LCA of Flexible Indoor Spatial Structure Systems

Emissions as Design Drivers

LCA of Flexible Indoor Spatial Structure Systems

NTNU_s/s18_AAR4817

Case Study of Student Housing

Theory Report by Marija Katrina Dambe

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ABSTRACT The recent rapid population growth together with change of overall society behavior towards increased levels of temporariness and short term functions affects as well the built environment. More and more often building life cycle is cut off due to no longer answering the needs of the users and new structures are built in its place. Such trends in the building industry cause as well increased greenhouse gas emissions and contribute towards global warming. In order to reduce the environmental impact from building sector, new ways to deal with the needs of society are needed to be searched.

With a view towards student housing development, large potential of experimentation and emission reduction lies especially in the use schedules of the building. Student accommodation like no other residential building type has the character of vacant periods. This study focuses on the potential development of a student housing unit that disappears during the empty use periods and can give place for a different function.

The study is done with help of historical research and material Life Cycle Assessment to propose a possible flexible unit with reduced Global Warming Potential and satisfactory performance in categories that affect the life quality such as sound insulation.

INTRODUCTION The relationship between architecture and sustainability has been often misunderstood as one of purely technical matter. What is not stressed enough are the social as well spatial aspects sustainability should deal with. Although the United Nations Sustainable Development Goals (UN, 2015) discuss and suggest the importance of sustainability in all of the meanings of the term, they are not legally binding and the translation of the guidelines in regulations and laws is reduced to the numbers of energy efficiency without connection towards social issues as well as architectural qualities of the built environment. The current growth of world population which is expected to reach 9.7 billion by 2050 (UN, 2015) requires strong architectural solutions in spatial organization.

Therefore architecture has to become one that is a step ahead of the social development and can suggest efficient, aesthetic and overall holistic ways to deal with sustainability and built environment.

Furthermore, a person no longer is a static inhabitant and commuter who can be satisfied with single type of static architecture.

“The arrival of new dynamics in social and working life contributes to the growing phenomenon of transitional living and the temporariness of architecture.” (Bologna, 2004)

Additionally, the strict lines between space and time have blurred and the effect can be seen both in social as well private life. This also affects the spatial requirements of an individual. The definition of private and public space can be questioned.

“What are people doing when, after sending emailing, texting, Skyping, and calling for seven hours from their private rooms, they go out on the street without their phones? Are they leaving their private spheres and entering public space, or is it the other way around? The terms to describe inside and outside, private and public, are eroding.” (Maak, 2015) How such changes in the society affect architecture? As well, how architects can help to accommodate the new type of society? “[...] Peter Buchanan’s recommendations in his study Ten Shades of Green: Architecture and the Natural World (200-2005) have a markedly cultural character, such as his advocacy of building according to the anti-ergonomic principle of ‘long life/loose fit’. This precept was naturally integral to the load-bearing masonry structures of the past, bequeathing us a legacy of eminently adaptable buildings, mostly dating from the 18th and 19th centuries, many of which we have been able to put to new uses. Such residual value is more

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difficult to achieve today on account of our standards of minimal space and our commitment to the paradoxically inflexible lightweight building techniques of our time.” (Frampton 2007: 362) In contrast to the past, when large, loose open structures allowed different uses of building during its lifetime, today, to prolong the life of a building, the space as well as structure must allow various mixed use constellations within the same compact spatial dimensions. Moreover, the need to house different functions does not appear only in long term perspective but rather on daily basis. Simultaneously existing functions within the same space, allowing the user to shift them according to the needs.

Several studies have dealt with the topic of spatial flexibility on the levels of architecture theory, spatial and structural questions as well as materiality. Though not many have tried to combine all in order to develop a functional research outcome. Therefore, the aim is to look closely at researches that have dealt with with the separate aspects deeply and further on develop a spatial unit that deals with different levels of the topics.

In a study from TU Delft “Permanent Temporality” (Hilhorst, 2013) the questions of flexible building refurbishments that deal with sustainable and architectural aspects have been addressed. As a starting point, the study assesses reasons for introducing spatial flexibility. While the reference deals mainly with vacant office spaces, the reasoning and understanding of building vacancy is highly important.

Especially with a view to student housing development which is considered as the reference project for assessment and development of this research. The case study of student housing has already embedded in itself seasonal vacancy. The spatial flexibility concept has to answer transformational possibilities within different seasons of use. “[...] architecture has the capability of changing and regenerating in response to the future, and that architectural form can be modified depending upon the way the space is used.” (Kurokawa, 1992)

