A BUILDING SYSTEM FOR CONNECTED SUSTAINABILITY Sotirios D Kotsopoulos1, Carla Farina1, Federico Casalegno1 Andrea Briani2, Paolo Simeone2, Raffaele Bindinelli2, Gaia Pasetto2

ABSTRACT: An innovative building approach for the envelope of a prototype connected house, as a modular, transportable structure of sustainable components, incorporating X-lam panels and wood, is presented. This demonstration shows that it is possible to use wood, for contemporary prefabricated connected, sustainable buildings.

KEYWORDS: Modularity, transportability, connectivity, X-lam, CLT. 1 INTRODUCTION 123 The use of a high thermal capacity building envelope, back to back with programmable materials and intelligent control methods, can have significant contribution in optimizing energy performance. This paper presents an innovative building system for a connected sustainable home, a prototype of which is at the final stage of construction, in Trento, (Trentino, N. Italy). In this prototype, the traditional features of a house are revisited with a view to integrate current advances in wood engineering, in electrically activated materials research, and in AI building control. A high thermal mass envelope made of prefabricated X-lam panels, is combined with a programmable façade, using electrochromic technology. Improving the energy efficiency of residential buildings is critical in addressing the global energy challenge. In 2008, residential buildings consumed 21.54 quadrillion Btu of energy in the U.S., which accounted for 21.52% of total energy usage in the country of that year. Artificial heating and cooling accounted for the largest portion of the residential energy consumption: 7.99 quadrillion Btu or 38.2% of the energy consumption in the residential sector. The connected sustainable home uses technological innovation to supply comfortable living conditions, while minimizing energy consumption. It is a lightweight modular, transportable, residential unit that elegantly blends passive and active energy conservation features, and provides a unique test-bed for exploring the future of sustainable ecosystems at a residential scale.

1 Mobile Experience Laboratory, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139, USA. Email: skots@mit.edu, cfarina@mit.edu 2 Cnr-Ivalsa, Trees and Timber Institute-National Research Council of Italy, via Biasi 75 38010 S. Michele all’Adige (Tn), Italy. Email: andreabriani@alice.it, simeone@ivalsa.cnr.it

This paper presents the building system of the house, its relationship to the other house systems and its contribution in maximizing the house performance. Traditional Western architecture had met the need for constructing durable shelters by making them massive. Thick and weighty structures are less easily overthrown by weather, or earthquake, and less maimed by fire. They offer better sound and thermal insulation and better heat storage capacity. While these features became customary in three millennia of European architecture, they were found to be conspicuously absent from light-weight modern buildings, which were promoted out of enthusiasm for the "machine age". Today, material engineering research and AI control methods, promise to add new dynamic features to buildings, including the adaptation of their visual presence and performance, based on given conditions. For example, by selecting the thermal transmittance value of windows, it is possible to regulate the amount of heat and light that gets admitted into a building's interior. Combined with efficient thermal conservation components, this apparatus can result to the drastic reduction of energy consumption from artificial cooling and heating. Further, polymer dispersed liquid crystal films (PDLC) and suspended particle displays, can eliminate the need for mechanical blinds and shutters and revolutionize building aesthetics. Buildings equipped with such capacities, optimally managed, will transform the ways of inhabiting built environments. The advantages in exploiting these new technologies at residential scale are discussed next in detail. More specifically, the prototype connected sustainable home (Figure 1) integrates uniquely 5 diverse systems: i) a passive high thermal mass envelope, ii) a programmable façade, iii) a high thermal mass base with heating and cooling capability, iv) a solar-powered cogeneration plant provides electricity, hot water and heated /cooled air and v) a control system, optimizing the performance of all of the above.

Figure 1: Rendition of the south façade of the prototype connected sustainable home, in N. Italy.

