WORKPLACE MEASUREMENTS IN A LOCAL BANK Marianna Luoma

Background The employees complained about draught in their offices (not the front desk) The house manager asked us to do draught measurements The measurements took place in February The instrument used was Swema air 300 + CO Sensor About the location of the measurement points Measurement point 6 was close to the window

Swema air 300 -instrument Can be used to measure air movements Omnidirectional probe Measures continuously Measurement duration may range from 15 seconds to 60 minutes Gives draught rate (DR%)

DR=(0,37 v Tu+3,14)(34-Ti)(v-0,05) 0.62 DR = Draft rate, % Ti = Air temperature, ºC Tu = Turbulence intensity, % V = Air velocity, m/s

*Supply air diffuser *Positioned in the ceiling *Horizontal air diffusion direction

Swema air and CO2-meter at the table

Results Average values: Air temperature 21,7 ºC Air velocity 0,1 m/s Draught rate 5 % Note! Operative temperature was not measured. It was assumed that operative temperature = air temperature

What is the optimal operative temperature for an office worker ? Clothing 1 clo Activity 1 met (sedentary person) Air velocity 0,1 m/s PMV = -0,07, when tº = 23 ºC PMV = +0,20, when tº = 24 ºC

What is the optimal operative temperature for an office worker ? Clothing 1 clo Ativity 1,2 met (standing) Air velocity 0,1 m/s PMV = -0,33, when tº = 20 ºC PMV = +0,10, when tº = 22 ºC

COMPARISON TO DRAUGHT CRITERIA: D2 and CR1752 D2: Design values for offices 21 ºC and 0.2 m/s

D2

Comparison to draught criteria: D2 The design value for indoor air temperature is 21 ºC according to the National Building Code of Finland, Part D2: Indoor Climate and Ventilation of Buildings For the draught free conditions the maximum air velocity is 0,2 m/s Based on this criteria, there was no draught

Comparison to draught criteria: CR1752 According to the EU report CR 1752 the highest draught rate in indoor class A is15%. In the local bank, the highest measured draught rate was 11 %. Based on this criteria, there was no draught.

How about the reality? Employees complained about draught There are personal differences! The mean values of the measurements do no help the person who suffers from draught! Things like what we are doing, how we are dressed and how we like the thermal conditions, affect our feeling of draught.

Thermal conditions at the workplace Operative temperature for normal office building is 21-24 ºC When the temperature is above this temperature or close to 24 ºC, our body tolerates higher air velocities compared to the situation when the temperature is closer to 21 ºC Sensibility to draught increases when the temperature is below the optimal operative temperature It is typical for Finland that indoor air temperature is close to 21 ºC which means that there is a high possibility for draught …. Besides, some employees have their tables close to the cool window

What can we do? In banks, there is a need for cooling even duringthe spring time → air flow rates and supply air temparatures have been designed based on the cooling needs → draught might occur If we decrease the air flow rates and rise the supply air temperature, the warmer indoor air may be considered stuffy The air flows could be readjusted and the diffusion directions of the supply air devices could be modified? The type of diffuser could be changed?