The idea of architecture that has the capability to regenerate and change in response to the future is one of the answers towards designing for the new type of society. Furthermore, by using a design parameter called as “solid”, it is possible to find a balance between traditionally built architecture and the temporary needs. A solid is a built structure that has the durability, structurality and functionality properties to enable full life cycle but at the same time it houses flexible temporary systems that can adapt to the needs of society. The more technical aspect of such approach has been addressed in another text from TU Delft “Designing for an “Xth” Life Cycle” (Durmisevic, Brouwer, 2000). The focus is payed to spatial and structural design process that takes in account the material service time as well as the level of flexibility. This can be understood as functional planning and layering where the solid elements of building are positioned as base and possess the longest lifetime. Where as flexible elements have often shorter service life time due to extensive use and therefore need to be easy accessible for easy replacement which would result as well in limited emissions during the replacement. When thinking of the case study of Brattorveita, it is important to consider the layering of materials and functions within the spatial unit as well as smart methods in joining the materials that allow easy assembly and disassembly in the flexible parts. Furthermore, easy access to each of the installed layers, from fixed to transformable, to avoid the need of full refurbishment in near future.

When one looks at a student housing, the dynamics of the user are easy to see. The use schedules for different functions deal with hourly changes. What type of unit would answer the needs of the user? Moreover, how to apply sustainability within this framework? It is needed to look closely at the potential user to define the framework of the spatial unit a student will inhabit.

Analyse of the daily movements, function needs, financial boundaries.

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OBJECTIVE

METHOD

From the viewpoint of sustainable architecture where every square meter counts for energy demand, student housing with the variable use schedules throughout days, weeks, months and seasons is a high challenge.

The concept of deployable unit that disappears during the empty use hours or periods and provides space for community functions could answer many of the questions. Therefore the main research aim is to find out: how to construct a flexible indoor unit with low embedded emissions that satisfies the requirements of functionality, sound insulation and structurality.

BUILT HISTORICAL EXAMPLES

The outcome of this research should form an architectural system that can be implemented in the case study project of student housing. Furthermore, the technical data should provided basis for further investigations in non-conventional indoor systems that achieve flexible space.

The report is structured (Fig. 1) based on the development steps - starting with the analysis and design of the unit base functions, defining the structural possibilities, continuing with material assessment for the different structural categories and concluding with a comparative analysis of the data that can be transformed into the final unit and implemented in the case study project.

IIn order to develop a unit that does not duplicate already existing built concepts but tries to link flexibility and mobile society tendencies with sustainability and architecture, research of historical examples will be done. Furthermore, the key elements of flexibility or functionality will be highlighted and used in the development of the unit.

FLAT PACKED UNIT As a next step, the functions within a unit will be set.

This will allow to determine the dimensions of the structure as well as consider the flexibility within the space. In order to gain the results, firstly, an analysis of body movement and dimensions will be done, this will set basic measurements that the unit has to incorporate and eliminate unneeded space.

FOLDABILITY AND STRUCTURE Based on the results of the previous step, possible allocation of the unit within a building’s structure will be chosen and the mechanical possibilities in relation to its foldability and shell material will be discussed.

Though no decision of the folding system will be done at this point. It will be modelled after gathering Life Cycle

Fig. 1. Theory report structure.

UNIT

FOLDABILTY

STRUCTURE SOLID ELEMENTS

FRAMEWORK

CABLES

SOLID MEMBRANE

BACKGROUND

compostite aluminium

INFLATABLE

LAYOUT

MATERIAL

cardboard

vinyl

acoustic curtain industrial barrier inflatable sound screen TPU panels ETFE film

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Assessment data and having finished the rest of comparative analysis . The step of foldability development is highly relevant when a spatial unit that has to disappear during the empty use periods has to be developed. Based on the foldability need, the materials for shell of the unit will be assessed from the viewpoint of the structural flexibility need.

To obtain emission data of the shell material, the first three stages of Life Cycle Assessment will be used A1-A3 (Fig. 2). Further steps of LCA are not taken in account since unit construction methods depend on material choice and no general comparative method can be chosen. In case a company will not provide Global Warming Potential data, the product will be separated based on used materials and a general GWP data on materials will be used instead.

LCA AND COMPARATIVE ANALYSIS In order to satisfy the requirements of a spatial unit with low embodied emissions what at the same time has high functionality, sound insulation and good structural properties, a Life Cycle Assessment on the shell material will be carried out. The assessment will take form of sensitivity analysis where materials, categorized in 3 sections, will be compared based on properties such as - weighted sound reduction index, thickness, weight, global warming potential and expected service lifetime. The base unit of evaluation will be taken the decibels of weighted sound reduction index since the proposed flexible unit has to have satisfactory performance of comfort to be able to compete with fixed built solutions. Furthermore, sound insulation is one of the main issues in lightweight structures, therefore has to be seen as the main challenge.

RESULTS Flexibility in the structure of living space has been discussed and experimented widely in the 60s and 70s of the last century with the works from Archigram, Cedric Price, Ettore Sottsass, Marco Zanuso, Haus Rucker Co and many others. Therefore it is worthwhile to look at the results from literature study on what has been already done in the field of flexibility and tackle the questions that have not yet been solved.

