Operational realities and capital planning considerations often lead property owners and management companies to replace rooftop units (RTUs) over several years instead of all at once.

• Capital budgets are often spread over multiple years
• Rooftop units fail at different times rather than all at once
• Some units may be newer than others due to past replacements
• Tenant spaces cannot all lose HVAC at the same time
• Replacement work can be scheduled during milder weather
• Roof sections may be replaced in phases
• Many businesses cannot shut down for a full building HVAC replacement project

In most commercial buildings, each rooftop unit serves a specific area rather than the entire building. A multi-tenant office building might have one unit per suite, while a warehouse or large open building might have several units that each handle part of the space.

Common RTU zoning layouts include:

• One unit per tenant suite in multi-tenant buildings
• One unit per floor in office buildings
• One unit per building wing or section
• Separate units for common areas such as lobbies or hallways
• Multiple units serving a large open area such as a warehouse, gym, or church
• Dedicated units for kitchens, server rooms, or other high-load areas

Replacing one rooftop unit usually only affects the area served by that unit, not the entire building. In a multi-tenant building, that might mean only one tenant loses cooling for a few hours while their unit is replaced.

In larger open buildings where multiple units share the load, the remaining units can often continue operating while one unit is being replaced.

To minimize disruption, rooftop unit replacement is often scheduled:

• During milder weather when full cooling or heating is not required
• After business hours or on weekends
• During tenant vacancies or planned shutdown periods
• With temporary cooling or heating equipment if necessary

Most phased rooftop unit replacement projects prioritize individual units based on:

• Equipment age
• Repair history and maintenance costs
• Units with higher failure risk
• Units using obsolete refrigerant
• Units serving critical areas such as server rooms or medical spaces
• Units causing comfort complaints
• Units with poor energy efficiency
• Roof replacement schedules
• Budget availability for each year

In addition to minimizing disruption (or at least limiting it to the fewest tenants possible at any given time), this approach allows capital costs to be spread across multiple budget cycles.

While phased replacement is often the least disruptive option for large-scale rooftop HVAC unit replacement projects, there are some challenges that facility managers should consider:

• Different equipment ages and efficiencies across the building
• Control system compatibility between old and new units
• Multiple crane mobilizations over several years
• Roof penetrations being modified multiple times
• Parts becoming harder to find for older units
• Maintenance complexity with mixed equipment ages

Planning phased replacement carefully and understanding the potential complications of the approach you choose can help reduce some of these issues.

In some situations, replacing all rooftop units at the same time may make more sense than phased replacement. Full replacement may make sense when:

• All rooftop units are the same age
• A full roof replacement project is planned
• The building is undergoing a major renovation
• The building automation or control system is being replaced
• Electrical upgrades are required for multiple units
• Financing is available for a full replacement project
• The building wants to standardize equipment across all units

If one or more of those factors apply to your project, completing all replacements at once may reduce long-term labor costs and avoid multiple crane mobilizations.

Tom’s Commercial works with facility managers, property managers, and building owners throughout Arlington, Fort Worth, and surrounding areas to plan rooftop unit replacement projects, including phased replacement plans and long-term equipment replacement strategies.

If you are planning rooftop unit replacement for your building and want help evaluating equipment condition, prioritizing replacements, or planning a phased replacement schedule, contact Tom’s Commercial at 817-857-7400 to discuss your HVAC replacement timeline.