The World of Fenestration

Robert Hoellirgl, President, Research & Development of Encraft

Robert Hoellirgl, President, Research & Development of Encraft

Construction industry is not a child’s play; staggering blocks of materials that are in stock. It’s a whole lot of complex permutation and combination process to address a particular situation. “It’s all about integrity. It’s refreshing to see that major Indian uPVC profile extruders are adapting, religiously, proven European technology despite the potential raw material cost savings.”

Windows are intended to be the eyes of the building, portraying the architects’ vision, but they are also the ultimate nightmare for any building contractor who has to fill holes in walls at the lowest possible price.  But as a comfort, this problem exists all over the world.

Since the beginning of the Indian high rise building boom, the window and door industry operating in the projects market faces a dilemma – how to provide strong and wind resistant fenestration at the lowest possible price?

How to arrive at the design wind pressure is comprehensively covered and explained in the Indian Standard IS 875 part 3. It is expected that windows and doors have to cope with the same wind pressure as the whole building, therefore frame static calculations are absolutely essential for every project at the quotation/tendering stage in order to establish the profile type, the reinforcement type and size (for uPVC) and the maximum permissible glass area depending on glass type and glass thickness. Providing frame prices to contractors prior to any static calculations, operational stability checks (for sliders), screen passenger loads and U-value calculations (if required) etc. has led to embarrassing situations when the whole budget had to be revised upwards because of under specification or due the occasional change of frame style. Common sense should prevail and all involved parties like architect, structural engineer, contractor and frame supplier should be able to agree a workable frame specification on which the prices should be based on.

Window static is not peculiar to uPVC. It applies to all known frame materials, equally, but no one thinks about the increased profile depth of vertical members (mullions) or frame coupling joints when looking at aluminium or wooden frames, especially historic wooden frames. But no one has ever considered the wind speed differences between India and Europe. For example: The lowest Indian wind speed is 33 metres/second (Bangalore) whilst the highest wind speed in the UK is 31 metres/second followed by Germany with 30 metres/second. India’s average wind speed of 44 metres/seconds (Mumbai, Hyderabad) used in high rise projects (up to 100 metres) results most of the time in design wind pressures for fenestration exceeding 2000 Pascal.

Frame suppliers are perfectly capable to submit static calculations for approval and acceptance based on their own IS 875 part 3 design wind pressure assessment. Then why the original (and government approved) design wind pressure of the building cannot be forwarded to the frame supplier?

Frame static is only one part specifying the ‘right or most appropriate’ frame style for any high rise project which is equally challenging because of customer expectations, mandatory compliance with standards and regulations, ergonomic and environmental considerations, child safety, safe cleaning ability etc.

One of the big advantages of uPVC is the inherent material elasticity and memory i.e. uPVC after being exposed to any pressure or force will always return to its original position whilst aluminium may stay deformed and wood will split or crack. Nevertheless, uPVC, like other frame materials, has to provide sufficient frame rigidity to cope with the imposed deflection onto glass and hardware.

It is correctly assumed that uPVC frames will resist UV rays and white uPVC frames will stay white but this is where the material differences between uPVC profiles will surface. Some uPVC profiles are manufactured from an upmarket PVC pipe formulation, processing a disproportionally, high amount of low cost filler (calcium carbonate) whilst ENCRAFT amongst others have continued or have adopted proven European recipes which were further enriched to suit India’s varied climate. ENCRAFT has gone a step further and tested their formulation beyond the standard for severe condition to a full 8000 hours rather than the 6000 hours prescribed. It’s all about integrity and long term reputation and it is refreshing to see that major Indian uPVC profile extruders are adapting, religiously, proven European technology despite the potential raw material cost savings.

Nowadays modern windows and doors can provide more than only a shelter from the elements. It has been recognised that a large proportion of costly energy used for cooling and heating is escaping through fenestration. Reducing energy consumption which subsequently leads to CO2 reduction is on top of every Government’s agenda. It is not a choice anymore, reducing CO2 is absolutely essential to secure a liveable environment for future generations. Critics may argue that only 30 to 45 percent of energy losses in high rise buildings are actually through fenestration but the factual energy savings with thermal efficient fenestration would be staggering. Diverting this saved energy cleverly would mean that the remotest Indian villages could receive the most needed electricity sooner.

Contrary to some misconception, the frame, albeit being the smaller area plays an important in the overall frame U-value assessment which is highlighted by the following example:
– 45 mm deep Aluminium frame, 76 mm sight line without thermal break, 5 mm single glazed frame to glass ratio 21/79 – U-value Aluminium frame = 5.9 W/m2K
– Encraft EN 62 uPVC frame, 95 mm sight line, fully steel reinforced, 5 mm single glazed frame to glass ratio 26/74 – U-value uPVC frame = 4.8 W/m2K

The overall frame U-value reduction of 1.1 W/m2K or 18.6% is mainly contributed to the inherent low thermal conductivity of uPVC, the multi-chambered uPVC profile design and the larger (warmer) frame portion. Obviously, changing the glazing from single to double glazing, utilising coated glass panes and warm edge spacer technology would reduce the frame U-value even further.

frames require a high degree of air tightness as well and therefore need to be accurately manufactured. Any short cuts in manufacture or installing with a ‘near enough will do’ attitude will be eventually highlighted by nature. For example: At the end of May 2015 a heavy sandstorm raced through Gurgaon, darkened the sky, exposed all double glazed frames to noticeable deflection and leaving some traces of sand inside our luxury apartment which is located on the 26th floor. Why?

Some of the sand penetration came through the drain slots located in the outer frame base member. The slots were punched straight through and NOT staggered (fabrication mistake). The other area of the sand in-take was created by the missing centre seals, normally located between the Patio door meeting rails (installation oversight). This is also one of the reasons why some owners in the condominium have now decided to replace their uPVC windows with ENCRAFT uPVC windows.

Because of manufacturing issues and missing components we cannot reap the true benefits of an frame. Unfortunately, the best glass combination housed in the warmest frame material is wasted when the frames are badly manufactured and nonchalantly installed.

The trend towards larger sliding frames and subsequently larger sliding sashes in high rise projects has reached alarming concern. In order to stay within the weight limit but achieve the desired heights without introducing fanlights, the sashes are getting taller and narrower thus creating operational problems, considering that a large proportion of the ageing population is occupying modern apartments. Operating heavy sliding sashes with an unfavourable height to width ratio equipped with unsuitable handles has become an insurmountable task for most users.

There is so much knowledge and experience, excellent guidelines and codes of practices which can help to specify ‘perfect’ windows and doors for high rise buildings. At Encraft, we have recognised that part of our business is to advise on fenestration issues because it is virtually impossible for any architect to stay up to date in terms of material development, product innovation, legislation etc. Hence the requirement is for genuine, knowledge based partnerships.

LOW or ZERO carbon homes / apartments utilising fenestration are not a myth anymore; they are being built whilst you are reading this article.

About the Author
ENCRAFT is a product brand of ENCRAFT India Pvt Ltd. ENCRAFT Door & Window systems are engineered with precision and are masterpieces of art. Incepted under the leadership of Robert Höllrigl, an Austrian Engineer with over 30 years of experience in uPVC tooling and extrusion, earlier associated with WHS Halo, one of the UK’s leading fenestration solution providers, he now heads up the R&D and technical department at ENCRAFT where he ensures that ENCRAFT Door & Window systems are at the forefront of the market through continuous innovation in product design. ENCRAFT systems offer a lifetime of style, strength and security. They come in a range of customized designs and wooden finish to match with all décors.

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