Space planning for services

By week eleven, the students' urban studio plans of the Riverlot building are crowded with rooms, cores and shafts, and their sections have started to show ducts, pipes and beams fighting for the same few inches. Carvalho spends the week on what she calls 'the architect's half of building services': the space. 'Engineers can design almost any system,' she says, 'but only you can give it a place to live. Most services problems I have seen in buildings were not engineering failures. They were rooms that were too small, shafts in the wrong place, ceilings that were too shallow or equipment that could not be replaced without taking the roof off.' This lesson brings together the space needs of all the systems from earlier lessons and shows how to plan them in plan and section.

How much space services take

At the start of a project, architects use rules of thumb for services space, refined as the systems are chosen. Space is needed for central plant, for vertical shafts, for horizontal distribution above ceilings or below floors, and for rooftop and outdoor equipment. The share of the gross floor area taken by plant rooms and shafts depends strongly on the building type: housing and simple offices need relatively little; schools, community buildings and retail a little more; hospitals and laboratories, with their large ventilation systems and many services, far more.

The Riverlot building's first budget, in lesson 1, came to about seven hundredths of its gross floor area, typical of mixed-use housing with retail and food. Since then, the students have chosen a central heat pump plant, heat pump water heaters with storage, a booster pump set, a fire pump, a main electrical room with a meter room, a generator and a dust collection system for the workshop. Carvalho asks them to check whether the rooms they have drawn match the equipment.

Plant rooms

Each plant room must hold its equipment with the clearances its manufacturers and the codes require, provide a route to bring it in and take it out for replacement, and meet the conditions it needs: drainage for pumps and water heaters, ventilation for transformers and generators, fire separation for fire pumps and electrical rooms, acoustic separation for anything that hums or vibrates, and a location that makes its connections short. Plant rooms are often drawn as boxes of a convenient size; they should be drawn with the equipment in them.

Two placement principles help. First, put plant close to what it serves and to its connections: water and electrical rooms where utilities enter, heat pumps near outdoor air and near the distribution shafts, water heaters near the homes they serve. Second, give each room a replacement route. A storage tank about 6 feet in diameter cannot pass through a 3 ft door; a switchboard section is heavy and long; a heat pump on the roof needs a crane path or a roof hatch and a clear route from the street. Many buildings have plant that was lifted in by crane before the roof went on and can now only leave in pieces.

Shafts

Shafts carry services vertically between floors. They are fire-rated enclosures, with fire-stopped openings where branches leave on each floor, and access panels or doors where valves, dampers and cleanouts need servicing. Good shafts are straight from bottom to top, placed beside the cores and the stacked wet rooms they serve, and sized with room for insulation, supports, joints and a share for future additions. Every offset costs ceiling space on the floor where it happens.

Carvalho asks Wren to size the main services shaft beside the Riverlot residential core from the elements it must carry.

# Sizing the main services shaft beside the residential core (studio values)
import math
elements = {          # name: (count, outside diameter or width x depth in in)
    "heating and cooling supply and return, insulated": (2, 6.5),
    "domestic hot water, return and cold water":       (3, 3.5),
    "sprinkler and standpipe riser":                   (1, 6.0),
    "cafe and grocery exhaust (rated, insulated)":     (1, (24, 18)),
    "electrical feeders and busway":                   (1, (20, 8)),
    "telecom conduits":                                (4, 4),
}
net = 0.0
for name, (n, size) in elements.items():
    a = size[0] * size[1] if isinstance(size, tuple) else math.pi * size ** 2 / 4
    net += n * a
    print(f"{name:50s} {n} x {a / 144:6.3f} ft2")
gross = net * 2.5            # clearances, supports, access and a share for the future
print(f"net {net / 144:.2f} ft2 -> shaft about {gross / 144:.2f} ft2 on each floor")
side = math.sqrt(gross)
print(f"for example about {side / 12:.1f} x {side / 12:.1f} ft, or a long narrow shaft beside the core")

heating and cooling supply and return, insulated   2 x  0.230 ft2
domestic hot water, return and cold water          3 x  0.067 ft2
sprinkler and standpipe riser                      1 x  0.196 ft2
cafe and grocery exhaust (rated, insulated)        1 x  3.000 ft2
electrical feeders and busway                      1 x  1.111 ft2
telecom conduits                                   4 x  0.087 ft2
net 5.32 ft2 -> shaft about 13.29 ft2 on each floor
for example about 3.6 x 3.6 ft, or a long narrow shaft beside the core

The shaft needs about 13 ft² on each floor, for example about 3.6 × 3.6 ft, or, better for planning, a long narrow shaft of about 2 × 6.5 ft along the side of the elevator hoistway, where it can be reached from the corridor through a rated access door. The largest single element is the café and grocery exhaust, which is why combining the two exhausts in one shaft, a value engineering item in the urban studio, saved so much space. Separate smaller shafts at each stack of bathrooms carry the drainage, vent and water risers to the homes, and the rainwater leaders from the roofs run in their own shafts or in the cores.