In 1968 Michael Webb (Archigram) introduced Suitaloon (Fig. 3). It is an inflatable suit that transforms into a house for its carrier. The “sleeping unit� consists only of inflatable plastic foil, therefore is lightweight as well as very compact in its deflated form. Furthermore, the deployed shape is spacious enough to allow free bodily movements and basic positions such as standing, sitting and laying. What has not been addressed in this case, is the level of privacy due to the transparency of shell material as well as sound and heat insulation.

Since the foldable unit will have to satisfy such sound requirements as set in other student housings in Trondheim, a reference material with desired properties is chosen. Further on, materials and products with high sound insulation properties and low thickness are chosen prior to low embodied emission materials such as wood.

Fig. 2. Life cycle stages of a building according to EN15978:2011 (CEN, 2011).

C4

D reuse, recovery, recycling potential

C3

disposal

C2

waste processing

C1

transport

B7

deconstruction demolition

B6

operational water use

B5

operational energy use

B4

benefits and loads beyond system boundary

end of life

refurbishment

B3

replacement

B2

repair

B1

maintenance

A5

use stage

use

A4

construction installation

A3 manufacturing

A2 transport

raw material supply

A1

transport

product stage

construction process stage

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In 1972 Richard Sapper designed a mobile housing unit (Fig. 4) that fit within an ISO container. The unit provided more than just sleeping function, the structural properties introduce also various spatial options for flexibility - from foldable furniture, to foldable walls and floors that expand once unit is deployed. In comparison to the previous example, this was built as a mini home, therefore the properties of insulation and privacy are considered within the design. A downside of the concept appears in the form of an undeployed unit which due to its solid built structure still covers a relatively large area and volume and therefore needs a special storage place while not in use.

As last built example it is worthwhile to look at a Mobile and Flexible Environment Module example from 1972

by Ettore Sottsass (Fig. 5). It considered different everyday functions as separate flat packed units that can be linked together. What is unique about this in comparison to similar spatial module experiments, Sottsass was not bound to any spatial position to access water, electricity or drainage. Due to the smart designed module which incorporated a tubing system that can be connected to any other of the spatial units, the definition of spatially fixed functions was erased.

Though what can be seen as a downside when the proposal is seen from the viewpoint of an inhabitable spatial unit, the system does not consider any enclosure for the user. It is more of a system of spatially unbound function deployment than encapsulation of them.

Based on the historical example principles, strategic development steps and the relation between unit, body and movement is to be assessed. According to the study “Design for an “Xth” Life Cycle” (Durmisevic, Brouwer, 2000), there are three main reasons for lack of flexibility : - overall integration between building components into dependent structural system - lack of accessibility to elements with short life cycle - use of chemical (fixed) connections It is suggested to think of the flexible design based on independent cluster systems. The clusters can be shaped based on their function or functional system.

Therefore the consideration of the lifespan of each used material is important, ensuring that the ones with shorter service life are the easiest to exchange or repair.

Furthermore, the connections between different clusters should allow independent interaction, therefore the jointing technique has to be rather technical and not chemical. The guidelines from this research link well together with the reference study of “Permanent Temporality” where the interaction between solid and flexible was investigated.

“The permanent part of a building forms a framework; within this change can take place.” (Hilhorst, 2013)

Fig. 3.,4.,5. Suitaloon by M. Webb, Mobile Housing Unit by R. Sapper and Mobile and Flexible Environment Module by E. Sottsass.

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Therefore, the process of the unit development will take in account the investigated strategies and follow the idea of independent cluster creation which differentiate in the level of flexibility. Starting with the fixed built cluster such as flooring beam system, moving towards partially flexible cluster of unit function flatpack, the entirely flexible deployment system and shell material.

FLAT PACKED UNIT This work does not focus on the detailed development of floor beam system as a task, therefore for the purpose of relation between various functional clusters, the floor structure is set as a simple grid shaped beam alignment that is totally detached in the structural form from any other floor-ceiling materials. The beam system will be used as the fixed base or the main “solid” of the building where the further developed flexible clusters can be placed in.

As a starting point towards the design of a spatial flexible unit, a consideration of basic functions that should be enabled within the space has to be taken.

“However, the units were not thought as rooms with reduced dimensions; the units were designed as a unique space, as a minimum home” (Rojo, 2016) Fig. 6.Part of dimension and movement analysis.

As it has been already previously argued, the lines between private and public actions or functions have been blurred.Therefore, it is possible to to distinguish only the most basic ones such as sanitary requirements, sleeping space and storage of belongings. Since sanitary requirements from the viewpoint of functionality and cost reduction are not considered as a question of deployable function (in the case study of student housing), they will be moved outside of the private unit and be set as fixed function.