Electrochromic technology permits the adjustment of natural light and heat at the house interior, by enabling the reprogramming of the chromatism and thermal transmittance of each individual windowpane. Varying the chromatism and the thermal transmittance of the south façade affects the performance and the visual presence of the house. Optimum façade configurations are achieved through the efficient management of the electrochemical properties of the windows by an intelligent control system. The control compiles statistic weather data and environmental feedback from sensors, in real time, to activate the electrochromic material as necessary, and to exploit the high thermal capacity of the envelope. During the hot summer days, keeping the interior temperature lower than the exterior is a high priority. To protect the interior from direct sun exposure, the control system sets the electrochromic material to allow minimum thermal transmittance. Conversely, during the cold winter days, taking advantage of the sun heat becomes a high priority. To expose the interior to the winter sun the control system sets the electrochromic material to allow maximum thermal transmittance, and makes the storage of sun heat in the high thermal mass envelope attainable. At any given moment, the control system reprograms the façade based on the weather and the preferences of the inhabitants, to achieve maximum comfort at minimum energy expenditure. Hence, the sun is used to maintain comfort at the interior, while elegant façade patterns are formed on the exterior. 2 BACKGROUND Massive structures absorb and store heat that is being applied to them, and return it to the environment after the heat source has been extinguished. A historical paradigm of such a design exists in Alberti's account of chimneys [1]. In general, heavy masonry has served to conserve the heat of the fireplace during the day, and return it slowly to the house during the night, when the fire has burned out. In the hot summer days, the thick walls hold solar heat and delay the rate at which the interior is affected by it. After sunset, the radiation of the heat is used to temper the chill of the evening.

In a more sophisticated version, glass is used as a filter to discriminate between light, which is allowed to pass, and heat, whose passage is barred. Thermal storage is called by Banham conservative mode of environmental management [2] in memory of the conservative wall at Chatsworth House devised by the environmentalist J. Paxton (Figure 2). The conservative mode has had become the norm in European architecture. It was combined with the selective mode, which employs the building structure not just to conserve desirable conditions, but also to selectively admit desirable conditions from outside. Hence, glazed windows admit light, but exclude the direct sun, a louvered grille admits ventilating air, but excludes visual intrusions, etc. Traditional building construction has always had to integrate the conservative and the selective modes, and also to involve the regenerative mode, which applies power to regenerate favourable conditions, as needed. Regenerative systems include artificial lighting, heating, cooling etc. Today, the increasing cost and scarcity of non-renewable energy sources, call for the embrace of more principles in the design and operation of buildings. Since artificial lighting and heating are energy-intensive, the management of sunlight and heat becomes essential. In reply to this necessity, a new mode of environmental management is introduced, aiming to radically improve energy efficiency. The responsive mode of environmental management provides adjustability of performance "in response to" given conditions. The key to this new mode of management is fine-tuning of the house systems, to maintain a state constantly aligned to the comfort levels at minimum energy expenditure. Along the above lines, the connected sustainable home combines conservative, selective and responsive systems to minimize the use of regenerative systems. A lightweight, high thermal mass building envelope, protects the house from the natural elements and conserves heat. A programmable façade selectively admits light, heat and view, and operates as an advanced alternative to a traditional screening system. While guaranteeing that the comfort levels are constantly maintained, the control proactively minimizes the use of electricity and the long-term energy consumption.

Figure 2: The green house of the Chatsworth House, by the early environmentalist J. Paxton, 1846.

Figure 3: The conservative part secures high thermal resistance and low conductivity. The selective part regulates airflow, sunlight and heat.

The conservative envelope (Figure 3) is a double-skinned wall made of cross-laminated timber panels (X-Lam) that serves multiple goals: (a) it is lightweight, b) it is modular and transportable, c) it provides high thermal resistance and low conductivity, d) it is made of natural materials, and (e) it is prefabricated. The selective south façade (Figure 3) is a matrix of individually addressable windows, offering precise automated regulation of: a) airflow, (b) heat, (c) light / shade, and d) privacy / view. This reconfigurable skin operates as a mediator between private and public life. 2.1 RELATED WORK The connected sustainable home research [3] links advances in wood engineering, electrically activated materials, computational design, and AI building control. An overview of previous work in these fields that is related to the prototype, follows next. One research objective of the connected sustainable home was to test the applicability of an original engineering system using wood. The structural configuration of the building envelope was developed by CNR-Ivalsa (Trees and Timber Institute of National Research Council of Italy). The research of Ivalsa covers the technological development of wood engineering including earthquake-safe structures [4], design, construction, testing and maintenance of such structures [5], and the advancement of low energy buildings [6]. The structural system of the connected sustainable home consists of pre-assembled modules made of sustainable materials. Some of the experimental methods used in the prototype were firstly applied in the Modulo Abitativo Ivalsa (MAI), a modular prototype that was produced to determine and test the efficiency of natural materials [7] in building construction. Electrochromic technology was used on the south façade of the house. A number of papers describe the state of the art in this domain. For example, [8] describes a study in which the effects of electrochromic technology are monitored in a cube 3.0 m x 3.0 m x 3.0 m; [9] presents a technical comparison of data determining the physical features of electrochromic glass; [10] offers an overview on lighting and energy control systems. AI methods to building control were used in managing interior conditions, while taking into account uncertainty. The development of such methods has been pursued by computational sustainability research. For example, [11] employs the stochastic model-predictive control (SMPC) approach to reduce the energy

