Specification
Machine room or machine-room-less: what the building actually gives up
How the choice of system affects height, space efficiency, maintenance and the flexibility of the architectural design.
2 min read
The question arrives late in most projects, usually as a line item, and by then the answer is already decided by the plan. A machine room is floor area: a room on top of the hoistway, with its own access, its own ventilation and its own structural slab. A machine-room-less unit does not need it, because the machine goes inside the hoistway, normally at the top and carried by the guide rails.
What the building gains
The obvious gain is the room itself. On a residential tower that room sits on the roof, and taking it out gives back a clean roofline, a terrace that is not interrupted, or the space for the equipment that actually has to be up there. The less obvious gain is what it does not need: no separate ventilation, no second structural slab, no stair or ladder access to a level nobody else uses.
What it costs
Three things, and only one of them is money. The first is a ceiling on performance: with the machine in the hoistway there is a practical limit to the sheave, the motor and the rope arrangement. The second is service: an engineer works from the car top and from a control cabinet placed at a landing, which means that cabinet needs a wall and a door somebody has to plan for. The third is heat, which now dissipates inside the shaft instead of a ventilated room.
| Machine room | Machine-room-less | |
|---|---|---|
| Maximum rated speed | 8.0 m/s (1,575 fpm) | 2.5 m/s (492 fpm) |
| Maximum travel | 400 m (1,312 ft) | 125 m (410 ft) |
| Maximum rated load | 20,000 kg | 5,000 kg |
| Floor area above the hoistway | Required | Not required |
| Service access | From the machine room | Car top and landing cabinet |
Where the line falls
For most residential and commercial buildings the machine-room-less range is not a compromise: 2.5 m/s over 125 m of travel covers a thirty-storey tower comfortably. Above that, or when the car has to carry 5,000 kg or more, the machine room stops being optional and starts being the only way to get the performance the building asked for.
What decides it is the section, not the price list: travel, rated speed and whether the roof can give up the area. Send those three and the answer is immediate.
