Specifying Windows for High-Performance Homes

Taking on a self build or major retrofit is an exciting opportunity to create a home that is not only stylish, but also perfectly tailored to your lifestyle and performance expectations. While energy efficiency is a major focus, a home should also deliver on security, durability and comfort.

Windows and glazing play a crucial role in this. They influence everything from heat retention and natural light, through to security and noise reduction. If you’re investing in quality insulation, airtight construction and efficient heating systems, then your windows need to match the same level of performance. Here’s how to ensure the glazing you specify meets – and exceeds – expectations.

Don’t Settle for Minimum Standards

The Building Regulations set out minimum performance requirements, but for a truly high-performing new build or retrofit that will stand the test of time, it’s wise to go well beyond these benchmarks. Key regulations to consider include:

• Part L (Conservation of fuel and power) This defines maximum allowable U-values, which measure thermal efficiency, for windows and doors. New windows in existing homes should achieve U-value of 1.4 W/m²K or better; in new builds 1.2 W/m²K or better. Aiming for 0.8 W/m²K or below will result in significantly improved performance and meet the requirements of Passivhaus.
• Part Q (Security) For new windows and doors, compliance with PAS24:2016 ensures robust resistance to forced entry. Internorm triple-glazed windows and doors include enhanced security features as standard and are PAS24 and Secured by Design certified.

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Specifying thermally efficient glazing can help to enable spectacular features, such as this near-frameless corner picture window by Internorm

Why High-Performance Glazing Matters

In a well-insulated home, the windows and doors will be the weakest link in terms of heat loss through the building fabric. Choosing high-quality glazing can make all the difference. Here’s what you should prioritise:

• Triple glazing While double glazing has been the standard in the UK, triple glazed products with low whole-unit U-values of 0.8 W/m²K or better provide considerably better insulation. This will reduce heat loss and improve comfort levels, especially during colder months.
• Glazing type Look for windows with low-emissivity (low-E) coatings, argon or krypton gas-filled cavities, and warm-edge spacers to reduce heat transfer. In addition, Internorm glazing units are bonded to the frame, improving stability, burglary protection and thermal insulation.

A combination of Internorm’s fixed and opening systems delivers wow-factor walls of glass in this striking project

• Frame design Always opt for well-insulated frames to maximise thermal efficiency. Both Internorm’s uPVC-aluminium and timber-aluminium frames include additional insulation to ensure that heat is not lost through the frame. Insulation is especially important in timber-aluminium windows to avoid excessive relative humidity on the wood’s surface, which could otherwise lead to mould growth.
• Triple gaskets These seals play an important role in minimising heat loss and improving airtightness. Internorm tilt & turn windows offer triple gaskets as standard.

Getting the Installation Right

Even the highest-performing windows will underdeliver if they are not installed correctly. A poorly fitted window can lead to thermal bridging, drafts and even moisture problems. To ensure a flawless installation:

• Position within the insulating envelope Ideally, windows should be installed in line with the insulation layer rather than flush with the outer brickwork/cladding.
• Address airtightness Use high-quality airtight tapes, expanding foam and/or specialist membranes to create a robust seal around the window frame.
• Avoid thermal bridges The junction between the window and wall must be insulated correctly in order to prevent any unwanted heat loss.
• Work with experienced installers Engage professionals who understand how to install high-performance glazing into a low-energy building fabric.

Internorm’s lift & slide doors feature high-quality mechanisms to ensure smooth operation in the long term

Glazing Strategies for Summer Comfort

A well-insulated home retains heat effectively. This is hugely valuable in winter, but it can contribute to overheating in summer without proper planning. Here’s what to consider to prevent excessive heat gain:

• Orientation & window size South-facing windows capture the most sunlight, so consider reducing glazing in these areas or using suitable shading solutions.
• External shading Overhangs, brises soleil, blinds and shutters can block direct summer sun, while still permitting plenty of natural light. Note that external solutions are always preferable to internal shading, particularly for windows on south- and south west-facing elevations. Nobody wants to live in a greenhouse!
• Solar control glass This type of glazing reflects a portion of solar radiation, helping to keep indoor temperatures manageable. The downside is that in winter, when you want useful solar gain, it reduces the effect.
• Ventilation Ensure windows allow for passive ventilation, particularly in bedrooms and living spaces to avoid overheating. The useful tilt function of Internorm windows can form part of purge ventilation.

Invest in Quality

When undertaking a major project, every design choice should contribute to a comfortable, efficient and high-performing home. Glazing is no exception. A balance of high-performance units, shading and ventilation will keep your living spaces comfortable year-round. So, invest in windows and doors that go beyond minimum standards, choose high-quality materials, use expert installation services and plan for year-round comfort. Take these steps, and your windows will enhance the aesthetics and performance of your home for years to come.

Vasilis Giannopoulos Vasilis Giannopoulos is specifications manager at Internorm UK and has worked in the window industry for over 30 years. He is a qualified Passivhaus designer and trainer, and is passionate about educating homeowners and architects about the benefits of quality, high-performance windows and doors. Call 020 8205 9991 or log on to Internorm UK’s website for more information.