Are your windows up to the job of keeping your home looking sophisticated and feeling snug? Here's our guide to making the most of this important feature.
architects William Russell and Sheila Muiry
When architects William Russell and Sheila Muiry were looking for a site for their new home, the couple searched for a space in east London that fell outside planners’ radar. This allowed them to be extremely free with their ideas – particularly the windows, which, along with the exposed concrete structure, are the house’s most striking features.
The whole of one wall has been glazed with translucent glass, allowing morning light to flood in. But the most incredible part is the two-storey, 5.5m high window that slides completely open to expose the living room to the outside world. The large panels of glass are supported by a secondary steel frame, and this also holds in place galvanised steel-covered panels which clad the rest of the building. Being versatile, durable and needing so little maintenance, steel was the ideal material for such a glazing project. ‘It’s an old modernist idea,’ says Russell. ‘With the windows open on a summer’s day it’s like being in a courtyard.’
To paraphrase Le Corbusier, the history of architecture is the history of the window. Windows are the eyes of the home, letting in light and framing the world outside. They can make or break a house, but aesthetic value isn’t the only factor to consider when buying windows: thermal performance, frame type, durability and maintenance are also important. Thermal performance, or insulation, has become increasingly significant since the government’s Part L emissions regulations were introduced in 2002 and became even more stringent in April 2006. They add to the regulations covering new-builds as well as replacement windows in existing homes.
Materials for framing
Hardwood Durable, biodegradable and with good thermal performance. If you choose hardwoods such as lark, oak and sweet chestnut there is no need for painting or preservatives, making this a very low maintenance – and beautiful – material. And if the wood is Forest Stewardship Council (FSC) rated, it will be eco-friendly as well.
Softwood This shares many of hardwood’s attributes, including good thermal performance, and is much cheaper to buy, but when bought from non- certified forests its logging can cause habitat destruction. Softwood cannot be left untreated, so if eco issues are a concern, go for plant- based paints to finish. Synthetic paints are toxic during manufacture and application, and have high levels of VOCs which pose a health hazard.
Steel and aluminium Used for ambitious glazing projects, steel is structurally versatile, durable, recyclable and very low maintenance. Steel currently contains around 20 per cent recyclate. Its downside is its poor thermal performance, and the toxic by-products of its manufacturing process. Ditto aluminium, which is a secondary material in many wood and uPVC frames as spacers. Aluminium has fallen out of favour as a framing material and is comparatively expensive to install, although the final results can be beautiful.
uPVC Despite its durability, competitive pricing and thermal performance, the uPVC window frame has not added too much to the world of glazing. White PVC can discolour with age, the frames are large in comparison to wood or metal and often require reinforcement – and the chlorine and petrochemicals used in their manufacture pose risks to the environment.
Style of frame
If your house was built before 1900, it will probably have sash or casement windows. It’s often more economic, and in keeping with the style of the house, to have dilapidated and broken sash or casement windows repaired rather than replaced. In many cases, having windows repaired rather than replaced also sidesteps the building regulations (see p126), saving time and money. Secondary glazing, where a second, detachable frame is inserted inside the existing frame to increase insulation, also avoids the need to meet building regs as the original windows can be retained intact. This is particularly useful for listed or historic buildings. If your house has original metal windows, companies such as Crittall and Clement Steel Windows produce Part L-compliant replacement windows.
Glass Until the Eighties, manufacturers improved energy performance by adding additional layers of glass. However, three recent developments in glass technology have steered purchasers away from triple-glazing.
Firstly, the thickness of the air space: increasing the distance between double-glazed panes has improved heat retention, reducing the need for an extra layer of glass. Then, as customers and architects demanded thinner profiles, filling the space between the panes with low- conductivity gas became popular. Gases such as argon, krypton and – ironically – CO2 allow a much thinner gap between panes, as they insulate more effectively.
Finally, the invention of low- emissivity (low-e) glass has had a huge impact on glass production and performance. Thin, invisible coatings of silver or tin oxide reflect infrared heat radiation back into rooms. This, combined with modern tinted glass to reduce heat gain, has helped create glass tailored to particular climates or sites – cutting out heat gain in south-facing conservatories, or insulating on north-facing elevations for example. Consumers are, at present, opting for low-e rather than choosing triple-glazed glass to meet the new Part L regulations.
