Amended part l and its impact on pvc-U windowmakers thermal efficiency

Since the earliest days of double glazing, the PVC window industry has played a major role in improving the quality and energy efficiency of the UK’s homes.

In the last decade in particular, we have seen significant advances in technology. Innovations ensure that fabricators can stay ahead of the game and provide highly future-proof solutions for householders, housebuilders and social housing providers.

Part L amendments

Ensuring the highest standards of energy performance are achieved in today’s windows is vital. The government has stuck to its plans to keep Part L of the Building Regulations under constant review to comply with the EU Energy Performance of Buildings Directive, but this is just the beginning.

Recent figures show that the UK is already failing to meet its targets to reduce carbon emissions, which means that the whole building industry will need to brace itself for even tougher future Part L legislation.

The likely outcome of the 2005 amendments where dwellings are concerned, Part L1, will be a split to consider new dwellings (L1A) and existing dwellings (L1B) separately. The objective will be to move away from simply looking at U-values of the various window elements to measuring the energy performance of the whole window, considering for the first time positive factors such as solar heat gain.

BFRC rating system

Whilst there is a degree of uncertainty over Part L1A in terms of exactly what the Building Regulations will demand from housebuilders, refurbishment projects under Part L1B will require an area weighted average whole window U-value of no worse than 2.0w/m2K. However, a much more user-friendly approach to measuring the whole window’s energy performance – and acceptable under Part L – comes with the implementation of the BFRC window energy rating system.

Under this system, each window will be independently rated for its energy performance in the same way that products such as washing machines and fridges have been for several years now.

The minimum grade for replacement windows under Part L1B will be ‘E’, but this will only be tightened as CO2 reduction rises higher and higher up the agenda in the coming years. This is why fabricators must look to the future, rather than just reaching the minimum standard today.

fabricators must look to the future, rather than just reaching the minimum standard today

Preliminary testing has demonstrated that Sheerframe PVC windows can deliver high ratings of ‘C’ and even ‘B’, depending on the configuration, under the BFRC system. But how has this high performance been achieved?

Developments

One of the most important developments of the last 25 years was the introduction of the co-extrusion process, which was pioneered in the UK by L.B. Plastics in 1996. Although commonplace now, this ability to reduce heat loss through better weatherseals continues to be vitally important in creating an energy efficient window.

A further development that aided the energy performance of windows was the introduction of a four and five chamber profile design. Compared with traditional two or three chamber profiles, this brings a substantial reduction in heat loss as the increased honeycomb effect brings improved thermal performance.

The latest development to improve the thermal performance of the PVC window was the introduction by L.B. Plastics of Thermlock. This new type of reinforcer reduces the problem of conductivity of steel or aluminium reinforcement compromising the energy efficiency of the frame. By encapsulating the metal reinforcer with a specialist thermoplastic compound, the performance of this component – and the window – is transformed.

Thermlock sales soaring

Reflecting the key role it plays, sales of Thermlock have soared since its launch only 2 years ago. In the past 12 months alone sales have increased by 1200%, while during the same period sales of standard aluminium and steel reinforcement have fallen.

This combination of advanced features has delivered a PVC window that sits extremely well with the tightening of Building Regulations. It has been achieved through a forward-thinking, continuous development programme by L.B. Plastics and offers the ideal solution for low-energy homes. Add in to the equation PVC’s excellent recycling potential and the real progress that the window industry has made to meet tough targets for collectable post-use frames, and Sheerframe windows score very highly in terms of overall sustainability.