February 4, 2019
Abstract
In an effort to achieve 2030 targets set by the Paris agreement, Canada is in desperate need to reduce its greenhouse gas (GHG) emissions. Residential housing accounts for 17% of Canada’s energy requirements and 16% of GHG emissions. Therefore, many are looking into greener alternatives to housing but with new constructions accounting as little as 2% of the housing stocks annually, something needs to be done with the existing houses. This paper proposes prefabricated deep energy exterior retrofits to achieve Net-Zero Energy (NZE) levels as a solution to the problem. The feasibility of a program similar to Energiesprong in Europe is analysed for the south eastern climates of Canada. A case study of a community housing retrofit in Ottawa was chosen as an example. The feasibility analysis was divided into three parts: construction feasibility, financial feasibility and political and social feasibility. It was found that, these retrofits can be built but a price point that cannot be justified in the short term on a simple payback analysis. The potential for the viability of this retrofit program lies in the hands of governments and financial institutions who have the power to make it feasible. A change of mindset of the general public regarding the future of the environment should be the first step to be achieved. This program has proven to work in Europe and provided that Canada enters with a good plan of action, it will be successful.
Acknowledgments
I would like to extend my appreciation to Professor Micheal Jemtrud of the School of Architecture for his guidance and support throughout the preparation of this technical paper. His knowledge on the field of Net-Zero Houses greatly helped my research and he was always very responsive to any of my questions.
Table of Contents
Abstract ii
Acknowledgments iii
Table of Contents iv
List of Figures v
List of Tables vi
1.0 Introduction 1
1.1 Current problem 1
1.2 Retrofit Methods 2
1.3 Energiesprong 2
1.4 PEER 3
1.5 Objectives 4
2.0 Case Study 5
2.1 Base Case 5
2.2 Upgrades 7
3.0 Results 10
4.0 Feasibility Analysis 12
4.1 Construction Feasibility 12
4.2 Financial Feasibility 14
4.3 Political and Social Feasibility 15
5.0 Discussion 16
6.0 Conclusion 19
References 20
Appendix A 22
Statement of Authorship 23
List of Figures
Figure 1 Current and Projected Housing Stock by Vintage (Source: Armstrong, 2018) 1
Figure 2 The Energiesprong Model (Source: Energiesprong, 2015) 3
Figure 3 The PEER Project and its Research Areas (Source: Carver et al., 2018) 4
Figure 4 Ottawa Community Housing Unit on Iris St in the West End of Ottawa (Source: SBC, 2017c) 5
Figure 5 Reference building modelled energy use (GJ) (Source: SBC, 2017c) 6
Figure 6 Reference building modelled heat loss (GJ) (Source: SBC, 2017c) 7
Figure 7 R-20 panelized roof assembly over existing roof (Source: SBC, 2017c) 10
Figure 8 R-35 panelized wall assembly over existing walls (Source: SBC, 2017c) 10
List of Tables
Table 1 Base file model inputs (Source: SBC, 2017c) 6
Table 2 Evaluation and comparison of panel systems (Source: SBC, 2017c) 8
Table 3 High performance mechanical systems in market (Source: SBC, 2017c) 8
Table 4 Solar potential of reference project unit (Source: SBC, 2017c) 9
Table 5 PEER panel upgrade model inputs (Source: SBC, 2017c) 10
Table 6 Variable refrigerate volume Air-source heat pump vs. Combination boiler system (Source: SBC, 2017c) 10
Table 7 Gas vs electric back-up model inputs (Source: SBC, 2017c) 11
Table 8 Energy performance summary of base file and upgrades (Source: SBC, 2017c) 11
Table 9 Scale of challenge and opportunity for retrofits to meet 2030 Paris Agreement (Source: Armstrong, 2018) 17
Table 10 Specification of base file and various upgrades (Source: SBC, 2017c) 22
1.0 Introduction
1.1 Current problem
Following the 2016 Paris Agreement on climate change, Canada established the Vancouver Declaration, which commits the nation to meet or exceed international carbon emission targets. The goal is to reduce emissions by 30% by 2030 compared to 2005 emission levels. This corresponds to a sector-wide emissions reduction from 747 to 523 Mtonnes of CO2e (CaGBC, 2017). Residential housing accounts for 17% of Canada’s energy requirements and 16% of greenhouse gas emissions (GHGs). With increasing efforts in sustainable development to mitigate GHGs, many are looking into greener alternatives to housing. At present, it is both viable and easy enough to build a new home that respects stringent energy specifications. However, new construction accounts for little as 2% of the housing stock annually (CMHC, 2008) (figure 1). Therefore, there is a need for improvement with the existing houses.
