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ASHRAE refutes office AC temperature ‘bias’ claims research

Revered US HVAC technical association ASHRAE has contested claims that office working temperatures are based on outdated standards that don’t take female staff into account.

The claim, by researchers from Maastricht University in the Netherlands, found that women prefer warmer working temperatures of 25 deg C (77 deg F) compared with 22 deg C (72 deg F) for men.

It bases its assertion on previous research from the 1960s, which used a standard ‘metabolic rate’ to work out a comfortable working temperature – the rate the speed at which bodies burn energy, and an indicator of how much heat is generated.

The Dutch scientists focused their research on 16 young women performing light office work, and found they required considerably less cooling than current air conditioning guidelines suggest – women have a metabolic rate that is typically 35 per cent lower than men.

Writing in the journal Nature Climate Change, Dr Boris Kingma and Professor Wouter van Marken Lichtenbelt said: “Thermal comfort models need to adjust the current metabolic standard by including the actual values for females.”

The research stated that the series of factors that make up the determination of ASHRAE’s Standard 55 Thermal Environmental Conditions for Human Occupancy included one assumption – male and female metabolic rates, and thus their bodies’ response to temperature changes – and was therefore out of date.

ASHRAE subsequently responded to the ensuing media excitement over thermal comfort in a statement, refuting the criticism of its Standard 55.

ASHRAE said: “Keeping building occupants comfortable while minimising energy use is a balancing act for engineers who design HVAC&R systems and buildings. One way they can achieve this balance is through requirements in a standard from an international technical association.

“ASHRAE’s Standard 55, specifies the combinations of indoor thermal environmental factors and personal factors that will produce thermal environmental conditions acceptable to a majority of the occupants within the space. Earlier this week, research that looks at the method used to determine thermal comfort in Standard 55 was published via an article, Energy Consumption in Buildings and Female Thermal Demand in Nature Climate Change.”

ASHRAE President David Underwood notes that the standard has been continually refined and updated since it was first published in 1966, reflecting changes in the industry and new research as it becomes available.  Standard 55 is based on an earlier document developed in 1938 by two predecessor societies of ASHRAE, titled Code for Minimum Requirements for Comfort Air Conditioning.

Mr Underwood said: “The standard continues to focus on defining the range of indoor thermal environmental conditions acceptable to a majority of occupants, while also accommodating an ever-increasing variety of design solutions intended to provide comfort and to respect today’s imperative for sustainable buildings.” 

ASHRAE has also brought in its heavyweight scientists to defend its workings: Bjarne Olesen PhD, a member of the ASHRAE Board of Directors, former chair of the Standard 55 committee and described by the body as “internationally renowned thermal comfort researcher” said: “The interpretation of the authors regarding the basis for Standard 55 is not correct – the part of the standard they are referring to is the use of the PMV/PPD index.

“This method is taken from an ISO standard 7730, which has existed since 1982. The basic research for establishing comfort criteria for the indoor environment was made with more than 1,000 subjects with equal amount of women and men.”

Dr Olesen pointed out that this study would not be affected by differences in metabolic rates, as the Dutch researchers claim: “In the main studies, where they did the same sedentary work and wore the same type of clothing, there were no differences between the preferred temperature for men and women. So the researchers’ finding of a lower metabolic rate for females will not influence the recommended temperatures in the existing standards.”

Dr Olesen contends the Dutch study is not comparative and therefore cannot be conclusive. “They only studied 16 females at a sedentary activity. They should also have studied 16 men at the same activity to be able to compare.”

Dr Olesen concluded that it is all down to clothing choice: “The reason why we, in some field studies, find that women prefer higher room temperatures than men is attributed to the level of clothing. Women adapt better their clothing to summer conditions, while men are still wearing a suit and tie.

“So if the thermostat is set to satisfy the men, the women will complain about being too cold. In the standard, this adaption of clothing to summer is taken into account, so if the standard is followed the women would be satisfied; but maybe not the men.”

Dr Olesen also noted that the Dutch researchers should have consulted other studies and technical guidance: “They should also have looked at the ASHRAE Handbook, Fundamentals, which explains the background for the standard and addresses differences between men and women, young and elderly with literature references,” he said.

Despite this, the Dutch scientists have now called for standard settings to be altered to take gender differences into account, adding that metabolic rate also lowers with age, meaning older employees could equally be feeling the chill.

