MAI, IVALSA MODULAR HOUSE

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1 MAI, IVALSA MODULAR HOUSE Andrea Briani 1, Paolo Simeone 1 and Ario Ceccotti 1 ABSTRACT: MAI-Ivalsa Modular House is an environmentally sustainable system of pre-fabricated housing modules with structural technology based on X-lam solid timber panels and hence is made with renewable materials. A new technological system is being investigated in this project that can use re-used X-lam for the load-bearing structure and that can be prefabricated at one site and successfully transported to another. KEYWORDS: X-lam, cross-laminated timber, CLT, modularity, transportability, prefabrication, recyclability, re-using of wood, energy efficiency 1 INTRODUCTION 1 The MAI-Ivalsa Modular House was designed by the architectural design team of Ivalsa-Trees and Timber Institute in The goals of the project were to design and build a small wooden prototype house that can be built and prefabricated in a controlled area, easy transported by truck (or train or helicopter) to the final destination and finally assembled to form a real house in few hours. The prototype, when leaving the production area, is ready to assemble and use: the heating-ventilationairconditioning system, electric installation, plumbing, interior finishing, lights, appliances and furniture are already installed. All the construction phases in the production area are organized to reduce the waste of materials, control air and water pollution, and achieve a highly efficient building process with respect to the environment and the workers. each other to form a real house was investigated and a good layout from an architectural point of view was achieved. The final prototype s layout consists of an assemblage of 5 transportable modules each module 2,9 m x 4 m (base) x 3,9 m or 3,2 m (height) to form a small wooden house 36 square meters (floor area) with 2 bedrooms, 1 kitchen, 1 bathroom, 1 living room and 2 terraces. [1] Defined by the shape of parallelepides, the final composition of the five modules is a simple and clear architecture that makes maximum use of the space. Looking at the plan (Figure 1), from a rectangular small terrace the door of the main entrance leads into a square access corridor the biggest free floor area of the prototype! where there are further accesses to the two bedrooms (4,8 square meters each), the bathroom (3,6 square meters), and the corridor to the kitchen (4,4 square meters) and the living room (5,9 square meters). 2 DESIGN The overall design took 2 months from the first ideas to the executive drawings. The first requirement that guided the design team was to define the right size of the largest module, as big as possible, to be transported by truck without any extra special permission under European law. At the end the overall dimensions were fixed: 2.9 m (width) x 4.0 m (length) and 3.9 m (height). Starting from these dimensions, a series of hypothesis for a system of single modules ready to assembly one to 1 Cnr-Ivalsa, Trees and Timber Institute-National Research Council of Italy, via Biasi S. Michele all Adige (Trento), Italy. simeone@ivalsa.cnr.it Figure 1: MAI floor plan.

2 At the end of the corridor, a full-height window (placed exactly in front of the door s main entrance) and one large French window light up the living room and the corridor, giving the pleasant sensation of being in a house bigger than the reality. The French window connects the inside to the big square terrace (12 square meters), extending the living room space to the outside. The natural light inside the prototype one of the most important aspect that guided the architectural design of Ivalsa Modular House was given considerable attention. In the small living room, sunlight can filter through the two windows and one big skylight, ensuring powerful natural lighting; in contrast in the bedroom module two small windows, one for each bed, let the sunlight pass through to provide soft lighting inside and to frame the view to the ouside. (Figure 2) Figure 3: External view of the terrace, living room and bedroom. 3 CONSTRUCTION SYSTEM Each module consists of a box of re-used X-lam panels which is extremely rigid yet lightweight. (Figure 4) The X-lam panels floor, walls and roof are connected by means of metal angles and hold-down connectors, self-drilling screws and ringed annular shanked nails. To be specific, steel angles ,2 mm (fixed with partial nailing), hold-down anchors mm (fixed with partial nailing and M16 anchor bolts), HBS wood screws 8 80, , mm and 4/60 ringed annular nails were used to joint the MAI s crosslaminated panels together [2]. Figure 2: MAI bedroom/kitchen section (AA) and living room section (BB). From outside (Figure 3), the MAI appears as a unique house generated by the union of two different houses: the bigger light coloured one with the plastered white walls and the ventilated double-pitched roof made of wood (and copper), and the smaller dark coloured one with the ventilated wooden facade and the flat green roof. Deducing the modular system of 5 transportable modules assembled together is not straightforward! Finally, the bathroom module is the real motor of the house in which a small technical room with its independent access (a door, near the main entrance, made of the wooden planks discarded from the production of the roof and the façades) was included without sacrificing the bathroom s floor area. Figure 4: The 5 modules made of re-used X-lam panels. The MAI construction system observes the Regulations for design, construction, inspection and maintenance [3] set up by Ivalsa-Trees and Timber Institute with the research project SOFIE (The SOFIE- Construction System Fiemme project on sustainable buildings was carried out by Ivalsa with the support of Provincia Autonoma di Trento with the scope to define the performance and the potential of a construction system for multi-storey buildings whose load-bearing elements are massive wooden X-lam panels, made of certified timber from the Trentino region) and is characterised by low energy demand, high levels of fire safety and sound absorption, high earthquake resistance and durability. (Figure 5)

