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What everyone ought to know about uPVC, the advantages and disadvantages

With the amendment to the national building regulations and to satisfy SANS 10400 XA and SANS 204, our love for massive windows to showcase our magnificent views is posing some interesting challenges. As windows transfer heat/cold over 10 times more than typical wall structures, and conventional doors struggle to keep the south easter/winter storms out, it makes sense to look at fenestration as it impacts the energy usage in buildings.

Lets face it, no one wants to compromise on their light or view, so one way to comply is to use more efficient glazing materials. Whilst researching what the rest of the world has been doing for decades and on a recent visit to the UK I rediscovered uPVC (unplasticised Polyvinyl Chloride).  I say “rediscovered uPVC” as it is not what I remembered and things have definitely improved.

Thermal Properties – Without a doubt there are clear thermal advantages to using uPVC, as the solar heat gain coefficient and thermal transmittance U values are far superior to aluminium, steel and in most cases timber (depending on the type of timber used). What this translates to are warmer houses in winter and cooler houses in summer, plus larger glazing areas (keeping your precious view) that comply with the regulations. uPVC prevents thermal bridging so prevents condensation unlike aluminium.

Cost – Some installation quotes have been cheaper but majority of quotes have been a bit more than timber and aluminium. However, it’s a bit like comparing apples and oranges. One thing that is sure enough is that in the long term the uPVC will give greater savings due to the energy efficiency, low maintenance and durability properties. House value increased in overseas markets and there is no reason why the same is not true here with the installation of uPVC.

Maintenance – A clear winner above aluminium, steel and timber. uPVC never rots, flakes, rusts, fades, pits, peels or corrodes. uPVC needs only a light soapy wash and a check of the seals for maintenance. Aluminium can scratch and chip on the surface coating leading to exposed damage, where uPVC typically has colour all the way through its profile so any scratches aren’t noticeable and it is tough on impact. Wood is becoming a gamble as to find good quality hardwoods is extremely difficult or expensive. The less dense woods of today need to be maintained almost annually and many people forget to factor scaffolding, pest control and wood treatment costs at their peril.

Expertise – Most uPVC suppliers both manufacture and instal, so cost is reduced and you have a better chance of getting the expertise to achieve what you want. Although uPVC is “new” to the SA market, it has been used worldwide for over 50 years and we are benefitting from the technological advancements over the years. The chance of receiving quality goods and service( as well as after sales service) greatly increases as you are utilising a one stop shop.

Aesthetics – This used to be a big disadvantage for uPVC as the look and quality used to be poor, with discolouration, cracking and poor UV ratings; but no more. With colour stabilisers, laminates and the ability to spray the frame with technology borrowed from the automotive industry; wood grain texture and any colour imaginable are now possible. This is such an advantage to extensions of older houses, as otherwise to match new timber to the old timber is extremely difficult and costly. An added bonus is the recent ability to have a different look internal to external, so it can fit into the look of the street while inside it can be as individual as your taste dictates. Nice.

Environmental impact – uPVC has minimal impact all the way through its life cycle. With PVC being the worlds 2nd most widely used plastic material, this non hazardous material recycles, so only 2 % found in waste stream. It is made from salt (from sodium chloride; chlorine is extracted) and oil (ethylene) so it has a relatively low embodied energy (1/3 of aluminium). Also in the pretreatment of aluminium many toxic chemicals are used throughout the process where this is not the case for uPVC. Tropical hardwoods are struggling to be sustainable, where all German uPVC is totally recyclable by law. Another consideration is uPVC lesser weight, making less transport costs.

Chemical resistance -  uPVC is a stable material so is pollution, sea water resistant and chemical proof. This makes for greater ageing resistance compared to the other fenestration types. Wood can swell and rot and aluminium and steel can corrode and have galvanic reaction to the fasteners.

Fire resistance – Fire tests have shown that uPVC materials, being naturally flame retardant throughout their product life, will not cause, support or enhance the development of accidental fire and are in fact self-extinguishing.

UV Sunlight – uPVC is sensitive to UV and oxidative degradation and this was one of its major disadvantages. Technological advances have addressed this problem by adding anti-oxidants and other stabilisers. To check this ask for the specification and UV warranty. The reason most uPVC colour is white is because it aids reflection of UV, thereby reducing heat build up. Wood, steel and aluminium are also affected by UV and regular maintenance  must be done to combat the ageing effect of the sun.

Water tightness and soundproofing – With uPVC unit being fuse welded all around it is sound, wind and rain sealed, unlike aluminium and wood which are mitre joined at the corners. These mitre joints are areas of weakness as the frame sections move to accommodate wind loads, climate expansion and contraction. With wood warping and swelling over time, air infiltration and reduced energy efficiency occurs.

Security – uPVC is reinforced with galvanised steel so as strong as other types of frames. Similar to the other types, added security features can be incorporated in the glazing. The uPVC profile can be made to have continuous beading on the outside unlike aluminium beading, which if know what to do can pop off glazing in seconds. With uPVC’s multipoint–tilt and turn hardware can change the sash window to a 10 degree tilting vertical window. This opening is secure whilst allowing ventilation.

Hardware (locks and handles) – There are many different types, quality, cost, aesthetics similar to the other types of fenestration so ensure the specification matches what you require. A big selling point for uPVC’s is the multipoint–tilt and turn hardware as gives the option to change from a sash window to a vertical tilting window.

Custom built – uPVC is manufactured to custom size so easy to replace existing retro fits to any shaped openings and can be profiled to Architects or clients pleasing shapes. To match existing cottage pane, the profile can be placed in-between the double paned glass to get similar look. Also in-between the glass a moving blind can be placed to help control the sun.

Regulation and quality – A word of caution, just like wood, glass, steel and aluminium; uPVC has varying quality depending on the class and specification. Depending on the company profile, steel reinforcing, fittings and hardware could be either German, Turkish, Chinese or Indian or a mixture of them all. This impacts greatly on quality and price ( up to 40 % more) so relate it to worldwide spec EN12608 and compare warranties.

With 3/4 of all new windows in Europe and USA reportedly being uPVC, the rise in popularity of uPVC is sure to happen here in South Africa.  This should further reduce pricing and increase quality and expertise. Talking to suppliers, architects and clients about uPVC generates a great positive response, and it’s refreshing to be part of the solution.

by Mathew Streatfield


Welcome, I am Mathew, a civil engineer with 20 years experience in construction. I now advise on energy efficiency in residential and light commercial buildings, and I would love to help you.

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