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A Comprehensive Guide To Double Glazing Energy Efficiency And Sustainable Comfort For Your Home

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The warmest June across Ireland since records began is an unlikely place to begin talking about double glazing. That said, if you have it installed you’ll have noticed that your rooms were noticeably cooler during the hot spell – just one of the many efficiency benefits that double glazing can bring. 

Double glazing is arguably the best way of making sure that your energy bills are kept to a minimum at a time when we’ve all seen huge energy price hikes. On a stormy winter’s night, when the wind and rain are battering the windows, people with double glazing can sit in cosy comfort, knowing that their home is well-protected – and that they don’t need to turn up their central heating! 

Like all the best ideas, the one behind double glazing is simple. Just two panes of glass are separated by a spacer, creating a sealed air gap which is filled with inert gas, such as radon. This helps to stop condensation forming between the panes, making heat more difficult to escape. Given that windows are the biggest source of heat loss in the home, this is a vital function of double glazing and probably the single biggest reason for why it is such a popular choice. 

Flush Sash Window

Thermal excellence

In these days of rising fuel bills and creeping inflation, householders are looking to make savings wherever they can. The insulation properties of double glazing are attractive because they will improve all-round thermal performance, leading to lower heating bills. The airtight seal that we’ve mentioned means that heat is unable to flow in and out; essentially, it’s trapped in your home, making it warm and very thermally efficient.  

U-values and window energy ratings explained

A U-value is a means of measuring ‘thermal transmittance’, i.e. how easily heat gets through windows and doors. To calculate a U-value, the heat transference rate is divided by the temperature difference on either side of the window or door. The end value is in watts per square metre per Kelvin W/m2K. (1°C = 1Kelvin). 

In less technical terms, this means that the higher the U-value, the more heat escapes. So what we’re looking for are lower U-values, keeping more heat in. The new regulations now demand a U-value of 1.6 W/m2k maximum for windows and doors in new-build properties, and  1.4 W/m2k maximum for replacement windows and doors in existing properties.  

The energy-rating system for double glazing works on an alphabetical system, so that windows rated A++ are the best, energy efficiency-wise, while E are the worst. Building regulations require all new windows to be at least C-rated. At Turkington we install a range of windows that can achieve Window Energy Ratings of A, which easily surpass the minimum requirements for windows.  

For example, take our range of uPVC casement windows. These are very popular across Northern Ireland, and are made to an energy-efficient ‘A’ rating (one of the highest that can be achieved) with typical U-values (another measure of thermal performance) of 1.2-1.4 W/M2K. The lower the U-value the higher the thermal performance, so these windows represent the very best in double glazing technology. 

White bay windows

Combatting drafts

Anyone living in Northern Ireland with experience of single-glazed windows living in Northern Ireland will know what happens when damp and drafts get in through cracks in the glass or window frame. Those mornings waking up in chilly bedrooms, condensation frozen to the inside of the windows, are memorable, but for all the wrong reasons! These days, it’s not just the cold that you’ll feel – it’s the effect on your pocket as your hard-earned money drains from it and heads towards the energy suppliers. And when older double glazing units begin to fail the seal becomes ineffective, allowing argon gas to escape and make the window next to useless in terms of thermal efficiency.  


A broken seal also causes air to seep between the panes, creating condensation. Not only is this mightily difficult to get rid of in a double glazed unit, but it can also cause mould and mildew growth due to the amount of moisture present. If this spreads it can cause structural damage and have an effect on human health, particularly around reduced lung function and asthma. 

If this is happening because you have single glazing, or older double glazing, it’s time to have a think about investing in new windows. Another advantage in doing so is that you will inevitably have to spend less time cleaning them. A lot of us lead extremely busy lives and the last thing we want to do with our spare time is spend it maintaining our windows. So, in another sense of the term, this also represents energy saving! Both uPVC and aluminium window frames require very little upkeep. A simple wipe over with a damp cloth occasionally is more than enough to keep your windows looking as good as the day they were fitted. 

As well as keeping heat in, a modern set of double glazed windows will also help to reduce noise pollution. The two glass panes plus the gas-filled vacuum between them have excellent noise reducing properties, perfect if you live on a busy road or in a built-up area close to other houses. 

Timber effect windows


At Turkington, we provide a wide range of aluminium and uPVC windows that are available in a variety of styles including tilt & turn windows, sash windows and casement windows. The quality of the windows is backed by a 10-year lifetime guarantee. With so many options, you are bound to find the perfect fit for your home. 

If you’re thinking ahead to winter, with one eye on reducing your bills while making your house much warmer, get in touch with us to talk through the options. You can contact us here, or give us a call on 0800 028 1812. We operate across Northern Ireland as well as in parts of the South, and we’re always around to discuss your ideas. 

Double Glazing Across Ireland

With showrooms in Lisburn & Portadown we are ideally placed to supply and install windows, doors and conservatories all across Belfast and Northern Ireland, as well as the greater Dublin area and counties Monaghan, Meath and Louth.

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