Double or Triple Glazing – Which is Better?

Triple glazed UPVC casement or tilt and turn windows, plus front doors, back doors and French doors are not that much more expensive than double glazing. Properly installed UPVC triple glazing offers unrivalled value for money when household energy savings and consequent financial savings are taken into account (i.e. painting and decorating), not to mention the other benefits of triple glazing over double glazing.

Corner Section of 70mm Wide Triple Glazed UPVC Casement Window Showing 36mm Sealed Unit
A Corner Section of a 70mm Wide Triple Glazed UPVC Window System With 36mm Sealed Unit

Top quality UPVC triple glazing, with a U-value of 1.0 W/m²k, is around 40% more thermally efficient that standard “A”-rated double glazing and 60% more thermally efficient than standard “C”-rated double glazing. This is a great benefit to UK home owners bearing in mind that between 2003-2009 gas prices (i.e. heating bills) rose by an average of 14% each year. Unfortunately, this trend does not look likely to reverse, or even slow down, despite the recent slight reduction by the big 6 energy companies of electricity prices by around 5%.

Going forward, future Building Regulations (which currently dictate a minimum 1.6 W/m²k U-value) are likely to call for windows used in new build homes and replacement windows to have a U-value of 1.4 W/m²k by 2013, and 1.2 W/m²k by 2016 to reduce carbon emissions from the UK housing stock. By investing in high quality UPVC triple glazing, with a U-value of 1.0 W/m²k or better, UK home owners are essentially future-proofing their home.

Triple glazing supplied and installed by Hazlemere Windows is all but identical to their “A”-rated double glazing with the main difference being the internal bead, so aesthetically there is little or no difference. The internal bead has been specially developed to enable a wider 36mm unit to be fitted into a standard 70mm profile. By using a 36mm triple glazed sealed unit, as opposed to the 44mm sealed units of other fabricators, Wakefield based UPVC manufacturers Conservatory Outlet has been able to develop a subtle bead that blends in with the overall aesthetics of the window and retains its concave form (sloping in towards the sealed unit). When a 44mm sealed unit is used in a standard 70mm profile, the internal bead often has to protrude from the frame of the sash, or “overhang” to allow for this much wider sealed unit. This can look rather clumsy and compromise aesthetics in my opinion.

Triple glazing is genuinely worth the added investment for 5 main reasons. Firstly, triple glazing is approximately 40% more thermally efficient than “A”-rated UPVC double glazing so the savings are going to be far higher, potentially in the region of £10,000 and 30 tonnes of carbon over the next 20 years. Secondly, “more comfortable” triple glazed windows and doors will further reduce draughts and cold spots in a room that currently has less thermally efficient windows and doors. For instance, research has shown that if it’s -5°c outside, and 21°c inside a home, the surface temperature of the inside pane of the triple glazed windows will be no less than 18°c. With single glazed windows the inside pane would register at a mere 1°c and standard double glazed windows would reach no higher than 11°c.

Thirdly, triple glazed windows and doors can reduce the impact of exterior noise. They do reduce noise and are not sound proof, but the extra pane of glass, being of a different make up to the two external panes, does help toward acoustic insulation. Fourthly, triple glazed windows and doors could save each UK home owner over £10,000 during the next 2 decades, which is not inconsiderable when the rising costs of fuel are taken into consideration. In many cases these savings could even offset the cost of having triple glazing installed in a home (over the recommended lifetime of the product).

Fifthly, a 3rd pane of glass, by definition, makes a triple glazed sealed unit much harder to break than a double glazed sealed unit — especially when the middle pane is made of toughened glass. What’s more, all Hazlemere’s “A”-rated UPVC triple glazed windows are internally beaded and the glass unit can only be removed from the frame by a person who is inside the premises.


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