Up to the early part of the twentieth century walls were generally built as solid brickwork of adequate thickness to resist the penetration of rain to the inside face and to safely support the loads common to buildings both large and small.
At the time it was accepted that the interior of buildings would be cold during winter months when heating was provided by open fires and stoves, fired by coal or wood, to individual rooms. The people of northern Europe accepted the inevitability of a degree of indoor cold and dressed accordingly in thick clothing both during day and night time. There was an adequate supply of coal and wood to meet the expectations for some indoor heating for the majority.
The loss of heat through walls, windows and roofs was not a concern at the time. Thick curtains drawn across windows and external doors provided some appreciable degree. of insulation against loss of heat.
From the middle of the twentieth century it became practical to heat the interior of whole buildings, with boilers fired by oil or gas. It is now considered a necessity to be able to heat the whole of the interior of dwellings so that the commonplace of icy cold bathrooms and corridors is an experience of the past.
In recent years an industry of scare stories has developed. Ill considered and unscientific claims by ‘experts’ that natural resources of fossil fuels such as oil and gas will soon be exhausted have been broadcast. These dire predictions have prompted the implementation of regulations to conserve fuel and power by introducing insulating materials to the envelope of all new buildings that are usually heated.
This ‘bolting the stable door after the horse has gone’ action will for very many years to come only affect new buildings, a minority of all buildings.
A consequence is that the cavity in external walls of buildings, originally proposed to exclude rain, has been converted to function as a prime position for lightweight insulating materials with exclusion of rain a largely ignored function of a cavity wall.