Furthermore, sleeping space has been already pre defined by the dimensions of standardized mattresses and therefore are to be considered in the dimension of 90 x 200 cm. To allow free body movements in the space, based on the body dimension analysis (Fig. 6), an extra width of 40 cm space is added. This allows for the inhabitants possibility to stretch in one of the directions, additionally, the space is used for storage purposes. The space under mattress is provided for building’s infrastructure deployment in each of the units. Due to the easy access, it suits as well the previously reviewed guidelines for flexible spatial design. In a different scenario this space can be as well used for additional storage. In addition, an analysis of everyday movements was done and the requirement for sitting and standing had to be fulfilled. As a result, the furnishing of the unit has been assembled to enable flexibility in the spatial

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transformations (Fig. 7). Such as, the mattress can be folded in positions to form a couch or a workspace seating. The latter requires as well a flat surface to position laptop, notebook or other working tools, therefore, the cover of the 40 cm wide storage space can be elevated in a height of a table. The results of this study form the flat packed Fig. 7. Actions and movements within the unit.

furnishing of the unit. The flat packed furnishing was modeled with help of 3D software and the volume of used material was calculated. It was chosen to use spruce plywood by Metsä Wood as material for the furnishing due to its low environmental impact and structural properties.

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As a result, furnishing of the unit takes a volume of 0.16 m3 and the global warming potential for manufacturing stages of the selected spruce plywood is 121 kg CO2 eqv. per m3, meaning that the embodied emissions of the unit are 19.7 kg CO2 eqv.(Metsä Wood, 2014).

FOLDABILITY AND STRUCTURE After having defined the functions available in the unit, the strategy of deployment has to be chosen.

In order to have easy transformation with the lowest spatial loss from the “flat packed” unit, it was chosen to be installed in the floor of the building. Such system would allow not only conventional distribution of units in space but as well easy installation of building’s infrastructure in the floor level that enables full spatial flexibility in future. As a result, the proposed foldable unit has taken in account the historical research and incorporated an improvement of the “storage” issue that arose in the case of Richard Sapper’s Fig. 8. Deployment systems and shell material categories.

Mobile Housing Unit, it has the quality of Suitaloon to satisfy infabitant’s everyday movements and has the functionality of Ettore Sottsass module where infrastructure can be independently linked to a larger system.

Based on previous research, three classical deployment systems (Fig. 8) are taken: solid element structure, framework structure and inflatable structure. Each of those have certain qualities and downsides in terms of space efficiency, user friendliness, adaptability for different purposes and technical or structural parameters. Furthermore, each of the systems is associated with certain materials such as solid element structures with material plates, frameworks with soft materials, inflatable structures with foils. The mechanical functionality will be looked at and discussed after results from shell material Life Cycle Assessment will be gathered.

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COMPARATIVE ANALYSIS OF UNIT SHELL MATERIALS A typical student housing bedroom wall has the properties of sound insulation in a level that reduces noises of surrounding amenities to a level of comfort.

This can be done by layering of materials with sound insulating properties in the construction of walls, ceilings and floors, as well as achieved when a material has a certain thickness. Furthermore, according to a study of Sound Quality in Dwellings in Norway (Løvstad et al, 2016), inhabitant annoyance towards surrounding noises was the highest for impact sounds such as footfall, while the lowest annoyance was towards music or speech in spaces around. This means, the importance of high impact sound insulation has to be considered in constructions of ceilings and floors, while walls should mostly provide the basic sound insulation requirements, such as sound reduction to at least 30 dB for airborne sounds. The level of 30 dB is similar to a person whispering or the ticking of an arm watch. In the case of deployable unit, the surrounding space is to be understood as common flexible living area, which means that the level of sound would probably not go above a group of people discussing loudly, this equals to the sound of maximum 60 dB (IAC ACOUSTICS, 2018).

As a result, it can be considered that a sound reduction index of 30 dB is required for the walls of the deployable unit.

As a second property of unit shell material evaluation is considered the thickness of structure, since the system has to be able to fold inside a floor. Additionally, the weight of materials as well as service lifetime is looked upon. Lastly the emissions of the material / product are calculated for the stages A1-A3. In order to be able to compare the results, a reference wall material, used in new built student housings such as Moholt 50/50 with the desired sound property, was chosen - 10 cm thick CLT plate with sound reduction index of 33 dB.The analysis was done in three categories - solid, membrane and inflated materials.

The category of solid materials is to be understood as

such that do not have the flexibility or foldability parameters already embedded in the material itself, therefore this is to be seen as plates or boards of certain products. Within this category, most of the products fall below the required sound reduction index.

The required 30 dB in most cases can be achieved with a certain thickness of material which cannot be afforded in the case of a deployable unit. To explain it further, the thicker the material, the thicker the flat packed unit which should have the possibility to be set in the floor of an already existing building, therefore causing issues of increasing floor thickness and reduction of interior ceiling heights below such that are set by regulations. The selection of research results with rather satisfactory balance between sound reduction, thickness and weight of material can be seen in the table (Fig. 9). Furthermore, within this category a material of a single structure, similar to a solid wood wall could not be found. In order to have the needed sound insulation properties, the products are composites of various materials such as the Soundproofing Wall Board or structures such as the Aluminium Lattice Panel. The information assessment and results on various products will be described further product by product.

