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Rooftop vs. Pad-Mounted Commercial Units: Which Setup Works Best for Your Building?

When business owners ask Tony whether they should install a rooftop packaged unit (RTU) or a ground-mounted packaged unit, they usually want a quick answer.

But here’s Tony’s honest take:
There IS a right choice — but it depends entirely on your building, layout, airflow, noise restrictions, access, code requirements, and long-term service needs.

Most commercial HVAC failures Tony fixes come from choosing the wrong mounting location for the right equipment.

This blog breaks down everything Tony evaluates before choosing between a roof install and a ground pad install — with real-world examples, contractor insights, airflow rules, and safety/code considerations most installers never tell you.

Let’s get into it.

1. First Question Tony Asks: “How Will Airflow Move Through This Building?”

Placement starts with airflow, not convenience.

Commercial packaged units push conditioned air through:

supply duct trunks
diffusers
zones
returns
economizers
fresh air dampers

Where the unit sits determines:

static pressure
duct length
energy efficiency
noise
air balance
response time

Rooftop units usually offer better airflow distribution because:

✔ ductwork drops straight down into the building
✔ shorter horizontal runs
✔ fewer turns → less static pressure
✔ easier zoning layouts

Ground units require:

✘ longer duct runs
✘ more elbows and transitions
✘ higher external static pressure
✘ more balancing
✘ more space for returns

Airflow is the #1 reason Tony chooses rooftop more often than pad mounts.

2. Structural Considerations — Your Roof Must Be Able to Hold the Weight

A 6–10 ton packaged unit weighs:

900–1,200 lbs for 6 tons
1,400–2,000+ lbs for 10 tons

That’s NOT something you drop on any roof.

A rooftop install requires:

✔ structural evaluation
✔ curb or curb adapter
✔ reinforcements in many older buildings
✔ leak-proof flashing
✔ drainage planning

If the roof can’t support it, installation becomes:

expensive
risky
code-violating

Tony always checks building age, roof type (TPO, EPDM, built-up), and joist spacing before approving a rooftop job.

(Reference: Mechanical Equipment Support Standards)

3. Ground Pads — Easier to Install, Harder to Protect

Ground-mounted units look easier.
And they are… at first.

But Tony sees these long-term problems all the time:

vandalism
copper theft
lawn equipment damage
snow accumulation
flooding
blocked airflow from vegetation
pest nesting

A ground unit must sit on:
✔ level concrete pad
✔ elevated to avoid water
✔ fenced (in many areas)
✔ clear of shrubs or debris
✔ engineered for airflow

Great for accessibility.
Not always great for reliability.

4. Noise: Rooftop Is Usually Quieter Indoors

One big reason businesses choose rooftop units:

Rooftops reduce indoor noise by 40–80%.

RTUs place:

compressors
fans
blowers
gas burners

…far above the occupied space.

Pad-mounted units sit closer to:

windows
seating areas
break rooms
indoor walls

Even when well installed, ground units transfer more noise into the building envelope.

But rooftop noise can affect:

neighboring buildings
rooftop patios
apartment units above retail spaces

Tony checks noise ordinances before deciding.

(Reference: Environmental Compliance Guidelines)

5. Installation Cost Differences — Rooftop Usually Costs More Upfront

Rooftop Installation Cost Drivers:

crane lift ($800–$3,500 depending on height)
roof curb
roofing modifications
structural verification
more labor hours
safety equipment

Ground Installation Cost Drivers:

concrete pad ($300–$700)
short duct connection
more flexible layout
no crane needed
faster installation

Rooftop = Higher upfront cost but lower long-term risk.
Ground pad = Lower upfront cost but higher maintenance risk.

6. Security & Environmental Exposure

Ground Units:

easy to steal copper from
easy to vandalize
easy to block with debris
exposed to flooding
exposed to snow drifts

Rooftop Units:

safer from theft
better airflow clearance
protected from most ground-level hazards
easier to secure with lockable access panels

Tony has replaced dozens of pad units destroyed by weather and lawn crews.
He’s replaced only a handful of rooftop units due to damage.

7. Serviceability: Technicians Love Rooftop Units (Mostly)

Tony prefers working on rooftop units for one reason:

Access doesn’t disrupt business.

On the ground:

Techs block driveways
Foot traffic is interrupted
Parking must be roped off
Condensate drainage gets messy

On the roof:

No customer interference
No indoor disruption
Easy access to panels
Noise isolated

BUT…

Rooftop service requires:

climbing ladders
harnesses
OSHA compliance
good weather
safe rooftop layout

Still, for busy commercial environments, rooftops win.

(Reference: Commercial HVAC Service Safety )

8. Ductwork Differences: Rooftop = Simpler, Ground = Complicated

ROOFTOP:

✔ vertical drop into mechanical room
✔ fewer 90-degree turns
✔ shorter duct runs
✔ easier zoning
✔ better pressure control

GROUND MOUNT:

✘ long horizontal duct runs
✘ more friction loss
✘ more elbows
✘ more insulation needed
✘ harder to seal

Duct modifications are usually cheaper on rooftop installations.

9. Gas Line & Electrical Routing Considerations

Rooftop Pros:

✔ gas lines can run straight up an exterior wall
✔ electrical conduits concealed
✔ cleaner aesthetic

Rooftop Cons:

✘ longer gas/electrical runs
✘ requires roof penetration sealing

Pad Unit Pros:

✔ short gas and electrical runs
✔ simpler utility connections

Pad Unit Cons:

✘ must trench lines in some cases
✘ exposed piping prone to damage

Tony evaluates:

distance from main electrical panel
gas meter location
trenching feasibility
building code requirements

Before picking one or the other.

(Reference: Electrical Routing Regulations)

10. Climate Plays a Big Role in Choosing Rooftop or Ground

Hot, Dry Climates (AZ, NV, NM, TX):

→ Rooftop preferred
Better airflow and less environmental risk.

Cold, Snow-Heavy Climates (MI, MN, NY, PA):

→ Rooftop strongly preferred
Keeps units above snow lines.

Hurricane or Flood Zones (LA, FL, Gulf Coast):

→ Rooftop is almost always required
Pad units get submerged or destroyed.

Mild/Moderate Climates:

Both work, but rooftops still win for airflow.

11. When Tony Recommends Rooftop Units

✔ buildings with enough structure to support equipment
✔ high customer foot traffic
✔ areas prone to theft or vandalism
✔ buildings with long run times
✔ multi-zone duct demands
✔ high solar exposure
✔ cities with dense commercial traffic

Most modern commercial buildings fall into this group.

12. When Tony Recommends Ground-Mount Units

✔ roofs too weak for mechanical equipment
✔ historic buildings
✔ low-rise buildings with easy pad access
✔ small single-zone applications
✔ cost-sensitive projects
✔ easy duct routing at ground level

Ground units are fine if protected and elevated — Tony insists on fencing and drainage.