It is the single most common call we get from this part of the valley: the downstairs is comfortable, but the upstairs master and the bonus room sit five to nine degrees warmer every afternoon and never catch up until well after dark. Homeowners assume the air conditioner is failing and start pricing replacements. In the two-story and three-story homes that fill The Vistas, The Paseos, Redpoint, and The Ridges, that is almost never the real problem. The equipment is usually fine. The air is just not getting where it needs to go.

Three Forces Stacking the Heat Upstairs

The first force is physics. Hot air rises. In a tall Summerlin floor plan with a two-story great room and open stairwells, warm air migrates up and pools at the highest occupied level. This is the stack effect, and it works against the upstairs all day.

The second force is the location. Summerlin South sits on the western shelf of the valley, and the sun stays above the Red Rock escarpment until close to sunset. The large west-facing windows that make these homes feel bright in the evening also pour solar heat into the upstairs rooms from about 2 PM onward. A west-facing upstairs bedroom can pick up hundreds of BTU per hour of pure radiant gain through the glass, on top of whatever the roof deck is dumping in from above.

The third force is the ductwork. Builders almost always hand homes over with the in-duct dampers left wide open. The system was balanced, if at all, on a mild model-home day. The supply runs closest to the air handler take the easy air, and the long runs to the far upstairs bedrooms starve. Nobody adjusted the dampers to send more air upstairs, where all the heat is collecting.

Why Replacing the AC Will Not Fix It

This is the part that saves Summerlin homeowners thousands of dollars. If the upstairs is hot because of stack effect, solar gain, and open dampers, a brand-new air conditioner will have exactly the same problem. A bigger system will not push more air upstairs if the dampers and duct design are sending it downstairs. We have re-balanced plenty of homes where the previous contractor sold a full system replacement to fix a hot upstairs, and the upstairs stayed hot because the airflow was never addressed. The fix is at the duct level, and it costs a fraction of new equipment.

What NCI Air Balancing Actually Does

Our techs are trained and certified through the National Comfort Institute, and air balancing is a measurement-driven process, not a guess. We arrive with ALNOR flow hoods, manometers, and rotating-vane anemometers. We log static pressure at the air handler, the total external static pressure across the whole system, and the actual CFM delivered at every supply and return register. Then we compare what each room is getting to what each room needs, accounting for that west-slope solar gain and the heat the stack effect is pulling up.

Where the numbers are off, we adjust the in-duct dampers to move air away from the over-supplied downstairs rooms and toward the starved upstairs ones. We modify trunk takeoffs and clear restrictions like crushed flex duct in the attic, which we find often in these homes. Every adjustment is re-measured, so the result is documented in numbers, not in a hand wave. The full process is laid out on our Summerlin South air balancing page.

The Zoning Systems Nobody Commissioned

Many Summerlin South homes were sold with a zoning system installed but never set up. Carrier Infinity Zone, Lennox Harmony, Trane ComfortLink, and Honeywell TrueZONE panels sit in attics across this submarket with dampers that were set once and forgotten, or worse, set wrong. A zoning system that is not balanced can make comfort worse, slamming air into one zone while choking another and driving static pressure up to the point that it stresses the blower. We balance the airflow first, then verify the zoning sequence so the upstairs and downstairs zones actually hold their set points instead of fighting each other.

The Return-Air Piece Most People Miss

There is a second half of the duct system that almost never gets discussed, and on a hot Summerlin upstairs it is often the real bottleneck. Supply ducts push cool air into the rooms, but the return side has to pull the same volume of air back to the air handler, and in these master-planned homes the return is routinely undersized. Builders count supply registers because homeowners do, but returns are expensive to run, so a two-story home frequently ends up with a single central return trying to feed a blower that wants far more air than one grille can move. When a bedroom door closes, that room can no longer breathe back to the central return, it pressurizes, and less cool air can enter it, which is exactly why a closed-door upstairs bedroom bakes on a summer afternoon even when the vent is open. The stack effect and the west-facing glass make it worse, but the starved return is what makes it stick.

When our measurements point at the return rather than the supply dampers, the fix is duct-side, not equipment-side: a second return drop on the upstairs level, a larger filter-grille return that also holds a deeper filter, or transfer grilles that let closed bedrooms breathe back to the central return. These changes drop the whole system’s static pressure and let the upstairs finally get its share of air, and like every other part of the job we re-measure afterward so the improvement shows up in numbers, not just in how the room feels. It is the piece most contractors skip because it is not glamorous, and it is often the difference between a balancing job that holds and one that drifts back within a season.

What Homeowners Notice After Balancing

Most Summerlin South clients call back within a week. The upstairs master finally holds the thermostat setting through the afternoon, the bonus room stops baking after 3 PM, and the system cycles off more often instead of running flat-out all evening trying to satisfy one starved return. There is a bonus on a high-glass home like these: a balanced system runs shorter cycles, which eases the wear on the compressor that the west-slope load was driving toward early failure. Better comfort and a longer-lived AC from the same visit. You can see the kind of work we do across the area on our Summerlin South service page.

Summerlin South Air Balancing FAQ

How do I know if my hot upstairs is airflow and not the AC?

The clearest sign is that the downstairs cools fine while the upstairs lags every afternoon. If the whole house struggles, it may be an equipment or refrigerant issue. We measure both the airflow and the equipment so you are not guessing.

How long does air balancing take on a two-story Summerlin home?

A typical single-family home runs 4 to 6 hours. Larger two and three-story homes with five or more bedrooms and multi-zone systems run 6 to 8 hours. We schedule for the travel between levels so it is done in one visit.

Do you have to replace any equipment?

Almost never. Air balancing works with the ducts you already have. If we find a failing component while we are in there, we tell you, but most jobs are pure damper, takeoff, and duct work.

What does air balancing cost in Summerlin South?

Residential air balancing is priced by home size, story count, and supply count. Multi-zone homes that need the zoning sequence verified sit at the upper end. Pricing includes re-measurement and a 30-day satisfaction window.

Will balancing lower my power bill?

Often. A balanced system satisfies the thermostat faster and runs shorter cycles. NCI data shows 8 to 18 percent runtime reduction is common on systems that were significantly out of spec. We do not promise a dollar figure because Nevada Power rate plans vary.

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