If you manage a building long enough, you eventually face the same decision: keep nursing an aging rooftop unit through another season, or plan a full commercial HVAC replacement. Budgets are tight. Tenants don’t like surprises. And winter cold snaps or summer heat waves won’t wait for your procurement cycle. Treat the replacement like a small construction project—scoped, scheduled, and commissioned—and you can control spend, hit dates, and keep people comfortable the whole way through.
The cleanest way to make the call is to compare what you’re spending to keep the unit alive against the total cost of replacement over the next three to five years. If annual repairs, parts delays, and energy waste start living in the 10–15% neighborhood of a new unit’s price, you’re past the inflection point. It shows up as repeated nuisance trips, unstable discharge air temps, or comfort complaints in the same corners of the floor. You’ll also see it on your utility bill when compressors short-cycle all summer or electric heat runs harder than it should in the shoulder seasons.
System selection matters as much as timing. Many facilities are moving to heat-pump RTUs or variable systems during replacement because they trim peak demand and smooth comfort across mixed-use spaces. When you need objective guidance for selecting a unit type, the Department of Energy’s Better Buildings initiative offers a practical Heat Pump Rooftop Unit Decision Matrix that helps match equipment to building needs without guesswork. If you want a quick refresher on scope and deliverables before you build a timeline, the commercial HVAC replacement service page is a helpful overview you can use to align stakeholders on what the swap actually includes.
Replacement budgets are a lot easier to defend when you label every line item before you touch the old unit. Equipment is only the start; rigging, controls, and commissioning carry real weight. For a typical RTU changeout on a mid-rise in Salt Lake County, expect the spend to spread across equipment and curb adapters; electrical changes; crane and traffic control; controls integration (BAS points and trend logs); test-and-balance; and commissioning with a short period of enhanced monitoring. Leave a small contingency for roof repairs around the curb and for duct transitions that aren’t obvious until demo day.
Controls are the number-one reason budgets blow up. New equipment introduces different logic—heat-pump defrost, economizer sequences, fan turndown—that older thermostats or legacy BAS platforms don’t always handle out of the box. The fix isn’t fancy: pull as-builts early, draft a one-page I/O list with your vendor, and decide who owns point mapping and graphics updates before you order parts. If distribution changes are part of the plan (new diffusers, zoning, or ventilation tweaks), treat it like a commercial HVAC installation scope, not just a one-for-one swap, so you budget correctly for sheet metal, TAB, and controls labor.
Policy and refrigerant transitions affect the math, too. Under the EPA’s Technology Transitions program, restrictions on higher-GWP HFCs begin January 1, 2025 for certain sectors, which influences which models are produced and shipped. Align your specification with compliant refrigerants and current product lines to avoid last-minute substitutions or price swings. If you need the regulatory overview for leadership, EPA’s summary of the Technology Transitions Program lays out the key dates and scope in plain language.
Projects miss dates for two reasons: parts that don’t exist yet and people who aren’t booked yet. Lead time isn’t just the unit—it’s the curb adapter, electrical gear, control boards, and the crane.
Scoping and submittals (about 1–2 weeks). This is where you finalize tonnage, heat-pump vs. gas heat, airflow targets, and control sequences. If you’re adding demand-control ventilation, coordinate with your TAB contractor now so the airflow plan is locked before you schedule a crane. For help justifying a heat-pump RTU to stakeholders, layer in the DOE’s decision matrix as an objective reference instead of sales copy.
Procurement and permitting (roughly 2–6+ weeks). Manufacturers’ allocation and refrigerant transitions can stretch shipments. If you’re ordering a curb adapter, confirm dimensional drawings before you lock the crane date. Mechanical permits for like-for-like swaps tend to be straightforward, but jurisdictions vary; build a small buffer so a missing document doesn’t push a pick day into the following month.
Crane day and swap (4–8 hours, typically). Street or lot closures, roof access, and fall protection all need to be coordinated. OSHA’s construction guidance is clear: once you’re six feet above a lower level, a compliant fall-protection plan is required, so budget for rails, anchors, or equivalent controls in your site plan and daily brief. If you need the reference, OSHA’s Fall Protection in Construction booklet outlines the baseline controls and planning elements.
Commissioning and turnover (1–3 days). You’re not done until trend logs show the unit holds setpoints across morning warm-up and late afternoon load. Confirm staging, defrost, economizer changeover, alarms, and ventilation baseline. Hand the facility team a simple O&M orientation, then tie the first 90 days to a light-touch service cadence so someone actually looks at those trend logs. If you need a service partner during that period, keep a line open to commercial HVAC service and repair for the quick return visits that prevent a small tuning item from turning into a callback.
The fastest way to lose goodwill is a building that bakes on Monday after a weekend lift. Plan comfort the same way you plan logistics. For cooling-heavy spaces—retail, call centers, server rooms—stage temporary cooling for the zones most at risk. Even a couple of portable spot coolers pointed at hot aisles buys you the time to complete controls checkout without rushing. In colder months, schedule the lift midday when solar gain helps you; a 9 a.m. pick in January can make reheat commissioning feel like a marathon.
Phase the work whenever possible. On multi-RTU roofs, replace one unit at a time so the remaining equipment can carry part of the load. On single-RTU buildings, choose a Saturday lift and pre-assemble what you can on Friday: curb adapter, disconnects, and any sheet-metal transitions. That way, most of Saturday is spent on the swap and BAS points check, not chasing fittings. Finally, communicate like an airline pilot. Give tenants a short, plain-language notice 48 hours before the outage window, then a quick “wheels up” message once the new unit is live. If you want the ops loop closed after turnover, align the first quarter of checks under commercial HVAC maintenance so filters, belts, and trend reviews don’t slip.
For a like-for-like RTU swap, plan four to eight weeks end to end. The unit and curb adapter lead times drive most of it, followed by crane scheduling and permitting. The physical swap usually fits into a single day, with commissioning and BAS verification wrapped up within another one to two days.
Controls integration. New units introduce heat-pump logic, economizer sequences, and fan turndown that older thermostats or BAS may not handle properly. Add a modest allowance for controls labor and testing, and confirm responsibility for point mapping and graphics updates before parts are ordered.
Yes. EPA’s Technology Transitions program restricts certain higher-GWP HFCs starting January 1, 2025 for defined sectors, which influences which models are manufactured and shipped. Align your specification with compliant refrigerants so you don’t face last-minute substitutions.
Pre-stage temporary cooling or heating for the highest-risk areas, schedule the crane for a weekend or off-hours, and pre-assemble the curb adapter and electrical work the day before. Then run a real commissioning script—verify cooling, heating, ventilation, and alarms—and trend setpoints for at least one occupied cycle.
Fifteen years is a fair planning assumption with consistent maintenance: filters on schedule, belts inspected, coils cleaned, and economizer dampers exercised. Roof exposure and particulate load matter; urban dust or nearby construction will push you toward more frequent filter and coil service.
Usually yes for mechanical, and sometimes electrical. Requirements vary by jurisdiction, but even simple swaps often require submittals showing equipment weight, clearances, and anchorage details. Confirm early so a missing permit doesn’t force a crane-day reschedule.
When the building’s use has changed—more people per square foot, new conference areas, added process loads—or when persistent comfort issues remain even after well-maintained equipment does its job. Treat that project like a new installation and revisit zoning, ventilation rates, and control sequences.
A proactive replacement is basically logistics with a comfort guarantee. Label the costs up front, book the people who make dates possible, and commission like you mean it. Do that, and the building barely notices the handoff—except on the utility bill.