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Slimline Double Glazing Sash Windows for Conservation Areas

Timber sash windows within properties that are located in a conservation area are normally unable to accommodate traditional double glazed units, and a number of planning authorities object to double glazing being installed in listed buildings and sensitive conservation areas across London and surrounding areas. Slimline double glazing is a suitable alternative that is accepted by a number of councils in many cases. Barnsbury Joinery supplies and installs Slimline double glazed units, designed to fit existing and traditional timber sash windows. By using a smaller, gas-filled gap between the glass panes, slimline double glazed units can achieve an energy rating that is on par with standard double glazing windows. This makes them perfect for buildings and homes within a conservation area across London and surrounding areas which need both the thermal benefits, energy efficiency and also authentic period appearance.

Slimline Double Glazing Features: 

  • They are designed to replace single glazed windows within a traditional sash window box 

  • Similar low U values to double glazing windows 

  • In-keeping with traditional property styles 

  • Ideal for listed buildings within conservation areas


At Barnsbury Joinery we work closely with a number of local authorities and conservation officers to find the best solution for your property. If slimline double glazing is not approved by local authorities, we can offer a draught proofing service within single glazed sash windows as well as traditional Victorian shutters.

Double Glazed Shutters:


We also manufacture and install ultra slimline double glazed shutters that can provide extra levels of insulation, whilst remaining sympathetic to the original design of your home or property. Our double glazed shutters do not interfere with the normal sash windows during winter and can fold away discreetly in the warmer months for a practical alternative to slimline double glazing.

Will it really look authentic? 

At just 12mm thick, the double glazed units will be virtually undetectable on the eye. They look like single glazed sash windows, from inside and out. The double glazed units will be puttied on the outside to give a traditional finish and in-keeping with the properties in the area.

What about heat loss? 


The rate of heat loss can be measured by it's U-value: the lower the U-value, the better it is at preventing heat loss. The average single glazed window has a U-value of around 5.6. Slimline double glazed units range between 2.2 U-value and 1.5 U-value, up to almost three quarters less, keeping your property warm during the winter and reducing your energy bills at the same time.

Can anyone have this done? 


Generally speaking yes but if you live in a listed building you will need to contact your local conservation officer to find out. Period frames are suitable and, where necessary, will be expertly restored by our experienced team, as part of the installation process. If not, they can be rebuilt to precisely match the originals.

To save time at Barnsbury Joinery we have implemented an online quote request system. Once we receive your request we will endeavour to contact you within 48 hours. If you require emergency assistance or would like to discuss your requirements, please do not hesitate to contact us directly on 0207-1646305.


At Barnsbury Joinery we service all of London and surrounding areas. Including Islington, Hackney, Hampstead, Primrose Hill, Camden, Stoke Newington, Clapham, Angel, Canonbury, De Beauvoir Town and Clerkenwell. Please call us now to find out if we work in your local area.

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