Eurolight Lightweight Board is a cardboard product composed of a honeycomb structure sandwiched between two laminated cardboard panels. While many material thicknesses are available, it was chosen to represent only the one with highest sound reduction index of 28 dB. Such board would have the thickness of 3.8 cm and weight of 12.4 kg per m2 . The emissions of the manufacturing process in terms of global warming potential were taken from the Environmental Product Declaration and are 2.07 kg CO2 eqv. per m2 of product (Institut Bauen und Umwelt e.V., 2013).

Soundproofing Wall Board is a composite panel layering acoustic plasterboard and dense fiber matting.

Here the product with lowest thickness at the same time with satisfactory sound reduction was chosen.

Therefore a board with the thickness of 1.5 cm and weight of 14.6 per m2 was taken. A product with such

properties would have the sound reduction index of 31 dB. Service lifetime of the product has not been specified due to many possible uses that can be applied and would have an impact on it. Since no environmental data was available on the product, the global warming potential of product was calculated based on individual materials used in this product. This results in 2.4 kg CO2 eqv. per m2 of acoustic plasterboard (Environmental Product Declaration, 2015), 3.6 * 3 kg CO2 eqv. per m2 of dense fiber matting (UL Environment, 2014) and 4.2 kg CO2 eqv. per kg (approximate amount used on a m2 of plasterboard) of resin based sealant (Institut Bauen und Umwelt e.V., 2015).

Soundalloy MPM is an aluminium composite panel with viscoelastic polymer layer. This was the thinnest found product in the category of solids with thickness of 0.21 cm. Such panel would have the weight of 5.4 kg per m2, nevertheless the sound reduction index of product was not specified as one of a set value but instead as a maximum of 30 dB sound reduction. The producer states service lifetime of between 10 and 25 years based on the use. No environmental data was available on the product, therefore a similar aluminium composite product was chosen to approximate the possible global warming potential of this product and it was calculated to be 72.60 kg CO2 eqv. per m2 (The International EPD® System, 2016).

Fig. 9. Comparative analysis of solid materials. material

SOLID

company

EUROLIGHT lightweight board

Soundproofing Wall Board

Soundalloy MPM

Aluminium Lattice Panel

Fitz Egger Gmbh

Noise Stop Systems

Pyrotek

Alucosun

acoustic plasterboard, dense fiber matting, Polyurethene D2655 Green

acrylic, aluminium

aluminium

image

MEMBRANE

material GWP (A1-A3), kg CO2 eq / m²

2.07

17.11

72.60

-

weight, kg/m²

12.4

14.6

5.4

4.3

thicknes, cm

3.8

1.5

0.21

0.4

weighted sound reduction index, dB

28

31

30

22

lifetime

not specified

not specified

10-25

not specified

material INFLATABLE

MATERIAL

10

CLT wall plate

thicknes, cm

10.0

weight, kg/m²

50.0

weighted sound reduction index, dB

33

Aluminium Lattice Panel is a product that sandwitches a lattice layer between two aluminium plates. It has the weight of 4.3 kg per m2 and thickness of 0.4 cm. The panel has a sound reduction index of 22 dB and therefore is well below the required 30dB border. As well this product as most of the before ones did not have environmental data available, furthermore, no comparative materials were found in production process to estimate the emissions.

The category of membrane shell materials (Fig. 10) consists mostly of sound insulating curtains used in theatres, industrial sites as well as aeronautics and marine. Here the products combine the parameters of

lightweight, reduced thickness, flexibility and high performance in sound reduction. Two types of research results can be distinguished - products that layer certain materials and products that consist of mainly one single material. When looking at the first type of results, the thickness of product is relatively high if sound reduction index of 30 dB is to be achieved.

Moreover, this would result in rather thick walls of the unit when deployed as well as when collapsed.

Furthermore, such type of products are not prone to folding, therefore can be only rolled, resulting in a structure that has issues with spatial flexibility solutions in case of daily deployment needs. The second type of products which consist of mainly one

Fig. 10. Comparative analysis of membrane materials material

MEMBRANE

SOLID

company

WAVEBAR NC

interior acoustic curtain

dBarrier

StratiQuilt blanket

Pyrotek

HOFA Akustik

Rhino Shrink wrap

Acoustics First

flame retardant PVC, sound absorbent foam

MLV, dense fiber matting,

-

29.63

image

material

mass loaded vinyl

GWP (A1-A3), kg CO2 eq / m²

15.92

weight, kg/m²

8

1.2

5.8

7.3

thicknes, cm

0.4

0.4

4.0

5.0

weighted sound reduction index, dB

31

12

21

29

lifetime

not specified

not specified

not specified

material INFLATABLE

MATERIAL

11

brushed cotton, FRM 211

14.6

202.7

5

CLT wall plate

thicknes, cm

10.0

weight, kg/m²

50.0

weighted sound reduction index, dB

33

12

material, have very good sound insulation properties as well as low thickness.

