Systems integration

Adaeze opens the week-five session with a drawing nobody else at the table has seen before: a section through the whole building in which the architecture has been drawn in faint lines and every service in a strong one. Ducts are blue, pipes green, electrical risers orange, sprinkler mains red. 'This is the building I'm designing,' she says. 'Yours is the faint one.' The drawing shows at a glance where the systems run, where they cross, and where they have nowhere to go. It also shows that every vertical service in the tower, eighty-odd stacks, ducts and risers, must somehow pass through the clinic on its way to the ground.

Systems as space

Mechanical, electrical, plumbing and fire protection systems take up space in three ways: in plant rooms where equipment sits, in vertical shafts that carry services between floors, and in horizontal zones, usually ceilings, where services run across each floor. In a simple building these can be found late, by squeezing. In a building like Marlow Station, with three users whose systems are different and a structure that has been carefully aligned, they must be planned with the structure and the plans, because each one competes for the same space. Kofi Mensah, the mechanical engineer who advised the students in third year, tells them that in his experience the commonest reason a mixed-use building is late and over budget is that its services were designed after its floors.

The team starts with the systems strategy for each user, agreed in the big room. All three share an all-electric source: air-to-water heat pumps on the tower roof, with thermal storage tanks, producing warm water for heating and domestic hot water and chilled water for cooling. A heat recovery chiller in the podium's mechanical room moves heat from where there is too much to where it is needed: from the clinic, whose exam rooms, lights and equipment need cooling much of the year, and from the café's refrigeration, to the homes' hot water. Each user then has its own distribution, metered separately so that each partner pays for what it uses.

The homes have four-pipe fan coils in each home and an energy recovery ventilator in each home, with its intake and exhaust in the window recesses, as in the mixed-use building the students studied in third year. The clinic has a dedicated outdoor air unit with energy recovery, serving the exam rooms through a variable air volume system, with higher filtration for its waiting areas and separate exhaust for its procedure rooms. The transit hall has a radiant floor, vestibules at its doors, air curtains and a small ventilation unit controlled by carbon dioxide sensors, because its occupancy swings from a few people to two hundred in minutes. Ines Carvalho, who taught the students' environmental systems course, reviews the strategy and asks why the hall is not simply left as a cool, sheltered room. Adaeze answers that the brief asks for a heated hall, and that the doors are the problem, not the temperature; the vestibules and air curtains are where the energy is saved.

Plant rooms

The team places the plant where it serves best and harms least. The heat pumps and tanks go on the tower roof, about 4,850 ft² behind an acoustic screen, where they have outdoor air and no neighbors above them. The clinic's air handling unit goes on the east end of the clinic's upper floor, in about 1,940 ft², close to the rooms it serves, with its outdoor air intake on the Marlow Street side, far from the bus stop's exhaust and the lane's garbage trucks. The electrical vault, the main switchboard, the water entry and the sprinkler room go on the ground floor along the lane, in about 3,230 ft², where the utility and the fire department can reach them.

Rafael raises the question of the outage rooms. The brief asks for a warm, lit room for each user during a power outage: the housing amenity room, the clinic's group room and a part of the transit hall. Each needs heat, light, outlets and ventilation from a protected circuit, and the clinic's medication refrigerators need power for days, not hours. The team chooses a battery in the electrical room, charged by solar panels on the podium roof and the tower's south face, sized to keep the three outage rooms and the refrigerators going for at least a day, with a connection for a portable generator for longer outages. The life safety systems, the emergency lighting, the fire alarm, the fire pump if one is needed, the stair pressurization and the firefighters' elevator, are on their own emergency supply as the code requires.

Shafts

In the tower, each home's bathroom and kitchen need drainage, vent, water and exhaust stacks. Back-to-back bathrooms can share a stack, and Ingrid has already arranged the plans so that each pair of homes on either side of the corridor has its bathrooms against a shared wall. The main mechanical riser, which carries the heating and cooling water between the roof plant and the floors, runs in the west core. The electrical and telecom risers run in the east core. The sprinkler and standpipe mains run in the stairs. The script below estimates the area these shafts take on each housing floor and compares two ways of bringing the stacks down through the clinic.

# Space for services: shafts on the housing floors and how stacks pass through the clinic
homes_per_floor = 12
stack_per_home = 6.5                  # ft2 per home for plumbing, exhaust and ventilation stacks
riser = {"main mechanical riser": 43, "electrical room stack": 27, "telecom": 11, "sprinkler and standpipe": 11}
floor_gross = 9050
per_floor = homes_per_floor * stack_per_home + sum(riser.values())
print(f"shafts per housing floor {per_floor:.1f} ft2 = {per_floor / floor_gross:.1%} of the floor")
offset_cost = 18000                      # dollars per stack per offset, both floors of the clinic
stacks = homes_per_floor // 2           # back-to-back bathrooms share a stack
for case, aligned in (("stacks offset at the clinic", 0), ("stacks aligned with clinic corridor walls", stacks - 1)):
    off = stacks - aligned
    print(f"{case:<44} {off:2d} offsets, about {off * offset_cost:,} dollars")
plant = {"roof heat pumps and tanks": 4850, "ground floor electrical and water": 3230, "clinic air handling (level 3)": 1940}
print("plant: " + ", ".join(f"{k} {v:,} ft2" for k, v in plant.items()))
print(f"total services space {sum(plant.values()) + per_floor * 8:,.0f} ft2 of {128150:,} gross")

