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Comparing façade
systems
Bryn Williams, quality manager at rainscreen cladding
manufacturer Steni UK, discusses the findings of an
ecological comparison of façade renovation systems.
R
ainscreen cladding systems are on environment, measured
something of a modern-day by the LCA factors.”
wonder product given their ability The study was conducted
Right: Before
not only to transform the using mainly Life Cycle
renovation
aesthetics of a building but also Analysis developed by the Above: After
appreciably upgrade its performance, Society of Toxicology and
Building Materials & Equipment
specifically in the area of thermal Chemistry (SETAC) – transportation and
insulation. the effects of the energy required for
Not only can such systems breathe renovation work were not taken into
new life into tired, badly-performing account.
buildings such as offices and residential The investigation considered seven
tower blocks, they are also a highly different system materials – glass fibre
effective method of branding buildings, reinforced polyester, fibre cement,
given their availability in a wide range of brickwork, concrete panel, plastering, thin
colours and finishes. film steel cassette and thin film aluminium
The principles of ventilated rainscreen cassette. Insulations studied were glass When Nutrification Potential was
cladding systems are governed by wool and expanded polystyrene. Framing studied, glass fibre reinforced polyester
BS 8200. The cladding is fixed back to the systems were aluminium, steel, wood systems were virtually matched in
main support structure, forming a studs and punctual fastenings. performance by 30mm of plastering
relatively lightweight, colourful weather- The Global Warming Potential, [0.6g (phosphate)/m² of wall surface and
resistant overcoat. The benefit of this Acidification Potential (AP), Nutrification 0.7g (phosphate)/m² of wall surface
system is that any moisture, either ingress Potential (NP), Photochemical Ozone respectively]. Fibre cement board
or humidity, is ventilated out of the cavity, Creation Potential (POCP) and Critical Air scored 1.3g (phosphate)/m² and 40mm
ensuring the insulation and the inner leaf Volume (CAV) were compared and in each concrete panel returned a reading of
of the building are not affected by category glass fibre reinforced polyester 2.5g (phosphate)/m². Brick façade (130mm
condensation. panels recorded the lowest – and thick) topped the NP scale with
A range of different cladding systems therefore most advantageous – readings. 10.5g (phosphate)/m², with thin film
are available in the UK, from thin film Indeed, in most cases, its results were aluminium cassette of 1.5mm thickness
aluminium or steel cassettes to fibre less than half of its closest rival. scoring 9.1g (phosphate)/m².
cement and glass fibre reinforced Take for example the GWP results. Glass fibre reinforced polyester
polyester composite panels. Fixing Glass fibre reinforced polyester rainscreen systems also performed well in tests
systems also differ – designers can select cladding panels 8mm thick returned a measuring the energy contents of façade
from wood, aluminium or steel stud in reading of 2,400g of CO
2
per square metre materials, registering the lowest score of
different thicknesses. But which cladding of wall surface. The next closest was 80MJ/m² of wall surface. The highest was
system to choose? 8mm-thick fibre cement boards at 130mm-thick brick façade, with a reading
A study carried out by the Tampere 5,800g CO
2
/m². An 85mm brick façade of 750MJ/m².
University of Technology (Department of was rated a massive 28,000g and a The study also demonstrated that
Civil Engineering, Institute of Construction 130mm brick façade even greater at framing materials have an impact on
Economics and Management) in Finland 39,000g CO
2
/m². environmental performance. In every
considered the environmental As mentioned previously, these results category, wood stud was the most
performance of the different cladding were mirrored in all but one of the ecologically-sound fixing medium. For
systems and fixing methods in renovation categories studied. Take the POCP results example in GWP tests, wood stud (30mm)
projects, concentrating on the impact of – 8mm glass fibre reinforced polyester scored 560g CO
2
/m² of wall surface,
manufacture and use and maintenance. composite panels returned a score of compared with 30mm aluminium stud
Its report, ‘Ecological Comparison of 5mg CO
2
/m² of wall surface. Its closest (8,800g CO
2
/m²) and 30mm steel stud
Façade Renovation’ helps designers rival was again, 8mm fibre cement board (7,600g (CO
2
/m²).
understand the environmental credentials with a score of 17mg CO
2
/m². Thin film To conclude the report, scientists
of systems and therefore make better- aluminium cassette (1.5mm thick) scored looked at the ecological impacts of a
informed design and specification 5,800mg CO
2
/m² and thin film steel modernised wall structure during a period
decisions. cassette (1.5mm) 7,700mg CO
2
/m². of 25 years from renovation. As would be
And its conclusion is unequivocal – Acidification Potential results also expected, the better insulated the
glass fibre reinforced polyester composite reinforced the sound environmental property, the less ecological impact it
rainscreen panels ecologically outperform performance of glass fibre systems, which caused.
competitors in a number of tests, ranging scored 15g CO
2
/m² of wall surface. Fibre The report stated: “The most ecological
from Global Warming Potential (GWP) cement board (8mm thick) was the next alternative of those studied proved to be a
to Photochemical Ozone Creation closest with a rating of 35g CO
2
/m². Other ventilated structure supported with
Potential. results included 1.5mm-thick thin film impregnated long length wood, insulated
The study states: “The comparison aluminium cassette – 136g CO
2
/m²; with 100mm thick glass wool and covered
shows that of those façade coating 85mm thick brick façade – 197g CO
2
/m² with glass fibre reinforced polyester
products examined, glass fibre reinforced and 130mm thick brick façade – composite.” www.steni.co.uk
polyester composite has the least impacts 274g CO
2
/m² of wall surface.
8 feature :: building materials & equipment Building & Facilities Management – November 2009
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