Thermal Comfort Standard ASHARE 55

-
Evaluation of indoor thermal environment has gained significant importance from the last three-four decades due to the high expectations of occupants towards thermal comfort. International Comfort Standards such as ASHRAE Standard 55, ISO 7730 and EN 15251 are commonly being used for evaluating indoor environment conditions irrespective of climatic conditions. Methods and guidelines are proposed by these international Standards for making the thermal environment more comfortable.

ASHRAE Standard 55 - Thermal Environmental Conditions for Human Occupancy defines that thermal comfort is that condition of mind which expresses satisfaction with the thermal environment and it is assessed by subjective evaluation. From literature, it is revealed that first thermal comfort Standard was introduced in 1966 followed by revisions produced in 1981, 1992 and 2004. ASHRAE Standard 55 2010 is being used currently for defining indoor environmental conditions for all types of buildings. This Standard has defined thermal comfort on the basis of heat balance model (Predicted Mean Vote- PMV and Percentage Predicted Dissatisfied- PPD) that is laboratory based and also on adaptive thermal comfort approach which is based on field study of thermal comfort.

ASHRAE Standard 55-2010 considers the effect of adaptation on thermal comfort and illustrates that increased airspeed improves comfort. Stephen in 2011 described that new version of Comfort Standard, i.e. ASHRAE 2010 includes extended provisions for evaluating the impact of elated air speed on comfort. Excessive airspeed (>0.8 m/s) needs, provision of individual/local control for improving comfort during higher temperature conditions in naturally conditioned spaces. Figure presented below shows the comfortable temperatures for variable air velocities i.e., with and without local control of air speed for different clothing insulation at an activity of 1.1 met. 
Acceptable range of temperature and air speed for comfort zone, Source: ASHRAE 55-2010

This Standard shows that comfort temperature can be increased up to a maximum of 4.4 oC as by varying the air speed maximum up to 1.6 m/s. Increase in room air velocity results improvement in acceptable temperature; however, this standard does not address the precise relationship between increasing in air velocity and magnitude of improvement in comfort temperature. Therefore, it is difficult to create an environment which provides satisfactory thermal conditions to all the occupants, since occupants have variability in exposure of climate, experience and expectations.

Comments

Post a Comment

Popular posts from this blog

What is adaptive thermal comfort ?

-
Image
Overview Field studies of thermal comfort have been conducted intensively at various climatic locations to define the range of acceptable thermal environment for air-conditioned and naturally conditioned buildings that led to the development of Adaptive Thermal Comfort (ATC) model.  Research on adaptive thermal comfort revealed a higher range of acceptable temperatures, which depend on climate, building type, behavioral controls, and other similar factors. Field studies have also revealed the role of thermal adaptation to conserve energy in air-conditioned buildings, and this concept is also useful for building design, and operation of naturally conditioned buildings as per the outdoor conditions.  Higher bandwidth of comfort temperature and energy conservation opportunities encouraged researchers to carry out intensive field studies of thermal comfort to propose robust adaptive thermal comfort model. Definition Adaptive principle states that if a change occur...
Read more

ISO 7730 for Thermal Environment Evaluation

-
ISO 7730 is an International Standard for 'Ergonomics of the Thermal Environment-Analytical Determination and Interpretation of Thermal Comfort Using Calculation of the PMV and PPD and Local Thermal Comfort Criteria’.  ISO 7730 illustrates methods to evaluate the general thermal sensation and the degree of discomfort for occupants exposed to moderate thermal environmental conditions. This Standard grouped the thermal environment into three different categories namely  Category-A,  Category-B and  Category-C  All there  categories  are described with the help of Table given below.  Category-A describes narrow comfort conditions, whereas Category-C prescribes wider comfort bandwidth (-0.7 < PMV < +0.7). The Standard describes the calculation of PMV and PPD indices for thermal comfort and for local discomfort. The Standard also defines the local clothing habits for indoor comfort and but does not provide information for cl...
Read more

EN 15251 for Energy and Thermal Environment Evaluation

-
Comfort standard EN 15251 (version released in 2007) is entitled to ‘Indoor environmental input parameters for design and assessment of energy performance of buildings–addressing indoor air quality, thermal environment, lighting and acoustics.’  The Standard EN 15251 deals with energy performance of buildings as well as indoor environment quality such as thermal environment, indoor air quality, acoustic comfort, and visual comfort conditions to provide more comfortable indoor climate and that is also energy efficient.  Previous research  (Nicol & Wilson conducted study in 2010)   has examined that EN15251 Standard helps building designers to optimise the building energy consumption, considering thermal, air quality, acoustic and visual comfort. Furthermore, studies carried out under SCATs (Smart Controls and Thermal Comfort) research project reveal that this Standard involve  only   European countries for energy and comfort evaluation. SCAT s...
Read more