consumption of a building with stochastic occupancy model. The plan executive of the home is built upon the Iterative Risk Allocation algorithm [12] and a deterministic plan executive [13], [14]. The next sections present the architecture of the house. It is exposed how the house is configured: its structure, its materials, and its system of modularity and transportability. It is also discussed the association of its systems and their contribution to the energy performance. 3 A SMART BUILDING SYSTEM The arrangement of the prototype follows an open plan, organized in a system of 3 modules and 2 side elements. The interior was left open for future experiments related to sustainable living. At this stage, there is a provision for a living area, and a kitchen. The building combines wood, glass and steel. Fundamental principles of the building system are the modularity and transportability of its components. Components can be substituted when new technologies are available. This approach, together with the requirement of transportability, greatly affected the delineation of the structural details. A small overall footprint was favoured, to facilitate the transportation. Each module measures 2.3 m x 6 m (base) x 3.65 m (height). The overall net square footage is 11.60 m2.

Figure 4: A modular, transportable house of 3 modules and 2 side components (section up, and plan down).

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The conservative component engages the larger part of the structure, and it is made out of spruce wood from the Trentino forests. The selective component engages the south façade and it is made out of Fiberglas, electrochromic glass, common glass, and steel. The responsive component, involves a network of sensors and actuators, planted in the building envelope, and the control system of the house. The order of the exposition of each component follows the above sequence, but emphasis is given to the structural system. The regenerative component including the energy production apparatus, the heating and the HVAC systems is not presented here. 3.1 CONSERVATIVE COMPONENT The conservative component of the house uses a system of X-Lam panels for the load-bearing parts. The cross-laminated timber is a rigid yet lightweight product that meets industrial standards and it is sustainable. This structural system demonstrates how it is possible to use wood, a natural material, to build contemporary, prefabricated, high-tech structures, in a way that is more economical, light, and environment-friendly than conventional construction. The house modules were prefabricated at one location and transported to another location for assembly. Beyond modularity and transportability, a parallel consideration was to reduce the construction time and to ensure the efficiency of the assembly process. The envelope was partitioned in base modules and house modules (Figure 5). This division is followed in the order of this presentation. 3.1.1 Base modules The functional purpose of the base is to insulate, to conserve heat and to transfer the loads of the structure to the ground. The base is constructed as a sequence of transportable modules. Each base module functions as the foundation of a house module. The base modules are massive wooden containers, which are placed side by side. The base is composed out of 3 modules and 2 side components, just like the house. The void of the base is filled with insulating material (Figure 6). The modules are joined with threaded bars (Figure 7). Each threaded bar rests within a slot, which was specifically made during the production and cutting of the X-Lam panels. The structural material of the base is X-Lam panel of 174 mm thickness. The side components are exposed to the natural elements, and are constructed with Glulam GL28 class. The side components are connected to the X-Lam panels of the two extreme modules with hold-down elements (WKR type 285 and 9050 WVS, by Rothoblaas) and the tightening is made with screws of type HBS, by Rothoblaas. X-Lam panels of 51 mm thickness, cover all the parts of each base module and function as a support for the remaining structure (Figure 8). On the top of each base module, rests a house module, and on the overall base rests the whole house.

Figure 5: The structural part of a module is a system of X-Lam panels stiffened by laminated beams & connected to a metal frame through a Glulam reinforced beam.

Figure 6: The base is a structure of 3 modules on which rests the house. The interior void of the base is filled with insulating granular material.

Figure 7: The connection between the vertical and horizontal X-Lam panels happens with angular anchor metal brackets Rothoblaas. Cuts in the structure host the clamping elements between modules.

Figure 8: X-Lam panels of 51 mm thickness cover each base module and function as a support for the structure.