“Therefore current indoor climate standards may intrinsically misrepresent thermal demand of the female and senior populations,” the scientists said.

research

Revered US HVAC technical association ASHRAE has contested claims that office working temperatures are based on outdated standards that don’t take female staff into account.

The claim, by researchers from Maastricht University in the Netherlands, found that women prefer warmer working temperatures of 25 deg C (77 deg F) compared with 22 deg C (72 deg F) for men.

It bases its assertion on previous research from the 1960s, which used a standard ‘metabolic rate’ to work out a comfortable working temperature – the rate the speed at which bodies burn energy, and an indicator of how much heat is generated.

The Dutch scientists focused their research on 16 young women performing light office work, and found they required considerably less cooling than current air conditioning guidelines suggest – women have a metabolic rate that is typically 35 per cent lower than men.

Writing in the journal Nature Climate Change, Dr Boris Kingma and Professor Wouter van Marken Lichtenbelt said: “Thermal comfort models need to adjust the current metabolic standard by including the actual values for females.”

The research stated that the series of factors that make up the determination of ASHRAE’s Standard 55 Thermal Environmental Conditions for Human Occupancy included one assumption – male and female metabolic rates, and thus their bodies’ response to temperature changes – and was therefore out of date.

ASHRAE subsequently responded to the ensuing media excitement over thermal comfort in a statement, refuting the criticism of its Standard 55.

ASHRAE said: “Keeping building occupants comfortable while minimising energy use is a balancing act for engineers who design HVAC&R systems and buildings. One way they can achieve this balance is through requirements in a standard from an international technical association.

“ASHRAE’s Standard 55, specifies the combinations of indoor thermal environmental factors and personal factors that will produce thermal environmental conditions acceptable to a majority of the occupants within the space. Earlier this week, research that looks at the method used to determine thermal comfort in Standard 55 was published via an article, Energy Consumption in Buildings and Female Thermal Demand in Nature Climate Change.”

ASHRAE President David Underwood notes that the standard has been continually refined and updated since it was first published in 1966, reflecting changes in the industry and new research as it becomes available.

Standard 55 is based on an earlier document developed in 1938 by two predecessor societies of ASHRAE, titled Code for Minimum Requirements for Comfort Air Conditioning.

Mr Underwood said: “The standard continues to focus on defining the range of indoor thermal environmental conditions acceptable to a majority of occupants, while also accommodating an ever-increasing variety of design solutions intended to provide comfort and to respect today’s imperative for sustainable buildings.” 

ASHRAE has also brought in its heavyweight scientists to defend its workings: Bjarne Olesen PhD, a member of the ASHRAE Board of Directors, former chair of the Standard 55 committee and described by the body as “internationally renowned thermal comfort researcher” said: “The interpretation of the authors regarding the basis for Standard 55 is not correct – the part of the standard they are referring to is the use of the PMV/PPD index.

“This method is taken from an ISO standard 7730, which has existed since 1982. The basic research for establishing comfort criteria for the indoor environment was made with more than 1,000 subjects with equal amount of women and men.”

Dr Olesen pointed out that this study would not be affected by differences in metabolic rates, as the Dutch researchers claim: “In the main studies, where they did the same sedentary work and wore the same type of clothing, there were no differences between the preferred temperature for men and women. So the researchers’ finding of a lower metabolic rate for females will not influence the recommended temperatures in the existing standards.”

Dr Olesen contends the Dutch study is not comparative and therefore cannot be conclusive. “They only studied 16 females at a sedentary activity. They should also have studied 16 men at the same activity to be able to compare.”

Dr Olesen concluded that it is all down to clothing choice: “The reason why we, in some field studies, find that women prefer higher room temperatures than men is attributed to the level of clothing. Women adapt better their clothing to summer conditions, while men are still wearing a suit and tie.

“So if the thermostat is set to satisfy the men, the women will complain about being too cold. In the standard, this adaption of clothing to summer is taken into account, so if the standard is followed the women would be satisfied; but maybe not the men.”

Dr Olesen also noted that the Dutch researchers should have consulted other studies and technical guidance: “They should also have looked at the ASHRAE Handbook, Fundamentals, which explains the background for the standard and addresses differences between men and women, young and elderly with literature references,” he said.

Despite this, the Dutch scientists have now called for standard settings to be altered to take gender differences into account, adding that metabolic rate also lowers with age, meaning older employees could equally be feeling the chill.

“Therefore current indoor climate standards may intrinsically misrepresent thermal demand of the female and senior populations,” the scientists said.

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