How to build with wwcb

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How to build with Wood Wool Cement boards
What sets WWCB apart from other building materials.
Properties:
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Good thermal insulation
Excellent heat buffering capacity
Wet and dry rot resistance
Fire resistance (B1 classified)
Termite/Vermin resistance
Good sound absorption
Excellent base for stucco and plaster
Light weight to handle;
Easy to process in construction;
Relative low energy consumption to produce;
No fossil fuel or binders used;
Limited impact on local natural resources.
No waste product at end of life cycle;
Nice and attractive ‘natural look’ visual appearance.
What is Wood Wool Cement Board?
In Wood Wool Cement Boards (wood wool is also known as excelsior in the USA) and panels each fiber is
coated with a thin film of Ordinary Portland Cement (OPC) that, when cured, partly petrifies the wood. In
that way the fiber will last indefinitely as long as the cement film is not damaged.
Is WWCB durable, sustainable and environmental friendly?
The first WWC boards came to the market as early 1900 and have proven their value ever since. Boards in
Italy used as wall insulation in buildings in the 1930 were still in good shape and were re-used in other
buildings when the old building had to be torn down. WWCB can withstand numerous freeze thaw cycles
and has been applied in Scandinavia for over 60 years in open contact with the elements without any sign
of detoriation.
Looking at the environmental discussions, cement has a negative CO2 signature despite the fact that when
OPC cures it binds up to 50% of the CO2 that was created for producing the cement. When applied in
WWCB the wood also binds a lot of CO2 during growth that stays in the WWCB product until it is no longer
used. When after several life cycles it is finally ground down it decomposes into compostable wood and
lime. Both are harmless to nature and as a result all homogeneous WWCB products have green labels in
Europe. A recent study of a large EU based cement producer showed that WWCB is also very effective to
produce new Portland cement. The wood partly replaces fossil fuels in the kiln where the cement breaks
down to components that again can react to water. So more WWCB in the kiln also means less new
quarried base materials needed. So WWCB can be considered to be both Cradle to Cradle and a green
building product. Looking at the above properties one could say it’s a win-win-win product.
Building with WWCB - points worth knowing:
General:
WWCB is available in densities ranging from 280 kg/m3 up to 1400 kg/m3. This allows for a wide range of
applications depending on the required properties of the product. Low density material is used for insulation
of sound and temperature, medium density material is applied more structural as the higher density also
gives higher bending strength than the low density material. In situations where one needs the qualities of
the low density material for walls, the structural strength of the building has to come from reinforced
concrete, steel or wood framing. The medium density boards have specific applications that make it a fire
and vermin/termite resistant competitor to conventional boards currently used in stick build construction. To
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define between the low density WWCB and medium density boards the medium density boards are
promoted as Wood Strand Cement Board WSCB or EltoBoard® as the 25cm (10") long wood fibers in
WSCB give it much more structural strength than the cement bonded (short) fiber boards currently in the
market. WSCB/EltoBoard® can also be seen as the lighter and stronger replacement of Cement Bonded
Particle Board (CBPB). Due to the relative high OPC content WSCB is heavier than OSB, but has none of
the disadvantages of OSB type products. (see properties).
Types of wood that are suitable are species of pine, poplar/aspen and eucalyptus. Preferably from FSC
certified sources. Other wood species are sometimes suitable. Prior testing is advisable.
Physical limitations related to construction method and geographical situations.
Temperature:
WWCB and WSCB are used all over the world in buildings that are specifically designed for local conditions
ranging from extreme cold to extreme hot and humid. Which type of construction method is used depends
both on the local economic situation, local building regulations and the willingness of builders to work with
the material when it is new to a specific market.
Depending on the local constraints it is possible to build walls with solid insulating WWCB boards or use
the boards as insulating casing/shuttering for pouring reinforced concrete. In Siberia WWCB is used in
combination with a layer of polystyrene to further improve insulating for extreme cold. Recent regulation
forbids the use of polystyrene in Russian buildings. Therefore it is likely that it will be replaced by mineral
wool which has similar properties. As WWCB can easily combine with a wide range of insulation sandwich
materials there is no constraint for the WWCB producer to switch to alternative insulating materials as the
individual Eltomation production lines are flexible in this respect. When applied as a solid large prefab
element there is no need to add either polystyrene or mineral wool. The material itself provides the required
insulation value. See large WWC Wall Elements.
