Sustainability goes far beyond green-house gas emissions. Aspects on all three levels, environment, economy, and society have to be addressed to ensure that current and future needs of the planet and its inhabitants are met. Our solution strives for the preservation and reuse of materials and creates a positive impact on the energy performance, allowing the lifetime of the dwelling to extend by at least 50 years. The concept employs prefabricated elements in construction sections, which introduces two advantages. On the one hand, it increases the efficiency of material usage, especially when these are fabricated on a large scale, diminishing waste and saving energy at the same time. On the other hand, it reduces the construction time due to simplified handling, especially with the urban application. Prêt-à-Loger primarily utilises passive solutions such as insulation and the addition of the glasshouse to reach the goal of at least energy neutrality. Only when these are not sufficient, active systems are employed to assist in reaching the desired comfort levels. Consequently, the active and passive systems in the glasshouse and the existing dwelling complement each other, not only minimising energy losses, but also utilising solar energy (e.g. with the heat exchanger) alongside the photovoltaic panels.
The sustainable built environment goes beyond that: It extends to the public spaces, which are incorporated and recaptured for the purpose of improving their sustainability performance and stimulating sustainable awareness. With this solution the focus is not on densifying the building stock, but on sustainable adaptation through the flexible densification of functions within the public space. When expanding and extrapolating the “Home with a Skin” to the urban level, the neighbourhoods will manage to reduce great amounts of energy and water. Over time, they will become self-sufficient through decentralised energy production in combination with a smart energy grid. Other changes will follow suit, such as the stimulation of sustainable awareness and shared interests, hopefully leading to a greater sense of community. These changes will be triggered by actively involving residents, fostering interaction and promoting a lifestyle in balance with the environment. Public transportation will contribute to this transition, facilitating not only the social network. It is also an inherent part of the energy network, where it helps to form a smart grid with the energy producing dwellings.
Retrofitting of the house begins with selecting materials, before incorporating them through the construction system. Guided by the principle of preservation and reuse, Prêt-à-Loger chose a procurement strategy that would give preference to durable, recycled and recyclable materials. The three most relevant materials (in terms of weight) are glass (1,962 kg), steel (1,036.2 kg), and wood (818.13 kg), all of which meet the desired criteria. Besides these, three material highlights can be found in the house. The window and door frames in the house are made from 100% recycled plastic. For the insulation, old newspapers and wood shavings are reused and subjected to the so-called cascade use: the material and energy recovery - the most favourable use of materials in terms of resource efficiency. Lastly, a green roof is added on the house, which is not only ‘green’ regarding its materials, but also adds insulation, rainwater retention function and a small habitat for animals.
What is less positive, but also essential to mention, is the toxicity that is caused. Human toxicity is the biggest impact category, accounting for 96%. The production of copper, and steel for the exterior joineries and façade are the largest contributors to toxicity, CO production and energy consumption. In total, the embodied energy of the materials amounts to 363,108.87 MJ, of which 76% was derived from fossil fuels. As a result, a total of 15,939.19 kg CO2 eq were emitted in the cradle to site phase. Since Prêt-à-Loger makes use of an existing building, the construction system is very limited, because fewer new materials are needed. This allows for a much faster construction, where efficiently prefabricated elements from mass production, both in individual houses and on urban scale, are installed. As a result, little energy is used and much resources are preserved, compared to demolishing and building a new house. Also, only a small amount of demolition rubble is generated. Most importantly from a residents’ perspective, the house is being renovated with the user remaining in the house, consequently avoiding this inconvenience in the user’s everyday life.