1.2 Retrofit Methods
In this paper, we look at the option of retrofitting houses in order to reach Net-Zero Energy (NZE) levels. A NZE house is one that produces as much energy as it consumes on a yearly scale (Finch, 2013). Over the last 25 years, over 1 million Canadian homes have received some type of energy retrofit. These include HVAC system replacement (53%), additional interior insulation and air sealing (43%), and finally exterior wall retrofits (4%). The general barrier to these retrofits is that they are too expensive, disruptive, complicated and risky (Carver et al., 2018).
Retrofits can be done from the interior or the exterior of the house. Interior retrofits are very unpractical, costly, time consuming and usually yield in smaller living spaces due to wall expansion. Therefore, for this analysis, we will be focusing solely on exterior retrofits as they have the potential to be viable and attractive.
Exterior retrofits can be done with various different methods. Examples of such methods include installation of exterior insulation; such as rigid foam to wall or roof, installation of cool/warm roof, reducing air infiltration, changing window properties, application of PCM and Aerogel in different envelope components, and adding overhangs (Kamel & Memari, 2016). These changes are usually done in a fragmented manner which is inconvenient to the property owners.
1.3 Energiesprong
The method we will be considering in this paper originated in Europe, more specifically in the Netherlands and is called Energiesprong. This program pursues a mass customization strategy which incorporates prefabricated facades and insulated roofing systems along with advanced heating and cooling and PV to deliver NZE retrofits. Prefabrication is a method that is used to increase quality and effectiveness of construction (Pihelo et al.,2017). This greatly minimizes time and disruption of the project making it possible to complete them in less than a week. The homes come with a 30-40 year guarantee on indoor comfort and energy performance (Amann, 2017). Additionally, the Energiesprong model aggregates enough demand to attract the private sector investment in solutions development, encourages capital investment in automated design and manufacturing of housing assemblies, and drives cost down as well as improves affordability through supply chain efficiency. In sum, it creates long-term comfortable, efficient, desirable and affordable homes (Singleton, 2017) (Figure 2).
1.4 PEER
The Dutch program focuses primarily on providing solutions for the social housing sector and is rapidly expanding to other countries in Europe (France, UK) and including a recent adaptation of the program in New York State (SBC, 2017d). The European model of retrofitting these low-rise townhomes is also well suited to the Canadian context. Indeed, Ontario and Quebec for example have many similarly designed dwellings, many of which are expensive to operate and in need of repair. In addition, the size and nature of these structures make them ideal from both a technology and construction perspective (Singleton, 2017). This interest and opportunity lead to the creation of a similar project in Canada lead by Natural Resource Canada (NRCan) and CanmetENERGY called Prefabricated Exterior Energy Retrofit (PEER) (Figure 3).
1.5 Objectives
As the main energy demand from a house comes from space heating, it is evident that its location has a big impact on its energy demand as colder regions will experience higher energy demands. Therefore, in this paper we will evaluate the feasibility of these prefabricated deep energy exterior retrofits in the south eastern climates of Canada (Ontario and lower Quebec) by conducting a feasibility analysis. To help our analysis we will be looking at a reference project in Ottawa. It is a community housing unit that was used in the Energiesprong Design Workshop held in Ottawa on July 11th, 2017 by Sustainable Buildings Canada (SBC). For the feasibility analysis, we will look at three main aspects: construction feasibility, political and social feasibility and finally, financial feasibility.