Wavebar NC is a mass loaded vinyl sheet with the thickness of 0.4 cm and weight per m2 of 8.0 kg. The resulting product has a sound reduction index of 31 dB. Although the material can be used alone as a sound barrier, it is suggested to provide a textile cover that would protect the material from damage and tearing and prolong the service life time of it. Since this product had no environmental data available, the global warming potential was calculated based on the Environmental Product Declaration of 1 kg of vinyl which was then further on calculated according to the weight of a m2 of the selected product. The resulting global warming potential of vinyl barrier alone is estimated 15.92 kg CO2 eqv. per m2 for the manufacturing stage (PlasticsEurope, 2015).

Interior Acoustic Curtain by HOFA consists of layers of molton fabric, also known as brushed cotton or dense cotton. A basic product has the thickness of 0.4 cm and weight of 1.2 kg per m2. Such curtain would have the sound reduction properties of 12 dB. Further on, the material can be layered to achieve double or triple sound insulation, which means that in order to have the desired 30 dB sound reduction, three layers of curtain would be needed. The expected service lifetime is to be at least 5 years. Since no environmental data was available on the product, the global warming potential was calculated from life cycle assessments of similar products. Nevertheless, two very differing results were acquired. This happened due to the use of fire retardant in the production process. The company has provided information of a fire retardant FRM 211 used in the manufacturing of curtain, though no analysis of the substance was available. Therefore it was not possible to evaluate which of the global warming potential data is to be considered for HOFA acoustic curtain and as a result, both possibilities are shown. In first case, the emissions of a fire retardant curtain were 14.6 kg CO2 eqv. per m2 of product (Yasin et al., 2016). At the same time the second case has results of 202.7 kg CO2 eqv. per m2 of curtain (Yasin et al., 2017). The large

difference in results of the manufacturing stage lies in the use of certain flame retardant. Considering the fact that FRM 211 is suggested as such with lower hazard to environment (EOC, 2018), it can be assumed that the emissions at manufacturing stage with the lower global warming potential correspond with the FRM 211 impregnated curtain. Nevertheless, to not misinterpret data, both results are kept. dBarrier is an industrial noise barrier that is made using a fire retardant PVC fabric and sound absorbent foam.

Such product has the thickness of 4 cm and the weight per m2 of 5.8 kg. The barrier has sound reduction properties of average 21 dB though can reach up to 46 dB depending on the type of noise.Since no environmental product data was provided, it was searched for individual materials used in the product.

Considering the fact that no specified material category was provided for the PVC layer or sound absorbent foam, it was not possible to gather valid and comparable data on the emissions of the product.

Strati Quilt Blanket consists of two layers of high density fiberglass batting, quilted between two layers of aluminum-vinyl coated fiberglass facing material, in the core of construction, a mass loaded vinyl sheet is placed. Such blanket has the thickness of 5 cm and a weight of 7.3 kg per m2. The sound reduction index of the product is 29 dB. Since no data of environmental impact was provided by the producer, the global warming potential was assessed based on manufacturing separate layers of the product. As a result, the global warming potential for manufacturing stages can be assumed to be a sum of gwp data for a mass loaded vinyl sheet, based on the data provided by the producer.

This is gwp data for glass fibre yarn manufacturing (Glass Fibre Europe, 2012) together with data on fabric weaving (van der Velden et al., 2013) as well as data for dense fibre matting (NAIMA, 2013), all together forming global warming potential in the stage of manufacturing 29.63 kg CO2 eqv. per m2.

Lastly the category of inflatable materials was assessed. In contrast to the previously looked at mate-

rials (Fig. 11), where the most thin products needed to be selected, here an advantage in the dimensions of the deployment system in deflated and inflated form is high. Such products allow to have a minimum size when not in use and only take the needed volume for sound insulation when put to use. Nevertheless, not many solutions can be found in this category since air does not contribute significantly to noise reduction.

One of the first sound reduction materials was found to be Mobile Inflatable Sound Screen. The product does not have much of specification information aside from the thickness of 20 cm in inflated stage and the sound

reduction properties of 20 dB. No specified material used in the product other than double layer of canvas was given, therefore no further environmental impact study could be done. Nevertheless, another type of considerable information was provided. The product sound reduction study shows significant increase of dB reduction in case the sound screen is filled with water.

