Set lighting power density for each space by standard space category.

ASHRAE 90.1-2019

Code Requirement Interpretation

The requirement aim to determine the interior lighting power density according to the Table G3.7. For spaces mixed multiple space types, weighted LPD is calculated and the occupancy sensor reduction is weighted by the lighting power density of the space.

Implementation Methodology

The method of assigning interior lighting power density for a single-type space is straightforward. However, when the space is a mixed-type, the lighting power density and occupancy sensor reduction are calculated in the example below.

Example:

Space num_std_ltg_types std_ltg_type01 std_ltg_type_frac01 std_ltg_type02 std_ltg_type_frac02
Perimeter_ZN_2 2 retail - whole building 0.8 retail dressing room 0.2
Where:
Space Type lighting per area (W/ft2) occupancy sensor reduction
————————— ————————— —————————-
retail - whole building 1.5 0.1
retail dressing room 0.89 0.1
The lighting power density of Perimeter_ZN_2 shall be determined as:
**Weighted LPD** = 1.5 W/ft2 * 0.8 + 0.89 W/ft2 * 0.2 = 1.2 W/ft2 + 0.178 W/ft2 = 1.378 W/ft2
**Weighted occupancy sensor reduction** = (0.1 * 1.2 W/ft2 + 0.1 * 0.178 W/ft2) / 1.378 W/ft2 = 0.1
## Key Ruby Methods
The function ‘space_type_apply_internal_loads` is used to calculate the LPDs and occupancy sensor reduction for each `Space` or `Space Type`. The logic is implemented by overriding this method in the `ashrae_90_1_prm_2019.SpaceType` class.
## Test Case Documentation
### Test case 1:
- Prototype: Small Office
- User data folder: /userdata_lpd_01
- Summary:
Space num_std_ltg_types std_ltg_type01 std_ltg_type_frac01 std_ltg_type02 std_ltg_type_frac02 std_ltg_type03 std_ltg_type_frac03 Target_LPD (W/m2)
—————— ——————- ————————– ——————— ————————- ——————— ———————- ——————— ——————-
‘Perimeter_ZN_2` 2 retail - whole building 0.8 retail dressing room 0.2 14.83267494
‘Perimeter_ZN_1` 3 retail mall concourse 0.2 retail - whole building 0.6 retail dressing room 0.2 15.26323154
‘Perimeter_ZN_4` 1 kitchen 1.0 12.91669806
‘Perimeter_ZN_3` 1 office 1.0 10.7639
‘Perimeter_ZN_5` 1 office 1.0 10.7639
‘Attic` 2 warehouse - bulk storage 0.5 workshop 0.5 15.06948107
### Test case 2:
- Prototype: Small Office
- User data folder: /userdata_lpd_02
- Summary:
Space Type num_std_ltg_types std_ltg_type01 std_ltg_type_frac01 std_ltg_type02 std_ltg_type_frac02 Target_LPD (W/m2)
———————————— ——————- ————————- ——————— —————- ——————— ——————-
‘Office WholeBuilding - Sm Office` 2 atrium <= 40 ft height 0.5 workshop 0.5 12.2452724
The ‘Office WholeBuilding - Sm Office` is the space type used by `Perimeter_ZN_1` through `Perimeter_ZN_5`.
- Note: In this test case, we also expect ‘Attic` to have `0 W/m2` LPD.
### Test case 2:
- Prototype: Small Office
- User data folder: N/A
- Summary:
‘Office` is used as the standard space type for all spaces except `Attic`. Therefore, in this test case, we are expecting LPD to be 10.7639 for spaces `Perimeter_ZN_1` through `Perimeter_ZN_5` except `Attic`.