Astragals

Posted by on Feb 15, 2010 in Building Surveying

No building element seems to offer such scope for bad design as the window. We are nowadays obsessed and confused by glazing bars (known as astragals in Scotland). Our ancestors did not even bother to draw them when they represented their buildings – they were a functional but visually undesirable necessity. Glazing bars (known as astragals in Scotland) were played down and painted a neutral colour so as to minimise their visual intrusion.

The modern idea of putting dummy glazing bars into double glazed windows would have seemed bizarre to a Georgian architect and as soon as glazing technology permitted it their successors got rid of astragals in favour of plate glass with enthusiasm. A large number of strategies have been adopted for glazing bars in double glazing, from nasty plastic inserts between the two layers of glass, to bits of wood stuck on the outside only, or on both sides of the double glazing with a stupid gap in between. The best of these is the “Finebar” system developed by¬†Blair Joinery which creates genuine glazing bars but minimises their thickness between the double glazing units but even this is an expensive and functionally pointless expedient designed to get round the Building Regulations requirement for better thermal performance that single glazing whilst satisfying the Planners in terms of the appearance of historic buildings. Whilst it is very good that the Building Regulations have taken up the cause of “sustainability” by raising thermal insulation standards, what they do not take into account is the initial input of energy built into a component like a window as compared with the saving of energy in the long term. If the decision to opt for double glazing were to be subjected to a proper cost benefit analysis it is highly doubtful, in most cases, that double glazing with complicated glazing bars could be justified.

Whilst acknowledging the adage that “no-one ever lost money underestimating the taste of the British public”, in new buildings fussy little panes of glass really are a backward step from the “form follows function” rule that was so hard fought for by generations of architectural reformers.