Earthquakes/hurricanes:
Both Earthquakes and hurricanes may set specific additional construction requirements for a building.
WWCB and WSCB/EltoBoard® should be used within the physical limitations of a specific product and
complementary to the wooden, steel or concrete design that complies to the local regulations set for the
construction/building in a specific geographical and geological setting. If used for permanent shuttering the
boards are more densely pressed (600-900 kg/m3) and used in countries like Japan to give both insulation
and additional strength to a (high rise) building in case of a natural disaster.
How to choose board dimensions for a specific building
Historically WWCB has been produced in Europe mainly for acoustic and
temperature insulating applications like ceilings for public buildings concert
halls, libraries and swimming pools. By definition non-load bearing. The most
used board dimensions have resulted in a board width in production of approximately 60cm wide. As the production process is a continuous mat, the
board length is determined by the length of the mould whereby the height of
the mould rim gives the thickness of the resulting board. Over the
years European producers have developed a wide range of different boards
with bevels, rims and colors that can all be produced on one type of WWCB
production line.
As the Eltomation production line has a 2 stage mould filling operation it is
possible to insert all kinds of sandwich materials like mineral wool or wooden laths/poles to create load
bearing roofing boards.
Both WSCB/EltoBoard® and the Large WWCB prefab wall elements are relatively new developments.
EltoBoard® being a patented medium density board from Eltomation while the large elements are a
development of Träullit in Sweden. The latter has also developed a pole reinforced low density building
board (240x60x10-15cm) that shows high potential for affordable, well insulated social housing anywhere in
the world. Depending on the construction and local conditions it is now possible to build all types of well
insulated housing with WWCB from 3,5 cm thick for moderate climates to walls up to 60 cm thick for
extreme cold or hot climates. Especially the use of the thicker low density WWCB material results in very
substantial reduction of energy cost for air conditioning and/or heating while the indoor living climate is
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strongly improved because these walls are breathing. They absorb heat and moisture and release it
gradually over a 24 hour period.
WSCB/EltoBoard® is a class in its own and as a product it has to compete with other structural boards like
OSB. This means that one of the essential requirements is that it should be available in board sizes of at
least 240x120 cm (8'x4'). As WSCB is produced on a standard low density WWCB line with an added
special hydraulic press, board size is currently limited to 60cm (2') wide. For most structures this is not a
problem, especially if the builder applies the boards horizontally over a stick frame construction. A
production plant for 120cm wide WWCB/WSCB awaits a launching customer. Meanwhile tests have proven
that it is very effective to use PU kit to fix 2 or more 60 cm wide boards together to form larger board sizes
that can be used to produce for SIP's and/or prefab walls.
In the following chapters the use of WWCB as ceiling boards is left aside as this use is well documented by
a number of EU producers like Knauf, Celenit, Troldtekt and Träullit. Detailed instructions for use have
been documented in the LeichtBauPlattenFibel. An instruction for use in the German language (last printed
in 1985) is also available in pdf. The next part of this article delves a bit deeper on how to implement WWC
boards and panels in load bearing structures.