The traditional sash
Location Camden, London
Window supplier The Sash Window Workshop
Stunning floor-to-ceiling sash windows were the deal-clincher when an estate agent first showed Alex Wiltshire and Hannah Barnes- Murphy this flat. It occupies the raised ground floor in a converted Victorian semi, and has a huge four-paned window at both the front and back.
When they moved in, the couple realised that though the windows provided the views and light they’d fallen in love with, the draughts and noise were a problem. Luckily, The Sash Window Workshop specialises in reconditioning old windows. The firm retained the original window frames and manufactured bespoke double- glazed units to replace the panes. Insulation was added down the side of the runners to improve the thermal performance further.
Alex and Hannah chose acoustic laminate glass, which has reduced traffic noise from the busy road outside their bedroom window. Now the windows are a dream to live with. ‘The house is not only quieter, but warmer too,’ Alex says. ‘In winter we used to have to close the shutters to keep the heat in, but now we can keep them open if we want.’ And the new window locks and security glass keep the couple’s 18-month-old son Jack safe. ‘He’s got a tendency to pound on the glass and it’s nice to know he can’t break it,’ Alex says.
Futuristic glass Nanotechnology has invaded glass production: the best of the bunch is Pilkington’s Activ self-cleaning glass, which uses an active layer of titanium dioxide that reacts with UV light, causing water to spread across the surface of the glass.
Ordering When searching for new windows, it is often difficult to find accurate quotes. If your house is a new-build, seek the advice of your architect or project manager. For replacement windows, if you cannot get a personal recommendation, look for a company registered with the Fenestration Self-Assessment Scheme (0870 780 3989; fensa.org.uk). Your windows will have the required certificate needed at the point of selling your property.
Building regulations Part L of the building regulations cover emissions in relation to replacement windows. From 2002, all new windows have had to achieve a particular level of heat loss (the U- value) dependent on the material of the frame. Glazing within critical locations must be replaced with safety glass; and existing measures for background and natural ventilation, and existing measures for means of escape, must be retained (if the window pattern is to be changed this may affect means of escape). In April 2006, Part L was updated to take into account new methods of calculating heat loss, based on the dwellings carbon emisssons rate (DCER). The DCER must not exceed the target carbon emissions rate (TER), which is about 20 per cent lower than for a house complying with Part L before 2006. There is an overall BFRC energy rating for a complete window, including all components – glass, spacer, frame etc – and the regs now also cover solar gain to guard against buildings that overheat. The regs are so comprehensive that wags have suggested it may soon be illegal to leave your windows open.
Bespoke effects A structural engineer will be needed for any project requiring large sections of glass. To customise a new window in your home, contact a glass artist such as Andrew Moor, who specialises in one-off bespoke work. Or look for decorative films which can revamp existing windows and increase privacy. For curved glass, Floatglass and Balcony Systems both have large-scale products that can be adapted for the domestic market.
Modern metal frames
Location Tufnell Park, London
Architect William Tozer
When Donnie and June Everitt extended into the loft of their home, they didn’t want to live in a dark attic, especially as the space was destined to become the master bedroom. Architect William Tozer’s response was to glaze almost the entire end of the room.
The 3m-wide window has an aluminium frame supplied by Sunfold Systems. To prevent weathering, William selected a satin anodised finish. ‘We wanted to retain the natural metallic look instead of using paint,’ he says. The exterior of the loft extension is clad in zinc, so wood or plastic window frames would have jarred.
Metal is becoming a more popular option for window frames. Its innate strength makes it very versatile, so designs can be ambitious. ‘Because it’s so strong you can use thinner profiles with larger expanses of glass,’ says William. ‘And having less frame means you get more view.’
The special opening mechanism means that the entire top half of the window concertinas back on itself to give a sweeping panoramic view over London. ‘We wanted it to feel like the room was outside,’ William says.
Mumford & Wood www.mumfordwood.com
Arbor Windows www.arborwinsys.co.uk
LPD Doors www.lpddoors.co.uk
Alfa Sash Window Co www.alfasah.co.uk
Slimlite Double Glazing www.slimliteglass.co.uk
Rational Windows www.rationel.co.uk
Urban Front www.urbanfront.co.uk
1st Folding Sliding Doors www.1stfoldingslidingdoors.co.uk
Marvin Architectural www.marvin-architectural.co.uk
JB Kind Doors www.jbkind.com
Olsen Doors & Windows www.olsenuk.com
The Sash Window Workshop www.sashwindow.com
Words: Andy Duck