Project Title:

CBE Thermal Comfort Tool

Creating a free online tool for evaluating comfort according to ASHRAE Standard-55.

Status (updated 6/21/2012): Ongoing

Funding sources: CBE Industry Consortium


Project Objective

Develop a web-based graphical user interface for thermal comfort prediction according to ASHRAE Standard-55. Include models for conventional building systems (predicted mean vote) and also for comfort using the adaptive comfort model, and with increased air speeds (for example, when using fans for cooling). Provide ongoing upgrades and new features, such as visualization of comfort boundaries within the psychrometric and temperature-humidity charts, and automatic generation of LEED documentation for thermal comfort credits.

Significance to Industry

In the design and operation of buildings and mechanical systems, an advanced understanding of human comfort presents opportunities to save energy and increase thermal comfort. The standard convention of attempting to maintain a narrow temperature band can be an energy-intensive practice. Instead, using CBEs comfort prediction tools with ASHRAE Standard-55 as a guide, designers may find that a wider temperature band will provide adequate comfort and save a significant amount of energy. In other cases, the tool can be used to assess the comfort of low-energy designs.

A building that has provisions for air-movement (such as ceiling fans or desk fans) can use the predicted mean vote (PMV) model with elevated airspeed. In a naturally ventilated building, the adaptive comfort model can be used. This tool provides options for both of these system choices, verifying compliance with ASHRAE Standard 55-2010.

In LEED v2009, two points can be earned for thermal comfort: one in design (EQc7.1) and one in verification (EQc7.2). In LEED v4, one point can be earned for both new construction (EQc5) and existing buildings (EQc3). LEED v2009 refers to ASHRAE Standard 55-2004, while the new version (LEED v4) refers to the ASHRAE Standard 55-2010. Our tool is able to automatically generate the needed documents for obtaining these points.

Research Approach

We have identified a number of features that will be important for practitioners, and will phase them in as we develop and improve the tool. We will include the ability to plot how the comfort area changes in the psychrometric chart when clothing, metabolic activity, air velocity or mean radiant temperature are varied within a given range.

Future enhancements to the tool include the ability to visually compare two or three thermal comfort scenarios. We plan to allow users to upload a weather file in EnergyPlus format (.epw) or comma-separated values (CSV) format to calculate the running average temperature for the adaptive comfort model. We will also enable the CSV import/export of the results.

The tool will be continuously updated based on any approved changes to ASHRAE 55 Standard 55-2013.

Video Tutorials

Overview of the tool's main features

Using the adaptive method features

Using the tool for LEED documentation

Local (indivdual body part) discomfort assessment

Publications

Hoyt, T., K.H. Lee, H. Zhang, E. Arens, and T. Webster. Energy savings from extended air temperature setpoints and reductions in room air mixing. Proceedings, International Conference on Environmental Ergonomics, 2009.

Schiavon, S., and A.K. Melikov. Energy saving and improved comfort by increased air movement. Energy Build, 2008.

The tool may be used to predict comfort in naturally ventilated spaces.

Comfort with enhanced ventilation, such as a fans, may also be predicted with this tool.