ladybug_comfort.local module

Utility functions for computing local thermal discomfort according to ASHRAE-55.

ladybug_comfort.local.ankle_draft_ppd(predicted_mean_vote, air_speed_at_ankle)[source]

Calculate the percentage of people dissatisfied from cold drafts at ankle-level.

The original tests used to create the model involved blowing cold air on subject’s ankles at a height of 10 cm off of the ground. The formula was officially incorporated in the ASHRAE 55 standard in 2020 with a recommendation that PPD from ankle draft not exceed 20%.

Note

[1] ASHRAE Standard 55 (2020). “Thermal Environmental Conditions for Human Occupancy.” American Society of Heating, Refrigerating and Air Conditioning Engineers.

[2] Schiavon, S., D. Rim, W. Pasut, W. Nazaroff. 2016. “Sensation of draft at uncovered ankles for women exposed to displacement ventilation and underfloor air distribution systems.” Building and Environment, 96, 228-236.

[3] Liu, S., S. Schiavon, A. Kabanshi, W. Nazaroff. 2016. “Predicted percentage of dissatisfied with ankle draft.” Accepted Author Manuscript. Indoor Environmental Quality. http://escholarship.org/uc/item/9076254n

Parameters

  • predicted_mean_vote – The full-body predicted mean vote (PMV) of the subject. Ankle draft depends on full-body PMV because subjects are more likely to feel uncomfortably cold at their extremities when their whole body is already feeling colder than neutral. The functions in the pmv module can be used to calculate this input.

  • air_speed_at_ankle – The velocity of the draft in m/s at ankle level (10cm above the floor).

Returns

ppd – The percentage of people dissatisfied (PPD) from cold downdraft at ankle-level.

ladybug_comfort.local.radiant_asymmetry_ppd(radiant_temperature_difference, asymmetry_type)[source]

Calculate the percentage of people dissatisfied from radiant asymmetry.

The comfort functions used here come from Figure 5.2.4.1 of ASHRAE 55 2010. Note that, if the resulting input results in a PPD beyond what is included in this Figure, the maximum PPD will simply be returned.

Note

[1] ASHRAE Standard 55 (2010). “Thermal Environmental Conditions for Human Occupancy.” American Society of Heating, Refrigerating and Air Conditioning Engineers.

Parameters

  • radiant_temperature_difference – The radiant temperature difference between two sides of the same plane where an occupant is located [C].

  • asymmetry_type –

    An integer that representing the type of radiant asymmetry being evaluated. Occupants are more sensitive to warm ceilings and cool walls than cool ceilings and warm walls. Choose from the following options.

    • 0 = WarmCeiling

    • 1 = CoolWall

    • 2 = CoolCeiling

    • 3 = WarmWall

Returns

ppd – The percentage of people dissatisfied (PPD) for the input radiant asymmetry.