After improving the house, it transitions into the use phase, where several systems are operated, resources such as water and energy are consumed and waste is produced. The three different energy systems present in the house and Skin are classified as passive, active or solar. The glasshouse part of the Skin on the south-west side of the house is the main contributor of passive climatic techniques. It provides a heat buffer in winter, induces cross and stack venti-lation throughout the year, catches rainwater and makes use of solar energy. Further passive techniques can be found in the insulation added to the north side and roof and the inherent heat retention of the brick structure of the existing house. Active systems are also present in the design, located mainly within the existing structure, which predominantly serve as complementary systems to the passive systems to maintain a constant comfortable environment. Active systems include a heat pump, heat recovery systems in the chimney, a water tank and active ventilation. Additionally, photovoltaic panels are present in the Skin to generate electricity, which are complemented by solar panels that simultaneously cool down the glasshouse and the panels and provide heat and hot water for the house. Especially the PV modules ensure that the house can be energy neutral, since they supply the house with a total of 161 MWh during 50 years of use. After accounting for the inherent energy of the modules that stems from manufacturing and transport, 143 MWh of the total amount is produced completely energy neutral.All climate systems in the glasshouse and the existing dwelling complement each other and work in close synchronisation to create a comfortable environment where not only energy use, but also material and water use is minimised. Freshwater use is limited by capturing and storing 2,000 litres of rainwater in the crawl space for use in the toilets, cleaning and irrigation, which results in 18% freshwater savings. In combination with the water saving sensors and devices in the house, the actual water use can even be reduced by more than 20% compared to the current situation. Waste is mainly prevented during the construction phase and by implementing a waste management system which facilitates recycling and composting of organic waste. Additionally, it is estimated that 80% of the materials used in the Skin can be reused or recycled at the end-of-life of the house, assuring waste prevention even after the use phase.Future FeasibilityIn order to demonstrate that the “Home with a Skin” positively contributes to the sustainable development, a Life-Cycle-Analysis (LCA) was carried out to quantify the environmental impacts. Furthermore, the consequences of scaling-up the product to an urban level were analysed.The LCA was carried out from cradle-to-grave, analysing the house in its local context for the lifetime of 50 years. The five main contributors (A, B, C, D, E) that form the main assembly ‘F’, the building, represent construction, transport of materials, materials, use phase, and transport of users, respectively.For the construction assembly, the engine, water and electrical consumption and the fall of materials and demolished matter were taken into account. It was estimated that 500 kg of water and 412.03 MJ of diesel (11.49 L) were consumed. Moreover, the old roof, outer layer of the north brick wall and windows and door that are demolished in the north made up the main share of the demolition waste.When analysing the transport of the materials needed during the construction and over the lifetime of the house, all trans-port modes, namely lorry, freight ship and aircraft were added up, amounting to 20,743.85 tkm. Here, the transportation of the photovoltaic panels via plane from China has the biggest share with about 86%. In the future, this value could be greatly reduced or even replaced when choosing a closer manufacturer or the common shipping method (freight ship).A highlight for the material evaluation concerns the above mentioned recycled window frames, which underwent a comparative study to determine if recycled window frames perform better than standard windows. The analysis verified that the recycled plastic frames are indeed more favourable in terms of environmental impact.To quantify the consumption of heating, cooling, lighting, sanitary hot water, ancillaries and specific electricity and the energy production, all the values were added up for one year and multiplied by 50, to account for the lifetime of the house. The total annual energy consumption and production values are 3184.9 kWh and 3753 kWh respectively, making the house energy positive, which even goes beyond the goal of energy neutrality. The transport of users entails the distances and transportation modes used by the family persona and occasional users who walk or take the bike, car, tram, train or bus measured in pkm per year.In order to quantify the impacts, the ‘ReCiPe Midpoint Method’, ‘Cumulative Energy Demand’ (CED) and ‘IPCC GWP 100a’ were employed. The ReCiPe Midpoint Method analyses a total of 18 indicators. For climate change, the indicator that is most prominently referred to, the largest contribution came from operating a personal car.Applying the Cumulative Energy Demand method resulted in the total energy demand value of 2,201,677.62 MJ eq. Here, the transport of users accounts for the biggest share with 80.6%, while the second largest contribution is made by the materi-als with 16.5%. The energy generation from the photovoltaic panels was represented in the negative value of -301,662.12 MJ eq, almost balancing out the energy needed to transport the needed materials.The IPCC GWP 100a served for the calculation of the CO2 eq emissions, which added up to 116,349.87 kg. Again, the great-est share was made up from the transportation of the users (81.56%).Conducting the LCA was extremely valuable for the impact eval-uation and the confirmation of design choices. Prêt-à-Loger at-tempted to strive for the