Thermal Comfort in Residential Buildings

Thermal Comfort is highly important in terms of people working performance at office or satisfaction living a room for their home. BS EN ISO 7730 points out the thermal comfort as '…that condition of mind which expresses satisfaction with the thermal environment.' , i.e. the situation about people's satisfaction about temperature level.  As the definition of thermal comfort present thermal range for human comfort, it is not possible to explain just with temperature satisfaction. Because, it is highly subjective calculation that contains many of attributes.

Factors of Thermal Comfort:

• Environmental factors
• Air temperature (dry bulb temperature C)
• Air velocity (measured in m/s)
• Radiant temperature
• Relative humidity (RH)
• Personal factors
• Clothing
• Metabolic heat
• Wellbeing and sicknesses

For instance, men and women are always in a conflict about temperature level in office buildings as
men desires colder environment women are on the opposite side. The Health and Safety Executive
(HSE) mentions that an environment can be accepted as a comfortable (reasonable comfort) while
approx. 80% of its occupants are satisfied in the aspect of thermally comfortable [1].

Thermal Comfort in Residential Buildings:

Thermal Comfort in residential buildings are favourably dependant outdoor climatic conditions, especially outdoor dry bulb temeprature (C). As standards defines the route for calculation of thermal comfort in the buildings, for residential problem gets more complex because both activity and living reflexes are different from other building types which could range largely according to situation. In addtion, residential buildings are considered different, i.e. buildings in which occupants can make many adaptations, including operable windows. For these reasons, it needs to be constructed specified algorithms in order to explain thermal comfort patterns in the residential buildings [2]. For office buildings activity level and occupancy are always goes same values for all parts of building on the other hand for residential buildings people perform different acitivities for different zones. Therefore, bedroom, living room and bathroom should be evaluated differently due to their own specific conditions during all year.

For each of these zones, the neutral temperatures, defined in present analysis, are based on measurements described in the literature and in that sense do consider the special case of each of the zones. But, both the neutral temperatures and the comfort bands are restricted by upper and lower limits.

Approach of Fanger:

Fanger suggested a technique in order to estimate actual thermal comfort from the perspective of humans when climate conditions can vary and parameters could not catch threshold values: the predicted mean vote (PMV).  He personally indicates as‘‘the difference between the internal heat production and the heat loss to the actual environment for a man kept at the comfort values for skin temperature and sweat production at the actual activity level”.

The sensation of thermal comfort is quantified by an adapted ASHRAE 7-point psychophysical scale with values ranging from -3, indicating cold, over 0, indicating neutral, to +3, indicating hot.  The method allows to predict what comfort vote would arise from a large group of individuals for a given set of environmental conditions for a given clothing insulation and metabolic rate. Chart shows that relation between PPD and PMV which defines the impossibility to satisfy all persons in a large group sharing a collective climate. Complaints cannot be avoided, but should be kept to the minimum [2].  The International Standard ISO 7730 indicates PMV and PPD indices to represent the thermal sensation of human who exposed to general thermal environments. The suggested temperature is the same for the different comfort classes, but the acceptable temperature range will vary as the allowed percentage of dissatisfied changes.

The resultving vurve presentation on the graphic, with a corresponding neutral thermal sensation, show a steeper slope for warmer outdoor conditions. This is due people adapting more easily to heat than they do to cold.

International Standards

As the ISO 7730[3], also the ASHRAE 55[4] is valid for healthy, adult people. The activities they perform, the clothes they wear and the thermal environment they occupy, all are determined by variable values within given limits. Besides the recommended PPD and PMV ranges, this standard increases the percentage of persons dissatisfied with 10% points, to incorporate the effect of local thermal discomfort, e.g. draft and temperature asymmetry. It also determines the values of acceptable temperature changes per given time interval. Thereby partly accounting for the dynamic effects ignored both by Fanger  and in ISO 7730.

Attention !!!

Both PMV and PPD indices are formed according to steady state laboratory conditions which subjects are prepared with standardize clothings and selected averagely metabolic rate. Various researches are conducted related this steady state conditions of two indices how they are false in order to predict thermal comfort. Therefore, it needs to be cautious about thermal comfort analysis [5-7].

References:

1. https://www.designingbuildings.co.uk/wiki/Thermal_comfort_in_buildings
2. https://www.sciencedirect.com/science/article/pii/S0306261908001785
3. https://www.iso.org/standard/39155.html
4. https://www.ashrae.org/technical-resources/bookstore/standard-55-thermal-environmental-conditions-for-human-occupancy
5. https://www.researchgate.net/publication/258291389_Thermal_comfort_Research_and_practice
6. https://www.sciencedirect.com/science/article/pii/S037877880200018X
7. https://escholarship.org/uc/item/9j03d7kq