Insulation

The insulating effect of double-glazing is affected by a number of factors, including the cavity width, the use of argon in between the panes or by using a low emissivity 'K' coating glass that reflects heat back into the room. It is virtually impossible to tell K-Glass apart from clear float glass apart from a minor effect it has on white light transmission.

Typical U values (the measurement of heat transfer through glass) using various combinations of cavity widths, air and Pilkington 'K' glass.

                                                                   Cavity width:12.0         16.0
Glass specification
Float/air/Float -                                                                  2.9            2.7
Float/argon/Float -                                                             2.7            2.6
Float/air/Pilkington 'K' -                                                      1.9            1.7
Float/argon/Pilkington 'K'                                                    1.6            1.5
Overall width of unit in millimetres                                      20.0          24.0

Regulations

With effect from 1st April 2002, all replacement window installations became subject to Document L of the Building Regulations (Listed Buildings are exempt from this regulation)

The lower the U value, the better the level of insulation. What was previously referred to as 'normal' double-glazing, ie two panes of glass separated by a spacer bar is very unlikely to conform to building regulations. To obtain the required level of insulation, it may be necessary to utilise 'K' Glass. Timber replacement windows should not have a U value higher than 2.0 W/m.

At Old Manor Cottages we ensure that approval is obtained from Building Control and Conservation Officers at your Local Authority.

Types of Period Glass

There are two main types of period window glass we can supply.

Genuine Handblown Cylinder Glass is used for matching existing original Cylinder Blown or Crown Glass where authentic replacement windows are required to match existing sashes in a period building

Period Style window glass is a lower cost alternative for complete glazing of windows or a facade where no original glazing of windows or a facade where not original glass remains and the fine quality of a handblown glass is not required.

Old Manor Cottages Limited, Turnpike Lane, Ickleford, Hitchin, Hertfordshire, SG5 3UZ.
Tel: 01462 456033. Email: oldmanorco@aol.com