The strategic implications for large, dynamically insulated buildings in cities.

The concept of dynamic insulation, where cold air is drawn through porous insulation in a building envelope from outside to inside, thereby returning heat energy normally lost by conduction back into the interior of the building, has been studied by several researchers, in Japan, Europe and Canada. However the work to date has largely concentrated on the physical processes in individual wall, floor or roof elements and only a small number of experimental buildings (all of a small domestic scale) have been adequately monitored. While these studies have been valuable there remain wider questions concerning the suitability and realistic usefulness of dynamic insulation for use in larger buildings and city blocks. The paper describes a series of parametric studies using a new computer model called BREATHE in which a dynamically insulated house and an office building are assessed for relative gains in energy efficiency, particularly in the light of current trends towards the passive heating, cooling and ventilation of large buildings. Results indicate that dynamic insulation is most effective in climates with a large internal I external temperature difference, in buildings having a low volume to surface area ratio and I or a high air change rate.