Reheat surcharge

All surfaces (including furniture, and excluding windows and doors) are taken into account to compute the reheat surcharge. Covered surfaces are only counted for 70%, and non-stony surfaces are not counted.

Operating mode

 HL
This option indicates whether a specific surcharge for business restriction applies:

•      Continuous; the operation is continuous, which means there is no heating surcharge. Therefore no business restriction occurs and consequently no specific surcharge for heat loss either;

•      Night set-back; if the operation is set to night set-back, periodically a specific surcharge for heat loss needs to be calculated, such that the building can be heated within a certain time. The night set-back can be entered using a wizard for non-residential buildings, residential buildings or using a custom value.

Reheat input

[Choice and W / m²] HL
The method used to calculate the specific heating surcharge is indicated here. This input depends on the room being either residential or non-residential. For more detailed information, please consult Heating surcharge.

•      If the room concerns a residential area, the calculations are applied using a wizard based on on ISSO 51, section 4.4.4;

•      If the room concerns a non-residential area, the calculations are applied using a wizard based on   ISSO 53 Annex E;

•      If a custom value is chosen, the wizard can be bypassed by entering a custom specific heat surcharge.

Building mass

 HL
If the reheat input for non-residential input has been selected, a global average building mass is required.

§ Light for light building masses, such as timber frame constructions

§ Medium for medium building masses, such as metal and glass

§ Heavy for heavy building masses such as concrete, masonry and other types of stone.

Night-time setback

 HL
If one of the two wizards has been chosen in the reheat input, a night-time setback is required. This represents the number of degrees Celsius between daytime operation and night-time operation of the system. The night-time setback can be set daily and multiday.

Time to reheat

[Hours] HL
This is the time from the moment the system is activated after a period of reduced operation until the temperature corresponding to PMV = -0.5 is achieved. The time to reheat is defined in design conditions.

Weighting factor internal mass

[Choice and factor] HL
The internal mass weighting factor is specified to take into account additional accumulating surface area due to internal mass in Heat loss calculations. In non-residential buildings this factor is 0, except for shopping stores, libraries, and archives. The weighting factor is multiplied by the surface area of the floor. You can find several guideline values ​​of the weighting factor in the table below.

Table12: Approximate weighting factor internal mass

Surcharge cold materials

 HL
The internal mass (machines and products) needs to be determined in rooms with non-residential area which are higher than 5m.  Based on this internal mass and the weighting factor, this surcharge should be specified in W.