Home Comforts: Insulating Historic, Listed and Heritage Buildings

If you live in an unmodified listed, historic or older property you will know that they can be very cold in winter and heating them conventionally can lead to problems with condensation.  So, what can be done to improve this?

Older properties often have single glazed windows and usually solid masonry walls. Neither are good in terms of thermal insulation. The fabric of the building gradually absorbs the cold air outside and the humid air within the property condenses, both on the cold panes of the single sheets of glass and on the cold internal wall surfaces.

Creating better ventilation for the house is a good idea, but easier said than done. Uncontrolled ventilation, experienced as draughts, does not help as it makes it difficult to heat the property as well as making it uncomfortable to live in. Work is needed to remove the humid air and prevent condensation in a controllable and comfortable way. Modern houses incorporate ‘trickle ventilation’ within their windows to provide a small amount of constant ventilation, which is ideal, but windows in older properties won’t have this feature and it is not currently possible to add this to existing traditional windows.

Changing those single glazed windows for double glazed ones is usually a non-starter on a listed home, though may be possible on unlisted older properties. Installing secondary glazing can be an option although unsightly and often detrimental to the internal character and appearance of the building. In some cases, a new replica ‘heritage’ double glazed window can be installed, incorporating a very narrow double-glazed panel which allows the traditional slender timber sections of the window to be retained. We have specified these a number of times to good effect and our own design studio has recently developed a trickle ventilation detail for a project, to work within the jamb of sash window replacements whilst maintaining their visual appearance.

There are several other solutions to help improve the thermal performance of a dwelling and one of these is to use a thin insulation to line the inside of external walls. The advantage of this system is that it generally allows the window jamb and skirting details to remain.

Maintaining breathability is important in older properties. Any insulation applied internally should allow the passage of moisture through the walls. Be aware that for this internal wall insulation to be applied, the existing wallpaper and sometimes plaster, will need to be removed. It is an involved process but can be worth it as part of a complete overhaul of a good listed or historic property, particularly when the external appearance must be maintained.

There are now also systems available that provide background or ‘trickle’ ventilation to older properties.  Some cleverly use the existing chimneys to achieve this whilst other systems use a natural stack effect in a duct connected to a roof cowl. In some cases, simply changing standard kitchen and bathroom fans for constant velocity or humidistat fans can make quite a difference.

There are however various other natural ventilation systems available on the market to ensure that a constant trickle of ventilation is maintained whilst minimising the intrusion on any historic fabric of the buildings. New technological advances are of course coming on to the market all the time and as architects with an eye to the future of our planet and our built environment, we consider it our duty to keep abreast of the best of these, so that we can specify proven up-to-date technologies on suitable projects.

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