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| How to find us ? |
| TEL: |
+86-21-68453855 |
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-86-21-52303505/6/7 |
| FAX: |
+86-21-50453855 |
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+86-21-52303508 |
| URL: |
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| Email: |
info@foameps.com |
| epsmachinery@foameps.com |
| ADD: |
201607.NO.368 Xindan Road.Shanghai.China |
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| Sandwich Constructions: Light Outer Walls |
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The need for rationalized building methods and employment of materials has encouraged the use of light prefabricated components. Lightweight walls are now largely assembled from such components, which are commonly sandwich constructions and may have provision for ventilated sidings.
In order to control the environment within buildings, high thermal inertia is often essential. In cool climates with heated buildings this is always the case; in warm climates much depends on the relative importance of daytime and nighttime use, the diurnal temperature range, whether or not the building is air- conditioned, and to what extent the building is exposed to direct sunlight. In general, all air- conditioned buildings need high thermal inertia.
The thermal inertia of a building can be indicated in several ways, but a simple measure is the quantity C/AU, where C is the total thermal capacity of the building and its contents, A is the area of the enclosing elements through which heat is lost or gained by transmittance, and U is the average thermal transmittance of the enclosing elements. The quantity C/AU has the dimensions of time; if it is large, fluctuations in inside temperature will lag behind fluctuations in outside temperature, and will be very much smaller.
The thermal capacity of outside walls decreases with their superficial mass. However, to keep C/~U constant, it is not necessary to reduce the maximum value of U in direct pro- portion to the superficial mass; floors, partitions, etc. make a considerable contribution to the total thermal capacity, C, and in any case many light materials have higher specific thermal capacities than masonry (e. g. wood, ca 2 j/g. k, compared with ca 0.8j/g. k for brickwork or concrete ). Guidance on the ~um thermal transmittances of lightweight walls is often included in national standards, which can take into account typical layouts and materials, both of which affect the thermal capacities of buildings. For
instance, in West Germany it has been recommended that the maximum value of U for most areas should be 0.9W/m2. k for wails with superficial masses of 200kg/m2 or more, falling linearly to O. 6w/m2. k at 50kg/m2.
Thermal bridging often requires considerable attention in lightweight walls; particular care
should be taken with the insulation of joints and metal frames. |
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