A highly sustainable window thanks to the Mother of Invention

It is true that "Necessity remains the Mother of Invention". When our backs are against the wall we are somehow inspired to create an innovative solution.

There have been many examples throughout history but one that springs to mind was the development of the Spitfire aircraft in the 1940's, not a moment too soon to help win the Battle of Britain and avert the imminent invasion of Great Britain.

Today, we are collectively facing an even greater threat to mankind, in the shape of global warming and climate change, which is requiring countries around the World to pull together in reducing the carbon emissions that are causing the problem, by burning less fossil fuel. Since fossil fuel includes gas, coal and oil, which is also used to create electricity, then the scale of the challenge begins to emerge. Historically, this has been our entire source of energy. Apart from nuclear fuel there is no other major source of energy available which can even hope to make significant inroads into supplanting current sources of energy, for many years to come.

So, if we can't create a cleaner fuel supply quickly, the only other way to reduce emissions is to reduce demand. That requires either going without altogether, or to design and refurbish our homes and buildings more intelligently, by improving thermal insulation and reducing heat loss so we consume less energy in the first place. This also saves us money of course, so is self justifying, anyway.

In seeking to reduce heating costs from buildings (50% of the total CO2 emissions from UK) there has been a Government initiative for some years to insulate roof spaces and walls better and in commercial premises, UK Building Regulations have increasingly required maximum levels of heat loss to be designed into all new construction.

With roofs and walls taken care of, the next major source of heat loss is through windows accounting for 25%. Interestingly, the main heat loss is not caused by the glass so much - but the window frames holding the glass that allow heat to escape through them. Insulated (double glazed) glass, today, can achieve a very low heat loss of around 0.6 - 1.0 'U' value. 'U' value measures the degree of heat lost so a lower figure is better. 'U' value is measured in W/M2K = Watts of heat lost per square metre, per 1 degree Kelvin drop in temperature.

So, in order to maximise heat loss through windows we ideally need window frames that are themselves low conductors. As we know, ironically, metal is a very good conductor - therefore, unavoidably, a rather poor insulator. For example, aluminium windows can only just reach maximum allowance under Building Regulations of 1.8 'U' value. PVC windows, too, must have large metal sections inserted to provide sufficient strength - but those concealed sections also act as a 'thermal bridge' and transmit cold inside, also lowering the insulation performance of the complete window. Timber windows perform better thermally - but their Achilles heel is the regular amount of expensive and unsustainable maintenance that they must have throughout their life - and it was to get away from that excessive maintenance burden that caused the introduction of PVC and aluminium windows in the 1970s and 80s!

This then, is the dilemma today, in finding the best and most sustainable solution for reducing heat loss through windows, without incurring maintenance or other unforeseen problems.

Typically, at the eleventh hour, in steps the Mother of Invention! Fibreglass is a well known and well respected material for long life, good durability, great strength and being impervious to all natural elements including salt/sea spray. But, until recently, it hasn't been able to be made in long lineal lengths essential for cost effective window frame manufacture. However, in the 1980/90s a revolutionary production process called 'pultrusion' was developed in North America, enabling continuous fibreglass to be made for the first time.

Fantastic! This meant that the enormous benefits of fibreglass could, at last, be brought to bear on the window frame market, with some dramatic results. Suddenly, a window frame material has become available at just the right time, which reduces thermal insulation significantly but without incurring any maintenance, or suffering from the UK maritime climate, or being susceptible to UV sunlight, or creating greenhouse gases and ozone depletion. In fact, this is the answer to a maiden's prayer in terms of sustainability, environmental friendliness and sheer fitness for purpose.

This Fibreglass material could not be better suited to the needs of our window frame market. Resilient, able to be repaired and repainted, unaffected by rain, sun, wind, ice and sea water, indestructible by natural forces, service life of 50 to 75 years, available in any colour, containing no chemical nasties and releasing none, coming from a 23% recycled source and being able to be 100% recycled at the end of its very long days. In addition it has twice the strength to weight ratio of steel and five times that of reinforced concrete, no less.

This is an astonishingly strong and proven compound. Pultruded fibreglass has been recently described by industry experts as "totally the future for window manufacture - nothing else even comes close". Just like those superior qualities of the Spitfire, so long ago!

Finally, despite the exceptional qualities and benefits, Fibreglass very often, actually costs less than aluminium, so it really is a 'no brainer'!