3.1.2 House modules Each house module is approached as a structurally independent, self-standing box, with its sides oriented towards north, south, east and west, respectively. Each box is open from south, west and east, and it is closed from north, top and bottom. For the structural components of each module (floor, north wall and roof) are used three X-Lam panels of different thickness. For the bottom structural panel, which rests on the base of the house, is used an X-Lam panel of 174 mm thickness. For the vertical structural panel, of the north wall, is used an X-Lam panel, of 135 mm thickness. For the structural panel of the roof, is used an X-Lam panel of 105 mm thickness. The north wall is further enforced by vertical elements in Glulam, 140 x 180 mm in section. Glulam is composed of several layers of dimensioned timber that is bonded together with durable, moisture-resistant adhesives. The Glulam is joined to the X-Lam panel with angular steel plates and hold-down. The X-Lam panels of the wall (135 mm in thickness), floor (174 mm in thickness), and roof (105 mm in thickness), are connected by means of metal angles, ringed annular-shacked nails and self-drilling screws. The thermal conservation features of the envelope are of paramount importance for the performance of the house. They are assured by a multilayered system of materials, where each layer serves a specific purpose. Figures 9 and 10, present a section of the vertical wall and the floor and roof of the prototype. In these Figures the layering of materials is numbered. The interior side of the vertical wall is covered with a double layer of fiber gypsum panels, (Figure 9, n. 8). This material improves the acoustic insulation and augments the collapse time, in case of fire. The air gap (Figure 9, n. 7) between the fiber gypsum slab and X-Lam panel (Figure 9, n. 6) improves the acoustic and thermal insulation, and provides space for hosting other components. In this air-gap, are hosted the electrical cable, the air pipes and the circuit boards managing the programmable façade. The next layer of materials includes a double sheet of insulating panels made of fiber wood (Figure 9, ns. 4, 5). Each of these sheets has different density. First the lower density panels (Figure 9, n. 5) improve the thermal insulation, and then the higher density panels (Figure 9, n. 4) improve the acoustic insulation. A breathable barrier film (Figure 10, n. 19 and Figure 9, n. 3) ensures the protection from the external humidity, while it remains permeable to air and humidity from the inside out. This film guarantees the natural transpiration of the wall and prevents the formation of interstitial condensation during the winter. The high thermal mass north wall is 72 cm in thickness to secure high-level heat transmission resistance (Figure 10, n. 16). The exterior layer of the wall is a cover of ventilated double board warping and larch trapezoidal cladding. The claddings are wood treated with Wood C, a product that accelerates the natural aging process of wood in a controlled fashion (Figure 11). The cover of the roof has the same insulation package with the wall. Above the ventilation chamber, is placed a wooden Osb panel on which is nailed a corrugated, pre-painted aluminum sheet (Figure 12).

Figure 9: Layering of materials of the floor and the wall.

Figure 10: Layering of materials of the roof and the wall.

Figure 11: The exterior is finished with a cover of ventilated double boards warping and larch trapezoidal cladding, treated with Wood C.

Figure 12: The corrugated aluminium plates of the roof.

This plate collects and brings the rainwater into the gutter. The roof cover is Larch wood treated with Wood C, similar to the external skin of the house. The roof tiles are spaced appropriately, to ensure the ventilation of the roof and the collection of the rainwater. Both the house wall and roof have a theoretical calculated value of U equal to 0.150 W / (m 2• K). The assembly of the X-Lam structure in the modular system was especially designed to make transportability possible. The structural requirements of transportability include the safe lifting of the individual modules and their maneuvering into a position. The system remains invisible and available to be reused every time the house is disassembled from a specific location, in order to be transported and reassembled into a different location. The lifting of the modules is secured by the insertion of threaded bars. The bars are inserted into the roof through four threaded holes and are attached to the X-Lam floor panel (Figure 13). The system was designed to follow the interior perimeter of the module, in order to facilitate the tiling of modules and to prevent the “blocking” of the boards at the contact points of adjacent modules. The threaded bars are inserted from above into the cover layers of each module, to avert undesirable discontinuities of the insulating coats and to prevent any infiltration of water, or thermal bridging. 3.2 SELECTIVE COMPONENT A programmable façade, incorporating operable, switchable windows, functions as the main selective component of the house. The south elevation of each module is covered with a 3 x 3 matrix of these windows. A structural grid, made of galvanized steel, holds the window frames and completes the structural system of the prototype. The dimension of the main section of the uprights is 50 x 150 x 4 mm. The connection between the metal frame and the wooden structure was made with metal plates bolted to the top X-Lam panel of the roof, and the base X-Lam panel of the floor (Figures 14, 15). For the upper structural element of the south elevation, it was used a beam of laminated wood. The beam was sectioned into parts, thus realizing a semi-joint. This beam accommodates a bar of post-tension in its lower part (Figure 14). The bar serves the task of stiffening the structure and counteracting the arc, which is generated by the loads of the structure and by the wind action on the solar panels, which are installed at the roof of the house, right above. For the window frames, it was used Fiberglass, by Rehau. Each windowpane is an overlay of two electronically switchable materials (Figure 16). The first layer, the electrochromic glass, is applied on the external glazing to provide the desirable degree of sunlight penetration, securing daylight and thermal performance. The electrochromic technology operates as an alternative to a traditional screening system. It allows light and heat transmittance (IJ) to vary from 60-75%, for idle glass, to 3-8% for active obscured glass.