2.0 Case Study
2.1 Base Case
The unit selected (Figure 4) is a relatively accurate representation of a typical social housing building stock in the City of Ottawa. Built in 1961, it is a 117 m2 vintage brick construction with double glazed windows, R-27 gable roof, uninsulated basement and open fireplace. The unit is heated by a force air condensing furnace, the water is heated with a natural gas water heater and the ventilation is provided by a principle exhaust fan in the bathroom located on the 2nd floor. It has an EnerGuide Rating System (ERF) of 11.3 and an air tightness of 8.42 ACH at 50 Pa (SBC, 2017c).
In order to compare the various upgrade options, energy modelling was done using HOT2000 V11.3 for the reverence model as well as the several upgrade scenarios. Table 1 outlines the energy model inputs for the base file and figure 5 represents the building energy usage prior to the workshop (SBC, 2017c).
With respect to figure 5, it can be seen that space hearing is the primary source of annual energy consumption with 47,3 GJ. Therefore, it is important to know where the heat is being lost. Figure 6 illustrates the heat loss through various building components.
With all this information at hand, the following priority areas of focus were identified to be upgraded:
1. Improve air tightness
2. Improve fenestration U-value
3. Improve wall R-Value
4. Improve below-grade heat loss
(SBC, 2017c)
2.2 Upgrades
Seven upgrade scenarios were modelled and compared to determine the best combination to achieve net-zero for this building. However, several efficiency measures were included in all of the upgrade cases, namely: triple glazed windows, R-20 basement insulation, R-28 + R-20 roof insulation, 84% SRE HRV, 1.5 ACHs, drain water heat recovery and 100% LED lighting. The different scenarios mainly proposed different wall assemblies and different space heating systems (SBC, 2017c).
The exterior wall systems were part of the PEER project which, similarly to the Energiesprong model, presented prefabricated panelized wall systems for retrofit. Specifically, two wall systems were considered: an expanded polystyrene (EPS) foam nail base and a wood-frame standoff wall. The following table summarizes and compares the performance of both walls.
With regards to the mechanical performance, the best in class systems considered for the Canadian social housing implementation of Energiesprong were modelled. Table 3 summarizes the performance of these aforementioned mechanical systems.
To achieve NZE levels, there are three main aspects that need to be followed
1. High Performance Insulation
2. Passive design
3. Energy production
Point 1 has been dealt with and point 2 is hard to be changed unless major structural changes are done to the building. Indeed, facing the house south and adding overhangs can greatly reduce the energy demands of the house but it is hard to change on existing construction. Therefore, point 2 is mostly valid for new constructions. Consequently, in order to reach NZE, we need include a source of energy production. Many options are available on the market, but for this specific case in Ottawa, the solution with the most potential is to add photovoltaic solar panels (PV) on the roof. Four different solar array sizes and 2 different module sizes (300 and 340 W) were modelled and the results are shown in table 4 below.
3.0 Results
The following section presents the seven different scenarios that were modeled and used for analysis. The first three models (Table 5) represented the reference unit with an R-20 panelized roof (Figure 7) as well as adding a R-25, R-30 and R-35 (Figure 8) to the walls.
The following two upgrade scenario dealt with space and water heating and compares two different systems: a variable refrigerant volume air source heat pump and a combination boiler system. Both systems are compared in table 6 below.
Finally, the last two scenarios (Table 7) were a comparison of two different models of mechanical heating system: gas and electric backup.
A table summarizing all seven scenarios inputs and the base case can be found in Appendix A. The modeling outputs highlighting the site energy consumption, GHG emissions and energy cost can be found in table 8 below.
