We are often asked “What is the best secondary glazing solution for box sash windows; side hung casements or vertical sliders?”, the answer is not just a question of taste there are also some practical considerations too.
Examples of box sash window styles
Box sash windows are, for some, a period detail dream as they provide the traditional design elegance that so many of us yearn for; but that design style comes at a price. They are generally single glazed, thermally inefficient, and are often leaky, draughty, and not particularly effective at stopping the ingress of sound. Adding secondary glazing to a box sash can offer the best of both worlds, traditional elegance with the performance of a modern replacement window. But which design of secondary glazing is best?
Selectaglaze hinged casement secondary glazing with original box sash windows
But beware, they are hinged and open into the room so you need to think carefully about anything which could restrict their operation. Blinds, curtains, kitchen taps, pelmets, bulkheads and furniture all need to be kept clear of the space immediately in front of the opening.
Consideration also needs to be given to how the building is to be ventilated. If the opening is to be used for natural ventilation, then the casement will need to be left in the open position, turned into the room, for the duration.
Another consideration comes in the form of glazing. The bead glazed arrangements on some casements allows a deeper glazing pocket, thus sealed units can be fitted, which could be a crucial factor if you are looking to achieve high levels of thermal performance.
Original box sash windows treated with Selectaglaze vertical sliding secondary glazing
Vertical sliders are also better when it comes to natural ventilation, the sashes can be held open in any position just like the primary window, in fact you can open opposing sashes providing the ultimate in ventilation control. The advantages for operation and ventilation are offset slightly by restrictions for cleaning the rear of the secondary glazing and access to locks and catches on the box sash. This restriction can be further exaggerated if the existing window has dissimilar size sashes or if the secondary glazing has to be fitted close to the primary window. In fact, minimum cavity is another consideration for the vertical slider, we recommend a gap of a least 75mm at the meeting style to provide access for cleaning.
You could be forgiven for thinking that selecting the right secondary glazing is a simple task, the truth is that buildings were not designed with secondary glazing in mind, there is always a lot to consider, and we have only just scratched the surface in this article. Sometimes there are compromises to be made but the advantage of retaining the original windows and the history of the building whilst achieving the comfort from modern day performance makes it all worthwhile. As for the challenges of selecting the right system, our experienced team of experts are always on hand to help you with the process.
Examples of box sash window styles
Box sash windows are, for some, a period detail dream as they provide the traditional design elegance that so many of us yearn for; but that design style comes at a price. They are generally single glazed, thermally inefficient, and are often leaky, draughty, and not particularly effective at stopping the ingress of sound. Adding secondary glazing to a box sash can offer the best of both worlds, traditional elegance with the performance of a modern replacement window. But which design of secondary glazing is best?
Side hung casement secondary glazing considerations
Side hung casements are a popular choice, a fully glazed unit fitted to cover the entire window with a single pane of glass. The result is a slick treatment with clean lines, ideal if you are aiming for that modern minimalist interior. They offer an uninterrupted view of the primary window as they do not add any new sightlines and when open, they provide full access for cleaning and maintenance of both the primary and secondary window.
Selectaglaze hinged casement secondary glazing with original box sash windows
But beware, they are hinged and open into the room so you need to think carefully about anything which could restrict their operation. Blinds, curtains, kitchen taps, pelmets, bulkheads and furniture all need to be kept clear of the space immediately in front of the opening.
Consideration also needs to be given to how the building is to be ventilated. If the opening is to be used for natural ventilation, then the casement will need to be left in the open position, turned into the room, for the duration.
Another consideration comes in the form of glazing. The bead glazed arrangements on some casements allows a deeper glazing pocket, thus sealed units can be fitted, which could be a crucial factor if you are looking to achieve high levels of thermal performance.
Vertical sliding secondary glazing considerations
Vertical sliders are another popular choice, matching the design of the existing box sash. They typically comprise of two sashes which slide up and down, each one suspended by spiral balances to support the weight in any position open or closed. Although they have a meeting rail, this is a slim section and similar in size to that of the box sash. Because the sashes slide within the frame, they have little or no impact on window furnishing, furniture or fixtures in front of the opening.
Original box sash windows treated with Selectaglaze vertical sliding secondary glazing
Vertical sliders are also better when it comes to natural ventilation, the sashes can be held open in any position just like the primary window, in fact you can open opposing sashes providing the ultimate in ventilation control. The advantages for operation and ventilation are offset slightly by restrictions for cleaning the rear of the secondary glazing and access to locks and catches on the box sash. This restriction can be further exaggerated if the existing window has dissimilar size sashes or if the secondary glazing has to be fitted close to the primary window. In fact, minimum cavity is another consideration for the vertical slider, we recommend a gap of a least 75mm at the meeting style to provide access for cleaning.
You could be forgiven for thinking that selecting the right secondary glazing is a simple task, the truth is that buildings were not designed with secondary glazing in mind, there is always a lot to consider, and we have only just scratched the surface in this article. Sometimes there are compromises to be made but the advantage of retaining the original windows and the history of the building whilst achieving the comfort from modern day performance makes it all worthwhile. As for the challenges of selecting the right system, our experienced team of experts are always on hand to help you with the process.- Date
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- Secondary Glazing in Practice