Be COOL with Realistic Comfort Expectations!
Back in the olden days people would dress for the weather, put another log on the fire or head to the beach to deal with extreme weather variations. Today we adjust a thermostat and expect immediate response and thermal gratification; independent of the capital, energy cost and GHG emissions that are required to support our high expectations for thermal comfort.
We are not talking about this type of EXTREME
In North America we have the luxury of being able to live and work in indoor environments that are conditioned to 22.5ºC +/- a couple of degrees. There are significant capital and operating costs associated with financing our addiction to cooling especially with our extreme Canadian climate, which in some regions our building systems need to handle variations in outdoor temperature from -40 to +40ºC.
For the next generation of buildings, just maybe we need to start lowering expectations, challenge the status quo and develop smarter more sustainable ways to achieve creature comfort and productivity. At the Mosaic Center for Conscious Community and Commerce they are utilizing alternate systems and strategies for optimizing comfort, capital and performance as they build a unique economically viable highly sustainable Living Building Challenge/LEED Platinum facility that will help set a new standard for the commercial real estate market.
“Sustainable Expectations” for comfort is one of the norms that is being tested as it has a huge impact on the size of the cooling and renewable energy systems that that are really only needed for 20 days of the year when temperatures are greater than 25ºC. So what are the acceptable limits for thermal comfort that take into account comfort & productivity, capital and energy saving?
To determine the acceptable indoor temperature ranges, Dennis Cuku President of OCE and his staff initiated a Responsible Adults Temperature Study (RATS) utilizing his staff of 25+ engineers as the sample population. This short study was conducted during the summer months. For the test period, employees were provided with red (hot) and blue (cold) buttons on their computers and asked to indicate when they felt uncomfortable.
For the males of which most were young and fit professional engineers they were hitting the hot button at lower than expected ranges of approximately 23 ºC were comfortable down to 16 to 17 ºC. In talking with Andrea who was monitoring the study, this relatively low range was contributed to the formal dress code where most engineers would wear collared shirts and long pants as well as having higher muscle mass than the females in the office. The range for the females was about the same but 7 ºC but at a considerably higher temperature from 27 to 20 ºC. This was attributed to the flexibility to be able to dress for the weather including shorts, skirts and open sleeves for warmer days.
The conclusion from the RATS experiment was that staff working in an office environment would likely not experience productivity decline or level of comfort satisfaction for temperature ranges of approximately 20 to 26ºC if the men were to adopt a more casual dress code. This has now been implemented at OCE.
To determine the cooling operating cost saving associated with allowing higher fluctuations in temperature, we refer to a study that IDI completed with Innovation Place Research Park for the 15,000 m2 Atrium building located in Saskatoon, Saskatchewan which has a climate very similar to Edmonton where the MC4 facility will be located. The energy model showed that by increasing the cooling temperature setpoint by 1ºC this resulted in a reduction of just over 4% in annual cooling energy or 126,000 MJ annually per ºC increase in cooling setpoint or $1000/yr./ºC in cooling costs. This small change in the temperature setpoint would result in energy saving equivalent to the power required for 4 homes or in taking 1.5 cars off the road or CO2 reductions equivalent to planting 184 trees. This same approach applies for heating and would result in approximately the same amount of cost saving of $1000/yr./ºC.
With regards to comfort and occupant health, higher cooling temperature set points could in fact have a positive affect on comfort when people are dressed in COOL summer attire. According to Occupational Health and Safety this change is beneficial for heath as there are guidelines for maintaining a lower temperature difference between indoor and outdoor temperatures.
This type of thinking is supported by a comprehensive study on Air Conditioning Comfort: Behavioral and Cultural Issues. (Amory Lovins, Rocky Mountain Institute) In this strategic issues paper RMI concluded that “Existing comfort standards are more stringent than can be physiologically or economically justified” and that “Understanding why people use air conditioning is central to the challenge of providing comfort with minimal energy use and economic cost”.
RMI also concluded that comfort engineering fails to take into account acclimation, dependence and psychological differences and how people react when given control over their environment. The “comfort range” equation as defined by ASHRAE Guideline 55 is 2.5 to 5.5ºC and can be as large as 9ºC for the average individual and individual variations can add +/- 7ºC to that range.
The RMI study suggests that there are ten degrees of freedom in achieving comfort in addition to the one that designers use almost exclusively dry bulb temperature, namely variations between individuals, variation over time, allowable excursions outside the comfort envelope, dynamic rather than static comfort conditions, metabolic rate, clothing, furniture, radiant temperature, air movement and humidity. Together these alternatives can offer 10% to 30% in energy savings without violating comfort conditions.
By developing design concepts and operating strategies around these degrees of freedom we can start to develop alternative ways to keep people comfortable utilizing much less energy.
Educating tenants on the IDEA of have more sustainable comfort expectations Providing more control of the environment such as opening windows
Providing technology such Big Ass fans that move larger volumes of air quietly to provide convective cooling
Furniture that facilitates heat gain or loss
Encourage the appropriate dress for the season
Controls that optimize temperature set points for time of day and variations between inside and outside temperature
Using night time cool air to pre-cool the building mass enable temperatures to be maintained with smaller cooling systems
Utilizing radiant cooling systems that have the inherent capability to keep people comfortable with higher variations in temperature.
Regulating agencies and policy makers need to get onboard with alternative strategies that make the best use of resources. From a cultural perspective the Japanese think that it is wasteful to heat and cool rooms that are not occupied. Why not go even further and consider task cooling just like we do for lighting as why do we need to condition the whole room? Since 2005 the Japanese Ministry of Environment has been advocating for warmer temperature settings and a relaxed dress code during the summer months. In 2007 the ministry estimated the CoolBiz campaign reduced Japanese CO2 emissions by 1.4 million tons.
As we prepare for the commissioning phase of the MC4 project it is important to understand the project requirements for comfort as there are many ways to achieve the optimum balance between comfort, expectations, smart design and the size of the renewable energy system that will be needed to achieve Net 0 energy use in our extreme weather conditions.
Murray Guy & Dave Palibroda