Wood Wool Cement Boards and massive WWC elements:
Climatex system labor intensive but simple: This system consists of assembling large self supporting
wall elements at the building site out of several Wood Wool Cement Boards and a reinforced concrete
framing. A foundation is only needed for the outer walls; the interior
walls are placed in recesses on the floor slab. The walls are assembled
from WWCB and laid-out on a flat surface according to their size, windows and doors on simple wooden frames. At about every meter, one
reinforced concrete pillar is poured in between the boards as well as
along the edges of the wall elements. The mould frames are placed
one on top of the other with the lower rim in the direction of their final
installation place don the floor slab. They are piled in the right sequence for demoulding. After hardening of the concrete, the wall panels
are erected and fixed to each other with sticking out steel wire at the
corners and T-junctions. Then the corners and T-junctions are filled
with concrete. Roof anchors are fixed to the top beam and roof beams can be installed. The corners and
T-junctions receive a wire mesh after which inside and outside is stuccoed in 3 layers totaling 1,5 cm on
each side. With this concept over 7,000 social houses were build in Brazil in 1982. Even after almost 30
years not a crack can be found. See: http://www.eltomation.nl/Eng/Publications/Climatex%20folder.pdf
Alternatives to the Climatex system have been developed over the years
and have resulted in concepts combining the boards with steel frame
structures but also with reinforced concrete poles where the boards slide
in grooves. In the Malaysia and some Balkan countries the boards were
applied in concepts where the boards were already in place and the rebar
openings with rebar were filled on site. Only in the place where the concrete has to be poured is temporary shuttering needed. Again a very effective way to build all kinds of well insulated housing at relative low cost.
Byggelements; a new Swedish alternative. Independently from other
alternatives Träullit in Sweden developed a roofing board of
240cmx60cmx15 cm with one (Bygg element) or two (Tak element) embedded poles. Originally meant for large span roofing (240cm(8')) these
reinforced boards, when placed fully vertical, are very effective for building
single story houses with 10-15 cm thick walls. In situations where the insulating value of the reinforced boards is insufficient, a second layer can be
added that is not reinforced but
may be solid or of the sandwich type with a mineral wool inside layer. Often this second layer is fixed horizontally to reduce cold or heat bridges.
The boards are fixed to the floor slab by a bolt that goes trough the pole(s)
in each board.
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On top a connecting wooden beam or cast reinforced concrete ringbeam add structural strength to the required specs and provide fixing
of the anchors for the roof construction. Combinations with (cold
rolled) steel beams and trusses are also possible. Finishing inside
and out is done by applying metal
or other mesh and several layers of
stucco. Water resistant on the outside and breathing lime on the inside.
Alternative for the inside finishing layer can be gypsum drywall.
Both the Climatex concept and the Bygg elements are very flexible for
design and allow assembly of complete walls on site or can be assembled
partly prefab when applied in large projects with a lot of similar houses.
Like Climatex walls, Byggelement walls can be used for insulating inside
walls as well.
Large Elements when labor is a substantial cost factor.
The Swedish architect involved in the research project of the Lund University for Passive Housing Materials, was the first to experiment with 40 cm thick walls made of solid WWCB. Because at that time this material was only available in boards measuring 240x60x15 cm, he cut blocks of 40 cm and build walls while
using the blocks as large bricks. Over a period of several years the cooperation between the WWCB factory and the architect resulted in ever larger WWCB blocks and currently the most effective size for building
and insulation is a solid panel of 600cm x 270cmx 40 cm with an R value of 5,3 per square meter. Basically
these large Elements are solid SIP's that under certain local conditions need additional reinforcement for
additional load bearing requirements, for example when snow loads, hurricanes or earthquakes are an issue. A building team of 3-4 and a small crane can place the walls of several houses in a single day. This
makes this building concept especially interesting for countries where labor cost are high. Because of its
insulating properties at 40 cm thick the large element system is also a very attractive alternative for both
cold and very warm climates as well as areas with frequent bush fires as it will not burn even after extended
exposure to extreme heat. (6 hours in 1200º Celsius)
From foundation to turnkey delivery in less than 4 months total building time.