3 Figure 5: The mechanical connections scheme. Adopting the SOFIE technical regulations, MAI s modules can resist the shaking stress produced by the moving, the transport and the assembly, and can keep their geometry unaltered without any breaking of windows, finishing, furniture, etc. With MAI first prototype 2010, the team tested these stressful mechanical conditions for the structure and in general for all the components and materials included. After two complete disassemble-moving-transportmoving-assemble cycles, the prototype was undamaged and only for the plaster were minimal repairs made done. 3.1 ASSEMBLAGE The 5 modules completely equipped with all service installations and furniture, and ready to be transported can be quickly assembled to the others by a system of simple steel connections exclusively designed for MAI. (Figure 6) Figure 7: The mechanical connection between modules using red steel plates with bolts. 4 TRANSPORTABILITY For the transportability of the prototype it was necessary to define the system for moving the modules from the production area to the truck, for unloading them from the truck to the site where the prototype must be assembled and for drawing a module near the next one to fix them together. For MAI first prototype 2010 a lifting method was chosen: each high rigid module made of X-lam panels was designed to be lifted by a Manitou with telescopic handlers and 8000 kg of lifting capacity. The external side of the module was prepared to resist the contact of Manitou s forks without any structural damage or breakage. (Figure 8) Figure 6: The mechanical connections scheme. For each module s side that must be connected to another module s side, 3 points of connection 2 included in the wall and 1 in the base assured the fixing between modules. (Figure 7) Figure 8: The lifting method employed to lift and move the 5 modules from the Ivalsa laboratory to the truck.

4 4.1 BUILDING SERVICES A particular plug-in system (Figure 9) for the HVAC, the plumbing and the electric wires was devised to assure the assemblage of the prefabricated modules to easily and quickly form a real house ready to be lived in. Cold/hot water tubes (for domestic water and the heating system), electricity (for lights, domotics and appliances) and air pipes (for the ventilation/airconditioning system) included in each module can be easily connected to the others to ensure all the systems are working. Figure 10: Construction phases for the MAI X-lam loadbearing structures in the Ivalsa open laboratory. Figure 9: The floor plug-in system for the building services, before and after the closing of the floor. 4.2 COVERED SLOTS On the prototype s floor, wood-plank-covered slots hide the points of connection of all building systems and allow easy access to them while, on the walls, red steel plates with bolts were left visible to show the system for the mechanical connection between modules. Close to the steel basement a specific area for the recyclable-waste collection was prearranged to control and divide all the waste products generated during the construction phases. At the end of the first day of construction, the X-lam boxes of the 5 modules were set up and after 5 days the wooden structures were completely fitted with the entire connection system. For about 12 days, the staff worked inside and outside the modules simultaneously for a more efficient and fast building process. Inside, the HVAC system, the plumbing, the electric installation, the home automation (domotics) technology and, outside, the wood fiber boards for walls and roofs and for thermal and acoustic insulation was installed. (Figure 11) 5 PRODUCTION AND CONSTRUCTION TIME Only 29 days were required to build the prototype, move it by truck 40 km from the Ivalsa laboratories to Rovereto city for an exhibition and make the set up for the opening (during the official opening the prototype was ready to be lived in with water in the kitchen and the bathroom, heating-ventilation air conditioning system on, etc). In a open laboratory of Ivalsa where a steel basement used for SOFIE tests was put on grass the construction site was organized. All 5 modules that comprise the prototype were prepared on the steel basement in a disassembled configuration and built separately to enable staff and workers to work efficiently. (Figure 10) Figure 11: Construction phases inside/outside the modules. Another 7 days were necessary to build the ventilated roof, to plaster 3 modules walls, to build 2 modules exterior wooden façade, to put down the floors, to put on the inside walls and to mount the windows and the doors.

