Overview

This article summarises how the Mechanical Ventilation Configuration presets work in the Natural Ventilation menu.

These presets are designed to make it easier, particularly for architects and those without access to Sefaira Systems, to adjust the way the mechanical ventilation system works to reflect a more typical design.

Mechanical Configuration Settings

In the Nat Vent tab you should see Mechanical Ventilation Configuration options such as those shown below.

1) Commercial Ventilation (Default)
2) School Ventilation
3) Residential Ventilation
4) Custom

The attributes that get pre-populated are described below. These adjust the HVAC system inputs regardless of what the DOAS system applied is. So if you have a project with VRF, for example, this will adjust the inputs for that system in the same way it would adjust them for fan coils.

Each option pre-populates values in the air-side tab to mimic the right kind of ventilation system as follows:

1) Commercial Ventilation

This is the default option for natural ventilation and the default option for all DOAS systems. It's designed to reflect an air-conditioned building that includes pre-conditioned primary air (for dehumidification and supplemental cooling) as well as in-zone cooling. 

When you choose this option, this is how the constant volume supply air is conditioned.

Key attributes are as follows

• The ventilation air has both mechanical heating and cooling
• The supply air temperature setpoint is constant at 13C / 55.7F
• There is simple heat recovery (50% sensible effectiveness only)
• The volume of air supplied is based on the ventilation rate required in each zone (based on the space use tab)
• Heating is done using the default heat source for the HVAC system type (gas fired boiler and heating hot water loop for fan coils)
• Cooling is done using the default cooling source for the HVAC system type (chiller and chilled water loop for fan coils)

2) School Ventilation

This alternate setting that can be selected that is more typical for a modern school or educational building, especially in Northern Europe. These buildings may or may not have air conditioning but do have mechanical ventilation to ensure outside air is delivered to the building.

This may not be the way schools work in your region. In many instances they may operate more similarly to Commercial buildings.

Key attributes are as follows

• The ventilation air has no heating or cooling
• The supply air temperature setpoint is set at 18C / 65F but effectively just supplies outside air unconditioned.
• There is no heat recovery
• The volume of air supplied is based on the ventilation rate required in each zone (based on the space use tab)
• No Heating
• No Cooling

3) Residential Ventilation

This is an alternate setting that can be selected that is more typical for a modern residential building with a heat recovery ventilation system. It would mimic a home that has some kind of heating and cooling system totally separate to ventilation (say a split system or radiant floor) which then combines with an MVHR ventilation system that operates all the time to provide ventilation.

Key attributes are as follows

• The ventilation air has no heating or cooling
• The supply air temperature setpoint is constant at 20C / 68F but what is supplied depends on the ability of the heat recovery system.
• There is good sensible heat recovery (80% sensible effectiveness, 0% latent effectiveness)
• The volume of air supplied is based on the ventilation rate required in each zone (based on the space use tab)
• No Heating
• No Cooling