Large WWC prefab Wall Element building system
During the last few years, a new revolutionary large-size wall system has been developed by one of
Eltomation’s clients, the company Träullit in Sweden. These large wall elements are made out of solid
(although light-weight) WWC with dimensions of up to 6 m (20‘) in length, 2,7 - 3 m (9’- 10’) in wall height
and up to 40 -50 cm (1’ - 4” to 1’ – 8”) thickness, subject to the local climatic conditions. In addition to the
excellent thermal insulation (0,19 W/m2 ºC when 40cm thick), these elements also provide a high thermal
storage capacity (250 kJ/m2 ºC). During the first years of production of the large WWC wall elements,
Träullit has further optimised its product using semi-automated production facilities, such as for forming,
demoulding, storage, cutting/finishing, etc. Eltomation has now developed a production line for the
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fully-automated production of such large elements at high capacity and reduced labour requirements. A
number of material properties of WWC are independent of density and or thickness. The testing of these
properties has been well documented by most of our customers. Especially accessible is the English
brochure of Celenit where pages 6 to 9 show some general properties of the thinner ceiling boards. For
homogeneous WWCB the figures of the product Celenit N are most compatible with the WWC as used in
Large elements. As the maximum thickness given is 75 mm extrapolation of the thickness range can give
some indication of likely values for LE panels ranging from 35 cm till 60 cm thickness.
See http://www.celenit.it/performance.asp and http://www.celenit.it/characteristics.asp
For practical reasons the low density WWC should not be included in construction calculations as this in
general requires that the material needs to be certified for load bearing properties. For calculating
constructions where the WWC is the insulator the calculation should always be based on the structural
strength of the wooden, steel or concrete skeleton. That way the restrictions for use in most types of
constructions is circumvented while the limited added strength of the WWC material give some added
strength above the calculated values for the load bearing structure.
LE’s ready for shipment
Principle of construction
CONSTRUCTION WITH LARGE WWC WALL ELEMENTS
Due to the low weight of the wall elements one can transport up to 108 metres of large wall elements on a
truck with a trailer. The elements are loaded into open containers, e.g. one container on the truck and two
on the trailer.
Economic (Just-in-time) transport
Placement of LE’s
The Träullit large wall element system consists of a column/beam system of reinforced concrete that is cast
on site after the elements have been mounted onto the foundation. In the joints between the large wall
elements vertical V-shaped slits form a square cavity (approx. 70 x 70 mm) when the elements are
mounted next to each other. At the crest of the large wall element the U-shaped groove (approx. 100 x 160
mm) forms the carrying (ring) beam that runs along the top of the element around the entire outer wall
crest. The vertical and horizontal cavities and grooves are reinforced with steel bars and are cast on site
after the elements have been stabilised with buttresses. During the mounting the corners can be stabilised
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with sharpened corner braces. These ensure stability for the casting process.
To get the correct cover layer of concrete around the reinforcement, rafter fastening irons are used. This is
an arrow-shaped, 3 mm thick piece of sheet metal that has punched gaps for fixing the reinforcement bars
and the fastening of the rafters. It is struck into the U-shaped groove of the large wall element crest. The
walls are mounted with a mortar levelling on the foundation. A reinforcement bar in the joint between the
large wall elements is anchored into the foundation and can be bound to the carrying (ring) beam. The
load-bearing structures are the joint columns and the carrying (ring) beam. These are reinforced in order to
be able to carry the appropriate loads. The large wall element itself has a compression resistance factor of
27kN per running metre. A possible bending down of the concrete beam is prevented by the large wall
element that works together with the concrete ring beam. Once the wall elements have been mounted and
the beams and cavities have been cast on site, the walls have to be air tightened so that no wood wool
cement remains visible. This is particularly important around windows and the crest of the building where it
will be impossible to plaster after the windows and the rafters have been mounted. Beams and struts that
are placed in direct contact with the outside wall must also be plastered before they are mounted. The
diffusion barrier on the inside of the roof is folded double and squeezed against the exterior wall with an
Lshaped sheet metal profile. Between the wall and the diffusion barrier an EPDM-rubber is fitted.