5 The last 3 days were spent finishing the interior finishing, furnishing the rooms with MAI-specialdesigned furniture and checking the technological and mechanical system for the modules assembly and moving. On 27 th day of construction, the 5 modules were completely finished and ready to be moved and transported. A truck with a 8.5 m flatbed trailer was used to transport 2 modules at once. (Figure 12) Figure 12: Transport of the kitchen and living room modules. 6 RE-USED X-LAM PANELS For this project, the team wanted to test the re-use of X- lam panels: the panels had been used for the construction of a 24-meter-high SOFIE 7-story building. (Figure 13) After the Japanese tests, all the X-lam panels were shipped to Ivalsa and since January 2008 they had been placed in the large square outdoor laboratories and simply sheltered. The natural weathering was only partially prevented and some panels were exposed to water and UV light. After more than 2 years, in May 2010, the team analyzed them and devised a moisture content measurement to determine if the wood would be usable for structural use in the MAI prototype. The goal was to re-use the maximum number of X-lam panels to make the Modular House as sustainable as possible. The original size of used X-lam panels was: 2.95 m (height), m (length) and 85/125/130/142/160 mm (thickness). The selection of the best used X-lam panels was done considering at least 2 important aspects: the quality of wood (moisture content had to be less than 20%, no major breakes and a good state of the glue between the layers of planks), the original size compared with the new size required for walls floors and roofs of MAI 5 modules. Finally 85/130/160 mm thick panels were chosen and then trimmed to remove the deteriorated parts near the edge where wood was much wetter. Grey stains on the external surface of the X-lam panels were examined: discoloration by weathering and sapstain were present, both of them well known as chromatic alterations which do not reduce the mechanical properties of wood and therefore permitted without limitations by all strength grading rules. (Figure 14) The cutting of the used X-lam panels to the new dimensions for the MAI prototype was done by a handheld circular saw and a chainsaw. Cutting through CNC machineries was absolutely not effective in this project. Figure 13: The MAI load-bearing structures built with the re-used SOFIE 7-story building s X-lam panels. The SOFIE building was constructed in 2007 on the NIED-National Institute for Earth Science and Disaster Prevention s Monster shaking table in Miki (Kobe) Japan where Ivalsa tested the seismic behaviour of a multi-storey building made of X-lam. After more than 10 consecutive tests (the magnitude Kobe earthquake included), no significant damage was recorded on the building. The structure was never altered, as it returned to its original position each time. [4] Figure 14: The grey stains on the external surface of the re-used X-lam panels. 7 ENERGY EFFICENCY AND SUSTAINABLE MATERIALS 7.1 ACOUSTIC AND THERMAL INSULTATION Wood fibre boards with different densities for thermal and acoustic insulation both on external and internal sides of the X-lam load-bearing structure were used in

6 the MAI prototype to secure an especially high-level heat transmission resistance with a maximum level of recyclability of the building components. To design the envelope and its insulation system SOFIE technical Regulations were considered. An appropriate combination of thickness and physical properties was chosen for the wood fibre boards in order to ensure a high-level heat transmission resistance and obtain a high thermal mass envelope. The stratigraphy of the external walls (378 mm thick) of the living room module, for example, from inside to outside consists of 6 elements (Figure 15): chalk fibre board (thickness 12,5 mm); high-density wood fibre insulation boards (thickness 60 mm, density 230 kg/m 3, thermal conductivity 0,047 W/(m K), thermal capacity 2100 J/(kg K)); X-lam panel (thickness 125 mm); low-density wood fibre insulation boards (thickness 100 mm, density 50 kg/m 3, thermal conductivity 0,038 W/(m K), thermal capacity 2100 J/(kg K)); high-density wood fibre insulation boards (thickness 60 mm, density 230 kg/m 3, thermal conductivity 0,047 W(m/K), thermal capacity 2100 J/(kg K)); hydraulic lime plaster (thickness 2 mm). ensure the waterproofing of the roof system and to prevent any possible infiltration of water or passage of moisture from wet vegetation to X-lam load-bearing structure. [5] A Blower Door Test was carried out to measure the airtightness and physically locate air leakage sites in the prototype. A blower-door fan was temporarily sealed into the exterior doorway to blow air into or out of the building (windows were closed and interior doors opened) to create a positive/negative pressure differential between inside and outside. Using a portable thermal hot-wire anemometer (with digital display and flexible telescopic probe) airflow velocity and temperature were measured to control the efficiency of the floor airtight access covers and the isolation