Temp conforto (ASHRAE ≈)
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
About this calculator
The comfort temperature calculator estimates ideal indoor temperature based on external temperature (Text) using the simplified formula T = 17.8 + 0.31·Text. This approximation is inspired by ASHRAE standards for climate-controlled environments. It works best under typical humidity and ventilation conditions but does not replace technical calculations.
Use this tool to quickly estimate comfort temperature for HVAC design, such as sizing air conditioning or heating systems. For example: if the external temperature is 30 °C, the calculator suggests 27.1 °C as a theoretical comfort value. It is useful for initial discussions but not for critical projects requiring calculations with additional factors (solar radiation, thermal insulation, etc.).
Cautions: The model does not consider relative humidity, wind speed, or direct solar radiation. In poorly ventilated or humid environments, the result may underestimate actual comfort temperature. For professional projects, complement with specialized thermal engineering software.
Frequently asked questions
What is the scientific basis for the formula T = 17.8 + 0.31·Text?
This formula is a practical approximation derived from ASHRAE studies correlating external temperature with indoor comfort in standard ventilation conditions. It's not an official equation but a simplified guideline.
Can I use this calculator for extremely hot or cold climates?
The formula is more reliable in temperate climates. In regions with extreme temperatures, adjust results considering the building's thermal insulation and climate control systems.
Why does the calculated temperature seem low in cold days?
The equation assumes heating systems compensate for heat loss. On very cold days, the theoretical value may underestimate real comfort due to factors like solar radiation or clothing use.
How to validate results in real projects?
Use thermal simulation software (like EnergyPlus or IESVE) that analyze multiple factors: humidity, ventilation, solar orientation, and climate equipment efficiency.