Costing secondary glazing; what is required for a quote?

For us to quote for your secondary glazing needs, we require certain details to be provided. This information along with the reasons why are listed below. It may seem like we ask a fair bit of detail, but there is a good reason for it….

1. Is the building Listed?

In general, secondary glazing is used to help improve the performance of old single glazed windows, which in the case of Listed buildings, cannot be changed. Although secondary glazing is widely accepted by conservation officers and heritage bodies as the only means of improving thermal, acoustic and security performance of primary windows, Listed Building Consent is still required. If we are installing the secondary glazing, the responsibility lies with us, so we want to ensure that all documentation is in place, as fines can be issued if changes are made to a Listed building without appropriate consent. We are happy to assist with Listed Building Consent Applications, or you can find help within the document produced by Historic England. Secondary glazing and Listed Building Consent - Advice note by Historic England Listed Building Consent advice by Historic England

2. Benefit – why do you require secondary glazing?

Understanding the reason to install secondary glazing helps us to design/suggest the best configuration of units to achieve the desired benefit. There are certain products in the range which lend themselves better in meeting different performance requirements. Low-E glass can be added if you are looking at sustainability and reducing heat loss, or acoustic glass can be incorporated if secondary glazing is needed to reduce the noise ingress of heavy traffic or even noisy neighbours. 

3. Dimensions

To enable the production of an estimate for secondary glazing, the following dimensions are required:
Dimensions needed for a secondary glazing quote / estimated cost
The height of the inside of the reveal of the window opening The width of the inside of the window reveal The reveal/cill depth; from the front of the window opening to the face of the primary glazing frame
Reveal/cill depth is not only required to ensure there is sufficient room for the secondary glazing but also room for a cavity which is important for noise insulation. The cavity or gap between the primary and secondary glazing needs to be maximised to achieve good dB reductions or acoustic insulation. At least 100mm gap is required, if not more, so having this dimension helps us work out the best fixing method to make certain that the cavity can be achieved. Don’t forget to ensure the units of measurement are clear and defined.

4. Photographs

Very few buildings are designed for secondary glazing. Images of the window openings are extremely helpful, not only in determining the best design but also if there are any restrictions; blinds, curtains, window handles, pelmets, radiators, the list goes on. To an untrained eye – a window may just be a window! However, to successfully install the units and maximising the benefit, timber sub-frames are first produced and fixed to ensure the opening is truly square and take up any irregularities such as splays. Photos will also indicate the material we will be fixing into, which helps us prepare and allow for all necessary equipment when it comes to the installation. An example of a heritage primary single glazed window with splayed reveals An example of a heritage single glazed primary window, with splayed reveals Photos assist in other ways too; often window reveals can be highly ornate and as our main objectives are to provide a good unobtrusive and discreet treatment, we can match the detailing with the timber sub frames by means of ovolo or bull nose finishes. We may also discuss the option of coloured secondary glazing to again; match and blend in with the original windows and surrounding décor. Heritage primary windows in a Listed building with shutters, needing secondary glazing Primary heritage single glazed windows with shutters The request for secondary glazing to windows with shutters, is technically demanding – how do you fix it to gain the desired benefit? Which style would be most appropriate to allow the operation of the shutters – if this is a requirement? So again, any photographs highlighting architectural details, or even any obstructions will be of great assistance. Our main goal is to get as much information from the outset, to enable us to provide you, our customer, with the best secondary treatment which meets your needs, and a representative estimate of the cost of the manufacture and installation of the units.

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