best and most feasible solutions on all levels of sustainability, not only the environmental aspects. It turns out that while the project managed to maintain a bal-ance between these levels, there is still room for improvement. Even though it was surprising that transportation accounted for most of the negative environmental impact, it is a relatively easy problem to tackle. Fortunately, Prêt-à-Loger has already developed various transportation strategies aimed at mitigating the harmful impacts.These transportation strategies are an important part of the urban approach Prêt-à-Loger utilises, in which a lifestyle in bal-ance with the environment is endorsed inside and outside of the homes with a Skin. The aim of this approach is to promote optimal land-use, shared goods and public space, and maximised use of materials, energy and food in the neighbourhoods and towns where the Skin is utilised, using a flexible urban tool-box. Central to this strategy is the urban application and use of the Skin while retaining the basic urban structure, but also the creation of green spaces and the aforementioned transformation of the transportation strategy. The active involvement of residents and the municipality is important to achieve all this, since the incorporation of their needs and wishes will ensure the success and applicability of the urban transformation.For the urban application of the Skin, two main target groups are of importance, namely housing corporations and individual homeowners supported by external investor funds. For both parties the urban application is expected to be feasible within two to three years and the implementation is envisioned to take place in three steps between 2020 and 2035.Accompanying the application of the Skin is the transformation of the public space using the urban toolbox. It is a highly flexible process that is needed to ensure that the transformation is fully appropriated to the specific location and urban context. Options such as urban farming, green zones and water retention are all analysed and the most suitable options are utilised in the neighbourhoods and towns.
For Honselersdijk, especially a transformation of the urban strategy forms an important part of the urban approach, with which the introduction of a shared electric car program lies at the centre. This program is introduced to stimulate sustainable travel and reduce CO2 emissions from short-distance travel by personal car. It will be integrated in the energy grid, containing the Skins and decentralised solar and wind energy facilities. This electric vehicle concept is further implemented by the introduc-tion of personal electric bicycles connected to the Skins, which allow residents to travel larger distances by bike in a sustainable manner.The use of sustainable modes of transportation is further en-couraged by transforming numerous service roads into green zones to better suit pedestrians and bicyclists, and by the in-tensification of the public transportation by green bus lines and light rail trains already planned by the Province of South Hol-land.InnovationThe approach that Prêt-à-Loger proposes, looks beyond creat-ing sustainable houses and instead focuses on transforming the existing and unsustainable building stock by using innovative interventions and materials. Preservation and improvement of existing structures is preferred over demolition and replace-ment and sustainable, economic and environmental potential of structures such as the post-war row house in Honselersdijk are analysed. This house is thereby adapted without undertak-ing major demolition works or implementing highly invasive interventions, directly saving on demolition and construction. This provides immediate benefits on a social, economic and en-vironmental level, since the construction time decreases dras-tically, less labour and materials are required and substantial amounts of waste and emissions related to construction works are prevented. The approach further introduces newly added living space and preserves the existing construction and lay-out of the dwelling, ensuring residents can improve and maintain not only their house, but also their home and their memories. The final product is an energy neutral, waste preventing and comfortable home resulting from a quick and economic inter-vention with a Skin that provides energy and extra living space.However, Prêt-à-Loger perceives sustainable improvement of the building stock as more than adjusting single dwellings and aims at improving the urban surroundings as well, even when the Skin is only applied to part of the building stock. To achieve this, a flexible urban toolbox is introduced which allows resi-dents and municipalities to be actively involved in the trans-formation, guaranteeing the interventions are highly adapted to the opportunities and needs of the specific location. This involvement of the local residents additionally supports sustain-able awareness and creates a shared feeling of responsibility for the neighbourhood and its public space. Even residents who didn’t implement the Skin will experience and profit from these interventions in their direct environment such as green car-free zones, urban farming and rainwater retention, which will sup-port environmental and social awareness throughout the neighbourhood and town.Related to the urban toolbox is the improvement of the transportation situation in Honselersdijk, which is currently predominated by short-distance travel by car. To reduce the emissions associated with personal and public transportation, a shared car program is introduced using electric cars powered by the Skins in combination with decentralised wind and solar energy. Additionally, electric bikes are introduced within this electricity network and the public space is redesigned to fit the needs of pedestrians and bicyclists better, making short distance travel by bike more attractive. This way, the foundation for a future smart energy grid is created and sustainable travel is encouraged.