4.0 Feasibility Analysis
4.1 Construction Feasibility
The construction for this retrofit can be divided into two main areas: the prefabricated retrofit and the electro-mechanical retrofit. First, the prefabricated retrofit will be evaluated, and its construction process can be split up into several steps:
1. Scanning or measuring of the building
2. Panel design
3. Off-site fabrication
4. Panel installation
(Carver et al., 2018)
For the construction of the project to be feasible, all steps need to be realized almost flawlessly. Indeed, this requires a great amount of precision and planning which means that the interaction between the design process and the construction process is of upmost importance (Pihelo et al., 2017).
However, before any construction starts, it is essential to consider the initial state of the building as this will be a decisive factor on the feasibility of the project (Pihelo et al., 2017). For example, the location and the shape of the building are very important factors of feasibility. A building located very far from any major city will be hard build with prefabrication. And a building with a very complex and irregular geometry will be very difficult build (Pittau et al., 2017). The Ottawa building considered in the analysis therefore satisfies these requirements and should therefore not be problematic.
The task starts with precisely measuring the building and this can be done in many different ways, namely: Hand measurement, theodolite total station, 3D laser scanning and photogrammetry. Out of all these options, 3D laser scanning is currently the best practice for application considering precision, pricing and rapidity (Carver et al., 2018). However, it this technology is still relatively expensive and is not commonly accessible. Therefore, only a few companies have the technology to build scan the building.
Once the scan is done, a scan to BIM technology uses the points gathered in the scan and creates a three-dimensional image which can be manipulated with a BIM software like AutoCAD or Revit (SBC, 2017b). From the software, the prefabricated panels are designed and sent to the factory for production. This step is easily feasible provided that the scan is accurate.
The off-site production can be a very tricky step especially in Canada. First of all, the production has to be done locally for it to be cost effective and environmentally friendly. In addition, in contrast to the Netherlands, each province has different climate zones and different building codes which makes standardization more challenging (SBC, 2017c). Therefore, it is important to see if there is a local manufacturer close to the Ottawa case study.
Finally, the panel installation is by far the most problematic step and requires the greatest attention. A larger and more established contractor is necessary for installing to ensure continued support in the future should part of the panel system fail. All parties involved would also need to follow proper training for installation. There are many areas of concerns to be addressed. Firstly, the windows are the bridging between the wall assemblies which makes them a potential weakness spot for moisture ingress. Secondly, the basement insulation is of concern. Although interior insulation would be more viable and easier, it is intrusive and non-intrusivity is a fundamental principle of Energiesprong. Therefore, a trench (“skirt”) would be needed for below-grade insulation. Finally, condensation in the panels are also of great concern which means that the EPS foam panel would be more desirable due to its lower risk of condensation (SBC, 2017c).
Once the prefabricated construction is done, we also need to assess the feasibility of the mechanical and PV systems. For heating, it will be important to regulate basement warmth to improve foundation durability. Also, the heating systems tend to be oversized and can be avoided by supplying to multiple units on the same block which is not always feasible. The ventilation of the new unit will make use of the existing ductwork to distribute ventilation air throughout the unit. There is a potential to run ducts in the pre-fabricated walls if necessary, but it requires much more planning. Therefore, it is important that the ductwork be present and functional. Finally, PV should have a long enough life expectancy (30 years) even though they lack aesthetics. Solar shingles would not be viable due to their shorter lifespan (SBC, 2017c).
4.2 Financial Feasibility
With modern day technologies and techniques, anything can be built but most of time the financial feasibility of the project controls if a project will go forward or not. This section will analyse the areas of the project where financial feasibility is a concern.
As mentioned previously, the 3D scanning equipment is relatively expensive and would require a very high upfront cost for the company that is contracted. It is therefore desirable that the company already has one. In addition, depending on the distance of the panel production plant, shipping might be expensive. This makes location and the choice of contractor very important to the financial viability of the project (SBC, 2017c).
