building envelope

The determination of building insulation levels is an indispensable part of low-energy residential building design. It is necessary to study the impacts of varying insulationlevels of outer walls and roof on room heating loads and cooling loads per square metre. Although diversity of researches on this subject have been carried out over the past years, simulation models have not been employed to evaluate the energy saving effect of different insulation levels all year, and the results were not quantitatively analysed.

Energy consumption in building accounts for 30 percent of all the energy consumption of external envelope takes an important part. But in China, because of the insufficiency in thermal behaviour of building external envelope, indoor average heating temperature is low, while heating energy consumption per unit area is 2-3 times as much as that in developed countries under the same climate condition. In this paper, according to measurement and analysis on some kinds of walls, windows and roofs, the detail methods in energy saving of these structures are described.

Makes a comparison between the effects on thermal performance and energy use of a number of pre-cooling and ventilation strategies, suitable for use to reduce peak power demands in office buildings in moderate temperature regions. Describes how simulations were performed for different building envelope parts, and for two levels of internal heat load. Lists the results as significant reductions of required daytime peak power loads which may be obtained by cooling strategies that contribute to lowering the internal mass temperatures.

Short analysis of possible retrofitting operations on the building envelope and on the heating system to save energy. An analysis of residential buildings in various parts of Italy has been performed using the Italian national calculation procedures (UNI) for the evaluation of winter energy need. A more detailed analysis in envisaged to extend the data obtained, using more sophisticated codes in order to calculate the annual energy consumption of the building. This would define normalised energy indices to ensure a more energy aware design.

Describes the results of the experimental evaluaton of two precast concrete sandwich panels. States that for best results for precast concrete walls, the air barrier must be sufficiently airtight to achieve static pressure equalization and there must be sufficient venting to achieve dynamic pressure-equalization. Similar results were obtained from research conducted on other wall systems. For precast concrete walls, these results are best obtained by minimizing the cavity volume and decreasing air barrier leakage before increasing vent area.

Describes the experimental evaluation of a brick veneer steel stud (BVSS) test specimen. The system was evaluated for air leakage characteristics, pressure equalization response, deflection and water penetration. Concludes that for best results for BVSS walls, the air barrier must be sufficiently airtight to achieve static pressure equalization and there must be sufficient venting to achieve dynamic pressure equalization. Similar results were obtained from research conducted on other wall systems.

The performance of a Ventilated wall component under real weather conditions was tested, during two weather seasons, winter and summer. The component was built in a 1:1 scale, consisting of two equal area parts, a Ventilated wall with and without a radiant barrier. It was installed at the South faade of a PASSYS outdoor Test Cell at CRES. Air openings were located at the bottom and top of each wall component in order to facilitate the air movement through the air gap.

Dynamic insulation is a very good example of a ventilation system integrated with the building envelope. The paper describes two recent studies carried out at Nottingham on dynamic insulation. One study concerns a system based on mechanical ventilation. The other describes a purely natural system. Although there are few existing applications of dynamic insulation, it is argued that there is potential for both systems, particularly with certain types of building. The natural system is technically more challenging than the mechanical system, but the potential energy savings are larger.

This paper briefly exams the role of the building envelope in determining the internal environmental conditions in buildings and the scope for holistic design of building services and building envelope. It then looks at how holistic design may be undertaken, the barriers to be overcome to enable this to happen and the incentives that are necessary.

A scale mock-up house installed with a "Breathing Wall" was constructed outdoors in order to consider the practical application of breathing walls in houses in temperate-climate regions. It was found that, under outdoor weather conditions, the Breathing Wall provides the necessary amount of ventilation, thermal insulation and moisture transmission required for application in a temperate climate region. No adverse effects on the indoor environment were found even when cold outdoor air flowed through the Breathing Wall.