CIBSE TM 52 utilises operative temperature for free-running buildings and PMV for mechanically cooled buildings. However, operative temperature does not fully allow for the effect of air speed on occupant comfort (see TM 52 box 1 and the CIBSE Guide A).
As the HVR product is designed to provide direct airflow on occupants during the appropriate mode assessing the comfort benefit needs to be carried out using the PMV method.
In the VistaPro > Comfort analysis dialog select the check box for ISO 7730 : 2005 and select a category suitable for the project, nominally Category B. VistaPro will then post process additional room variables and these will be shown in the VistaPro > variables picker with the following prefixes:
1. PMV (ISO 7730 …
2. PPD (ISO 7730 …
A number of these variables are provided for different air speed settings so that the benefit of the HVR unit can be assessed and compared. Variables prefixed ISO 7730 nom & elev air speed … apply the elevated air speed per time-step when the PMV calculated at the nominal air speed exceeds the selected category upper limit (for category B this is PMV +0.5) thus reflecting the function of the HVR unit.
Clothing affects comfort; this is set for each room by template or on space data:
As comfort is post-processed these inputs can be changed post-simulation. CLO value can be fixed, set by profile or set to a min or max value per time-step to give a best result (See VE help); these options provide a means to mimic occupant behaviour. Sensible default values are applied when HVR is assigned or re-assigned to a space.
Typically, one might compare PMV (ISO 7730 nominal air speed) with say PMV (ISO 7730 nom & elev air speed cat B) to assess the benefit of the HVR summer operation.
