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Mechanical

Fresh Air Requirement Standard

Fresh Air Requirement Standard , also known as Mechanical Ventilation (see Overview page) is used for calculating air changes, which is used in the Heat Loss and Heat Gains calculations. It also calculates the minimum ventilation flow rate based on various global standards, such as CIBSE, ASHRAE, and Building Regulations, and is used to size ductwork and ensure adequate ventilation in the building.

Infiltration Air Change Rate

Infiltration Air Change Rate (see Overview page) is uncontrolled air leakage through the building envelope measured in air changes per hour and is added onto Fresh Air Requirement, which is used in the heat loss and heat gain calculations.

For Heat Losses / Heat Gains we would consider Total Air = Fresh Air + Infiltration.

For Ventilation Purposes we would only consider Fresh Air Requirements.

EN12831-1:2017

EN12831-1:2017 standard has 4 additional options for it and Infiltration Air Change Rate can't be altered as it depends on those options:

  • Building Air Tightness: Defines the air leakage characteristics of the building envelope. Accuracy here is critical, as low tightness in rural areas can lead to significant heat loss.(m3/h∙m2).

    • Air Tightness Value: There are 5 options - High Tightness (Class 1), Mid-Level Tightness (Class 2), Moderate Tightness (Class 3), Low Tightness (Class 4) & Custom. For Custom option - a custom value can be inputted. This can be described as "Air Flow Per Area" - Air Permeability ACH looks at volume, this looks at floor area.

  • Building Exposure/Shielding: Adjusts infiltration based on the building’s environment and wind protection

    • Dense Urban/Forest (Intensive Shielding) - Inner city or forested area

    • Suburban/Light Trees (Normal Shielding) - Loosely surrounded by buildings or trees

    • Rural/Open Area (No Shielding) - Open countryside or exposed locations

  • Design Pressure Difference of ATDs: A specialized parameter for the reference pressure difference used for sizing Air Transfer Devices (ATDs). Only takes part in the calculation if an External Air Transfer Device is added onto the room, in real life these would be Air Bricks or Trickle Vents as an example, the value here is the pressure difference across that device i.e. outside pressure against inside pressure. The standard says if no value is available to use default of 4 Pa.

  • Exponent for Leakage: A constant used in the infiltration formula to represent building leakiness characteristics. Only takes part in the calculation if an External Air Transfer Device is added onto the room. This is how a user can define the flow characteristics of the air, the range should be between 0.5 (turbulent flow) & 1 (laminar flow). Most users would use 0.65 for an ATD, as it is a mix of both & and this is a globally used value, however set out in the standard if no value is available it is stated to use 0.67

The values for Design pressure Difference of ATDs and Exponent for Leakage are default values from the standard, but can be changed by the user.

EN12831-1:2017 Video

District Heating

This selection defines how the diversity in the district heating system is calculated.

If you would like for Diversity / Diversification to be applied, you would have to use Heat Interface Unit Equipment for District Heating.

Duct Sizing Method

Choose between three options for duct sizing:

  1. Maximum Velocity: Ensures the duct does not exceed a set maximum velocity.

  2. Maximum Pressure Drop: Ensures the duct does not exceed a set maximum pressure drop.

  3. Maximum Velocity and Pressure Drop: Ensures the duct does not exceed a set limit on both velocity and pressure drop.

Pipe Sizing Method

Choose between three options for pipe sizing:

  1. Maximum Velocity: Ensures the pipe does not exceed a set maximum velocity.

  2. Maximum Pressure Drop: Ensures the pipe does not exceed a set maximum pressure drop.

  3. Maximum Velocity and Pressure Drop: Ensures the pipe does not exceed a set maximum on both velocity and pressure drop.

Percentage of Ventilation Heat Loss / Heat Gain Recovered

This setting is used when a mechanical ventilation heat recovery (MVHR) system will be on the project but not part of your design. This applies to all rooms in the project.

The total heat loss from air changes is adjusted accordingly by specifying a percentage of heat loss to recover (e.g., 50%).

Note this Setting is overridden if an MVHR system is on the design.

Ambient Temperature

The ambient temperature is used in the pipe heat load calculations.

The ambient temperature is used in pipe heat load calculations, but you can only specify a single value for your heat load—there’s no option to differentiate between internal and external temperatures; if this distinction is needed, we recommend selecting an ambient temperature that represents a suitable average for the pipe’s location.

Heat Pump Noise Assessment Criteria

  • MCS 020 a)

  • MCS 020

Heat Pump Performance Estimate Standard

  • MCS 031 Version 3: Utilizes SCOP (Seasonal Coefficient of Performance)

    • If this option is chosen, SCOP values (usually provided by the manufacturer) have to be entered on the Heat Pump under Energy tab.

  • MCS 031 Version 4: Utilizes SPF (Seasonal Performance Factor)

    • If this option is chosen, Version 4 applies SPF based on flow temperatures outlined by MCS.

Please note: For the Heat Pump results in the Heat Load Report to populate all the Emitters and Equipment need to be connected via pipework throughout the system.