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THE INCREASING USE OF LOW TEMPERATURE WATER SYSTEMS | 3
If there are no surface area changes in the building
elements and the ventilation air-flow rates remain
unchanged as well, we can calculate the influence of
the improved insulation. The transmission losses will be
reduced to 31%, when the area weighted U-values, Uw.
mean = 1.3 W/m 2 K go down to Uw.mean =0.40 W/m 2 K.
Thus the ventilation remains unchanged and the total
heat loss reduction will be only 44.3%.
Note: This type of widespread insulation improvement
project is often motivated by a need for better windows
and a more attractive façade or by need of higher thermal
comfort and healthier indoor environment.
The new share of losses will be:
- Ventilation and infiltration 65.1 %
- External walls 11.4 %
- Windows and exterior doors 16.1 %
- Roof 3.6 %
- Ground 4.4 %
sum 100 %
The heat load will be 44.3% smaller than in the original
case. New specific load is about 67 W/m 2 , and from Fig. 3.9
we can see that the corresponding heating demand value is
about 100 kWh/m 2 a.
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