Whether you’re self building or renovating, the windows will form a huge part of your home’s finished character. Aesthetics and budget are bound to give you a big steer towards the best window options, and there will be a lot of to-ing and fro-ing involved to get the balance right. But fenestration is functional, too, and your windows will need to deliver on security, ventilation, provision of daylight and much more besides.
The first step when selecting your windows and glazing is to identify the overall look you’re after: is yours a heritage home or period-inspired new build project? If the latter, then a traditional window style will work best – with the possible exception of adding a contemporary extension to an older house.
With traditional windows, you may well be able to find inspiration in surrounding homes and the historic context of your property. Do you want leaded lights in those cottage casements, for instance?
Should your new sash windows be in a Georgian six-over-six pane arrangement or feature larger glass panels for a Victorian or Edwardian look? Once you’ve got the basics down, you can begin to flesh out aspects such as materials, glazing bar styles and decorative details like ironmongery.
Do I need planning permission?
On a self build project, the basic window design and spec will be developed as part
With renovations, replacing existing windows for models of the same size (or upgrading to double glazing) can be done under permitted development (PD) rights – but anything above and beyond that is likely to need a formal planning application. In some cases, you’ll always need consent – for instance when dealing with listed buildings or conservation areas. Check in with your local council if you’re unsure whether PD rights apply.
Learn more: Guide to Permitted Development
If you’re building in a more contemporary style, that’s likely to be reflected in your choice of window frame materials and opening configurations. You’ll probably be looking for products that deliver maximum glass with a minimal framing to let in as much natural light as possible and deliver the best views out.
Alternatively, you might have your sights set on using the wubdiw frames to add architectural interest. Could a pop of colour make the statement you’re after; or do you want timber windows to bring a touch of warmth and texture to white-washed interiors?
Much of this outline information will be established at the initial design stages – but it’s amazing how quickly you need to start developing this into something resembling a formal spec, as the windows will impact on a host of follow-on decisions.
Thankfully, most window suppliers will be keen to work with you and your architect as early as possible. This way, they can help you to identify details such as maximum panel sizes, performance criteria, threshold details, how far the units should be set back into the wall, mission-critical sightlines (how the framing matches up across storeys etc) and establish what’s achievable within your budget.
A wealth of window frame options is available to suit your project goals. Some are lower-maintenance, while others major on sustainability, slim profiles or affordability.
Here are the main pros and cons of the key players:
The overwhelming majority of windows are now supplied fully factory-glazed, pre-finished and completely sealed, which provides the reassurance of quality control when it comes to achieving high-performance units.
The thermal efficiency of windows is measured by their U-value, with lower numbers indicating better heat retention. As a rough guide, a single-glazed window might achieve a U-value of around 5.0 W/m2K, whereas most modern double glazing hits around 1.4-1.2 W/m2K.
For context, a typical new wall insulated to a decent spec might achieve around 0.20-0.14 W/m2K.
There’s a raft of choices when it comes to glass specification – including the use of special coatings and gas-filled cavities to improve insulation. But the first question most self builders and renovators will want to tackle is whether triple glazing is worth the investment compared to double.
Thanks to the extra pane and airgap, there’s no doubt that trple glazing offers better U-values (down to as low as 0.6 W/m2K). As a rule, this will translate into better comfort levels in winter, with the innermost pane staying warmer than in a double glazed unit, minimising issues with draughts and condensation.
Heat retention isn’t everything, however. There’s an argument that few UK homes actually need triple glazing to achieve a good standard of performance, for example. What’s more, it’s easier to maximise solar gain – free heat from the sun – through double glazing .
The thickness of a triple glazed window also makes it difficult to incorporate this type of glazing into heritage projects.
Learn more: Solar Gain, Thermal Mass & Sustainable Design
All of these elements, and more, must be factored in by your design team at the early stages if you’re to stand a chance of identifying whether triple glazing is worth the 10-15% additional investment for your home.
Even the best window will only perform as expected if it’s properly fitted by an experienced crew. So, consider working with companies who operate on a supply-and-install basis, so that you have a single point of contact to deal with and you know your site crew are experienced with the products they’re fitting.
One area of window specification that’s come into sharper focus in recent years is security, particularly since the government introduced Part Q of the Building Regulations in 2015.
This standard, which applies in England and Wales, sets out the basic requirements for how any easily accessible doors and windows should resist physical attack by burglars. Scotland’s guidance is detailed in Building Standard 4.13.
Fundamentally, any basement, ground floor or otherwise easily accessible window (including rooflights) fitted into new homes must be designed, manufactured and installed to meet the British Standard PAS 24 (or an equivalent accepted standard). That includes the glass, frame, lock and how the unit is fixed into place.
QUICK GUIDE Acoustic performance in windows
Triple glazing is often lauded for its ability to enhance sound deadening in windows.
This is a complex area, especially when you start to add optional extras such as specialist acoustic glass into the mix. So, if you live near a busy road or simply want more peace and quiet, be sure to speak to your supplier about how you can achieve the level of acoustic performance you’re after.
One way a manufacturer can demonstrate its products comply is to gain the police-approved Secured by Design accreditation – although there are other accepted certifications, too. If security is a paramount concern on your project, be sure to inspect such documentation thoroughly and verify that the approval applies to the exact product you’re installing.
Some suppliers have responded to the regs by upgrading all their products to be PAS 24-compliant, regardless of where they’re installed in the building. Further upgrades are available, such as using laminated glass (which is more difficult to break than the standard toughened glass).
Windows are a major investment, and will likely represent a hefty chunk of your project budget – so you should always see the products in person before ordering.
So, get down to your supplier’s showroom and ask them to give a comprehensive demonstration of the units you’re considering. Take this opportunity to find out more about the ordering and installation process (do they use in-house teams or sub-contract the work, for instance?).
Heritage Windows: Repair or Replace?
Original fenestration plays a vital role in establishing the authentic appeal of a period home – in fact, if you live in an historic house, it’s likely to have been one of the chief design features that attracted you to it in the first place. With that in mind, you won’t be surprised to learn that retaining the old windows, wherever possible, is the best way to preserve a building’s character and value.
The trick lies in identifying whether the existing units are salvageable; and you may be surprised to learn that the answer is almost always yes.
Old windows were made with high-quality, slow-grown timber that’s far more durable than a lot of standard modern wood. What’s more, even apparently rotting units can often be cost-effectively repaired by a specialist joiner – who will probably also be able to give them a draught proofing overhaul at the same time.
Learn more: Should I repair or replace old windows?
If the original windows are beyond repair, then in general it’s best to go for like-for-like replacements that are as accurate to the originals as your budget will allow. Bear in mind that you’ll need specific consent for such works if your property is in a conservation area or you live in a listed building.
And don’t be afraid to ask to see product certifications so you can satisfy yourself everything’s up to scratch.
When it comes to developing and placing a major order, you’ll need to work alongside your architect/designer and window company to draw up a full window schedule.
This should detail elements such as the planned size of each opening, performance targets and the frame material you want to use (if known).
This basic document will then need to be fleshed out in full. There will be questions to answer on glazing spec, opening configurations, ironmongery styles, locking requirements, frame finishes (do you want a dual-colour design, for a different effect inside and out?), reveal depths and more.
Most window manufacturers work to a lead time of around six to 12 weeks for standard made-to-measure products – but check in with the supplier on this, so you can factor their timings into your build schedule.
It may be possible to order some of the windows based on the structural drawings and technical package. To ensure an accurate fit, complex glazing will probably need to be measured up and produced after the builders have created the openings on site.
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