CFD Evacuation Lift Olympics – Gold Medal! - Innovation Fire Engineering

CFD Evacuation Lift Olympics – Gold Medal!

Innovation Fire Engineering has completed four internal CFD case studies to investigate various ventilation strategies for the common corridor and the evacuation lift lobby within a residential building. Four possible ventilation options have been assessed, as shown in the table below.

Solutions 3 and 4 jointly receive the gold medal for ventilating an evacuation lift lobby; see details below.

Table 1 – Ventilation options modelled in Solutions 1–4

Solution	Common Corridor	Evacuation Lift Lobby
1 (‘Code-compliant’)	1.5m² Natural Shaft	1.5m² natural smoke shaft
2 (‘Fire Engineered’)	Mechanical Shaft	Cross-vented via stair AOV (double ‘floppy door’)
3 (‘Fire Engineered’)	Mechanical Shaft	1.5m² natural smoke shaft
4 (‘Fire Engineered’)	Mechanical Shaft	1.5m² AOV

In March 2024, amendments were made to Approved Document B Volume 1 (ADB V1) seeking to provide new guidance on residential buildings over 18m and evacuation lift lobbies. As well as requiring a second stair in residential buildings taller than 18m, ADB V1 amendments stated that an evacuation lift lobby should provide a refuge area for those waiting for the evacuation lift, to not be directly accessible from any flat and that any smoke control system designed to protect the staircase should extend the same level of protection to the evacuation lift and evacuation lift lobby.

CFD Modelling Details – Solutions 3 and 4

The CFD geometry is based on a generic corridor and lift lobby arrangement, whereby the maximum travel distance within the common corridor is 7.5m. The building is assumed to be over 30m in height and the single stair is modelled to its full height.

In Solutions 3 and 4, the common corridor is ventilated via a 0.6m² mechanical smoke shaft. The evacuation lift lobby is vented via either a 1.5m² natural smoke shaft (Model 3) or a 1.5m² AOV (Model 4), using a ‘floppy door design’ to allow resupply air.

The fire size, CFD parameters, and timeline are consistent with industry practice and recommendations in CFD guidance documents.

CFD Results – Solutions 3 and 4

Please see links to the smoke and visibility videos below.

For Solutions 3 and 4, the evacuation lift lobby and stair remain free from smoke ingress, providing acceptable conditions during escape and firefighting.

Discussion

The CFD results for Solutions 3 and 4 show acceptable conditions for escape and firefighting. These solutions also benefit from resupply air within the evacuation lift lobby. If space allows, Solution 3 or 4 is preferred over Solution 2.

Conclusion

The results demonstrate that fire-engineered designs outperform code-compliant solutions. Mechanical ventilation offers flexibility but comes with higher maintenance and cost considerations. Innovation Fire Engineering recommends mechanical ventilation where appropriate.

We invite you to share your thoughts on the CFD Evacuation Lift Olympics and encourage discussion around these solutions.