Figure 13: Detail of the lifting system of threaded bars, in plan (up), and section (down).

Figure 14: The beam of laminated wood forming the upper structural component of the south elevation and the metallic frame on which the windows are attached.

Figure 15: The connection between the metal frame and the wooden structure was made with metal plates.

The second layer, the polymer dispersed liquid crystal film (PDLC), is applied on the internal glazing to provide the desirable degree of visibility, securing privacy. The windows admit natural light, heat, and air, or exclude any of the above as needed. The state of the programmable façade is directed by the central control system. But also, each window is driven by its own software and custom electronics that enable the activation of its switchable materials. Since the switchable materials have varying response times and exhibit different optical, thermal and power consumption characteristics, their activation processing is pre-planned. The slow dimming response of 8 minutes, of the electrochromic glass, is suitable for controlling sunlight and heat, while the instant transition of the PDLC film is useful for controlling shade and privacy (Figure 18). 3.3 RESPONSIVE COMPONENT This section briefly describes the responsive component of the house. The core component is a computer managing the states of the building materials, the temperature, the humidity and the daylight conditions at the house interior [14]. These environmental parameters are managed by a computer program, implemented in C++. Uncertainty in outdoor conditions is taken into account. The hardware hosting the controller is a standard computer with 8GB of RAM and Intel Core i7 processor. A Mini-ITX secures low energy profile during the operation of the controller. The controller allows the residents to specify desired ranges of room temperature as well as their time schedule. It executes plans with time-evolved goals, which are specified as a sequence of state and temporal constraints. Then, it optimally adjusts the operation of windows and the HVAC system, based on the interior conditions, so that the specified constraints are satisfied. While guaranteeing that the goals are achieved, the controller minimizes the use of energy consumption, from heating, cooling, lighting etc. Optimal plan execution is susceptible to risk when uncertainty is introduced. The house management involves a risk of failure to maintain the room conditions within a specified range due to unexpected weather changes. In the winter, when the residents are absent the energy consumption can be minimized by turning off heating. But, this involves a risk that the pipes may freeze. Such risks must be limited to acceptable levels specified by the residents. The plan executive guarantees that the system will operate within these bounds. Such constraints are called chance constraints. At any time, the schedule confines a temperature range to maintain over some time duration. In our tests, it was assumed that a resident could specify one of 3 ranges: Home, Asleep, and Away. In actuality, one is able to select any number of temperature ranges. In the experiments, it was assumed that the temperature must remain between 20° and 25° C while the resident was at Home, between 18° and 22° C while Asleep, and between 4° and 35° C while Away, to ensure that the pipes would not freeze.

Figure 16: Axonometric section. Each triple glazed windowpane has an overlay of two switchable materials: PDLC film (interior) and electrochromic glass (exterior).

Figure 17: A 3 x 3 matrix of operable windows. The window frames are made out of Fiberglass.

Figure 18:The overlay of window materials: (1) the electrochromic and the PDLC layers are inactive; (2) the electrochromic layer is innactive and the PDLC layer is active; (3) the electrochromic layer is active and the PDLC layer is innactive; (4) the electrochromic and the PDLC layers are active.

