Meeting/Event Information

Thomas S. Weaver, P.E.

President & CEO of Conservation Mechanical Systems Inc.

Thomas Weaver graduated in 1983 from California Polytechnic University San Luis Obispo with a B.S. in Mechanical Engineering and is a Registered Professional Engineer in California.

He began his engineering career as a field engineer on a 130 MW geothermal power plant in Northern California where he was involved in all aspects of the power plant’s mechanical systems. Tom went on to become a project manager for many large construction projects in San Francisco, supporting the HVAC systems’ installation while working for a mechanical subcontractor.

Tom became president of Conservation Mechanical Systems with Mike Scofield in 2008. He is an active member and past president of the Golden Gate ASHRAE chapter as well as a past president of the Redwood Empire Section.

As we move into the winter Flu Season, it is best to understand what facilitates the spread of airborne infectious microorganisms in the built environment. As it turns out, we catch cold in the winter not because it is “cold” in winter but because it is “dry” in winter. When we bring in dry outdoor air to ventilate our schools and office buildings, the indoor relative humidity (RH) drops. Recent research has shown that, when  room RH drops below 40 %, the droplet nuclei containing the pathogen stays buoyant and viable in the human breathing zone for a longer period. Also, artificially high room air change rates and air turbulence in the breathing zone spreads the airborne virus further from the host to susceptible humans within the room.

Overhead delivery Variable Air Volume (VAV) supply air systems remain the most popular HVAC cooling design for schools and office buildings in California. The use of a Heat Recovery Economizer (HRE) and an adiabatic Direct Evaporative Cooler/Humidifier (DEC/H), during the dry California winter condition, will offer a  remedy. This all outdoor air design offers the building owner significant cooling and heating energy savings while furnishing all outdoor air for better Indoor Air Quality (IAQ).

This presentation is based on an ASHRAE Journal , May 2016, article entitled “Variable Air Volume System Heat Recovery Economizer”.