Ceiling and floor zones

Horizontal distribution takes height. On each floor, ducts, sprinkler pipes, drainage offsets, cable trays and lights compete for the space between the underside of the structure and the ceiling. The structure itself may have downstand beams that services must pass under or through. The floor-to-floor height is the sum of the structure, the services zone, the finished ceiling height and the floor finishes, and every 2 in matters in a building limited by a height rule, as the Riverlot building is.

# Floor-to-floor height check for two floors of the Riverlot building (ft)
floors = {
    "residential (mass timber)": {"CLT floor and topping": 0.95, "acoustic layers": 0.2,
                                   "corridor ceiling zone (ducts, sprinklers)": 1.2, "finished ceiling height": 8.0},
    "workshop (concrete podium)": {"slab": 1.0, "downturned beams below slab": 1.5,
                                    "services below beams (ducts, dust, sprinklers)": 2.0, "clear height to underside": 9.5},
}
given = {"residential (mass timber)": 10.5, "workshop (concrete podium)": 14.0}
for name, parts in floors.items():
    need = sum(parts.values())
    for k, v in parts.items():
        print(f"  {k:46s} {v:5.2f}")
    print(f"{name}: needs {need:.2f}, designed {given[name]:.2f}, margin {given[name] - need:+.2f} ft")

  CLT floor and topping                           0.95
  acoustic layers                                 0.20
  corridor ceiling zone (ducts, sprinklers)       1.20
  finished ceiling height                         8.00
residential (mass timber): needs 10.35, designed 10.50, margin +0.15 ft
  slab                                            1.00
  downturned beams below slab                     1.50
  services below beams (ducts, dust, sprinklers)  2.00
  clear height to underside                       9.50
workshop (concrete podium): needs 14.00, designed 14.00, margin +0.00 ft

On the residential floors, the stack works with a small margin, and a shallow services zone along the corridor works only because the students chose an energy recovery ventilator in each home, so that no large ducts run through the corridors to the homes; the homes' ceilings stay at the full height, and the corridor ceiling drops just enough for the fan coil pipes, sprinkler branches and ventilator ducts at each entry. On the workshop floor, the services zone must pass below the downturned transfer beams, and the margin is zero: the design works, but there is no room for error or for a larger dust collection duct. Carvalho suggests two remedies: penetrations through the beams at planned locations, agreed with the structural engineer, or routing the largest ducts between the beams in the direction of the beam lines, so that they never cross below them.

Roofs and outdoor equipment

Roofs carry heat pumps, exhaust fans, the generator, the elevator penthouse, vent stacks, roof drains, solar panels and sometimes terraces and gardens. Each needs space, access and clearances, and many need structure for weight and vibration. Outdoor air intakes must be kept away from exhausts, vent stacks and the generator; heat pumps need free airflow around them and must not recirculate their own discharge air; equipment must be raised above the snow and accessible for maintenance in winter. A roof plan drawn early, with every element in its place and a screen designed around them, avoids the cluttered roofs Carvalho showed in the first week.

Outdoor equipment at grade has its own needs: the transformer pad and its clearances, the gas meter if there is gas, the dust collector in an enclosed yard, the garbage and recycling area, the fire department connection and the hydrant. On the Riverlot building, the lane frontage is now nearly full: loading bay, garbage room, transformer pad, electrical room, water entry, sprinkler valve and fire pump rooms, the bike room door and the stair exit. Wren draws a lane elevation to check that the doors, louvers and equipment read as one ordered facade rather than a collection of service doors.

Acoustics and vibration

Mechanical equipment makes noise and vibration that can travel into homes, offices and quiet rooms. Fans, pumps, compressors and transformers each have characteristic sounds, and low-frequency hum is especially hard to block. Good planning keeps noisy rooms away from bedrooms and quiet rooms, puts buffer spaces between them, mounts equipment on vibration isolators and inertia bases, uses flexible connections on pipes and ducts, lines ducts and adds silencers where they pass between noisy and quiet spaces, and specifies low-noise equipment. Rooftop equipment over the top floor's homes in the Riverlot building needs isolated supports on a structural frame, not directly on the roof deck above bedrooms.

Flexibility and the future

Buildings outlast their services. Heat pumps last perhaps fifteen to twenty-five years, water heaters ten to fifteen, elevators' machines twenty to thirty, while the building may stand for a hundred. Commercial tenants change, and the grocery may become a different shop; the workshops may become offices; car chargers will multiply. Good services planning leaves spare capacity in shafts and electrical rooms, routes for replacing large equipment, and accessible valves, dampers and cleanouts. It also avoids embedding services where they cannot be reached, such as pipes cast into slabs without access, wherever possible.

Exercise 11: services coordination drawings

This exercise takes one week.

• Draw every plant room of the Riverlot building with its main equipment and clearances, and a replacement route for the largest item in each.
• Size the main services shaft and the bathroom stacks, and show them on every floor.
• Draw sections through a residential corridor and the workshop floor showing structure, ducts, pipes, cable trays, sprinklers and ceilings, with the floor-to-floor stack.
• Draw the roof plan with every piece of equipment and its clearances, and the lane elevation with every service door and louver.

Self-critique checklist

• Is every plant room drawn with its equipment, not as an empty box?
• Can the largest piece of equipment in each room be replaced?
• Do the shafts run straight from bottom to top?
• Is there a margin in the services zone of every floor?