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.
1.
Educating tenants
on the IDEA of have more sustainable comfort expectations Providing more
control of the environment such as opening windows
2.
Providing technology
such Big Ass fans that move larger volumes of air quietly to provide convective
cooling
3.
Furniture
that facilitates heat gain or loss
4.
Encourage
the appropriate dress for the season
5.
Controls
that optimize temperature set points for time of day and variations between
inside and outside temperature
6.
Using night
time cool air to pre-cool the building mass enable temperatures to be
maintained with smaller cooling systems
7.
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.
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 systems that are needed to achieve Net 0 energy use
Murray Guy
& Dave Palibroda
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