According to English Heritage, ‘many historic windows, frames and glazing, have fallen victim to inappropriate double glazed replacements’ with Part L the agent for their thoughtless destruction. Addressing the need for a solution to champion the UK’s rich tradition of different window designs and materials through the ages, Holdens SupaSeal have developed the SupaSlim IGU.

SupaSlim is designed for timber window manufacturers looking to produce a thinner, more discreet profile window e.g. sash windows with glazing bars for specialist applications or in conservation settings.

”Window openings and frames
establish the character of a building's
elevation.They should not generally
be altered in their proportions or details,
as they are conspicuous elements
of the design”

- English Heritage