Energy Efficiency Heating up the triple debate Neil Ginger, Origin CEO, re-visits the discussion of whether triple glazing is necessary for achieving the best levels of thermal performance, or whether the issues outweigh the benefits for incorporating this degree of glazing installation. Over the last five years, Origin has seen a steady rise in the demand for triple glazing as building regulations become more stringent and the industry becomes increasingly conscious of the thermal efficiency of homes. At Origin, we know how hard it is to strike a balance between the design of modern homes and achieving a high level of thermal efficiency, especially where there is a large expanse of glass. Quite often this is thought to only be achievable through the installation of triple glazing. Production Origin has been offering the choice of triple glazing in its bespoke aluminium bi-fold doors for the last three years, so understands the main issues faced by manufacturers. Whether a window unit or a bi-folding door, the product must be designed to accommodate triple glazing, which is achieved by changing the gasket or bead size. Manufacturers will have to review the tolerances of each component to ensure they are capable of bearing the extra weight, which will involve product testing. This may lead to product development or alterations for stronger components. As a British manufacturer, Origin has complete control over the design, manufacture and fabrication of its systems and can offer a zero lead time service on its bespoke products. However for companies that outsource fabrication, this will not be as simple. A larger amount of space and stock are needed to 52 December 2014 produce the triple glazed units, while operations and processes have to be seamless to avoid errors as the order moves along each process. Thermal efficiency In some cases, the efficiency of high performance double glazed doors is almost as good as, if not better than, a triple glazed bi-folding door. Simply asking for triple glazing is not the answer; ‘U’ values vary greatly depending on the manufacturer. Origin’s double glazed bi-folding doors can achieve 1.67 W/(m²K) using 24mm units which is superior to some manufacturers’ triple glazed products. Origin’s aluminium tripleglazed bi-folding doors have a certified ‘U’ value of 1.3W/(m²K), surpassing the British Building Regulations by an industry leading 27%. Strength and weight The extra glass will mean the sets will be significantly heavier. The maximum weight loads for vans or lorries means fewer units can therefore be delivered at any one time, affecting the number of journeys an installer makes to site with the units. A glass lifter may also be required, increasing the cost of installation. Bi-folding doors create a view of the garden and let in the maximum amount of daylight. However, due to the additional weight of triple glazing, the maximum panel size available for a bi-folding door is smaller than a double glazed alternative. This is because larger triple glazed doors would be too heavy to operate and would not be fit for the end user. By reducing the maximum panel size, an additional door is also required, which increases the amount of door frame interrupting the view. For buildings that include a large expanse of triple glazed glass, a strong material is required for the frames to support the additional weight. Aluminium frames are extremely strong, yet weigh 67% less than steel. This allows bi-fold doors to be made with comparably narrow frames to let in maximum amounts of light. Aluminium is also versatile and strong enough to easily make complex layouts within a building design, such as moving corner posts and bay setups, without being too heavy. Cost Triple glazed bi-folding doors and windows can cost up to twice the amount of a double glazed alternative. Triple glazing is recommended to achieve Passiv Haus standard, however for homes that do not require such a high level of insulation, the house builder will have to assess whether the value added to the property will outweigh the high initial cost of triple glazed units. After all, it will be the homeowners who benefits from the energy savings in the future. Despite the issues regarding triple glazing, each project is different and it is clear that triple glazed units can be beneficial to the thermal efficiency of homes. By weighing up the pros and cons of triple glazing, it is apparent that more consideration must be given to the issues if the construction industry is to consider this as a viable alternative to double glazing.
GGP December 2014
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