Furthermore, moving towards an all-electric energy mix can be expensive. In Canada, this will vary greatly with each province. In Quebec for example, most systems are already electrical which makes the switch more viable. However, for regions where natural gas is used, like the one our case study is located in, the switch from natural gas to a heat pump is more difficult to justify on a cost basis alone. With regards to water heating, for units using fuel oil, switching to an electric heat pump would be cost-effective (SBC, 2017c).
Overall, in the Canadian context, the energy savings will most likely not cover the capital cost which can be slightly offset by the revenue from the PV cells. The financial feasibility of this project will mostly rely on the presence of additional sources of funding such as grants from the government. Unfortunately, there are not enough incentives for building above code for it to be viable. However, our case study is a social housing which makes it’s a good candidate for additional sources of funding from the government. Additionally, there may be a resulting overall aesthetic improvement of the building which may improve retail value of the house (SBC, 2017a).
4.3 Political and Social Feasibility
As previously mentioned, the financial feasibility will depend on the sources of funding. Therefore, is important for the government to promote and fund these retrofit and encourage the general public to have a paradigm shift on the importance of the problem. For it to be feasible, it has to be attractive to the public. The community housing we analyzed is a good candidate for this type of retrofit since one single person can make a decision about multiple units and the overall building design. However, there is an uncertainty concerning the presence of market demand outside social housing. One area of concern is that the occupants need to be properly educated to avoid misusage of the unit. For example, they need to be aware of how to operate an HRV to avoid issues arising from the unit being switched off (SBC, 2017c).
For this program to be desirable, a collaborative approach is needed between the worlds of engineering, financing and social programming. The Energiesprong program really encompasses this well and that’s one of the main reasons for its success. They essentially sell this program as a package which includes a 30-year warranty and they have a division that puts clients into contact with financial institutions who gives them price reductions. The clients can even stay in the house while the retrofit is being done. This collaboration makes the program desirable and that is the way it should be marketed by the government for it to be feasible. Financial institutions need to work hand in hand with the government and public institutions to encourage the public to make the switch.
5.0 Discussion
The feasibility analysis provided much insight on the viability of these retrofits in the south eastern part of Canada. With regards to construction, this program would be feasible, but the projects need to be very well-planned and the choice of contractor has to be thought out. With all the technologies available in the market nowadays, pretty much anything can be built but usually, it comes at a high price. Therefore, the net-zero retrofit is technically feasible but cannot be justified in the short term on the basis of a simple payback analysis alone. However, if there are other motives to replace the barrier of the building such as window and cladding replacement, moisture issues or thermal comfort issues, it would be a key time to retrofit. Additionally, if the house already looks unattractive, this retrofit will make it more aesthetically pleasing and give it more value (Finch, 2013). Finally, what will actually determine if this retrofit program is feasible is the implication of the government and financial institutions. If they are able to sell a product that is desired and encourage people to switch using monetary incentives such as grants or tax reductions, they can definitely reduce the financial gap and make this project viable. The general public also needs to change their mindsets and see this as an investment on the environment and on the health of future generations to come.
The Energiesprong program has already proven to be successful in Europe with over 5000 built houses and 20000 more planned retrofits (Energiesprong, 2015). They are currently starting to move to north America with a few projects in Canada and in New York. The main reason they are successful is due to their collaborative approach which makes the project desirable and affordable. Since space heating is the most important energy usage in a house, location has a great impact on the feasibility of the retrofit. Europe is therefore in a better position to accomplish these retrofits but this paper demonstrates that it can be applied to the harsh climates of south eastern Canada.
Naturally, these technologies are still relatively new which explains why they come at this price point. Nevertheless, following the concept of economies of scale, the more is built, the more the process is perfected and the cheaper it becomes. Also, as energy becomes more expensive, the retrofits become increasingly viable (Finch, 2013). Thus, the future of net-zero retrofits looks very bright with a lot of houses to operate on. All that is required for it to be feasible is a good government involvement combined with a good plan of action. In order to meet the 2030 target for the Paris agreement, table 9 shows the breakdown of the work to be done if only these retrofits were used as corrective measures. This shows the scale of the challenge Canada is faced with and the scale of the opportunity for these Net-Zero retrofits.