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Home and Asleep episodes, were associated to a single chance constraint class, with risk bound 10 %. This is the risk the resident is willing to take that the temperature may become uncomfortable. Away episodes were associated to a single chance constraint class with risk bound 0.01 %. This is the risk the resident is willing to take that the pipes may freeze. The building envelope is modelled within the controller with the aid of a stochastic plant model (Figure 19). An example of a resident schedule for a day is presented next. The schedule is described in plain English, as follows: "Maintain a comfortable sleeping temperature until I wake up. Then, maintain room temperature until I go to work. I may work at home, but I have to do 5 hours of work at the office sometime between 9 am and 6 pm. No temperature constraints while I am away. When I get home, maintain room temperature until I go to sleep. The probability of failure of these episodes must be less than 1%. The entire time, make sure the house doesn't get so cold that the pipes freeze. Limit the probability of such a failure to 0.01%." This schedule appears in Figure 20, in a graph structure called chance constrained qualitative state plan or CCQSP [14]. The graph represents the way the schedule is modelled in the controller.

Figure 19: The building envelope is modelled in the control system with the aid of a stochastic plant model.

Figure 20: An acylic directed graph depicting the resident's schedule in the planning example.

Figure 21: The current implementation of the prototype consists of 3 modules and 2 side components that can be easily moved from one site to another. The base is composed of equal number of modules.

Figure 22: Simulation depicting the incoming sunlight through the south facade in clear sky conditions in an average winter day, at 1 PM in Trento, Italy.

4 CONTRIBUTIONS Improving the energy efficiency of residential buildings is critical in addressing the global energy challenge. The connected sustainable home is a residential unit that combines a high thermal mass envelope, a programmable façade and an intelligent control system, to ensure comfortable interior conditions, at minimum energy cost. The house, a prototype of which is at the final stage of construction, in Trento (Trentino, N. Italy), is a lightweight, modular, and transportable structure that elegantly blends conservative and reconfigurable features, to provide a unique test-bed for exploring the future of sustainable ecosystems at a residential scale. The main contribution of the paper was to demonstrate how it is possible to use wood, to build a contemporary, prefabricated, high-tech structure for the connected home, in a way that is more economical, light, and environment-friendly than conventional construction. It was presented the architecture of the prototype, how the home is configured, the distribution of materials and its system of modularity and transportability. Further, it was discussed the association of the house systems and their contribution to the house performance. Conventional sustainable architecture engages high thermal capacity envelopes, combined with devices that selectively admit desirable elements from the exterior environment (glazed windows, louvered grilles, etc.) and systems that use power to regenerate favourable conditions (lighting, heating, cooling, etc.). The connected sustainable home employs a new mode of environmental management, to adjust the interior environment, "in response to" given conditions, in real time. The key to this new mode of management is fine-tuning of the house systems, to maintain a state constantly aligned to the comfort levels, at minimum expenditure. Hence, the connected sustainable home combines conservative, selective and responsive systems to minimize the use of regenerative systems. An intelligent control apparatus, allows the residents to specify desired ranges of indoor conditions, and maintains these conditions automatically. Uncertainty factors in weather and occupancy patterns, posing a risk of failure to keep the environment within the specified range, are explicitly addressed by the control system. The prototype follows an open plan, and it is organized in a modular system (Figure 21). The house modules can be disassembled, transported, and quickly assembled in a new location. Determining an architecture that allows maximizing the thermal and light gains without restricting the openness of the design was a central consideration. Computer simulation pointed towards optimum strategies of orientation, material selection and distribution. A parallel consideration was to reduce the construction time and to ensure the efficiency of the assembly process. The requirements of modularity and transportability, greatly affected the way the structural details were delineated. Transportability requires the safe lifting of the modules and their maneuvering into a position. The lifting of the modules was secured by the insertion of threaded bars that were inserted into the roof.

