1. Zones that are heated to a lower temperature than the main building:
For lower temperatures, e.g. the rooms are only kept frost-free, a reduction factor can be calculated using the MS Excel tool provided by PHI. The tool uses a conservative approach and is only recommended for buildings, for which the influence on the total specific heating demand is small or moderate.
Auxiliary calculation for reduction factor X (PHPP Areas worksheet) to extensions which are kept frost-free or heated to a low temperature
2. Unheated buffer zones:
If a more accurate calculation is desired, the reduction factor can be calculated from the relation of the conductance of the area between the two zones and the conductance of the exterior envelope of the buffer zone. Ventilation heat losses should also be considered, if relevant, thus it may be easiest to determine the conductance of the buffer zone by setting up an extra PHPP.
3. Zones heated only occasionally, but then with 20 °C :
If heated regularly, e.g. once a week: In this case it may already make sense to include it in the thermal envelope. If not, a reduction factor of e.g. 6/7 can be used (for 1 day per week). This would be conservative as it ignores the fact that it takes some time until the space has cooled down again, especially if the partially heated space has good insulation against the ambient air. In order to also take the cool-down period into account, a dynamic simulation would be needed.
|
PHPP “Areas” worksheet summary with the temperature zone X in the bottom row |