Open Ring-beam
Anchors in ring beam for floor
Pouring of concrete
The rafters are anchored to the large wall elements by the arrow-shaped sheet metal pieces that were cast
into the carrying (ring) beam. The actual amount of nails/screws needed for the anchoring of the rafters is
determined by the wind load on the roof. Under each rafter a moisture proofing sheet must be placed to
ensure no moisture is carried to the wood rafters. The gable walls are anchored to the roofing with screws
and plugs all the way to the concrete beam in the large wall element joints to ensure a tight fastening of the
gable. If the building is more than one level, the large wall elements are placed on top of each other and
the joint column runs all the way to the top of the upper carrying (ring) beam. The elements on the ground
level must be mounted, reinforced and cast first before the large wall elements of the upper level can be
mounted. Depending on the wind load the building must withstand (depending on location), the columns
may have to be cast larger and be better reinforced to be able to ensure stability. The beam layout of a
multilevel building can be made of wood or concrete. If wood is the chosen material, a strut with a cast-in
threaded stainless steel bar is anchored onto the wall which the rafter can be hung into with an iron joist
hanger. Concrete based rafters can be made of lightweight concrete or similar. All rafters, regardless of
material, are mounted onto the inner crest of the large wall elements.
The elements are always lifted and handled by a crane and two or three construction workers that fit the
elements together, buttress them, and manage the concrete casting on site. Such a work team can
manage to lift down 5-6 large wall elements from the truck, fit them, and buttress them in an hour. A
complete mounting with reinforcing, caulking the joints and casting on site naturally takes a longer time. On
average one can complete a mounting of about two elements per hour.
Electricity fittings are simply milled into the wall since the large wall element is very easy to work with.
(note: in the new fully-automated Large Element Line, an integrated CNC Centre can optionally provide all
such openings for cables and piping in the plant). When all the fittings are finished the milled fittings are
plastered over. After that the entire surface of the interior wall can be plastered.
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Ready villa (215 m² living space)
Inner walls prior to stuccoing
Fastenings for e.g. kitchen cupboards and fittings are usually made with screws and plugs. The hole for the
plug should be drilled a couple of millimetres smaller than what is recommended for the selected plugs.
The drilling hole should be cleaned and air-proofed with e.g. mounting glue before the plug is mounted.
After this the interior fittings can be mounted into place. A normal 10 millimetre plug has a vertical pulling
load of 165 kilos per mounted screw. Stiffer plugs of the type that is used for lightweight concrete have a
vertical pulling load of 300 kilos per mounted screw.
Träullit Large Wall Element, Thickness 400 mm Technical Data
U-value
0,19 w/m² °C
Fire rating
REI360
Heat storage capacity
250 kJ/m² °C
Critical RH (preliminary
90%
tests)
Air permeability
20 m³/m²hPa
Bending strength
27 kPa
Load carrying strength 27 kN per running metre of wall
Density
Fire tests on LE showing 6 hour fire resistance.
Approx. 300 kg/m³
Main Technical Specification of Large Element
The Träullit large wall elements have obtained the highest fire-rating in Sweden. When tested the large wall
element was subjected to a continuous fire during six hours. The temperature of the fire was 1200 degrees
centigrade on the fire side of the wall, while the other side of the wall held a temperature of only 45 degrees
Centigrade.
Cost analysis of Large WWC Wall Elements.
The Large WWC Wall Element System has proven to be very competitive in view of its relative low
production costs, efficient installation and durability. The (ex. Works) sell price of the Large WWC Wall
Element in Western Europe is up to approx. EUR 100,-- per square meter (subject to quantity and complexity per Element). The cost for the Elements for all outer walls of a typical single story house of 100
m2 living space will therefore be approx. EUR 12.000,- to 15.000,-- only.
Considerable savings apply in the reduced construction time. For example 3 persons can install all such
Elements for a 100 m2 single story
house within one working day. During construction no heavy cranes are required. In addition to the quick
and easy installation, the Elements are easy to be worked on for e.g. cutting slots for electrical wiring (when
not already done in the work-shop) and applying stucco.
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Wood Strand Cement Board / EltoBoard®, when others fail.
EltoBoard® is a relative new development by Eltomation aimed at applications that seek a structural panel
that is lighter and at the same time stronger and cheaper to produce than conventional mineral bonded
competitors like Cement Bonded Particle Board (CBPB), Backer Board and some of the magnesium
bonded boards Eltoboard is not affected by fire, mould, fungus or vermin, including termites. This makes
EltoBoard a strong competitor for OSB in areas where OSB is currently not appreciated for stick build
construction. Production wise it is a great advantage that EltoBoard can be produced on an extension of
the standard Eltomation WWCB plant. Due to its green and durable properties WSCB will allow for higher
market prices as its use gives a significant boost to the future value of a building.
