building envelope

Since the mid 70's, the construction industry has made significant advances in energy conservation and improved indoor conditions. These improvements, however, are shadowed  by an increase in building envelope problems to include water penetration, condensation on and in roofs and exterior walls and cladding damages in many of our newer buildings; These problems have been attributed to uncontrolled air leakage.

A model for the application of probabilistic methods is the estimation of heat loss caused by convection and heat conduction through the material is developed. Temperature difference (delta T) between inside and outside of a building, air change rate (ACH) and coefficient of thermal transmittance (U-value) of the building structure are treated as random variables. The mean value and standard deviation of heat loss are estimated for different parameters of distribution for temperature difference, air change rate and thermal transmittance.

The concept of 'build tight - ventilate right' requires minimising air infiltration through theenvelope of a building and then providing adequate ventilation in a controlled manner tosatisfy the fresh air requirements of occupants. This paper describes a simple-to-use designtool (PC based and in spreadsheet format) for predicting the airtightness of office buildingenvelopes either at the design stage or before a major refurbishment.

The utilization of Hybrid Solar Systems in buildings allowed a rational use of energy required to obtain proper comfort conditions inside the building itself. During some research programmes carried out at !CITE, prototypes of test cells capable of supplying significant information on the energetic behaviour of technologically innovative building envelopes for passive and hybrid solar control, have been designed and built.

As a further development of the degree-days concept, a simple parameter which takes into account site's metereological conditions as well as building envelope performance is proposed in this paper. Such a parameter shows good correlation with building energy requirements, both in winter and in summer conditions.

In the near future a large number of dwellings in Switzerland dating from the 50s to the 70s will need to be retrofitted in order to upgrade the comfort levels to today's standards and to reduce the energy consumption. By carrying out an overall retrofit of both the envelope of the building and the building services this can be successfully accomplished. Two retrofit projects of apartment blocks, one in Meilen and one in Cossau, demonstrate how a well-balanced strategy can achieve a comprehensive and economical retrofit.