The transportability system was designed to be reusable every time the house is moved into a new location. A small home footprint was favoured, to facilitate the transportation in the narrow streets of the European cities. Each module measures 2.3 m x 6 m (base) x 3.65 m (height). The overall net square footage is 11.60 m2. The conservative system of the house engages the larger part of the base and the structural elements, using X-Lam panels for the load-bearing parts. The cross-laminated timber (X-Lam) is a rigid, lightweight industrial material that it is natural and sustainable. The modular base of the house insulates, conserves heat, and transfers the loads of the structure to the ground. Three different types of X-Lam panels were used in the structural part of the house modules. For the structural panel of the floor, it was used X-Lam panel of 174 mm thickness. For the structural panel of the north wall, it was used X-Lam panel of 135 mm thickness. For the structural panel of the roof, it was used X-Lam panel, of 105 mm thickness. The X-Lam panels of each module were connected with metal angles, ringed annular-shacked nails and self-drilling screws. The north wall was enforced with Glulam, 140 x 180 mm, joined to the X-Lam with angular steel plates and hold-down. The thermal conservation and insulation features of the envelope were ensured by a multilayered system of natural materials. The interior side of walls was covered with a double layer of fiber gypsum panels, improving the acoustic insulation and delaying the disintegration from fire. An air gap between the fiber gypsum panels and the X-Lam panels improves insulation, and provides space for electrical cables and air pipes. A double layer of fiber wood panels of different density was used to improve thermal and acoustic insulation. Finally, a breathable barrier film was applied to offer protection from the external air and humidity, while it is permeable from the inside out. The complete high thermal mass north wall is 72 cm in thickness securing high-level heat transmission resistance. The exterior layer of the wall is covered with ventilated double board warping and larch trapezoidal cladding. The roof of the house has the same insulation package with the wall, while the roof cover was made of Larch wood, similar to the external skin of the house. The selective system of the house engages the south façade. A structural grid made of galvanized steel, holds the window frames in place and completes the structural system. The connection between the metal frame and the wooden structure is made with metal plates bolted to the X-Lam panels of the roof, and floor. The window frames are made with light, reinforced Fiberglass. Each triple-glazed windowpane involves an overlay of two electronically switchable materials. The first layer, the electrochromic glass, provides the desirable degree of sunlight penetration. The second layer, the polymer dispersed liquid crystal film (PDLC), supplies the desirable degree of visibility. The house systems operate in a concerted manner to attain complementary objectives. The electrochromic glass of the south façade permits the regulation of the incoming natural light and heat by enabling the programming of the chromatism and transmittance value

of each windowpane. The windowpanes are managed by the control system, which compiles real time feedback to activate the electrochromic material, as needed, in order to exploit the thermal capacity of the building envelope. For example, in order to expose the house interior to the warmth of the winter sun, the control system would set the south façade to its maximum thermal transmittance, thus allowing the storage of sun-heat in the home’s high thermal mass walls and base (Figure 22). Hence, the sun would be used to maintain comfortable conditions with minimum use of the heating system. Fundamental challenge of the connected sustainable home was to propagate the evolution of an exemplary home living experience, through connectivity and building innovation. The prototype optimizes energy performance, automates climate control, and encourages ecologically responsible behavior. But furthermore, it introduces a consistent building philosophy: i) Modular design, at every scale. ii) Efficient assembly; disassembly; transportability. iii) Thorough material selection; distribution. iv) Efficient combination of conservative, selective and responsive modes of management. v) Real-time performance evaluation; user feedback. vi) Mathematical simulation risk and uncertainty modelling of performance. vii) Performance driven design, in view of aesthetic, social, and cultural effects. Beyond the capacity to minimize energy consumption, sustainability is about establishing consistent building principles. This mirrors our view that sustainability does not happen in a vacuum, it happens by design. Using natural solutions, which require less energy to be produced, and which enhance the local economy, is consistent to sustainability. The building system of the connected home is both generic and specific. It is generic in that it demonstrates a concept. The ideas driving the design are conceived as generic methods to achieve sustainability, in any building. But, it is also specific, because its context is present, wedded inexorably to the location and the culture of the place. The selection of wood for the implementation of the connected home, turns it into a superb design experiment on customized sustainability. The wood is a renewable resource produced in the forests of Trentino, adding value to the local forest and boosting the economy. The building system used for the house, makes it possible to construct dwellings in a controlled manner, in the factory. These structures can be constructed in modules, with all their technological systems in place, and can be transported for assembly. This process can allow for flexible and elegant residential arrangements to emerge, where building components can be substituted, or upgraded, whenever improvements become available. Building innovation can allow for single houses, or entire villages, to get built fast and safe, like cars. ACKNOWLEDGEMENT This research was conducted within the Green Connected Home Alliance between the Mobile Experience Lab, at the Massachusetts Institute of

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