EltoBoard with different finishes
EltoBoard before final finish
The production of medium-density Wood Strand Cement Board (WSCB – EltoBoard) is accomplished on a
standard WWCB Plant to which a special EltoBoard Press has been added, which will compress the fresh
wood-cement mat to a much higher density. The result is a medium density board with structural strength
(bending strength of up to approx. 20 MPa). Board dimensions are typically 60 cm wide and 240-300 cm
long.
Board thicknesses range from 8 to 25 mm. Eltomation is currently also developing a production line to
produce WSCB - EltoBoard as 120 cm (4’) wide boards, which will allow the client to cover a broader
market-range, e.g. for replacing other structural boards such as Cement Bonded Particle Board (CBPB)
and Oriented Strand Board (OSB), for reasons of moisture-, fire- or insect resistance.
For a detailed description of the production process of WSCB, reference is made to the IIBCC 2006 (Sao
Paulo) paper of Mr. G.J. (Gerry) van Elten. This Publication is available on the website of Eltomation
(www.eltomation.com) under “Publications”. There you can also find a presentation of Mr. Matt Aro of the
Natural Resources Research Institute, Duluth MS, USA specifically on the properties of WSCB/Eltoboard.
WWCB and WSCB/EltoBoard and Large Elements: some facts
General: the properties, certification and working instructions of WWCB low density are well documented
on the individual sites of EU producers (see Eltomation reference list) and general instructions as
documented in the Leichtbauplatten-fibel. As the Large WWC Elements are implemented in load bearing
walls below facts concentrate on a number of regular asked questions from potential producers, architects
and project developers. Some of the facts are LE specific others are valid for all WWCB products.
A number of material properties of WWC are independent of density and or thickness. The testing of these
properties has been well documented by most of our customers. Especially accessible is the English
brochure of Celenit where pages 6 to 9 show some general properties of the thinner ceiling boards. For
homogeneous WWCB the figures of the product Celenit N are most compatible with the WWC as used in
Large elements. As the maximum thickness given is 75 mm extrapolation of the thickness range can give
some indication of likely values for LE panels ranging from 35 cm till 60 cm thickness.
See http://www.celenit.it/performance.asp and http://www.celenit.it/characteristics.asp
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Maximum dimensions of the Large Elements.
The dimensions of the Large Elements are determined by the size of the mould and the width of the
distributing machine that feeds the moulds. The most recent design of the Eltomation LE line allows for
moulds up to 300 cm wide and 6 meters long.
To handle this size of panel a certain minimal thickness of the panels is required. Experience shows that at
40cm thick the panels can be demoulded without damage when the density is at least 280 kg/m3. For
thinner panels the combination of density and thickness will need to be determined per production line as
the actual bonding of the locally available cement type used may influence the overall bonding of the
individual fibres in the panel. The maximum thickness of the panels is determined by the height of the
moulds. Panels of 60cm thick have been produced in Sweden.
Density (kg/m3) of Large Elements.
There is extensive experience available in Sweden as Träullit SA has produced substantial volumes of
these panels over the last 5 years. Mostly 40 cm thick but recently also 60 cm thick. Based on the semi
automated process in Sweden the density is given as an average of 280 kg/m3. As local ingredients may
result in deviations in density Eltomation calculates the density conservatively on 300 kg/m3. Actual
reachable minimum densities will depend on a number of factors that can only be found when producing in
a certain location. Besides the quality of the location, the type and quality of wood and the thickness of the
fibres influence the thickness of the mat that is distributed in the mould. Also the weight of the matt
pressing on the material below has influence on the resulting density of the end product. Until more
accurate figures are available from actual production of a specific Large Element plant in a specific location
it is advised to calculate constructions with the value of 300 kg/m3.
Calculated moisture content and water absorption ability.