Table 9 Scale of challenge and opportunity for retrofits to meet 2030 Paris Agreement (Source: Armstrong, 2018)
Total Canadian GHG emissions in 2015 747 Mt CO2 eq.
2030 Target (Paris Agreement) 523 Mt CO2 eq.
Reduction required to meet target (747-523) 224 Mt CO2 eq.
Currenwt residential emissions @9% of 747 67 Mt CO2 eq.
No. of Canadian households in 2015 13.3 Million
Annual household avg. GHG emissions (67/13.3) 5 Tonnes CO2 eq.
Reduction target for the housing sector (9% of 224) 20 Mt CO2 eq.
Total no. of households to Net-Zero Carbon (20/5) 4 Million by 2030
4 million NZC houses by 2030/12 years 330,000 Houses per year
New NZC houses built each year 20,000 New NZC houses
Total no. of NZC retrofits per year 310,000 Houses Needed
As mentioned previously, another reason the Energiesprong program works so well is that they only really operate in one climatic zone in the Netherlands for example. In Canada however, we each province has a different climatic zone with different building codes and different energy price and mixes. Therefore, when considering a scale up on a national scale, these elements need to be considered. For example, electricity in Quebec is relatively cheap and is almost exclusively hydroelectric. In contrast, its neighbour Ontario has a higher price point for electricity which is not as clean as Quebec. Consequently, Ontario produces three times more Carbon emissions than Quebec (CaGBC, 2017). Ontario would thus benefit much more from a retrofit program compared to its neighbour province.
Once again, only the government has the power to make this feasible by marketing this program as a solution to climate change. All technical elements exist in isolation and it has been done in other continents, the real innovation is to bring all these elements together creating a project that is both desirable and feasible. The general public needs to view public funds as an appropriate source of money for this program. Instead of doing a smaller number of deep retrofits, the government could finance shallow retrofits for a higher number of homes in order to meet 2030 GHG targets. However, this in turn would erode the business case for future changes required to meet future targets. That being said, this proposed exterior deep retrofit program should also be seen as an investment to future generations and not just as a mean to reach 2030 GHG levels. All the potential lies in the governments hand and their ability to change people’s mindsets (SBC, 2017c).
6.0 Conclusion
The purpose of this paper was to assess the feasibility of prefabricated deep energy exterior retrofits in existent housing to reach NZE levels in the south eastern climate of Canada. In doing so, a case study of a community housing retrofit in Ottawa was analysed. It was found that a program similar to Energiesprong could be feasible provided that the government fully committed itself to it. Although it is currently financially hard to justify, through the concept of economies of scale and improvements in the field, a foreseeable future awaits these retrofits. They are a great solution for climate change mitigation and could help Canada achieve their 2030 goal for the Paris Agreement. The first step towards the implementation of this program would be to change the general public’s mindsets regarding climate change and to categorize this program as a necessary leap of faith towards a more sustainable future. Pilot projects should be built and analysed across all Canadian provinces in an effort to create the best plan of action for the nation. At the moment, there are only very few projects to study from which makes it hard for the program to take off.
This study focuses on the problem of existent housing but hopefully the new housing will never have to deal with retrofits. All new constructions should be built with the environment’s future in mind. To do so, some codes and norms will have to be updated and efforts in both the public and private sector will need to be done. This will require many people to put their short-term financial gain aside and invest in the earth’s future. Hopefully, this retrofit program can be applied worldwide, especially in the world’s leading economies such as China and the United States.
References
Amann, J. T. (2017). Unlocking Ultra-Low Energy Performance in Existing Buildings. Retrieved from https://aceee.org/sites/default/files/ultra-low-energy-0717.pdf
Armstrong, J. (2018). PEER – Prefabricated Exterior Energy Retrofits. Spring Training – Cold Climate Building Inc.
