It's the second week of May and your AC has already run continuously for four days straight. The thermostat in the hallway reads 78°F, but the back bedroom feels like a sauna — and your NV Energy bill is creeping toward numbers you'd rather not think about. Before you blame a failing compressor or an undersized unit, there's a far more common culprit hiding directly above your ceiling: a duct system that's quietly dumping conditioned air into a 140-to-160°F attic space before it ever reaches your living areas. Duct leakage is one of the single largest sources of wasted energy in Las Vegas homes, and May is exactly the moment to fix it — before triple-digit heat turns a fixable problem into a miserable summer.

Why Las Vegas Attics Are Especially Brutal on Ductwork

In most parts of the country, attic temperatures on a hot day might reach 120–130°F. In the Las Vegas metro — Summerlin, Henderson, North Las Vegas, Anthem, Enterprise — attic temps routinely climb past 150°F from June through September. At those temperatures, the flexible duct material used in most residential installs expands, contracts, and eventually separates at joints and connections. Mastic sealant that was applied ten or fifteen years ago dries out and cracks. Metal duct collars pull away from boots. Flex duct inner liners tear at bends.

The result: your air handler pushes 55°F supply air into a duct system that's sitting inside an oven. Even before any physical gaps, heat transfer through thin duct walls raises that supply air temperature. Add physical leaks at joints and you can lose a significant portion of the cooling you're paying for — often estimated in the range of 20–30% in a home with unsealed or aged ducts — before a single cubic foot of air exits a vent register.

Signs Your Ducts Are Leaking Right Now

Duct leakage rarely announces itself with an obvious failure. Instead, it shows up as a collection of symptoms homeowners often misattribute to other causes. Watch for these warning signs as temperatures climb in May:

  • Rooms that never cool evenly: A back bedroom, a bonus room, or any space far from the air handler that consistently runs 5–8°F warmer than the thermostat setpoint — especially if it was fine a few years ago.
  • Excessive dust on supply registers: When return ductwork leaks, it pulls unconditioned attic air (full of insulation particles and desert dust) into the system. Registers that film over with gray or brownish dust between cleanings are a classic tell.
  • AC running nearly non-stop in May: If your system is cycling continuously when outdoor temps are still in the 95–100°F range, it's struggling to meet load — often because conditioned air isn't reaching the living space.
  • Utility bills noticeably higher than last year: Compare your May NV Energy bill year-over-year. An aging duct system that has degraded further over winter can show a meaningful jump even before peak summer rates kick in.
  • Humidity feeling higher than usual indoors: July monsoon season is still a couple of months out, but even in May, leaky return ducts can pull in unconditioned air and undermine your system's dehumidification.
  • Visible disconnected flex duct in the attic: If you've ever glanced into your attic access, a visibly sagging, kinked, or fully detached flex duct run is an obvious red flag.

How Duct Leakage Is Actually Tested

A visual inspection of accessible duct runs is a starting point, but it doesn't tell you how much air you're losing or where the worst leaks are. The industry-standard method is a duct blaster test (sometimes called a duct pressurization test). A technician seals all supply and return registers, then attaches a calibrated fan to the system and pressurizes the ductwork to a standard pressure — typically 25 Pascals. A meter measures how much airflow is required to maintain that pressure. That flow rate is the leakage. The result is expressed as a percentage of total system airflow, and in pre-2010 Las Vegas homes it's not unusual to find leakage rates well above 20%.

Thermal imaging can complement this test by identifying exactly which joints and connections are leaking — cold spots on the duct exterior in an attic that hot tend to pinpoint escaping conditioned air precisely. Our maintenance plan includes a duct inspection as part of the pre-summer AC tune-up, which is a practical starting point if you're not sure whether a full blaster test is warranted.

Seal vs. Replace: What Each Costs and When Each Makes Sense

This is the decision most homeowners need help thinking through. Duct sealing and duct replacement are not the same thing, and the right choice depends on the age and condition of your existing ductwork.

Duct Sealing

If your duct system is structurally intact — flex duct in good condition, metal trunk lines not corroded — but joints and connections have failed, professional sealing is the cost-effective fix. Sealing involves applying UL-181-rated mastic compound (a paste-like sealant) and reinforcing mesh tape at every joint, boot, and collar. Aeroseal, an aerosol-based internal sealing method, is another option for leaks inside the duct walls that are hard to access physically. Professional sealing on a typical Las Vegas single-story home commonly runs in the $800–$1,800 range, depending on system size and attic accessibility. The payback in reduced cooling costs can be meaningful, though actual results vary by home.

Duct Replacement

If your flex duct is more than 15–20 years old, has suffered rodent damage (a real concern in Centennial Hills and Green Valley), or is kinked and undersized, patching leaks on compromised duct material is throwing good money after bad. Full duct replacement — new insulated flex duct, properly sized trunk lines, sealed boots — typically runs in the $3,500–$7,000+ range for a full home, again depending heavily on system size and attic layout. This is also the right time to address any design issues, like long duct runs with too many bends that restrict airflow. If you're also considering an equipment upgrade, pairing a new duct system with a new AC installation ensures the system is sized and designed as a matched unit.

A rough rule of thumb: if a blaster test shows leakage above 15% and the duct material is in reasonable shape, sealing first is usually the sensible path. If leakage is above 25–30% and the ductwork is aging, replacement likely pencils out better over a five-to-ten year horizon.

The Indoor Air Quality Dimension

There's a second reason to address duct leakage that goes beyond the energy bill. Las Vegas hard water, desert dust, and attic insulation fibers are not things you want cycling through your living space. Leaky return ducts are one of the primary pathways for particulates to enter the airstream in a home. If anyone in your household has asthma, allergies, or respiratory sensitivities, a compromised duct system compounds those issues. Sealing ducts is one of the most effective — and underappreciated — steps toward better indoor air quality in a desert home.

When to Call a Professional

If you're noticing uneven cooling, spiking bills, or excessive dust as May temperatures climb into the upper 90s, don't wait for July to investigate. Duct issues caught now — before the system is running at full load for 14 hours a day — are easier to address, and a properly sealed duct system going into peak summer makes a real difference in both comfort and operating costs. We serve the full Las Vegas metro, from Summerlin to Henderson to North Las Vegas, and we carry NV License #0072282. To find out where your duct system stands, call us directly at (702) 830-7116 or get a 60-second instant quote online and we'll schedule a pre-summer duct inspection before the heat makes attic work significantly more difficult.