Arizona Homes Used 32% Less Electricity in Summer: What Was Different?

How much difference can a home's insulation and building envelope make during an Arizona summer?

A BASF energy case study of Arizona homes found that four high-performance model homes used 32% less electricity on average than four homes with the same floor plans built with the builder's standard construction package from May through August 2020. One floor plan used 45% less electricity, and the four high-performance homes used 13,615 fewer kWh in total during the study period.

BASF compared complete building-envelope systems rather than a single insulation material. The high-performance homes combined different wall, roofline, attic, insulation, and air-control measures. The case study therefore gives a useful real-world comparison of how two building-envelope approaches performed through extreme Arizona summer conditions.

BASF Arizona Study Results at a Glance

• 32% less electricity: Average difference across the four high-performance model homes.
• 45% less electricity: Largest percentage difference recorded across the four floor-plan comparisons.
• $399.51: Average electricity cost difference per high-performance model home over the four-month study.
• $679.10: Largest four-month electricity cost difference recorded for one floor plan.
• 13,615 kWh: Combined electricity difference across the four high-performance model homes.
• 83°F or below: Highest temperature recorded in the sealed, unvented attic when outdoor temperatures exceeded 115°F.

Electricity Savings by Floor Plan in the BASF Arizona Study

The BASF high-performance homes used 15% to 45% less electricity than the standard-construction homes with the same floor plans, with an average difference of 32% across the four comparisons. BASF measured electricity use and electricity costs from May through August 2020.

Across all four comparisons, the high-performance model homes used 13,615 fewer kWh of electricity. The combined electricity cost difference was $1,598.02, equal to an average of $399.51 per home over the four months.

The electricity savings reflect the complete BASF high-performance building envelope, which combined several insulation materials, air-control measures, and a sealed attic design. The 32% average therefore represents the performance of the complete system used across the four high-performance model homes.

How Did BASF Compare the Eight Arizona Model Homes?

BASF compared eight model homes across two Arizona communities. Four model homes in a west-side Phoenix community used the BASF high-performance building envelope. In comparison, four homes with the same floor plans in an east-valley Mesa community used the builder's standard construction package.

BASF also reports one equipment difference outside the building-envelope package. The high-performance homes had sealed-combustion 90-plus AFUE furnaces, while the standard homes had 80 AFUE furnaces. AFUE is a heating-efficiency rating, and BASF states that the comparison assessed the cooling season rather than furnace efficiency.

BASF notes that the limited visitor activity resulted in minimal human impact during the study period. Energy use in an occupied home also varies with factors such as property design and size, existing insulation, HVAC equipment, thermostat settings, occupancy, household behavior, local electricity rates, and weather.

What Was Different About the High-Performance Building Envelope?

The BASF high-performance homes and the standard-construction homes used different building-envelope assemblies. The high-performance package changed the wall assembly, continuous insulation, roofline insulation, and attic design rather than adding spray foam to an otherwise identical finished home.

What Is a Sealed, Unvented Attic?

In the BASF high-performance homes, the sealed, unvented attic had no outdoor ventilation and used open-cell spray foam at the underside of the roof deck instead of insulation at the attic floor. The roofline insulation placed the ductwork and air-handling equipment inside what BASF describes as a semi-conditioned attic space, with the attic brought inside the insulated roofline.

The attic setup matters because the next major study result came from inside that space. The U.S. Department of Energy also explains that unvented, conditioned attics can improve energy performance when HVAC ducts are located in the attic because the ducts are brought inside the insulated enclosure.

What Happened in the Attic When Outdoor Temperatures Exceeded 115°F?

When outdoor temperatures exceeded 115°F, BASF reported that data loggers in the sealed, unvented attic never recorded a temperature above 83°F. The attic therefore remained at least 32°F cooler than the outdoor temperature during those periods.

The attic temperature matters because the ductwork and air-handling equipment were located in that space. The high-performance building envelope changed the conditions around the mechanical systems as well as the insulation in the walls and roofline.

The 83°F reading reflects the sealed attic as part of BASF's complete high-performance building-envelope system, where roofline insulation, air control, and attic design worked together around the home's mechanical equipment.

