I am struggling to make spaces with a low metabolic rate (1.2 or below) comply with ASHRAE 55 at the current temperature setpoints (75 summer, 70 winter - air speed is 40 FPM and RH is 55%).
I can't change the metabolic rate as the type of space determines this value. This leaves me with only the temperature setpoint and the CLO level in order to achieve the requires 9% PPD or below for each space.
Is it better to adjust the operating temperature and prove that the designed system is capable of adjusting up or down to the new setpoint or to use ASHRAE 55 to determine a new CLO level consisting of reasonable garments for the space type and season (no heavy jackets to meet comfort in summer, no shorts and t-shirts in the winter, and so on)? Could a mix of both be used with the inclusion of a narrative with a justification for the non-ASHRAE default CLO level and new operative temperature?
Melissa Kelly
Sustainability SpecialistGensler
85 thumbs up
June 24, 2015 - 11:11 am
Hi Adam,
If the occupants of your building are likely to change their clothes seasonally, you should definitely change the CLO value between the summer and winter design calculations to make sure that the PPD is accurate. This is standard practice, so justification of a non-default CLO value is only needed if for some reason the occupants have a highly unusual dress code. If the CLO values are made to be accurate and the PPD is still too high, then the temperature set point should be adjusted until it's compliant.