Hello Harry, your question about "optimal room temperature for thermal comfort" is a tricky one...

A chamber that is maintained at "perfect room temperature" was recently featured on the NBC comedy show "Community". This was funny...because optimal room temperature doesn't exist. Unless, of course, the room is only being used by one person, living in a never-changing climate, subject to never-changing physiological conditions, wearing exactly the same clothes, performing exactly the same task, for all eternity.

That sounds anything but "optimal," if you ask me.

The cop-out answer to your question is "it all depends". But, fortunately for HVAC design engineers and technicians, there are guidelines to help us determine where to set the thermostat, and what temperatures to plug into our energy models to give us realistic expectations for building energy use.

ASHRAE and Ideal Temperature for Thermal Comfort

These guidelines, published by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), are an organized compilation of knowledge gleaned from decades of tedious scientific research by some of the earliest, best, and most innovative HVAC engineers and scientists. These guidelines are called, simply, "ASHRAE Standards & Guidelines" and are essentially the bible of HVAC engineering and design.

ASHRAE 55, Thermal Environmental Conditions for Human Occupancy, is chock-full of helpful charts, guidelines, and design procedures to help you design an HVAC system that accounts for the varying climates, working conditions, humidity, and occupant densities of a building.

This guide, along with ASHRAE 90.1, Energy Standard for Buildings Except Low-Rise Residential Buildings, and the ASHRAE Handbook, will give you many of the resources you need to design an HVAC system that will make most of the people comfortable, most of the time.

But if I had to put a number on it, I'd say 72 degrees F with 50% humidity would make most people comfortable where I live.

Many thanks and good luck finding your optimal room temperature!

Related Advice:

• ASHRAE 55 and LEED: The Standard for Thermal Comfort



• LEED 2.2 EQ Credit 6.2 Controllability of Systems Thermal Comfort: What's Available?



• Indoor Environmental Quality: Quantifiable Improvements in Worker Productivity?