Glass Specification and "U" Values

In today's world of climate change and high energy costs, windows and doors now have to conform to strict standards set out by the government and controlled by local building authorities or authorised agencies such as Fensa, BuildCheck, the BFRC and Certass. This area of compliance can get quite complicated but be rest assured that all our folding doors, sliding patio doors, composite doors, casement and tilt and turn windows comply. The choice is how well you want them to perform. Windows use an energy rating system as set out by the BFRC, but doors are measured by their "U" value. The lower the "U" value, greater the performance. All licences are held by our sister company WeatherShield Ltd.

When referring to the mystery "U" value, this applies to the overall product, including the pvc frame, cill, glass and any reinforcement used, not just the glass. However by reducing the "U" value of the glass itself, will improve the overall "U". This is achieved by a combination of the choice of Low 'E' coating (1), Spacer Bar (2) and internal glass type (3). The lower the 'U' Value the higher the specification combined with lower energy costs and comfort.

UPVC Bifold Doors

Bifold doors require an overall "U" value of no worse than 1.8 W/m² K to conform. When ordering your bespoke folding door you have the option of four different glass "U" values to achieve your desired overall "U" value.

Option 1 Glass.

Low E Coating  = Soft
Spacer Bar     = Aluminium
Internal Glass = Standard Float
Cavity Gas     = Air
Glass "U" Value= 1.5 W/m² K

Overall "U" Value= 1.7 w/m² K
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Option 2 Glass.

Low E Coating  = Soft
Spacer Bar     = Aluminium
Internal Glass = Standard Float
Cavity Gas     = Argon
Glass "U" Value= 1.2W/m² K 

Overall "U" Value= 1.5 w/m² K
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Option 3 Glass.

Low E Coating  = Soft
Spacer Bar     = Swiss Spacer
Internal Glass = Standard Float
Cavity Gas     = Argon
Glass "U" Value= 1.2 W/m² K

Overall "U" Value= 1.4 W/m² K
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Option 4 Glass.

Low E Coating  = Soft
Spacer Bar     = Swiss Spacer
Internal Glass = Soft
Cavity Gas     = Argon
Glass "U" Value= 1.1 W/m² K

Overall "U" Value= 1.3 W/m² K
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UPVC Casement Windows

On casement windows we adopt the window energy rating system (wers), run by the British Ratings Fenestration Council (BFRC). Accepted throughout the U.K as the most recognized method of conforming to the regulations. When ordering casement windows online you have the option of purchasing an "A"(cert. No. 2382) or "B"(cert. No. 2384) rated window.

Aluminium Casement Windows

To comply with buiding regulations, aluminium windows are covered by the window energy rating system. The exception are aluminium windows using solar control glass which are covered by a "U" value certifcate.

UPVC Tilt and Turn Windows

On tilt and turn windows windows we adopt the "U" value calculation method as used on folding doors. We only offer glass option two and three when ordering on line. Their "U" value calculations are as follows:

Option 2 Glass.

Low E Coating  = Soft
Spacer Bar     = Aluminium
Internal Glass = Standard Float
Cavity Gas     = Argon
Glass "U" Value= 1.2 W/m² K

Overall "U" Value= 1.6 w/m² K
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Option 3 Glass.

Low E Coating  = Soft
Spacer Bar     = Swiss Spacer
Internal Glass = Standard Float
Cavity Gas     = Argon
Glass "U" Value= 1.2 W/m² K

Overall "U" Value= 1.4 W/m² K
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