One of the really tangible benefits of extending your house, whether its upwards (a loft conversion) or outwards (extending the building) is that the new building envelope has to be really well insulated.
A new wall is about six times more efficient than an old Victorian wall for instance. A new insulated roof can be thirteen times more efficient than an old Victorian roof. By wrapping new building around the old building effectively wraps the house with insulation. Of course you can seldom take the extension all the way round and so some clever remedial tricks should be employed to improve the insulation of the old exposed walls. It can make a dramatic difference to an old building.
Building Tectonics can advice on this and other related matters.
building-tectonics.co.uk 01908 366000
Written by Tony Keller – Building Tectonics Ltd.