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 But that data is outdated.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.