In such case the sound reduction index reaches up to 48 dB. Another product in the category of inflatable sound systems is the AirHush panels. The product has the thickness of 15 cm in inflated stage and weight of 14.7

Fig. 11. Comparative analysis of membrane materials material

SOLID MEMBRANE

mobile inflatable AirHush panels sound screen

Nowoflon Etfe film

Buitnik Technology

Pinata Acoustic

Birdair

material

-

TPU, MLV, aluminium frame

ETFE

GWP (A1-A3), kg CO2 eq / m²

-

-

40.7

weight, kg/m²

-

14.7

0.35

thicknes, cm

20.0 (inflated)

15.0 (inflated)

depends on cushion size

weighted sound reduction index, dB

20

34

10

lifetime

not specified

not specified

>15

company

image

material INFLATABLE

MATERIAL

13

CLT wall plate

thicknes, cm

10.0

weight, kg/m²

50.0

weighted sound reduction index, dB

33

14

kg per m2. Furthermore, the product states to have 34 dB of sound reduction. This can be achieved due to combined use of inflated TPU film and MLV sheet covering. Nevertheless, the product has a downside of being formed from a fixed frame aluminium structure in dimensions of 60*68 cm. Such fixed dimension can cause issues in the stage of flat packed unit and deployment where the elements are to be fixed to each other in all of the stages and not to be constructed new for each use. Furthermore environmental data for the product was searched. While the data for MLV sheets was already previously gathered and information regarding steel frames can be found on all the large environmental declaration webpages, no study or assessment of extruded TPU film and its impact towards environment was found. Multiple studies in the field of chemistry had been done to find replacements for the most emitting ingredients of TPU production process and one of such outcomes is the Bio TPU by Lubrizol, nevertheless the sustainable replacements of the original TPU film do not state any environmental information either, therefore no further study could be done.

the same time having sound reduction index of only 10 dB. Although the sound insulation properties fall low below the set requirements for unit design, it was important to include the results of ETFE foil since it was the only inflatable product with given environmental impact data.

Lastly in the category of inflatables and ETFE cushion was assessed. It has the weight of 0.35 kg per m2 and the thickness of inflated state can be adapted to the needs of project. Furthermore, the product states to have service life of 15 or more years and global warming potential of 40.7 kg CO2 eqv. per m2 of film. Though at

In order to form a result that can be used in the case study of student housing, the two materials with satisfactory sound reduction level, lowest emission level and lowest material thickness were taken for designing the final unit and calculating end emissions of it. Since the two chosen materials are from the category of mem-

After having gathered information from each category, the results with satisfactory sound reduction index with over 30 dB were gathered in a comparative graph (Fig. 12). Here the gathered information from previous steps was multiplied to represent the emissions for the surface of unit shell material. The resulting surface was designed and calculated with the help of 3D software based on interior ceiling height of 2.4 m and unit dimensions of interior space of 1.3 times 2m. What can be seen, the material with lowest emissions is the HOFA acoustic curtain with result of 222.7 .kg CO2 eqv. per unit shell. Second follows the mass loaded vinyl barrier with result of 259.1 kg CO2 eqv. per unit shell. After can be seen the Soundproofing wall board with 1181.7 kg CO2 eqv. per unit shell. And lastly the Saundalloy MPM with 3299.3 kg CO2 eqv. per unit shell.

Fig. 12. Products with at least 30 dB sound reduction index

product Soundproofing Wall Board

weight, thickness, kg/m² cm

weighted sound reduction index, dB

lifetime, years

14.6

1.5

31

-

Soundalloy MPM

5.4

0.21

30

10-25

Wavebar NC

8.0

0.4

31

-

Hofa Acoustic Curtain

1.2

12 *3

>5

0.4 * 3

global warming potential (A1-A3), kg CO² eq / unit shell 278.5 ... 1181.7

259.1 222.67 ... 3299.3

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branes, the supporting structure of framework lifting system had to be chosen and a hydraulic scissor lift was found the be the most space efficient and functionally performing. The result can be seen in Fig. 13.

DISCUSSION The development of environmentally friendly student housing has to deal not only with energy savings and smart material use but as well with spatial development systems. The latter is especially important when considering the seasonal vacancy such building category implies. While little to no emissions are caused from vacant buildings, they can propose a possible Fig. 13. The resulting flexible unit elements

unit elements and emissions

substitute function during the vacant stage and so help to avoid the need of building certain new facilities such as exhibition spaces, cafes, small movie theaters etc.

This is highly relevant since buildings account for 36% of European Union CO2 emissions (European Commission, 2018). While the guidelines suggest ways to improve energy efficiency in new built and already existing buildings, not much is spoken regarding space efficiency. Every new built structure contributes to the emissions and therefore ways to avoid new built structures and instead search ways to multi use already existing spaces as well as retrofit flexible systems can be recommended.

As first step of the assessment, already historical built and theoretical examples were looked at and resulted

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in a list of guidelines for design process of a flexible element that would enable multi purpose use of the same space. The report then takes the results further to develop such unit and be able to assess emissions of manufacturing elements. The second step formed functions of the unit and analysed body measurements to set dimensions of the design space. This allowed to reduce the outer boundaries to minimum of 2.4 x 1.3 x 2.0 m for selected everyday actions of the potential user and therefore save space and increase the number of potential inhabitants per m2 and as a result showing not only potential of emission reduction due to multi use space but as well a potential solution of space efficiency for the case of population growth that has been discussed earlier in this study.

