Date posted: 26th September 2018

Energy efficient windows for your home

With shorter evenings and a chill already in the air, Mark Pearce, Managing Director, KJM Group explains how energy efficient windows can cut your heating bills keeping your home warmer and more secure this winter.

How energy efficient windows could save you hundreds of pounds from your heating costs. 

Home heating costs are on the rise. At the end of August British Gas announced a 4% increase in energy costs, a jump on the average bill of £44 to £1,205 a year. The second price increase this year, British Gas parent company joined E.On, SSE, Npower, EDF, ScottishPower and Bulb which also introduced increases in blaming the rise on a jump in wholesale energy costs.

This has increased by around 21% in the last six months (22% for gas and 20% for electricity). Accounting for around 43% of the average dual fuel bill, these increases are now biting, with retail energy prices jumps already hitting consumers.

Gas prices are forecast for particularly sharp increases, up from 34.6p per therm, in the last year to 47.5p. per therm by 2023 -  a forecast jump of 37%.

With increases forecast and winter just around the corner, new energy efficient replacement windows and doors, could play an important part in helping you to keep a lid on spiralling home energy costs.

Can new windows and doors cut the cost of heating my home?

According to the Energy Saving Trust after energy leaking roof space and walls, windows account for around 20% of the heat lost from your home. It means that if you haven’t already done so, replacing them could pay back dividends in the long run and at the same time contribute to a significant reduction in the carbon footprint of your home.

The exact savings will be dependent on your property and the windows previously installed but the Energy Saving Trust suggests that Energy efficient windows and doors can cut heat loss by up to 75 per cent.

In a detached three-bedroom home, this can equate to an annual saving over and above single – and in many cases, older double-glazed windows - of up to £160 a year in heating bills.

A point worth noting is that this figure is based on current energy prices. If you take forecast increases in gas to 2023, you could easily be adding a further £59 per year to this figure within five years.

With savings of £200 a year* total savings could top £2,000 over a 10 year period. With an average window service life of 15 to 20 years, new energy efficient windows and doors can pay for themselves, depending on their specification, material and finish choice.

*Savings based on Energy Savings Trust figures and percentage forecast increases in gas prices.

Which windows are most energy efficient – wood, aluminium or PVC-U?

Timber windows and energy efficiency

Timber remains a highly popular window framing material offering slim sightlines and stunning aesthetics. Timber is also aesthetically warm, making it a timeless choice for your home.

We supply Stormproof timber windows from Dempsey Dyer. With enhanced weather performance they’re available in Sapele, Oak, Accoya and European Redwood, offering exceptional through life performance.

Sourced from verified FSC or PEFC sources, this includes a top performing Window Energy Rating A Rating, when manufactured in Accoya. 

Where timber has a slight disadvantage compared to aluminium and PVC-U systems is that by definition its manufactured in a solid material. This means that timber window and door manufacturers cant employ the same multi-chamber manufacturing and thermal breaking methods, used in PVC-U and aluminium manufacture.

Some window manufacturers have attempted to get around this by combining aluminium faces and thermal breaks with timber frames inside. Although significantly improving thermal performance these composite windows at a significantly higher price point.

Specification of higher performing glass is another way to boost the thermal perfomance of timber windows.  The costs in this case are marginally higher compared to a standard energy efficient unit.

Energy efficient aluminium windows

As an extruded product, aluminium windows offer stunning sightlines and significant design flexibility. With more aluminium inline sliding patio and bi-folding doors being fitted, demand has also increased for aluminium windows.

The use multiple chambers and special polyamide thermal breaks to stop cold air outside transferring through the metal to the inside of the frame.

This has allowed manufacturers of aluminium windows to reduce heat loss and achieve u-values – the measure of heat loss – on a standard double-glazed aluminium window of around 1.2 KW/m2 on the very highest performing to an average 1.4 KW/m2 or 1.6 KW/m2.  This equates depending on your choice of glass to a WER A, B, or C rating.

We supply aluminium windows from two leading aluminium system suppliers, Sapa and Smarts, in  addition to a wide choice of aluminium bi-folding doors and inline sliding patio doors.

Energy Efficient PVC-U windows

u-PVC windows like aluminium windows and doors are extruded so that the feature a honeycomb of chambers. The big advantage PVC-U has over other materials is that it’s not only low maintenance, but it’s also less conductive than aluminium.

This means that PVC-U window and door manufacturers can achieve higher u-values more cost effectively and without having to resort to by definition, far more expensive triple-glazed units to do it.

We offer an extensive range of PVC-U windows and doors from high performance standard PVC-U windows to premium flush casement options from Residence 9 and Deceuninck Infinity, as well as the Beaumont Window from Dempsey Dyer, which hand finished, has been designed to bridge the gap between uPVC and timber products.

These top end PVC-U systems can be a good choice if your options to improve the energy efficient of your home are limited, for example you live in an older property with solid walls, providing the maximum in energy efficiency while replicating the appearance of a traditional timber window.

What else should I consider when choosing energy efficient windows?

Your choice of material type plays its part in how energy efficient your new windows and doors will be and how much money they will sve you but the single biggest influencing factor is your choice of glass.

All of the double and triple-glazed glass units that we supply use smart low-e coatings on glass - a one-way door for trapping and holding energy. 

We also use warm-edge spacer bars, which separate the sheets of glass in double and triple-glazed units to put ‘space’ between the cold air outside and warm air inside.

This cavity is filled with argon gas. It’s completely inert in the environment and you can’t see it but because it’s denser than air, it creates a highly effective insulating barrier, helping to keep your home warm and cozy on event the coldest of days.

If you’re looking for help in planning your next home improvement, or simply want to talk about any of the points raised in this discussion, please don’t hesitate to contact me or a member of the team for more by calling 01264 359355 or emailing email sales@kjmgroup.co.uk