How Do Insulation and Air Sealing Affect Home Energy Use?

Insulation reduces heat flow through the building envelope, while air sealing limits unwanted air movement through cracks and openings. The U.S. Department of Energy Energy Saver Guide also explains that a larger temperature difference between indoors and outdoors increases the energy needed to maintain comfortable indoor conditions.

The DOE guidance on heat flow and air leakage helps explain the BASF comparison. The high-performance homes used different insulation assemblies across the walls and roofline, while the spray-foam components and sealed attic also affected air control. The sealed attic kept the ductwork and air-handling equipment inside the cooler space created by the high-performance envelope. Together, those changes formed the building-envelope system behind the 32% average electricity difference recorded in the study.

ENERGY STAR provides broader evidence for the same relationship. The U.S. Environmental Protection Agency estimates that homeowners can save an average of 15% on heating and cooling costs by air sealing their homes and adding insulation in attics, floors over crawl spaces, and basements. The ENERGY STAR estimate reinforces the link between insulation, air sealing, and energy use seen in the BASF study, where stronger insulation and air control formed part of the system associated with lower electricity use.

Why Do the BASF Results Still Matter for Arizona Homeowners?

The BASF results remain relevant because Arizona continues to experience extreme summer heat that puts home-cooling performance under pressure. The National Weather Service Phoenix recorded an average temperature of 98.5°F in August 2026, which was 4.1°F above the 1991 to 2020 normal and made August 2026 Phoenix's fourth-hottest August on record.

That heat also coincided with record demand on the Arizona Public Service system. Arizona Public Service reported that customers used 9,164 MW between 6 p.m. and 7 p.m. on August 2, 2026, surpassing the previous record of 9,053 MW set on July 24.

Extreme summer heat and high cooling demand make building-envelope performance especially relevant for Arizona homeowners. Insulation, air leakage, and attic conditions can influence how much heat reaches conditioned space and how hard the cooling system has to work.

What Could the BASF Results Mean for Your Home?

The BASF results show that a home's building envelope deserves attention alongside the air conditioner when a home is difficult or expensive to cool. Attic insulation, air leakage, and the condition of existing insulation can affect summer comfort, energy use, and HVAC performance.

Insulation or air leakage may deserve a closer look if you notice:

• An air-conditioning system running for long periods.
• Rooms that are consistently warmer than others.
• Upstairs areas that are particularly difficult to cool.
• High summer electricity use.
• An attic that becomes extremely hot.
• Existing insulation that appears thin, damaged, or uneven.
• Noticeable drafts or potential air leakage.

These signs give homeowners useful reasons to check the building envelope alongside the HVAC system when a home struggles through extreme summer heat.

How Can iFOAM Help With Insulation and Air Sealing?

The BASF study shows how insulation, air control, and attic design work together as part of the building envelope. If your home has uneven temperatures, high summer electricity use, or an extremely hot attic, the next step is to find out what is happening in your building envelope.

iFOAM starts with a free in-home assessment. The team evaluates existing insulation levels, looks for potential air leaks, and recommends improvements based on the property, climate, budget, and energy-efficiency goals.

Depending on what the home needs, iFOAM services include:

• Attic insulation to improve insulation coverage at the top of the home.
• Air sealing to close gaps and openings that allow unwanted air movement.
• Spray foam insulation for projects where insulation and air control are both part of the solution.
• Blown-in cellulose insulation for spaces where blown-in insulation is the better fit.

The BASF study is useful because it shows that home performance comes from several parts of the building envelope working together. An iFOAM assessment applies the same whole-home thinking by reviewing existing insulation and potential air leaks before recommending the services that fit the property.

Homeowners who want to learn more about one of those options can also read iFOAM's guide to the benefits of spray foam insulation, including how spray foam affects heat transfer and air infiltration.

Are Poor Insulation or Air Leaks Making Your Home Harder to Cool?

Find out where your home's insulation or air sealing may need attention and which improvements make sense for your property. Call (855) 935-4723 for a free consultation, or find an iFOAM location near you.