Inward-turning air roll (IDW)
Air is drawn from the room side and discharged above the opening. The roll closes towards the interior. This arrangement is particularly relevant for balanced pressure, slight overpressure or sheltered entrances.
Entrances · Door systems · Thermal comfort
Control draught at doors and revolving entrances
Topic
Comfort and operational reliability
An open entrance can become an airflow path through the entire building
Facade wind pressure, stack effect and opposing openings can drive a strong cold-air inflow whenever a door opens. In tall lobbies or busy buildings, the effect may extend far beyond the immediate entrance zone.
Air-curtain principle
The direction of the recirculating air roll determines the barrier
An entrance air curtain is more than a vertical jet. Intake side, discharge position and pressure difference form a recirculating air roll. We compare inward- and outward-turning arrangements under the actual wind pressure.
Inward-turning air roll (IDW)
Outward-turning air roll (ADW)
Outward-turning air roll (ADW)
The air roll is directed against incoming outdoor air. It can provide a more robust barrier under negative pressure, exposed entrances or higher wind loads, but often requires more heating output.
CFD result · Temperature field
The simulation reveals how far cold air penetrates into the room
A horizontal slice shows how cold outdoor air enters through the doorway and mixes with warmer indoor air. The temperature distribution identifies penetration depth, affected occupied zones and remaining warm areas. Air curtain, vestibule and revolving door options are compared under identical boundary conditions.
Wind-driven air infiltration
How wind penetrates the building through an open door
The velocity field shows how external wind pressure creates a concentrated jet at the opening that can reach far into the room. The transient simulation also tracks the resulting cold-air spread and room-temperature change. The same boundary condition is then applied to air curtains, revolving doors and vestibules.
- Penetration distance and velocity of the cold airflow
- Temperature and draught risk in occupied and circulation zones
- Airflow rate and heat loss during door opening
- Interaction with wind pressure, stack effect and ventilation
System and energy comparison
Block cold air effectively with the lowest practical energy use
Air curtains, revolving doors, vestibules and direct openings are compared under identical weather and usage conditions. Shielding performance and comfort are assessed together with heat loss and fan, heating and drive energy.
Direct door opening
The reference case reveals unrestricted air exchange and the resulting heating loss.
Vestibule
Offset or sequential doors can reduce exchange with little additional energy.
Revolving door
Separated compartments limit exchange without a continuously heated air jet. Drive energy, rotation speed and pedestrian flow are included.
Air-curtain system
Air volume, discharge velocity, angle and heat output are optimised to block cold air reliably without wasting energy.
CFD system comparison · Wind load
High wind pressure can break through an air curtain
The transient simulation shows how outdoor wind deforms the air jet and pushes cold air through the opening into the interior. In the case shown, barrier performance deteriorates noticeably at an outdoor wind speed in the order of about 2 m/s. The precise limit depends on door geometry, pressure difference, discharge velocity and discharge angle.
Air curtain under wind pressure
Wind deforms the recirculating air roll and pushes cold outdoor air through the opening.
Revolving door with an interrupted flow path
The rotating compartments limit direct air exchange while people pass through.
Method
From a full weather year to the best energy solution
We analyse site-specific weather data and select both a cold winter design day and a representative average winter day. External flow around the building supplies pressure and velocity conditions for the open doors in the interior model. We then compare air curtains, revolving doors, vestibules and other options in steady or transient mode, including shielding, room cooling and energy demand.
- 01
Analyse a full year of temperature, wind direction and wind speed data
- 02
Select a cold winter design day and a representative average winter day
- 03
Calculate external flow around the building and surroundings for governing wind directions
- 04
Transfer pressure and velocity boundary conditions at open doors to the interior model
- 05
Assess system options by internal flow, shielding, room cooling and energy demand
Optimise comfort and energy
The best barrier is not automatically the highest output
The target is a solution that reliably limits cold-air infiltration and draught while using as little operating energy as practical. This avoids oversizing, reduces heating loss and enables demand-based design of air curtains or revolving doors.
Air velocity and temperature in the lobby
Penetration distance and transient development of cold air
Air exchange, heat loss and fan, heating and drive energy
Energy comparison of door, vestibule, revolving door and air curtain
FAQ
Frequently asked questions
When is an analysis worthwhile?
For exposed entrances, high pedestrian frequency, tall lobbies, opposing doors or known draught complaints.
Should door opening be simulated transiently?
Transient analysis is particularly useful for short opening cycles and changing pressure conditions.
Can vestibules, revolving doors and air curtains be compared directly?
Yes. Dimensions, opening times, rotation speed and discharge conditions can be assessed under identical boundary conditions.
Next step
Request a projectPrevent entrance draught early in design
We define the door system, winter boundary conditions and suitable assessment criteria with you.