Insulating an Existing House in a Conservation Area

7 January 2019
by Alex Murray

We are renovating and extending our home. The house has stone quoins on all corners and pebbledash in-between.

This is a conservation area and we have planning permission for external insulation boards of 40mm and 10mm render between the quoins on the walls, instead of pebbledash.

However, this will not provide enough insulation. I had previously thought of adding Kingspan stuck to plasterboard on every wall but have realised that this is not actually possible as it would involve moving a staircase and destroying wood panelling in two rooms.

So, is it better to just externally insulate and cavity fill the existing empty cavity (late 1930s house, likely a 50mm cavity) or should I scrap cavity fill and internally insulate all possible rooms leaving a couple of rooms cold?

One Answer

  1. It’s difficult to draw conclusions without really understanding the site, design and its context.

    But personally I am a fan of adding cavity wall insulation but only in areas of low exposure and obviously with reputable companies.

    If you have pebbledash on a 1930s building then this is likely to be pretty hard and the walls should be quite rain/shower proof as a result.

    Thereafter I would probably be inclined to add any additional insulation where I could on the inside face of the external walls although this is of course quite disruptive as you suggest.

    One other thing to consider is adding heat recovery to your new thermal envelope which will help enormously in controlling condensation risks including interstitial condensation.

    This way the external proportions of the house should stay intact.

    Good luck.

    Tim Doherty, Build It expert

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