The Intricacies Behind Thermal Comfort

When you think about thermal comfort, what comes to mind? Insulation? Heating and cooling systems? The thermostat? Of course, these are all critical components to interior spaces that are conducive to happy, productive occupants. However, to truly master the science of thermal comfort, a more in-depth investigation can be beneficial.

While radiation, air speed, and humidity might be the most studied aspects of thermal performance, let’s shift our perspective to that of the end user. Specifically, how do activity, age and clothing affect comfort in interior environments?

Believe it or not, studies by ASHRAE indicate that clothing has very little impact on comfort. To reach this conclusion, ASHRAE used a unit of measure, clo, to determine the insulating capacity of clothing. Clo is based on the amount of insulation that allows a person at rest to maintain thermal equilibrium in an environment at 70 degrees Fahrenheit in a normally ventilated room. The difference in clo, which equates to 0.88 r-value, between summer and winter fashion selections is roughly 1.5 clos — a miniscule factor in terms of comfort.

However, when you consider the age of occupants it’s a different story. A 25-year-old employee bouncing off the walls and drinking a Red Bull experiences comfort much differently than a 50-year old manager who sits at a desk 8-plus hours a day.

Why? The rate of metabolism, which is influenced by age among other things, can create an awful lot of heat.  Since heat production varies from person to person, individual actions are taken to reach equilibrium that impact the entire space, such as opening a window, allowing more sunlight into the area or adjusting the thermostat.

The lesson here is that architectural professionals and building owners should be mindful of age in their designs to ensure long-lasting comfort for building occupants. For those of you that want to take a deep dive into the nuances of thermal comfort, check out ASHRAE 55-2013.

The Greening of the 2012 Building Codes: Air-tightness Testing – A Must Have for Consumers


Blower Door Testing

Blower Door Testing

The 2012 energy code, which we are very excited about because it is very advanced compared to the 2009, requires two things which have never been required by aU.S. code before.  These are:

  • Blower door testing of houses
  • Duct pressure testing for leakage

These two things are extremely influential on energy efficiency and have always been assumed were part of best practices. We have seen changes in the codes saying “install air barriers or tighten up your duct work” but they never required that these tests be conducted to ensure that the house is airtight.

These are two physical tests that need to be conducted on every new home if the 2012 building codes have been adopted by a state. While this is one of the best ways to ensure efficient thermal comfort for home owners, the potential impact on the builder must be understood. If you are building a house in say 120 days scheduling someone to come out to conduct this testing could severely impact the building schedule: these tests need to be conducted before installing the drywall. No drywall until you have passed the inspection- imagine it.

But who conducts this testing?  Code officials are not typically trained or funded to execute this type of testing.  This testing has been done in the past for NAHB, Energy Star and other programs by internally or externally certified raters. Home Energy Rating System (HERS) raters are a great example of one group that is trained to do this testing.

However, there is no organized resource, clearinghouse or national database for building professionals to find all of the various local professionals who can conduct these tests. To ensure that these tests are conducted and that states do not “opt out” of this requirement, a national database needs be developed so that third-party testers can be easily found and scheduled.

This is an important part of the 2012 code that qualifies for the consumer that the home is energy efficient and that some of the most critical passive elements of that efficiency were done right.  It’s not what you spec; it’s what you inspect.