SESSION38,ARCHITECTURALTECHNICALISSUES2
Auckland New Zealand
15 - 19 July 2012
World Conference on T imber Engineering
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
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.
270
Auckland New Zealand
15 - 19 July 2012
World Conference on T imber Engineering
SESSION38,ARCHITECTURALTECHNICALISSUES2
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 energyintensive, 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.
271
SESSION38,ARCHITECTURALTECHNICALISSUES2
Auckland New Zealand
15 - 19 July 2012
World Conference on T imber Engineering
S
N
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 preassembled 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).
272
Auckland New Zealand
15 - 19 July 2012
World Conference on T imber Engineering
SESSION38,ARCHITECTURALTECHNICALISSUES2
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 XLam 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.
273
SESSION38,ARCHITECTURALTECHNICALISSUES2
Auckland New Zealand
15 - 19 July 2012
World Conference on T imber Engineering
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 XLam 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 highlevel 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, prepainted 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.
274
Auckland New Zealand
15 - 19 July 2012
World Conference on T imber Engineering
SESSION38,ARCHITECTURALTECHNICALISSUES2
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 (τ) 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.
275
SESSION38,ARCHITECTURALTECHNICALISSUES2
Auckland New Zealand
15 - 19 July 2012
World Conference on T imber Engineering
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.
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.
Optimal plan execution is susceptible to risk when
3
1
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
4
2
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 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.
276
Auckland New Zealand
15 - 19 July 2012
World Conference on T imber Engineering
SESSION38,ARCHITECTURALTECHNICALISSUES2
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.
277
SESSION38,ARCHITECTURALTECHNICALISSUES2
Auckland New Zealand
15 - 19 July 2012
World Conference on T imber Engineering
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
278
Auckland New Zealand
15 - 19 July 2012
World Conference on T imber Engineering
SESSION38,ARCHITECTURALTECHNICALISSUES2
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
Technology and the Fondazione Bruno Kessler in
Trento, Italy.
REFERENCES
[1] Alberti L. B.: On the Art of Building in Ten Books.
Rykwert J. Book V, p. 148. The MIT Press, 1991.
[2] Banham R.: The Architecture of the Well-Tempered
Environments. The Architectural Press, London,
1969.
[3] Kotsopoulos S, Cara, G, Graybill W, Casalegno F, 2012, “The dynamic façade pattern grammar ”,
Massachusetts Institute of Technology, (in review).
[4] Ceccotti, A.: “New Technologies for Construction of Medium-Rise Buildings in Seismic Regions: The
XLAM Case”. In Structural Engineering International,2/2008.
[5] Ceccotti A., Bonamini G. (editor): “CNR-Ivalsa, SOFIE-Sistema Costruttivo Fiemme. Relazione
scientifica finale. Disciplinare di progettazione,
costruzione, collaudo e manutenzione”,Trento,2008.
[http://www.progettosofie.it/]
[6] Benedetti, Cristina; Timber Buildings. Low-Energy
Constructions, Bolzano University Press, Bolzano,
2009
[7] Cecoti A., Simeone P., Briani A., MAI-IVALSA Modular House, Proceedings of
2010, pp. 70-75.
Smart Sustainability
[8] Lee, E. S., Di Bartolomeo D. L., Klems J. H.,
Yazdanian M. and Selkowitz S. E., 2006, “Monitored energy performance or electrochromic windows
for daylighting and visual comfort”, ASHRAE Summer Meeting, Quebec City, Canada.
[9] Hausler T., Fischer U., Rottmann M. and Heckner K. H., 2003, “Solar optical properties and daylight
potential of electrochromic windows, International Lighting and Colour Conference, Capetown.
[10] Selkowitz S., Aschehoug O. and Lee E. S., 2003, “Advanced interactive facades – critical elements
for future buildings?”, presented at USGBC expo.
[11] Mady A. E. D., Provan G. M., Ryan C., and Brown
K. N., 2011. "Stochastic model predictive controller for the integration of building use", Proceedings of
Twenty-Fifth AAAI Conference on Artificial Intelligence (AAAI-11), Special Track on Computational
Sustainability and AI.
[12] Ono M., and Williams B. C., 2008, "An efficient motion planning algorithm for stochastic dynamic
systems with constraints on probability of failure", Proceedings of the Twenty-Third AAAI Conference on
Artificial Intelligence (AAAI-08).
[13] Leaute T., and Williams B. C., 2005, "Coordinating agile systems through the model-based execution
of temporal plans", Proceedings of the Twentieth
National Conference on Artificial Intelligence.
[14] Graybill W., 2012, Robust, Goal-Directed Planning and Plan Recognition for the Sustainable Control
of Homes. Master's Thesis, Massachusetts Institute of Technology.
279