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Heat Dome Havoc
24, Jun 2025
Heat Dome Havoc: Rethinking HVAC Capacity in Texas and the Southwest

Heat Dome Havoc: Rethinking HVAC Capacity in Texas and the Southwest is no longer a seasonal issue. It’s a design emergency. Record-breaking heatwaves, rising nighttime temperatures, and overloaded power grids have exposed the limits of traditional HVAC systems.

From Houston to Phoenix, buildings are struggling to keep up. Many HVAC units were not designed for 110°F+ temperatures, nor for weeks of sustained stress. As a result, tenants suffer, equipment fails, and operating costs skyrocket.

This blog explores how MEP design engineering must evolve in response. We cover system sizing, energy strategies, and why MEP engineering companies must rethink old standards in a changing climate.


What Is a Heat Dome?

A heat dome is a high-pressure system that traps hot air over a region. It prevents cooling at night and drives extreme daytime temperatures.

In 2023, Texas and the Southwest experienced:

  • Sustained highs over 105°F for multiple weeks
  • Increased nighttime lows above 85°F
  • Record-setting heat index and humidity

Buildings weren’t designed for this—and the failures were widespread.


Why Traditional HVAC Design Is Failing

Most HVAC systems in Texas and the Southwest were sized using historical climate data. But that data is outdated.

Key problems include:

  • Undersized systems that can’t maintain indoor comfort
  • Continuous runtime leading to rapid equipment wear
  • Overloaded condensers in poorly shaded or ventilated areas
  • High indoor humidity even with systems running at full speed

Heat Dome Havoc: Rethinking HVAC Capacity in Texas and the Southwest means engineers must move beyond 30-year climate baselines.


Rethinking Cooling Load Calculations

1. Use Updated Weather Files

Designers should shift to recent Typical Meteorological Year (TMY3 or TMY4) data reflecting new temperature norms.

  • Old design days are no longer extreme
  • Use 99% percentile temperatures instead of 1%
  • Factor in extended heat events, not single-day peaks

Customized MEP solutions for building design begin with accurate environmental data.


2. Increase Safety Margins

Traditional design included 10–15% safety margins. That’s no longer enough.

Consider increasing capacity buffer to 25–30% for key systems, especially in multi-family and medical projects.


3. Add Latent Load Analysis

Texas heat often comes with high humidity. Many HVAC systems were only designed for sensible (dry) load.

Include latent loads in:

  • Load calculations
  • Equipment sizing
  • Ventilation design

Dehumidifiers may be required even in fully conditioned spaces.


HVAC Equipment Choices That Work in Extreme Heat

1. Variable-Speed Compressors

Systems that modulate can adapt to changing conditions without shutting off or cycling excessively.

Benefits:

  • Lower energy bills
  • Longer equipment life
  • Better humidity control

2. Oversized Condensers with Coil Guards

Larger condenser coils allow more heat transfer in high ambient temps.

Design Tips:

  • Avoid placing condensers in direct sun
  • Provide shaded, ventilated areas
  • Use UV-rated materials

3. Dedicated Outside Air Systems (DOAS)

DOAS units control ventilation separately from cooling, improving both air quality and system performance.

They also help:

  • Reduce indoor humidity
  • Maintain positive pressure
  • Improve occupant comfort in high-density spaces

4. Energy Recovery Ventilators (ERVs)

ERVs precondition incoming air using outgoing air energy.

  • Reduce cooling demand
  • Improve system efficiency
  • Allow greater airflow without higher utility bills

MEP engineering firms for custom designs should include ERVs in schools, offices, and healthcare settings.


Electrical System Coordination

As HVAC loads rise, so does electrical demand. Engineers must:

  • Size panels and breakers for longer runtimes
  • Evaluate transformer capacities
  • Plan for heat-induced voltage drops
  • Add surge protection for sensitive HVAC electronics

Energy-efficient MEP design engineering is about matching cooling goals with safe, stable power delivery.


Roof Design and Thermal Protection

Rooftop units (RTUs) face extreme exposure. Heat domes increase surface temperatures to over 150°F.

Structural and MEP strategies include:

  • Reflective roofing membranes
  • Ballasted or vegetative roofs
  • RTU platforms with shading screens
  • Roof penetrations sealed against heat-induced expansion

MEP engineering companies must collaborate with structural teams to reduce HVAC stress through better roof planning.


Ductwork and Insulation

Ducts in unconditioned attics or above ceilings lose efficiency fast in heat domes.

Recommendations:

  • R-8 insulation minimum
  • Encapsulated or conditioned attic spaces
  • Duct sealing and testing for leakage
  • Short, straight duct runs to minimize heat gain

Heat Dome Havoc demands ductwork designed for both airflow and thermal protection.


Controls and Smart Thermostats

More homeowners and businesses use smart thermostats to manage demand and reduce peak load charges.

Benefits:

  • Adaptive scheduling
  • Remote access
  • Demand response integration
  • Better occupant behavior during heat events

MEP design engineering should specify compatible controls for both residential and commercial systems.


HVAC System Zoning

One-size-fits-all doesn’t work anymore. Zoning divides buildings into sections with independent controls.

  • Saves energy
  • Improves comfort
  • Reduces stress on equipment

Zoning is critical in:

  • Multi-family housing
  • Large custom homes
  • Schools and government buildings

Customized MEP solutions for building design include flexible systems that adapt room by room.


Commissioning and Testing

Post-installation commissioning ensures systems perform under real conditions.

What to test:

  • Runtime at peak conditions
  • Thermostat response and accuracy
  • Humidity removal capability
  • Outdoor unit airflow and coil temps

Re-commissioning existing systems is key for retrofit projects in older buildings.


Retrofits for Existing Buildings

Not every building will get a new HVAC system. Engineers must help owners retrofit.

Options:

  • Add split units to overloaded areas
  • Seal ducts and upgrade insulation
  • Replace aging thermostats with programmable models
  • Add shading to south/west walls and windows

Retrofit strategies help preserve equipment and maintain tenant comfort without major overhauls.


Code Impacts and Permitting Considerations

Heat dome conditions have prompted local updates to building codes.

Check:

  • IECC updates on mechanical efficiency
  • Local mandates for insulation and envelope improvements
  • Load calculation methods used for permits
  • Grid-interactive HVAC incentives (like in Austin Energy’s Smart Thermostat Program)

MEP engineering companies help clients stay compliant while future-proofing designs.


Final Thoughts

Heat Dome Havoc: Rethinking HVAC Capacity in Texas and the Southwest is no longer optional. It’s a must.

Old design assumptions can no longer withstand today’s extreme conditions. HVAC systems must run smarter, cooler, and longer. Electrical panels must carry more load. Ducts must insulate against desert heat. Controls must adapt in real time.

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