Since foldability of the unit was a crucial point in development of spatial system as it would allow the private space of user to disappear during day, week or season and give space for different functions, materials with minimum thickness but at the same time with satisfactory sound insulation properties to keep the levels of comfort high were searched. During the product study, two of the materials showed outstanding results. The performance of mass loaded vinyl sheets as well as HOFA dense cotton curtain. These products stood out due to their reduced thickness in comparison with very high sound reduction index, as well as properties of foldability and rather low emissions when compared to products of similar class. Furthermore, the results from solid elements had two products with satisfactory sound reduction index. While the Soundproofing Wall Board has the required sound insulation and rather low emissions, the material thickness is nearly too high to consider it for a foldable lightweight system that has to be able to be packed in a floor of a building. Meanwhile the surprisingly thin Soundalloy MPM aluminium plate does not guarantee a minimum sound reduction index but only states the maximum. Such result cannot be taken for further work without proving the reliability of the sound insulation material. Moreover, the global warming potential with 72.6 kg CO2 eqv. per m2 of product has one of the highest results from material assessment and therefore can be considered as not

suitable for a sustainable refurbishment. Lastly, the category of inflatable materials showed an interesting potential for flexible space development, having the benefit of reduced storage space requirements in comparison to other materials. Nevertheless, lack of environmental data did not allow to implement these results as part of the unit development.

This study tried to find the practical use of flexibility for the case of student housing development in new or already existing buildings. The outcome of this study shapes a flexible unit for development of student housing with mixed use functions, allowing it to disappear during the empty use periods and give space for other functions. Based on the historical example and literature study, the developed unit took in account the benefits of found results and tried to solve previously not considered issues. Towards the development of transitional housing that could accommodate the new type of society with its blurred lines of privacy and publicity, the unit proposes a new type of student housing, similar to one of urban camping. Allowing the space to be reversed to its empty state after the tenant leaves and inviting new functions in its place. Furthermore, the developed unit took in account body dimension requirements and everyday movement needs as the Suitaloon project by Archigram did, nevertheless, avoiding the level of shell transparency which would reduce the level of privacy for the tenant. However, the developed unit did not consider much further the principles of Flexible Environment Module example by Ettore Sottsass, where the free distribution of sanitary functions was planned, since all sanitary functions were chosen to be taken out of the private deployable unit and considered as a common function. Nevertheless, the idea of easy infrastructure distribution was considered by providing an empty 10 cm space under the unit, to allow uninterrupted infrastructure distribution through the building and units. Similar as suggested in the “Design for an “Xth” Life Cycle” and “Permanent Temporality”, the development of flexible unit was based on creation of functional and structural clusters.

The framework of a building was understood as a given fixed boundary within which the flexible unit was

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layered according to the level of flexibility each cluster has.

Based on all previously discussed points, the proposed unit has a fixed plywood interior, a steel hydraulic scissor lift for the deployment function and shell material to be chosen between mass loaded vinyl or an acoustic curtain. Each of the elements was chosen to be attached with mechanical connections for easy disassembly in case of replacement need. What can be seen from results, the chosen steel deployment system has rather high emissions that could still be reduced.

This is a matter for further study to investigate deployment systems wit lower embodied emissions and at the same time same level of functionality and stability, as well as compactness.

Lastly, based on the research, certain guidelines could be withdrawn for further topic investigation as well as for pursuing the project in real refurbishment projects.

Such as lightweight sound insulation materials have high potential in development of mixed use spaces that can contribute to emission reduction due to lower new built structure need and the environmental impact of such materials should be studied further to not only estimate the environmental potential but arrive at set values that allow to choose the best materials for each project.

CONCLUSION One of the most widely used ways to assess sustainability in the building sector is to focus on energy efficiency of the buildings. This can be seen in various building regulations and guidelines where the focus lies mostly on the numerical value outcome and not as much on social as well as architectural sustainability means.

This study aimed to show an untraditional way of emission reduction in building sector what has not yet been

widely discussed. Furthermore, the study showed that it is possible to construct a flexible unit that can disappear during empty use hours and therefore allow other functions to exist in the same space. Such approach would allow to reduce emissions from new built structures and instead rediscover ways to reuse already existing volumes. Furthermore, the Global Warming Potential of materials used for such unit was assessed and the best performing and lowest emitting materials selected.

By further exploring the topic of flexible spatial systems in connection with sustainable development, new ways of emission reduction from building sector can be found. Moreover, sustainability could be no longer seen as one that deals with numerical calculations alone but as well addresses the needs of changing society.

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ELSEVIER.

Figure 3: Source: http://revistabifrontal.com/archigram-la-arquitectura-como-rebelion-nomada/ Figure 4: Source: http://richardsapperdesign.com/products/1970-1980/mobile-housing-unit Figure 5: Source: http://www.sightunseen.com/2013/12/hans-ulrich-obrists-lost-interview-with-ettore-sottsassfrom-surface-magazine/