Insulation and air sealing: current and emerging trends in European masonry buildings.

Across the world, the dominant form of building construction is heavy, load-bearing masonry or poured concrete, not timber- or steelframe. It is possible to make these buildings very energy-efficient, but they present very different problems from those associated with timber-frame buildings.

Much of the initial development of highly energy-efficient masonry dwellings occurred in Sweden, Denmark and Switzerland. However, the same principles are now being applied in other countries with a masonry building tradition. Valuable lessons have been learned. As a rule, it is considerably easier to reach good airtightness in masonry buildings than in site-built timber-frame ones. Conversely, to avoid thermal bridges needs much greater care in loadbearing masonry structures than in woodenframe ones.

With care, very similar levels of insulation may be reached in masonry buildings and in timberframe buildings. The comparison is seen most vividly in Denmark and Sweden, where designers routinely achieve U-values of less than 0 .2 Wtm2K, in both heavyweight and lightweight building structures.

Under changing conditions, two parameters affect the behaviour of superinsulated heavyweight buildings. As well as their thermal resistance, discussed in the last paragraph, one must consider their thermal capacity.

The dynamic thermal behaviour of lightweight superinsulated buildings is stab1e, and fa irly predictable. In response to a sudden heat input, or the onset of a spell of cold weather, they heat up and cool down at a noticeable rate. However, high mass, superinsulated buildings have an exceptional level of thermal inertia, and they behave in a way which is outside most peoples' everyday experience. This has potential benefits, but also has a few disadvantages. Both are discussed.

With the aid of examples from Scandinavia, mainland Europe, north America and the UK, this paper presents experience to date with the improved insulation of masonry buildings and attempts to reduce the level of air infiltration. Some noteworthy case studies are described.