41692
July 2024
Stop heat loss in your home with CosyGlazing - the secondary glazing systems from Mitchell & Dickinson
Pictured isCosyGlazing,the advanced secondary glazing solution
As a nation,we losean averageof£770m each year in heat loss through poorly insulated homes. For some homes,it's an easy decision to specify new windows to stop the draughts but,for the nation's 2% which are categorised as listed properties,it is not such an easy choice as the windows cannot be replacedwith modern alternatives; while the original aesthetics and fabric of the building cannot be changed.Mitchell & Dickinsonhas developed the perfect draughtproofing and elegant and advanced secondary glazingsolution, which iscompliant for listed propertiesand will retainheat loss and bring the property to modern standards of thermal efficiency without comprising the original exterior features.
"20% of heat is lost from glass and 30% from draughts, so in total, 50% of heat is lost from single glazed draughty windows and doors."
When it comes to heat loss in old buildings, windows are among the biggest culprits. Not only are they draughty around the moving parts but the glass itself acts as a significant thermal bridge due to its high thermal conductivity. These factors result in higher energy bills, condensation, mould and discomfort. The temperature asymmetries close to poorly performing windows mean we tend to move away to stay warm and avoid losing body heat. As a consequence, the usable space within a room is reduced.
At one time, these issues were simply endured and, to a degree, mitigated by using heavy curtains or shutters. Today, the cost of heating homes and the climate emergency mean more efficient solutions are needed. The addition of supplementary or secondary glazing to the inside of existing windows is seen increasingly as the most cost-effective, least damaging and non-intrusive answer to improving energy efficiency when dealing with old windows.
Secondary glazingsuchasCosyGlazingnot only minimises the risk of compromising the historic integrity of a window but has the added potential to provide acoustic insulation and security. Creating an insulating air gap, its overall thermal performance can be as good as or better than double glazing, reducing heat loss by up to 70%.
Clunky and ugly secondary glazing is generally a thing of the past, superseded by innovative, aesthetically pleasing systems that are easy to install anduse.Even so, there is plenty to think about. At its most basic, secondary glazing adds an extra pane of glass or plastic to the inside of the window; this may be fixed, sliding or integrated to move with the window. It is sometimes removed and stored during the warmer months of the year.
Fixed secondary glazing
Normally installed over both the window and its frame, fixed secondary glazing is ideal where windows do not need to be opened and a high degree of air tightness and acoustic insulation is required. Access to the window itself is limited except for occasion maintenance, so a fixed system is not suitable where ventilation or an escape route in the event of a fire is required.
Proprietary systems often employ a bespoke light-gauge aluminium frame. This may be powder-coated with a finish that complements the interior decoration of the existing window. The units can have a subframe which is screw-fixed and mastic sealed to the window frame or be fixed in conjunction with a magnetic system. Alternatively, a wooden frame may be made up by a joiner, most often of oak or a modified timber. The frame must be dimensionally stable, as any distortion will result in air leakage. As wooden sections tend to be larger than those of aluminium, they are invariably more visually intrusive and may require substantial fixings that can be damaging to the building's fabric.
Another option that lends itself to fixed installation is plastic glazing held in place with magnetic tape. It provides a quick, lightweight, cost-effective solution and is particularly suited to difficult to access windows. It is easy to remove for cleaning and maintenance.
Opening secondary glazing
Secondary glazing units that can slide either horizontally or vertically are versatile. They offer a good balance between improved energy efficiency and comfort and the need for ventilation and easy maintenance but tend to be less discreet than fixed systems.
Highly bespoke, the units are generally manufactured of light-gauge aluminium. To be visually acceptable their structural elements must be as slim as possible and match exactly with the meeting rails or mullions of the window with which they are paired.
An alternative opening system utilises a hinged casement that opens inwards. Offering good ventilation and a means of escape if required, these units can appear cumbersome and not in keeping with an historic interior, especially when open.
Integrated secondary glazing
Virtually invisible, integrated solutions, such as Mitchell & Dickinson'sCosyGlazing, enable windows to be opened and closed as originally intended. Although removable for cleaning and maintenance, no additional frame is required.
TheCosyGlazingsystem employs Plexiglas fixed with magnetic tape. It is fully integrated with the windows which are reengineered and draught proofed. Draught proofing is essential because, unlike many fixed or opening systems, the secondary glazing does not cover the junctions between the window and the frame.
Integrated secondary glazing works with all types of windows, whatever their shape and size, and can be used on stone mullions.
Glazing types
With glass secondary glazing, toughened safety glass should be standard. In some cases low-emissivity (Low-E) glass, which has a special coating that improves the thermal efficiency of the glass by reducing heat transfer, is employed to enhance energy efficiency and help lessen overheating from solar gain.
Plastic glazing options such as Plexiglas and polycarbonate provide distinct advantages over glass and have become popular due to their lightweight, durability and versatility. Plexiglas is seven times more effective as an insulator than glass; both Plexiglas and polycarbonate are fire-rated. Plexiglas is fully UV-proof and is stronger but softer than glass so can be scuffed by abrasives, although scuffs may be polished out.
Magnetic tape
Adhesive magnetic tape is widely used to hold secondary glazing in place. The tape - typically 12 mm to 20 mm wide - is attached to the edges of the double-glazing panel. A second strip of magnetic tape, or in some cases asteeltape, is bonded to the frame or, in the case of integrated systems, to the sash or casement itself. It is vital that the polarity of the two magnets is aligned correctly.
Using magnetic tape has the advantage that screws or other fixings that involve drilling into the substrate are avoided, minimising damage to the window frames. The secondary glazing may easily be removed during the warmer months or for cleaning, leaving only the magnetic tape in place on the window frame.
Maintenance and performance
All systems require both the secondary and original panes of the glazing to be periodically cleaned, as well as the void in between. How regularly will depend on local conditions. With opening systems, the tracks or hinges may need to be lubricated periodically.
The longevity of secondary glazing will, to a certain extent, depend on how it is treated. Abrasion and over vigorous cleaning will almost certainly have an impact on some plastics. Warrantees and life expectancy claims vary and should always be checked -CosyGlazinghas a design life of at least 30 years. The overall effectiveness of any system will depend on how well it is detailed and installed. It is worth remembering that the needs of the various windows in an old house may vary significantly so, within one building, a range of secondary glazing solutions may be required.
For further information, please visithttps://mitchellanddickinson.co.uk/
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Editor's note
Mitchell & Dickinson specialises in delivering bespoke insulation solutions for period homes and listed buildings in the UK.Products include a unique, advanced secondary glazing system known asCosyGlazinghigh-qualitydraught proofing for windows and doors, and specialist sheep's wool insulation for underfloor, sloping ceilings and lofts which will greatly improve the energy savings, soundproofing and ventilation. Mitchell & Dickinson's insulation solutions are installed on site, by expert craftsmen all of whom are direct employees and fully trained in house. The company also offer restoration services which often precede the installation of
One of the founding principles of Mitchell & Dickinson is to cut carbon; the carbon savings that result from the work carried out are 50 times greater than the carbon footprint which ensures Mitchell & Dickinson is a carbon-negative company. So far,over 100,000 tonnes of CO2e has been saved since Mitchell & Dickinson started insulating homes in 2010, which equates to 800,000 flights to Paris, or 50,000 cars taken off the road for a year.
With compliments:
Taylor Alden
7 Bell Yard
London
WC2A 2JR
Email:media@tayloralden.co.uk