system between connected modules. (Figure 16) Figure 16: The airflow velocity and temperature measurements on the floor inside the prototype. Figure 15: The stratigraphy of the living room module s external walls The calculated U-value for heat transmission resistance of the wall is 0,156 W/m 2 K and the calculated φ phase displacement (the span of time, hours, needed by a temperature wave to travel from the exterior side of a construction part to its interior side) is 12,4 hours. The same stratigraphy was adopted for the roof of bathroom, kitchen and living room where a ventilated roof system was fixed on top with a breathable waterproof and UV resistant underlay interposed. Using a breathable waterproof and UV resistant underlay was ideal for MAI waterproofing walls and roofs with open and ventilated façades and also necessary for the durability of the entire prototype: this membrane in fact is highly breathable to allow water vapour diffusion from inside to outside so to prevent water vapour condensation in the different layers of the walls and roof. In the two bedroom modules with green roofs on top XPS (Extruded Polystyrene Foam) panels were used instead of the external layers of wood fibre boards to Thanks to its natural origin and properties moisture regulator plus excellent durability Kenaf Band (natural Deccan Hemp in strips) was used to isolate the mechanical connections between modules by strips directly fixed on the X-lam panels exterior sides. PU foam was used inside the floor covered slots in which air tubes, heating tubes and electrical wires of each module were jointed to the next module s ones to fill the air gaps in junctions between the structure s halls and tubes. The efficency of both the isolation system for the modules connections and building services covered slots on the floor was verified by Blower Door Test. 7.2 EXTERNAL TREATMENT Special natural treatment on wood surfaces and special thermally modified wood both tested in the Ivalsa laboratory were used in the external façade of MAI prototype to test new solutions for limiting the aging of timber elements for external uses. For the external treatment of the bedroom modules ventilated façades a natural paint called Legno-C made of acetic acid was tested on the wooden planks. The team was conscious that, in general, proper design in details and the choice of good quality wood species could assure the durability of a wooden façade in an economical and intelligent way. So the team proposed the Legno-C treatment for one fundamental reason: solving the natural and inevitable discoloration of wood under the natural wheathering. (Figure 17)

7 Inside the two bedrooms, the team decided to keep the re-used X-lam walls and roof visible so that all the scratches from the original Japanese Tests could been seen in order to demonstrate that re-using of X-lam panels for structural purposes in a new building is possible. Figure 17: The bedroom modules ventilated façades with Legno-C treatment. Legno-C infact accelerates the natural aging process of a wood surface and gives it in just a few hours, a "patina" equal to what would be obtained only after many years of exposure. The dark color of the larch planks hadn t changed after 2 and half years of natural wheathering. For kitchen and livingroom modules roof planks (22 mm thick) made of red spruce (Picea abies) and white fir (Abies alba) with special thermal modification ( C) were used. [6] Since September 2010 durability, dimensional stability and discoloration have been tested by Ivalsa researchers and the results will be presented in an official conference this year. 7.3 INTERIOR Going inside the prototype (Figure 18), the internal finishing of walls made of chalk fibre board was used for better thermal insulation and especially for the fire resistance of the X-lam structure and the entire prototype. (A full-scale natural fire test carried out by Ivalsa at the Building Research Institute in Tsukuba in 2007 demonstrated that by protecting the timber structure with non-combustible chalk fibre board the damage of the Xlam solid timber panels is not significant after 60 minutes of fire!). [7] 7.4 FLOOR For the floor, another environmentally friendly material was used: linoleum produced from natural renewable materials. The top layer of linoleum called Marmoleum Click made of natural linseed oil mixed with wood flour, resin and limestone, and bonded to HDF core material (structural element) with a backing of cork and machined with a mechanical locking system was installed without any need of glue directly to the under-floor heating system on the modules base. The high-thermal mass base s stratigraphy consists of (from bottom to top): re-used X-lam panels (160 mm thick) for the load-bearing structure, low-density wood fibre insulation boards (thickness 80 mm, density 50 kg/m 3 ), extra high-density wood fibre insulation boards (thickness 14 mm, density 500 kg/m 3 ), polystyrene boards (thickness 40 mm) with polyethylene tubes and top layer Marmoleum Click (10 mm thickness). 