Why Henderson & Summerlin Two-Story Homes Run Hot Upstairs and Freezing Downstairs

It’s a chilly January evening, and the furnace has been running for an hour. Upstairs feels warm and stuffy, yet your feet are still cold on the couch downstairs. For many Henderson and Summerlin two-story homeowners, this scene probably sounds familiar.

Maybe you’ve even asked, “Why is my house cold downstairs when the heat is on?” Most homeowners blame the furnace first. Others close upstairs vents or plug in a space heater. Yet the same imbalance returns every winter.

Here is what is really happening. Warm air naturally rises, and in a two-story home it travels up through hidden gaps in the floor system between stories. As heated air escapes upward, cooler air gets pulled in down low. Sealing and insulating those floor-system gaps evens out both floors without touching your HVAC equipment.

A free evaluation from an existing residential insulation expert can pinpoint exactly which floor-system gaps are pulling heat upstairs in your home.

According to the Building America Solution Center, warm air naturally rises within a space while colder air falls. This movement is called convection.

In a two-story home, warm air has a whole extra floor to climb. That’s why every two-story home is a stack effect house to some degree. Heated air rises and slips out through any upper gap it can find. As it escapes, it pulls cold outside air in through leaks on the lower level.

Pressure imbalances caused by duct leakage and exhaust devices can make it worse by pushing air right across your insulation. When insulation and the air barrier are out of line, heated air flows around the insulation. This often happens at dropped ceilings, soffits, and floor systems.

Many tract homes also use a single thermostat to control both floors as one zone. It only reads the air in one spot, so one floor ends up too warm or too cool. This is a building-science issue, and your HVAC equipment may be working just fine.

Most of the Las Vegas Valley falls within Clark County’s climate zone 3B. Areas in Clark County above 4,000 feet of elevation are treated as climate zone 5B. That places most Henderson and Summerlin neighborhoods in the warm, dry 3B zone. A few higher foothill homes in Summerlin may sit near that cutoff, so a quick elevation check is smart for those addresses.

Many homes in these master-planned communities are stucco tract builds. Here, the floor system between stories does much of the work of keeping heat where it belongs. When gaps form there, warm air slips past the insulation, just like the misalignment described above. That’s why quality Henderson and Summerlin insulation work has to look at the floors as closely as the attic.

The stack effect shows up in summer too, as hot air collects upstairs. For that side of the story, read “Vegas Heat: Can Your Insulation Handle It?”

Every home has a rim joist, also called a band joist, where the floor framing meets the foundation. A two-story home has a second one. It wraps around the house just above the first-floor ceiling, hidden from view. This second ring is a leak point unique to multi-story homes, and it’s often ignored.

Fiberglass batts are common in these spaces, but air passes right through them, making them a poor option for air sealing at these framing connections. The air barrier at floors should line up with the outer face of the insulation at the rim joists in every climate zone. That’s why careful rim joist air sealing matters.

Many Henderson and Summerlin tract homes have cantilevers, such as a second-floor room that hangs past the wall below or a bay window bump-out. These cantilevered floors in existing homes are frequently uninsulated and not air sealed. That leaves cold or hot spots in the rooms around them.

The underside of an overhang is part of your home’s thermal boundary, so it must carry the same air, vapor, and thermal control layers as the wall above it. Missing cantilevered floor insulation often explains why one or two rooms feel nothing like the rest of the house.

Insulation only performs well when it’s in direct contact with a solid air barrier. When they’re separated, heated air can bypass the insulation entirely. Floor systems and soffits are common trouble spots.

The order matters. A continuous air barrier should be in full contact with the insulation around your entire home. In a two-story house, that means sealing every rim joist and cantilever, plus each spot where a floor meets a wall.

Rigid or spray foam is the most effective material for floor insulation and air sealing. It is recommended for rim joists and cantilever floor cavities because it functions as both an insulation and an air barrier.

Rim joists and cantilever cavities are tight, awkward spaces. Spray foam insulation expands to fill those gaps and seals them as it insulates. One application handles both jobs, which makes it a strong fit for the hard-to-reach spots between stories.

Fixing a two-story home temperature imbalance pays off in more than comfort. The EPA estimates that homeowners can save an average of 15% on heating and cooling costs by air sealing and adding insulation to key parts of their home. A tighter home also holds its temperature longer, which makes it easier in summer to lean less on your AC during peak hours under NV Energy’s time-of-use rates.

A good evaluation treats your home as a connected system. An installer will check the rim joists at both the foundation and the mid-floor level. They’ll inspect cantilevered bump-outs and bay windows. Floor sections next to the garage get a close look, along with the attic floor plane above stairwells. The goal is to find exactly where your home leaks and fix those spots with the right material.

The fix for a home that runs hot upstairs and cold downstairs lives in the floor systems between stories, not the furnace. A professional evaluation finds the rim joist and cantilever gaps specific to how your home was built. Then the right mix of air sealing and insulation closes them up.

The uneven heating in two-story homes Las Vegas families deal with every winter has a clear solution. Battle Born Specialties has helped Las Vegas-area homeowners stay comfortable since 2018. Our team specializes in existing residential insulation upgrades and understands how Henderson and Summerlin homes are built. Contact us today to request your free evaluation.

References

ENERGY STAR. “Why Seal and Insulate?” U.S. Environmental Protection Agency, www.energystar.gov/saveathome/seal_insulate/why-seal-and-insulate.

Pacific Northwest National Laboratory. “Building Science Introduction – Heat Flow.” Building America Solution Center, U.S. Department of Energy, https://basc.pnnl.gov/information/building-science-introduction-heat-flow.

Pacific Northwest National Laboratory. “Continuous Air Barrier in Exterior Walls.” Building America Solution Center, U.S. Department of Energy, https://basc.pnnl.gov/resource-guides/continuous-air-barrier-exterior-walls.

Pacific Northwest National Laboratory. “Insulating and Air Sealing Existing Floors Above Unconditioned Spaces.” Building America Solution Center, U.S. Department of Energy, https://basc.pnnl.gov/resource-guides/insulating-and-air-sealing-existing-floors-above-unconditioned-spaces#edit-group-description.

Pacific Northwest National Laboratory. “Insulating and Air Sealing Existing Floor Overhangs (Cantilevers).” Building America Solution Center, U.S. Department of Energy, https://basc.pnnl.gov/resource-guides/insulating-and-air-sealing-existing-floor-overhangs-cantilevers.

Southern Nevada Building Officials. Southern Nevada Amendments to the 2021 International Energy Conservation Code. Clark County, NV, 2023, www.clarkcountynv.gov/adobe/assets/urn:aaid:aem:988dc5cc-6e3b-4964-939f-b3dd54636491/original/as/2021-iecc-southern-nevada-amendments.pdf.