Ventilation In Lift Wells
What is the requirement for the ventilation of liftwells?
Historical standards define that for all circumstances the level of ventilation should be 1 percent of the plan area of the liftwell. But is this sufficient or too much for all circumstances?
Is this defined space the free area of the ventilation or does it need to be factored for louvers or ductwork transition or the ductwork length?
Does the ventilation need to be directly to the outside? Within many retail developments this can be impossible.
For some scenic situations the heat gain from solar heat factors can create temperatures in excess of 45 degrees C. In some poorly designed situations, where there has been insufficient liftwell ventilation this has caused the landing doors to bend with high solar heat gain.
Indeed, in some situations the solar heat gain can be so great, under certain conditions, that a significant risk can be created. For example, a scenic glass lift stuck in a glass atrium could cause unbearably high temperatures that could be potentially harmful to elderly or frail passengers.
In some situations the liftwell may need to be ventilated to reduce levels of condensation. Condensation can, if untreated, increase the risk of failure or accelerate corrosion of the lift components.
How does the use of pressurisation systems effect the liftwell ventilation?
How does the liftwell ventilation effect the operation of the doors at the ground floor in tall buildings with open door ways?
So many questions but what are the answers.
For Firefighting Lifts it has been found in recent studies that a ventilation level of 1 percent in these circumstances is insufficient.
New standards have been written on the basis of identifying the risk. Maybe one of the benefits of the new European legislation is its’ determination not to take requirements for granted without first researching the hazards and risk associated.
Research conducted by a member of the standards committee identified the following relevant information:
- The Building Regulations for England and Wales have deliberately removed the generic requirement for liftwell ventilation as the normal 1% is not sufficient for smoke dilution or removal.
- BSEN calls for suitable ventilation and only makes a reference to what this may mean in a note. The note does not form part of the standard.
- For normal lifts the ventilation provided by the gaps around the doors may be adequate without the need for liftwell head ventilation and as there is no deviation from BSEN81, Notified body approval is not required.
At Elevate Consulting Ltd we believe that the need for liftwell ventilation (or not) should be defined on a project by project basis and that the use of any global rules of thumb can lead to an unsatisfactory results.
The key areas to be considered are:
- Does the liftwell need to be fire rated meaning any ventilation if required will also need to be fire rated?
- Is the liftwell pressurised for Firefighting lifts?
- Is the lift a Firefighting Lift requiring smoke removal from the liftwell?
- What are the heat outputs of the equipment being placed in the liftwell? Greater care will be required for hydraulic or MRL type lifts.
- Are there other factors that could contribute to heat in the liftwell such as lighting, heat drawn from high landing conditions?
- What is the likely ambient temperatures within the liftwell and will there be a need to heat or ventilate the liftwell?
- What is the solar heat gain for scenic lifts or liftwells? Can external measures be used to reduce solar heat gain such as shading or the use of solar limiting glass specifications?
In conclusion, at Elevate Consulting Ltd we do not take it for granted that ventilation in liftwells is required or when required that the satisfactory level is 1% . We need to take account of all the factors involved in each specific project design.