with a thermal envelope and the individual heating system is replaced by a central gas and district heating supply.
- In the third case study (III), the building is transformed into an energy-producing building through the addition of thermal collectors and photovoltaic panels on the roof and façades. High quality insulation of prefabricated materials is added.
Building renovated according to strategy III: on the left, high- quality façade; to the right, facing before renovation.
The increase in temperature caused by climate change primarily affects the demand for heating and air conditioning. The report of the Austrian Panel on Climate Change (APCC) forecasts a 20% decrease in heating demand by 2050 and 30% by 2070—at the end of the building’s life— as compared to the 2010 demand, if we follow the logic of linear decrease. The effects on household demand for hot water and electricity will then be considered negligible. As a result, the influence of climate change on heating demand will focus research efforts.
The different scenarios are modeled in accordance with European Standard 15978. Only equipment replaced or added to the building, transportation, and operating energy are incorporated into the models. Only the renovation phase is taken into account, so the initial structure, the preparatory work and the recycling are not included in the calculations.
The life-cycle analysis used here is the systemic methodology for assessing the environmental impacts of the product during its lifetime. Its objectives are to compare the various renovation scenarios over a period of 60 years, equivalent to the lifetime of the building, and to assess the conversion’s sensitivity to climate change.
When fossil fuel-based intake is replaced exclusively by a gas supply, the results obtained for the three environmental indicators studied separately are:
- A halving of the demand for non-renewable energy;
- A 76% improvement in the global warming potential, in other words, a risk reduction of greenhouse gas impacts;
- A 71% improvement in ecological saturation, corresponding to the environmental impact assessment of polluting emissions.
The first phase in a green renovation will always be to change the energy supply source of heating. Shifting from gas heating to central heating improves energy performance and is considered the best environmental solution.
The investment payback corresponding to the grey energy ratio (energy spent during the renovation) on the cumulative operating energy throughout the life cycle of the building allows the scenarios to be classified. Considering only the reduction in non-renewable energy consumption, both models (II) and (III) are profitable after only three years and lead to a reduction in the inhabitants’ consumption by more than two thirds.
The third scenario is the most expensive in grey energy, but its operating energy consumption is much lower than the other models. It is the most interesting solution in the long term. Indeed, the installation of photovoltaic panels doubles the amount of grey energy and the production of prefabricated materials is more polluting. A combination of photovoltaic panels and solar collectors proves to be the most economical choice for operating energy. Moreover, this association is the most robust because of its capacity to adapt to future climatic conditions, according to the multi-criteria analysis reflecting the sensitivity of the models.
In future discussions, the authors propose the inclusion of a dynamic life-cycle analysis considering potential emissions and climate change as well as an in-depth assessment of the energy factors and distribution of energy provided by and for the building.
Life-cycle analysis reflects the potential impact of different stages of building life as closely as possible and helps in the choice of design type and building materials.
According to the results obtained, the optimal renovation consists of covering the building with a thermal envelope of prefabricated materials, and installing solar collectors and photovoltaic panels. The selected environmental indicators guarantee the lowest environmental impact over a period of 60 years thanks to this type of renovation. A shift in energy supply to collective heating is beneficial and should be implemented as quickly as possible in our cities as a first step in this renewal.
A large number of buildings require rehabilitation. The use of prefabricated panels greatly reduces construction time, which supports high quality renovation. Moreover, they adapt to all climates, so the model is exportable worldwide. The building must be efficient from an environmental, a social, an economic and a technical standpoint. The replacement of these façade elements is designed so as not to cause inconvenience to the inhabitants during the construction period. The key argument in favour of high-quality rehabilitation is that it leads to improved comfort.
The next logical step is the construction of buildings that produce more energy than they consume in the course of a year.
For more information on this research, see the following reference article: Passer, A., Ouellet-Plamondon, C., Kenneally, P., John, V. and Habert, G. (2016). « The Impact of Future Scenarios on Building Refurbishment Strategies towards Plus Energy Buildings ». Energy and Buildings, Volume 124, pages 153-163.
The authors wish to thank all partners and Dr. Karl Höfler from AEE INTEC for his excellent collaboration as the lead project manager of the research project e803ˆ-Buildings, which serves as the basis for the case study described in this paper. This project was funded by the Federal State of Styria and the “Building of Tomorrow” program of the Austrian Federal Ministry of Trans- port Innovation and Technology (BMVIT) via the Austrian Research Promotion Agency (FFG).
Marion Ghibaudo, a student from France, came to Montreal in August 2016 to earn a double degree, in partnership with the French École Nationale Supérieure des Arts et Métiers and ÉTS. She is a graduate student in Construction Engineering.
Program : Construction Engineering