Avoiding Thermal Bridges 1

Preventing Thermal Bridges 1 What is a “thermal bridge”? In a cold climate, it is any route by which heat can escape to the outside of the building through the roof, walls, windows, doors and so on. In a hot climate, the problem is reversed - excessive heat enters the building. This infra-red image shows a thermal bridge as a dark area - in this case around the edge of a poorly-fitted double-glazed window unit. Much of the benefit of the double-glazing is being lost. At this housing development in Ostia, near Rome, the architect designed the walls to avoid thermal bridges and so prevent the summer sun from overheating the apartments. In the winter, on the other hand, the design maximises the solar gain. The energy performance of this development has been achieved through two strategies. A passive strategy, that’s through the characteristics of the walls and an active strategy through the equipment installed. For example, the design of the balconies on almost every facade of the buildings shades the walls so we reduce the solar radiation onto them. The storey height, the internal height of the apartments is about 10% higher than normal in apartments in Italy, to give better natural air circulation. The windows are full height, giving more direct sunlight in the winter. We avoid solid panels at the floor level - the windows are floor to ceiling. The design of the exterior walls is highly energy efficient, both the walls and the windows. The walls have two skins of brick. The inner skin is a honeycomb block, a 12cm block with high thermal efficiency. Then we have a 5cm air cavity and the outer brick skin which you see. In the cavity we have used a heat reflecting insulation to prevent heat transfer, external heat coming from outside, and also from inside to keep up the internal temperature. When the heating system shuts down overnight at the coldest time, in the morning we have lost just half a degree Celsius. The external wall is masonry and has two elements: the inner skin of 12cm lightweight clay blocks, a cavity with a 5cm air gap with an aluminium foil in the middle and an outer skin of 12cm traditional brick for the exterior.