In the wake of Copenhagen, there is a new impetus for finding new ways to reduce carbon emissions in the built environment, affecting both new build and refurbishment projects.
Traditional materials are now being re-examined from the aspect of sustainability, in order to assess the damage which they may cause to the Planet during their manufacture as well as throughout their life and upon disposal.
This has caused many specifiers to become dissatisfied with their historically traditional materials - and who are now seeking a more benign and longer lasting alternative. Areas of discontent (supported by Greenpeace and Good Homes Alliance) are -
* Human toxicity and greenhouse gases from PVCU
* Tropical rainforest destruction and continuous maintenance of Timber
* High embodied energy and poor insulation properties of Aluminium.
Clients and specifiers are increasingly demanding higher sustainability standards through increased levels of performance under BREEAM and Code for Sustainable Homes. Carbon neutral construction is also being mooted and whic women's jackets h is scheduled to be adopted in Wales by 2012. One of the single most important criteria in these higher standards is thermal insulation.
50% of all CO2 emissions in UK is due to heat loss from buildings, whether commercial offices or housing. Windows are the weakest point of insulation in all buildings, accounting for over 25% of that heat loss, a prodigious proportion of the total UK carbon footprint.
The weakest point in the insulation performance of a window is not the glass but the frame that holds it. So a well insulated double or triple glazed unit can be let down by using poorly insulated window frames that allow heat to escape around the glass, more easily.
non housing projects requiring thermal U values of less than 1.6 are increasing - and the dominant incumbent supplier, aluminium, cannot generally achieve better than about 1.8. Building projects often specify lower U values down to 1.0 and on which aluminium has had to be completely discounted. Fibreglass has inherently low thermal conductance and can therefore provide U values as low as 0.9 and still without compromising the other performance criteria of aluminium.
Pultruded Fibreglass is a strong and durable alternative, which has many beneficial properties (detailed below) - but one of them, critically, is very low thermal conductance, which means it can provide exceptionally low U values for windows, from 0.9 - 1.6 W/m2K. So, it is with ideal timing that this 'new' material has become available for window frame manufacture, when it is most needed - but many industry professionals remain unaware of it.
Fibreglass (or GRP, or 'Composite Material') is a Fibre Reinforced Polymer (FRP) which is strongly recommended by BRE for heavy duty external applications within the building industry. BRE set up 'NGCC' (Network Group for Composites in Construction) in 2001, solely to promote the benefits of FRP to the entire industry. Fibreglass windows are available which are fully certified by BRE and have considerable independent support test data and accreditation.
"Pultrusion" is a manufacturing process for producing continuous lengths of glass fibre reinforced thermosetting resin, developed for window frame manufacture in North America in 1980s/90s. Windows made with fibreglass frames have been proved to provide much lower U values than other materials for any given glass specification (0.9 - 1.6 W/m2K). Fibreglass also provides longer life (50 - 75 years), better acoustic performance (Rw 38 - 41) and can potentially achieve 3.5 additional credits in an assessment for BREEAM or Code for Sustainable Homes.
Advantages of GRP Fibreglass fall into 4 main areas:-
* Performance:
o Already widely used to manufacture the best skis, tennis racquets, fishing rods and golf clubs. Even the new Boeing 787 'Dream-Liner' has 94% of wings and fuselage made from FRP nano-composites.
o Fibreglass is unaffected by climatic conditions, including moisture, salt/sea spray, UV light, or extremes of heat or cold.
o The coefficient of expansion is negligible and can be discounted for all practical purposes.
Pultruded GRP has a strength to weight ratio of double that of steel and five times reinforced concrete and therefore much greater than aluminium - and far more resistant to distortion and impact damage.
o Requires no strengthening metal inserts like PVC, which transmits cold (thermal bridging)
o Service life is 50 - 75 years. This is at least double the life of all other window materials.
* Sustainability:
o A recent independent "Sensitivity Report" comparing Pultec with BREEAM - has concluded that 3.5 BREEAM credits are potentially available from using Fibreglass, due to the accumulation of numerous significant benefits.
o Some of these include, recycled source material, no VOC's, low embodied energy, zero potential for Global Warming and Ozone Depletion (GWP and ODP), Very long life, excellent heat and sound insulation and zero maintenance required.
o Ultimate disposal is also an environmental positive, by grinding the GRP down and using it as a filler in concrete to improve the binding nature of the mix.
* Maintenance:
o Every window material, except Fibreglass, is susceptible to UK weather conditions.
> Timber rots when wet - so must be regularly painted to slow down that inevitability. This is an unsustainable and expensive process over the life of the window.
> PVC can discolour or craze in UV light and become brittle in cold and soften in heat - but however it discolours or crazes, it cannot be rectified.
> Aluminium is susceptible to the salt/sea corrosive element in our maritime climate, exacerbated by the on-shore prevailing winds. This attacks the aluminium and will quickly exploit any exposed metallic surfaces, scratches or surface damage to its essential powder coat protection - and which cannot then be repaired.
> Fibreglass is completely impervious to sea-water spray and requires no surface protection from the elements. The colour is applied for aesthetic purposes only. Ironically, however, Fibreglass can easily be repaired and/or re-painted if ever required, during its very long life, when no-one can know what damage may occur in the future. It is reassuring for clients to know that no such damage should require the replacement of any window before the end of its natural, predicted life.
> Appearance. All man-made pigments will fade. What matters is, a) how quickly will they fade - and b) what can be done about it? Even if undamaged, aluminium and Fibreglass will lose some colour at about the same slow rate over 20 years. However, Fibreglass retains the option to have the colour easily re-applied if/whenever required, whilst aluminium can only continue to decline aesthetically until replaced. In fact, the poor appearance could trigger premature replacement, where aesthetics are all-important. In future, such issues need to be considered at the design stage for these new, longer life products.
* Value:
o Fibreglass and aluminium are similarly priced, window for window - despite fibreglass providing significantly lower U values and longer life for a similar unit cost. The extra BREEAM credits can also prove invaluable.
o Add to this, the greater flexibility (and peace of mind) re maintenance options - and the ability to maintain the highest appearance of fibreglass throughout its life, with little danger of sustaining any terminal damage necessitating premature replacement.
o Finally, it is maintaining all the benefits over the 50 - 75 years life which proves irresistible in determining that Fibreglass is the far better value for the client, contractor and community at large.
o Fibreglass tends to be more expensive than timber or PVC to purchase, however,
> A BRE Whole Life Cost report demonstrates the better value of Fibreglass than PVC over 30 years. 20 - 45 years still remain.
Furthermore a specific report "Cost comparison with softwood" demonstrates the significantly better value of GRP over softwood both financially and environmentally!
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