Tenant build-outs in Schaumburg and Wheeling fall apart in the same place almost every time: the mechanical and electrical scope. The architect’s plan shows a beautiful open office or a new suite layout, the landlord’s lease says the base building HVAC is “as-is,” and nobody has confirmed whether the existing rooftop unit and panel can actually serve the new use. Three weeks before opening, that becomes everyone’s problem. This guide is for property managers, brokers, and tenants who want to catch it early.
Start With the Lease, Not the Drawings
Before any design work, get clear answers on three questions:
- Who owns the HVAC equipment serving this suite? Landlord-owned rooftop units versus tenant-owned units changes who pays for replacement and who controls maintenance.
- What is the base building condition? A “warm lit shell” delivers conditioned air and a panel; a cold dark shell delivers neither. The gap between those two is often $40,000–$150,000 of mechanical and electrical work.
- What is the tenant improvement allowance, and what does it cover? Many allowances explicitly exclude equipment replacement, which is exactly what an aging RTU will need.
We have watched deals stall because a tenant assumed “HVAC included” meant “HVAC adequate for my use.” A 15-year-old 7.5-ton unit on a suite that is about to house 30 people and a server closet is not adequate, regardless of what the lease says about condition.
The Mechanical Scope Nobody Budgets For
Capacity vs. Actual Use
Office space is commonly designed around 350–400 sq ft per ton. But use matters enormously:
| Use type | Typical cooling load | Common surprise |
|---|---|---|
| General office | 350–450 sq ft/ton | Open plan raises occupant density |
| Call center / dense office | 250–300 sq ft/ton | Existing RTU undersized by 30–50% |
| Medical / dental | 250–350 sq ft/ton | Ventilation and pressurization requirements |
| Fitness / studio | 200–300 sq ft/ton | Huge ventilation and humidity load |
| Restaurant / food service | 150–250 sq ft/ton | Hood exhaust and make-up air dominate |
| Light industrial / warehouse | Varies widely | Process heat, spot cooling, gas capacity |
Ventilation and Code
Outside air requirements scale with occupancy and use type. An existing unit may have an economizer that no longer functions, dampers seized shut, or an outside air opening sized for a prior tenant’s lower headcount. Bringing ventilation to code for the new occupancy often requires damper and control work at minimum, and sometimes a new unit with a larger outside air section or a dedicated energy recovery ventilator. Our commercial ventilation work usually starts with measuring what the existing system is actually delivering, not what the original drawings claim.
Distribution
Demolishing walls changes airflow. A build-out that keeps the existing ductwork but reconfigures the floor plan almost always produces hot and cold complaints, because supply and return were balanced for a layout that no longer exists. Budget for duct modification and a test-and-balance report at the end. It is a small line item that prevents months of callbacks.
Zoning and Controls
A single-zone RTU serving a suite with private offices on the west wall and an interior conference room will never satisfy both. Adding zoning with bypass or VAV boxes, or splitting the suite across two units, is far cheaper during construction than after.
The Electrical Scope Nobody Budgets For Either
- Panel capacity. Existing suite panels are frequently full or nearly full. A build-out adding lighting circuits, receptacles, IT, and kitchen equipment often needs a new subpanel or a service increase — which may involve the utility and a long lead time.
- Utility coordination. If the suite needs a new meter or increased service, that is a multi-week to multi-month item. It belongs on the critical path from day one.
- Lighting and code compliance. Energy code drives fixture efficiency, occupancy sensing, and daylight controls. Reusing existing fixtures often is not permitted once you touch the circuits.
- Life safety. Exit and emergency lighting, fire alarm device relocation, and duct smoke detector coordination with the mechanical scope. Duct detectors in particular are a classic gap — the mechanical contractor assumes the alarm vendor is handling it and vice versa.
- Dedicated equipment circuits. Server rooms, medical equipment, commercial kitchen gear, and EV charging in the parking area all need their own feeders and load calculation.
Realistic 2026 Budget Ranges
| Scope item | Range |
|---|---|
| RTU replacement, 7.5–10 ton, with curb adapter and crane | $18,000–$34,000 per unit |
| Duct modification + test and balance, 4,000 sq ft suite | $9,000–$22,000 |
| Zoning retrofit on existing single-zone unit | $6,500–$18,000 |
| New 200A suite subpanel with feeder | $7,500–$16,000 |
| Full electrical fit-out, 4,000 sq ft office | $12–$28 per sq ft |
| Full mechanical fit-out, 4,000 sq ft office | $14–$32 per sq ft |
| Restaurant hood, make-up air, and gas | $35,000–$95,000 |
Ranges reflect suburban Cook County conditions, union and non-union mixes, and normal permit paths. Sites with roof structural limitations, long crane reaches, or occupied-building work schedules land at the high end.
A Sequence That Works
- Pre-lease walkthrough. Nameplate every unit, note age and refrigerant type, open the panel, photograph everything. Two hours here saves six figures of surprise.
- Load and capacity check against the intended use, before design is locked.
- Critical-path items identified: utility service, long-lead equipment, and anything with a landlord approval gate.
- Coordinated drawings. Mechanical, electrical, and fire alarm reviewed against each other — not just against the architectural plan.
- Permit submission with the village, understanding local review times in Schaumburg and Wheeling.
- Rough-in, inspection, finish, test and balance, and commissioning with documented results handed to both tenant and landlord.
- Maintenance plan in place at turnover so warranty terms stay intact — see our maintenance agreements.
Frequently Asked Questions
How early should mechanical and electrical be involved?
Before the lease is signed, ideally. At minimum, before design development. Late involvement means designing around whatever was already committed, which is always more expensive.
Who pays for an RTU that fails during the build-out?
It depends entirely on lease language and equipment ownership. This is why the pre-lease walkthrough matters: documented condition gives both parties a factual basis instead of an argument.
Can an existing unit be reused if it is old but working?
Sometimes, and we will say so when it is true. The questions are refrigerant type (R-22 systems are expensive to service), age against expected life, capacity against new load, and whether the economizer and controls can meet current ventilation code.
How long does a typical build-out take?
For a 3,000–6,000 sq ft office suite: four to ten weeks of field work, with permits and long-lead equipment often driving the overall schedule longer than the labor does.
Do you work as a subcontractor to a general contractor?
Yes. We work directly for tenants, for property managers, and as a mechanical/electrical sub under a GC, and we are comfortable with occupied-building phasing and off-hours work.
What documentation do we get at the end?
As-built markups, test and balance results, equipment submittals and warranty registration, control sequences, and a recommended maintenance schedule.
Get a Pre-Lease Assessment
If you are evaluating a suite in Schaumburg, Wheeling, or anywhere in the northwest suburbs, have the mechanical and electrical conditions documented before you commit. MMDS handles commercial HVAC, electrical, and plumbing under one roof, which removes the coordination gaps that cause most build-out delays.
Call (847) 221-6280 or contact us to schedule a walkthrough. We will tell you what the space can support, what it will cost to get it where you need it, and which items belong on the landlord’s side of the table.