The information made available by Träullit are based on a density 290 kg/m3:
The given absorption ability is 8% average at RH of 50%.
Air permeability coefficient (m³/m²hPa)
The Swedish Large Elements have an Air permeability of 20 m3 mhPa at 40 cm thickness.
Bending strength, tensile strength, modulus of flexture.
At 40 cm thickness the bending strength as tested on the Träullit Large Elements is 27 kPa. As the product
is applied in Sweden as the insulating mould of a (steel reinforced) concrete skeleton, the dimensions and
load bearing strength of the concrete columns and ringbeam combined determine the overall strength and
stiffness of the total construction. As the individual property parameters of a panel may vary depending on
density, dimensions and quality of the ingredients it is advised to base the calculated strength of a
construction mainly on the load bearing capacities of the concrete, steel or wooden skeleton. For certifying
authorities this is the most acceptable method and thus both the most safe and practical approach to get
approval of any type of construction with LE. So by ignoring the above properties of the large element and
by considering it only as insulator in the construction, any constructor/architect can calculate the
construction according to existing local regulations.
Hardness index and resilience
WWCB as a material itself has limited hardness. The actual hardness of a wall is the result of the density of
the Large WWC Element in combination with the thickness and quality of the layers of stucco that cover the
walls on either side. Also the mesh to avoid cracks in the first stucco layer can give additional hardness and
strength. The steel mesh will be more resilient than a nylon mesh. Test done by Träullit show a
compressive strength of 27 kN per meter of wall at 40 cm thick. This value shows that the test was done
only from the top down as that is the most relevant figure for the load bearing capacity of the wall.
Thermal conductivity and thermal resistance
At the given density of 280 kg/m3 and 40 cm thick the U value of the LE is given as 0,19 w/m2 ºC.
The corresponding R value is therefore 5,263. For the US this R value= 30 for 1'6" thick LE walls.
The thermal storage capacity at 40 cm thickness is 250 kJ/m2 ºC.
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Calculated frost resistance cycles.
Although no specific test has been done on the LE material the various producers of the same material for
ceiling boards give test results for no loss of properties after 20 cycles of frosting and defrosting in water.
Practical exposure of raw WWCB in Sweden show same results after 60 years of Swedish summers and
Winters.
Fire resistance.
WWCB as a material has been tested over the years for fire resistance according to protocol DIN 4102 and
received a classification of B1 (hard to ignite) The modern EU classification is now EN 13501-1 and the
obtained fire resistance class is B-s1,d0. The explanation for the Swedish REI 360 is that even after 360
minutes of fully deployed fire the material shows no loss of load bearing properties. The test results of a
test in Sweden were 1200 ºC on one side resulted in 45 ºC at the outside after 6 hours.
WWCB has been ASTM E84 tested in the passed and received an A label: flame spread 15, smoke 0.
Toxic emissions
Possible smoke from burning or glowing of WWCB does not contain harmful emissions of any kind.
Variable production capacity/volumes
These depend on the actual thickness of the panels to be produced. A separate excel spreadsheet is
available showing volumes of output in panels and the required input of main production material to reach
that volume.
Certification
For practical reasons the low density WWC should not be included in construction calculations as this in
general requires that the material needs to be certified for load bearing properties. For calculating
constructions where the WWC is the insulator the calculation should always be based on the structural
strength of the wooden, steel or concrete skeleton. That way the restrictions for use in most types of
constructions is circumvented while the limited added strength of the WWC material give some added
strength above the calculated values.
References:
LeichtbauplattenFibel (1985)
Eltomation website /publications general and specific.
IIBCC 2008, Ruckert (Nike Arkitekts Sweden)
IIBCC 2008, Aro (NRRI, USA)
Lund University study Sweden
Websites:
http://www.traullit.se/
http://www.eltomation.com/
Eltomation B.V.
Dr. Willem Dreeslaan 33
3773 CX Barneveld / Holland
P.O. Box 203
3770 AE Barneveld / Holland
Phone: +31 342 476 353
Fax: +31 342 475 618