Canada Green Building Council. (2017). A Roadmap for Retrofits in Canada: Charting a Path Forward for Large Buildings. Retrieved on December 20th, 2018 at https://www.cagbc.org/cagbcdocs/advocacy/CaGBC_Roadmap_for_Retrofits_in_Canada_2017_EN_web.pdf
Canada Mortgage and Housing Corporation. (2008). Approaching Net-Zero Energy in Existant Housing. Retrieved on December 20th, 2018 at http://publications.gc.ca/collections/collection_2008/cmhc-schl/nh18-22/NH18-22-108-104E.pdf
Carver, M. Plescia, S. Charlton, D. Armstrong, J. (2018). PEER – Prefabricated Exterior Energy Retrofit. Building Capture Technology. 13th Annual North American Passive House Conference, Boston, MA. Retrieved on January 1st, 2019 at http://www.phius.org/NAPHC2018/2018.09.21%20Building%20Capture%20NAPHC.pdf
Energiesprong. (2015). UK Transition Zero. Retrieved on December 20th, 2018 at https://energiesprong.org/wp-content/uploads/2017/04/EnergieSprong_UK-Transition_Zero_document.pdf
Finch, Graham & Hanam, Brittany. (2013). Net Zero Building Enclosure Retrofits for Houses: An Analysis of Retrofit Strategies. Retrieved on December 20th, 2018 at https://www.researchgate.net/publication/305347611_Net_Zero_Building_Enclosure_Retrofits_for_Houses_An_Analysis_of_Retrofit_Strategies
Kamel, E. and Memari, A. M. (2016). Different methods in Building Envelope Energy Retrofit. In: A. Memari and S. Klinetob Lowe (eds) 3rd Residential Building Design & Construction Conference, Penn State, University Park, 2-3 March 2016. [Online]. Pennsylvania: The Pennsylvania Housing Research Center – PHRC, pp.64-84. Available at: http://www.phrc.psu.edu/Publications/2016- RBDCC-Papers.aspx [Accessed 1 January 2017].
Pihelo, P., Kalamees, T. and Kuusk, K. (2017). nZEB Renovation with Prefabricated Modular Panels. Energy Procedia, 132, pp.1006-1011.
Pittau, F. Malighetti, L. Iannaccone, G. Masera, G. (2017). Prefabrication as Large-scale Efficient Strategy for the Energy Retrofit of the Housing Stock: An Italian Case Study, Procedia Engineering, Volume 180, Pages 1160-1169, ISSN 1877-7058, https://doi.org/10.1016/j.proeng.2017.04.276. (http://www.sciencedirect.com/science/article/pii/S1877705817317836)
Singleton, M. (2017). Energiesprong – a market transformation strategy. Sustainable Buildings Canada.
Sustainable Buildings Canada. (2017a). Barriers to Net-Zero Energy, Waste, and Water for a High-Density MURB in Toronto. IDP Workshop Summary. Retrieved on December 20th, 2018 at https://sbcanada.org/wp-content/uploads/2017/04/Barriers-to-Net-Zero-Workshop-Summary.pdf
Sustainable Buildings Canada. (2017b). Energiesprong Phase 1 Report: Background Research and Design Workshop. Report on the Energiesprong Design Workshop Held in Toronto. Retrieved on December 20th, 2018 at https://sbcanada.org/wp-content/uploads/2017/09/Energiesprong-Toronto-Report.pdf
Sustainable Buildings Canada. (2017c). Energiesprong Phase 1 Report: Ottawa Design Workshop. Report on the Energiesprong Design Workshop Held in Ottawa. Retrieved on December 20th, 2018 at https://sbcanada.org/wp-content/uploads/2017/09/Energiesprong-Ottawa-Workshop-Report.pdf
Sustainable Buildings Canada. (2017d). Energiesprong Summary Report: Background Research, Design Workshop Results and Recommendations. Retrieved on December 20th, 2018 at https://sbcanada.org/wp-content/uploads/2017/09/Energiesprong-Summary-Report.pdf
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