7.5 FURNITURE All the furniture specially designed for each module by the team is completly made of massive panels of 3- layers of larch wood (19 mm thick) laminated on both the external surfaces with PaperStone a special material made from FSC-certified 100% post-consumer recycled paper saturated with petro-free phenolic resins (containing ingredients like cashew nut shell liquid) and selected natural pigments. PaperStone was used in the prototype not only for its eco-friendly properties but especially for its good fire performance: class A fire and smoke rating, and heat resistant to 180 C. (Figure 19) Figure 19: Interior views of the kitchen, the living room from the corridor and the bedroom. Figure 18: Internal finishing of the living room walls. 7.6 ENERGY PRODUCTION For solar energy production, a new sustainable energy solution was tested in the prototype. On the roof of the bathroom module, the innovative integrated radiationabsorbing roof system TECU Solar System

8 constructed entirely in natural green patinated copper sheets was installed instead of thermal modified planks. (Figure 20) The integrated and hidden (by the copper sheets) solar thermal collectors were connected to the main heat pump system located in the same module to supply hot water. ACKNOWLEDGEMENT The MAI-Ivalsa Modular House is a research project carried out by Cnr-Ivalsa Trees and Timber Institute with the support of Provincia Autonoma di Trento, Ceii Trentino and Habitech. The prototype an important outcome of public/private collaboration has been invented and planned by CNR- Ivalsa architectural design team Andrea Briani and Paolo Simeone under the supervision of Prof. Ario Ceccotti and built by 13 Trentino-based handicraft companies associated with the wooden housing industry, under Ivalsa s supervision. The authors would like to thank all the members of staff of Ivalsa and, in particular, the staff of the Mechanical Testing Laboratory, the Laboratory of Wood Drying and Thermal Treatment, the Windows and Curtain Walls Laboratory and the Fire Laboratories for their precious participation in this project. Picture credits: Romano Magrone (Trento, Italy). Figure 20: External view of the prototype during the assembly phases of the 5 modules. In the bathroom module s roof (the green one) an integrated radiationabsorbing roof system TECU Solar System is installed. Inside a small technical room (about 1,3 m 3 ) included in the bathroom module, with its independent access from outside a 200 litre boiler and high efficiency heat pump was installed to distribute produced heat (hot water) at a low temperature to the underfloor heating in every room in the prototype. A small AHU (Air Handling Unit) for controlled mechanical ventilation was also included in the same module inside the false ceiling to condition and circulate air inside the rooms assuring high-level indoor environmental comfort. 8 CONCLUSIONS The MAI-Ivalsa Modular House demonstrates that it is not just possible but advantageous to use wood for modern prefabricated, transportable and sustainable buildings and, at the same time, employ re-used X-lam for the load-bearing structures. Using this first MAI prototype as a starting part, CNR- Ivalsa is now developing a potentially major innovation: a new construction system based on wood (from FSC and PEFC certified forests) that can be used in the design of small houses, but also multi-story buildings with different plans and sizes. The new system will entail significantly reduced costs, shorter construction phases and less pollution than incurred for a conventional construction system. Furthermore, it will do so while respecting the environment. REFERENCES [1] Ceccotti, Ario; Simeone, Paolo; Briani, Andrea; MAI-IVALSA Modular House Meets MIT-Mobile Experience Lab, in Proceedings of Smart Sustainability 2010, MIT Mobile Experience Lab Publishing, Cambridge (USA), 2010, pp [2] Ceccotti, Ario; New Technologies for Construction of Medium-Rise Buildings in Seismic Regions: The XLAM Case, Structural Engineering International, 2/2008. [3] Ceccotti, Ario; Bonamini, Gabriele (a cura di); CNR-Ivalsa, SOFIE-Sistema Costruttivo Fiemme. Relazione scientifica finale. Disciplinare di progettazione, costruzione, collaudo e manutenzione, Trento, [ [4] Okabe, Minor; Ceccotti, Ario; Yasumura Motoi; Minowa Chikahiro; Kawai Naohito; Sandhaas Carmen Sandhaas; Shimizu Hidemaru; Comparison with Measuring Method of Internal Story Drift on Shaking Table Test of 7 story X- LAM Building, in WCTE 2010 World Conference on Timber Engineering Proceedings, Riva del Garda (Trentino-Italy), June 20-24, [5] Benedetti, Cristina (a cura di); Costruire in legno. Edifici a basso consumo energetico, Bolzano University Press, Bolzano, [6] Allegretti, Ottaviano; Ferrari, Silvia; Uetimane Junior, Ernesto; Terziev, Nasko; Experimental study of thermal treatment in variable pressure conditions, in 11th International IUFRO Wood Drying Conference Proceedings, Skellefteå (Sweden), [7] Frangi, Andrea; Bochicchio, Giovanna; Ceccotti, Ario; Lauriola, Marco Pio; Natural Full-Scale Fire Test on a 3 Storey XLam Timber Building, in WCTE 2008 World Conference on Timber Engineering Proceedings, Miyazaki (Japan), June 2-5, 2008.