Add Occupants

Occupants add heat and moisture to the indoor environment, affecting the building’s thermal balance. The body generates heat through metabolism, releasing it into the air, while breathing and sweating add moisture.

Occupant density, expressed as people per square metre (m² per person), determines internal gains. For example, in a 100 m² office with a density of 10 m² per person, there are 10 people (100 ÷ 10 = 10).

Occupant density combines with schedules to reflect changes in occupancy throughout the day, week or year, improving the accuracy of internal gain calculations.

Occupants

Set Occupant Density

To define occupant density, navigate to 'Spaces' and select the 'Default Space' or any other space available. Then navigate to 'Occupants' and left-click 'Design Level'. Next, left-click the occupant density field and use the slider to set the m²/person for the space.

Set Occupant Schedule

To define an occupant schedule, navigate to 'Spaces' and select the 'Default Space' or any other space available. Then navigate to 'Occupants' and left-click 'Design Level'. Next, left-click the schedule field to open the detailed schedule builder.

Here, you can set the 'Day Type', which determines when the schedule applies to your space. You can also set the fraction for each hour manually, apply a 'Bulk Update', or create a 'Stepped Schedule'. Once you have made your changes, click 'Update' to save and return to the space.

Set Multiple Occupant Density & Schedules

When annual variability is required for occupant density and schedules, these can be defined in detail. By default, occupant density and schedules are applied the same for all 365 days of the year. However, you can set different values for specific periods if needed.

To do this, go to 'Spaces' and select either the 'Default Space' or any other space you want to edit. Navigate to 'Occupants', then left-click on 'Design Level'. In the left panel, click the '+' button under 'Level' to add a new value for a specific date range. An additional entry will appear under 'Level', covering the remaining days of the year.

Left-click the first entry and go to 'Calendar'. Here you can select the start and end dates (day and month) for when the first occupancy period applies. Once this is set, the next 'Level' will automatically update to cover the remaining days. Repeat these steps for the 'Schedule' if applicable, and when everything is set, click 'Update' to save the changes.

Activity Level

The metabolic rate of people in a space is defined as 'Activity' and is measured in watts per person (W/person). This value represents the energy produced by human metabolism, which affects thermal comfort, the building’s energy balance, and HVAC load calculations. The metabolic rate changes depending on the activity level. For example, a sleeping person has a lower metabolic rate than someone performing heavy physical work.

The ASHRAE 55 standard and ISO 7730 provide typical values for different activities as follows:

• Sleeping: around 70 to 80 W/person

• Seated, quiet (for example, office work or studying): around 100 to 120 W/person

• Light work (for example, standing or light manual labour): around 120 to 160 W/person

• Moderate work (for example, light industrial work or house cleaning): around 165 to 230 W/person

• Heavy work (for example, heavy industrial work or athletic activity): can exceed 400 W/person

To define Activity Level, navigate to 'Spaces' and select the 'Default' Space or any other space available. Then navigate to 'Occupants'. Next, use the 'Activity Level' slider to set the W/Person for the Space. When applicable, the 'Schedule Type' associated to the 'Activity Level' can be updated from a default constant value to 'Varies by Date' or as a 'Detailed Schedule'.

Air Velocity

Air velocity influences thermal comfort and is set as a fixed input, representing indoor air speed in metres per second (m/s). Moving air increases heat loss from the body through convection and evaporation, helping people feel cooler, especially in warm or humid conditions.

In building simulations, air velocity is typically low, around 0.1 m/s or less, reflecting calm indoor conditions. Higher velocities may occur with natural ventilation, ceiling fans or other air movement and can be modelled as needed.

To define air velocity, navigate to 'Spaces' and select the 'Default Space' or any other space you want to edit. Then navigate to 'Occupants'. Use the 'Air Velocity' slider to set the m/s value for the space. As elsewhere, the 'Schedule Type' associated to the 'Activity Level' can be updated from a default constant value to 'Varies by Date' or as a 'Detailed Schedule'.

Clothing Method

The method of defining clothing insulation will depend on the specifics of your project and the level of accuracy you require. While using a constant or scheduled value might be sufficient for many applications, using a calculated value can provide a more realistic representation of how people might adapt their clothing to changing conditions, potentially improving the accuracy of your thermal comfort predictions.

To define a Clothing Method, navigate to 'Spaces' and select the 'Default' Space or any other space you want to edit. Then navigate to 'Occupants'. Next, use the 'Clothing Insulation Method' dropdown to nominate a method for the Space. A 'Fixed' method is set by default. assuming the same 'Clothing (when fixed) value for the year.

Where a 'Dynamic' 'Clothing Insulation Method' is selected, a dynamically calculated clothing insulation value based on indoor and/or outdoor environmental conditions is set. This is achieved using a Clothing Insulation Model, as proposed by the ASHRAE-55 standard, which adjusts the clothing level based on the mean monthly outdoor air temperature. According to the 2017 version of ASHRAE 55, the dynamic clothing insulation model is represented by the following formula:

where:

• Icl is the clothing insulation in clo

• Tavg is the average monthly outdoor air temperature in °C

As elsewhere, the 'Schedule Type' associated to the 'Clothing Insulation Method' can be updated to 'Set by Date' or as a 'Detailed Schedule'.

Clothing

Clothing is the insulation value of occupants and plays a key role in thermal comfort calculations. Measured in clo (where 1 clo equals 0.155 m²K/W), it represents the insulation provided by clothing. Typical values are as follows:

• Naked: 0 clo

• Underwear: 0.04 clo

• T-shirt: 0.09 clo

• Trousers: 0.15 clo

• Sweater: 0.2 - 0.4 clo

• Suit jacket: 0.2 - 0.4 clo

• Light overcoat: 0.5 clo

• Heavy overcoat: Up to 1 clo

For typical indoor activities such as office work, clothing insulation is usually between 0.5 and 1.0 clo. The exact value can vary depending on outdoor climate, indoor temperature, age, gender and personal preference, making it difficult to define precisely.

To define clothing, navigate to 'Spaces' and select the 'Default Space' or any other space you want to edit. Then navigate to 'Occupants'. Use the 'Clothing' slider to set the clo value for the space.