Original data and independent reporting for the HVAC trade
The HVAC Brief: independent HVAC trade reporting and original data
Analysis & data
Newest first-
Best Temperature for Sleeping: What Sleep Studies Show, by Age and Humidity
Sleep studies put the best bedroom temperature near 66 to 70°F for adults and 68 to 77°F for people over 65. Heat costs more sleep than cool air, humidity near…
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Sick Building Syndrome: Symptoms, Causes, Ventilation Evidence and How to Fix It
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Corsi-Rosenthal Box: Measured CADR, Safety Tests and a Step-by-Step Build
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Cool Mist vs Warm Mist Humidifier: Burns, White Dust, Germs and Watts Compared
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AC Cage: Theft Data, Maker Clearances and the Code Rules a Cage Must Meet
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Mercury Thermostat: How to Spot One, State Disposal Laws and Where to Recycle It
Industry news
From the trade-
Heat-Related Deaths in the US (2026): Counts by Year and the Air Conditioning Link
US deaths with heat on the death certificate hit 2,394 in 2024 and 2,114 in 2026 through October 17. Medical examiner reports show most indoor victims had AC that was…
- Still allowed
R-410A equipment built before 2025 can still be installed
EPA’s final rule removed the installation cutoff for inventory manufactured or imported before January 1, 2025. New R-410A equipment cannot be built or imported. Several states are stricter. Full rule detail
- Expired
The federal 25C heat pump tax credit is gone
The credit, worth up to $2,000, applied to property placed in service before December 31, 2025. Installation date controls, not purchase date. State and utility rebates are unaffected. What this costs you
- Still rising
Equipment prices set another high in August
Producer prices for HVAC equipment are up 60% since 2019 against 31% for consumer prices. August 2026 is the highest reading in the series. See the index
Refrigerants
All refrigerants-
R22 Replacement Refrigerants Compared: Maker Data, Oil Rules and No Drop-In
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R290 Refrigerant: Where Propane Is Legal, Charge Limits, Pressures and Safety
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Nitrogen Pressure Test: PSI by Manufacturer, Hold Times and Temperature Correction
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Refrigerant Oil: POE vs Mineral, PVE, What R-410A Uses and When You Can Mix
Equipment
All equipment-
Marine Air Conditioner: How Boat AC Works, Sizing Math, Seawater Flow and Power
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Spot Cooler: How It Works, Where the Heat Goes, Sizing and the DOE Gap
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Chimney Liner Rules: When Code Requires One, Which Type and How It Is Sized
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Combustion Air: The IRC and IFGC Rules, Opening Sizes and a Worked Example
Codes & Standards
All codes & standards-
Fume Hood: Face Velocity, ASHRAE 110 Tests, Hood Types and Energy Use
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Gas Bans by State in 2026: Which Laws Are Live, Paused, Preempted or Struck Down
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Landlord Air Conditioning Laws by State and City: Maximum Indoor Temperatures
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Landlord Heat Requirements by City and State: Minimum Temperatures and Dates
Business
All business
Homeowners
All homeowners-
Oil Filled Radiator: How It Works, What It Costs to Run and Its Safety Record
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Hygrometer: How Accurate Yours Is and How to Check It With the Salt Test
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Office Temperature: What OSHA, ASHRAE and the Productivity Studies Actually Say
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Fireplace Insert Guide: Wood, Pellet, Gas and Electric Compared on Federal Data