054 GGP 1214

GGP December 2014

Energy Efficiency Secure energy efficiency With energy saving measures set to continue, Jamie Lewis, business development manager at SFS intec, discusses the importance of sourcing high performance solutions to prevent losing the intended benefits of energy saving applications. Part L of the Building Regulations (Nov 2013) stated that any PVC-U or timber framed window (installed vertically) or fully glazed door, should have a Window Energy Rating (WER) of band C or better, or a ‘U’ value of 1.6W/m²k or below. But as ‘U’ values continue to fall and airtightness levels increase, it becomes paramount to identify and prevent the sources of potential heat loss at the initial design stage. One such measure that has seen a growth in popularity over the past few years is external wall insulation (EWI). EWI can improve a building’s thermal performance by minimising heat loss and heat gain, reducing bills by as much as 40%. But when you add EWI to the exterior of a property, the windows need to be fixed outboard from the structure over the insulation zone to ensure and optimise energy efficiency levels. But failure to consider the window’s position in an EWI application will have a dramatically negative effect on the window’s ‘U’ value, which in turn can lead to lack of conformity to the required Part L specifications. It can also effect the interior environment as condensation build-up can result in black mould growth leading to serious health issues for occupants, rectification costs and, ultimately, loss of income for the building owner. 54 December 2014 The surface of triple glazing More recently, we have begun to see the specification of triple glazed window units on EWI applications to combat poor ‘U’ values. These systems impose significantly more weight and loads on the structure which must be properly calculated in order to reduce the likelihood of the frame sagging, dropping or simply failing. The resultant damage of such a failure could have significant financial and possibly, legal implications. Given the fairly infant nature of this application, many windows are being installed over external insulation zones using cobbledtogether solutions as few suitable products are currently available. This can include strips of wood or steel beams which are often fitted as a ‘make do’ option, resulting in cold-bridging, a major cause of heat loss. Such practices fail to recognise the importance of factors such as the hardware used, dead and imposed loads of the unit, and the cantilever distance, all of which have an effect on the resultant ‘U’ value, safety and overall performance of the system. Engineered solutions A specifically designed, engineered support system which will accommodate the increased dead and imposed loads acting on the frames is imperative to ensure peace of mind and continued performance. A suitable solution should be made up of jamb and sill brackets that are secured from the inner wall leaf, attaching to the window unit at numerous vital support points. The brackets should be specified based on the mass of the window unit versus the cantilever projection – ranging between 30mm and 150mm – in order to establish the dead loads on the system. Dependant on the cantilever distance, the correct bracket can be chosen to ensure the most suitable selection for the job. In support of this, systems specified should meet the requirements for IFT Rosenheim testing – static positive and negative pressure with +/- 2000 Pa, non-permanent additional load up to 800N on an open sash and also simulated use with 10,000 leaf/sash movements. Don’t cut corners Concerns about the energy performance and airtightness of buildings are not going to diminish, if anything they will continue to be more prominent across the industry in the coming years. So, as the market for EWI and similar energy saving applications continue to grow, we must ensure that due care and attention is invested into the installation methods to gain the true benefit. Both specifiers and installers need to identify the best products and systems which will ensure the long-term safety and quality of the build. “These systems impose significantly more weight and loads on the structure”


GGP December 2014
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