shafts per housing floor 170.0 ft2 = 1.9% of the floor
stacks offset at the clinic                   6 offsets, about 108,000 dollars
stacks aligned with clinic corridor walls     1 offsets, about 18,000 dollars
plant: roof heat pumps and tanks 4,850 ft2, ground floor electrical and water 3,230 ft2, clinic air handling (level 3) 1,940 ft2
total services space 11,380 ft2 of 128,150 gross

On each housing floor the shafts take only about 2% of the floor, which is typical. The problem is not their area but their route. If the tower's stacks come down wherever the homes' bathrooms happen to be, they arrive in the clinic in the middle of exam rooms and must be offset sideways in the clinic's ceilings to a wall where they can continue down. Each offset costs money, takes ceiling space and adds bends where drains can block. If instead the homes' wet walls are placed on the column lines that bound the clinic's corridors, the stacks can drop straight through the clinic inside the corridor walls. Ingrid moves six pairs of bathrooms by a few hundred millimeters, and five of the six offsets disappear.

Tomasz adds a structural reason to like the result. In the post-tensioned floors, every penetration must avoid the tendons, so a stack that drops straight through every floor in the same place can be planned once and the tendons laid around it. A stack that wanders is a set of different penetrations, each a chance for a cut tendon.

Ceilings and floor heights

The horizontal zones are set by the floor-to-floor heights fixed in the structural session. Adaeze draws a section through each type of floor, showing the depth of the structure, the depth of the services zone and the ceiling height that remains.

On the housing floors, the homes' living rooms have the full height under the structure, about 8 feet 8 inches, and the ceilings drop only in the corridors, the bathrooms and the entries, where the fan coils and the short ducts to the energy recovery ventilators run. On the clinic floors, the 15 foot floor-to-floor leaves a services zone of about 3.5 feet above the corridor ceilings for the main ducts, and lets the exam rooms have ceilings of 9 feet 6 inches. On the ground floor, the hall's ceiling is high and the services run above the shops and the bike hub along the lane, where the ceilings can be lower. Mensah checks the clinic's main duct size against the services zone and finds it fits, with about 6 inches to spare, if the duct runs flat and wide in the corridor between two beam lines rather than crossing them.

The team records a rule from the session: main ducts and pipes run parallel to the beams, in the zones between beam lines; only branches cross the beams, and only through openings Tomasz has approved. The rule takes thirty seconds to state and saves, Mensah says, about half the clashes he usually finds in a model.

Fire protection and the high building

Danielle Roy, the fire protection engineer, joins the end of the session. At about 128 feet to its top floor, the tower is a high-rise under the code, which brings extra measures: smokeproof or pressurized stairs, a fire command center at the main entrance, a fire service access elevator, standby and emergency power, and emergency responder radio coverage throughout. The whole building will be sprinklered, with standpipes in both stairs. The sprinkler room on the lane needs a connection for the fire department on the street, and Roy asks Hamid to make sure the fire trucks can reach it without blocking the bus stop.

Roy also notes a coordination question that has defeated many mixed-use buildings: the fire separations between the transit hall, the clinic and the homes. Every duct, pipe and cable that crosses a fire separation needs a fire damper or a tested firestop system. A building with three users stacked on top of one another has a great many crossings. She asks the team to show each separation on the services drawings, and to keep the number of crossings as small as possible by giving each user its own risers in its own part of the building. The team's decision to meter each user separately helps: separate meters encourage separate risers.

Exercise 6: systems integration

• Agree a systems strategy for each user, and locate the plant rooms, the shafts and the main horizontal zones.
• Trace every vertical service from the roof to the ground, and show how stacks pass through any floors below the ones they serve.
• Draw a section through each type of floor showing structure, services and ceiling height, and check the main ducts fit.
• Show the fire separations between users and count the services that cross them.

Self-check

• Does every stack in the tower reach the ground without an offset you could avoid?
• Do main ducts and pipes run parallel to the beams?
• Have you planned the outage rooms and the life safety systems on protected supplies?

Mensah closes the session with a reminder about maintenance. Every piece of equipment the team has placed must be reachable, removable and replaceable without demolishing anything. The heat pumps on the roof need a route for a crane or a lift; the clinic's air handling unit needs a door large enough for its largest section; the battery needs ventilation and a clear path for its replacement in about fifteen years. Adaeze adds a column to her equipment schedule for the replacement route of each item.