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A methodology for the comprehensive evaluation of the Indoor Climate based on the human body response--part 1: environment and man--theoretical principles.


To create the desired indoor environment that serves the building's purpose is the main aim of every architectural structure. But it is not successful in all cases. Thus, an evaluation of the indoor microclimate at the project stage should be conducted, which can also be the basis for the design of the "intelligent building" system.

But, additionally, this study can be useful in solving the problems of the so-called sick building syndrome (SBS), which usually manifests itself with headaches and symptoms associated with colds of occupants of modern buildings. Therefore, according to medical opinion, SBS should be called, more precisely, building related illness (BRI). SBS, or BRI, could be the reason for the interruption of work on buildings even of the highest architectural value.

SBS is typical for modern buildings; in older buildings, it is a rare occurrence. According to a survey conducted by a German trade union for banks and insurance (HBV) (Weber 1995), almost one-third (27.1%) of employees complained about the hygrothermal microclimate, 13.5% about noise, 10.6% about illumination, 10.2% about tobacco smoke, and 9.9% about the lack of space. It is the environment (with 71.3% of workers' complaints) that dominates discomfort in the workplace. They do not complain as much about overtime (8.9%), their supervisors (4.0%), or their colleagues (2.9%) (Figure 1).


The HBV survey was confirmed by INFRATEST_INQUIRY, published by the Association of Ecological Research Institutes (Weber 1995), from which it is additionally evident that the majority of complaints arise in air-conditioned spaces (Figure 2). Most often they complain of being cold (19%), muscular membrane irritation (16.5%), overall irritability (12.8%), headaches (11.6%), fatigue (11.4%), rheumatism (9%), lack of concentration (8.3%), and dazed state (4.2%). There was a noted remarkable decrease in complaints in spaces without air conditioning.


From NASA research (Rohles 1971; Jokl 1989) it is evident that optimal environment--without SBS--is achieved when all its components are at an optimal level, i.e., hygrothermal, odor, toxic, aerosol, microbial, ionising, electrostatic, electromagnetic, electronic, acoustic, and psychical (Figure 3). Rohles (1971) introduced for them the term constituents, e.g., odor microclimate can be called the odor constituent.


Therefore, it is advantageous to conduct an evaluation of the microclimate, and the possible level of all its individual components, as part of every architectural project. The following also influence the quality of the indoor environment: odor, toxic, aerosol, microbial, and electronic components.

In office and residential buildings, the dominant and decisive constituents are hygrothermal, odor, and acoustic (Figures 1 and 2). They affect both man's psychology, impacting his mental activities, and man's physiology.


The impact of the environment on man's psychology is described by the Weber-Fechner law (WFL). The WFL states that the intensity of the perception of brightness, warmth, pressure, etc., is directly proportional to the logarithm of the intensity of the stimulus, expressed as a multiple of the smallest perceived (threshold) stimulus, i.e., human body response R is proportional (k = coefficient of proportionality) to the logarithm of the stimulus S.

R = k * logS (1)

Response R depends on the stress theory by Selye (1974): the response to each constituent is caused by one type of stress of the human body, and only by agencies or complex of agencies of this type of stress. It is the physical criterion of the interaction between man's psychology and his environment; k depends on the threshold value and limit of stimulus, and S depends on the environmental differential equation (EDE) (only agents resulting in flows affecting the human organism can be taken into account) (Jokl 1989). It is the physical criterion of interaction between man's physiology and his environment.

At the threshold of this millennium, the exponential function was accepted as reflecting most phenomena (von Baeyer 2000). Its course rises from low values that show an almost horizontal trend and then change into an almost vertical rise, therefore perfectly representing, for example, population explosions, the spread of the AIDS virus, and similar phenomena. The reciprocal of the exponential curve describes radioactive decay and also the fading peal church bells.

However, it is evident that there are disciplines--cosmology, embryology, information science, and others, all of which will be of great significance in the coming decades--that are poorly described by the exponential function. However, there is another, similar function that can help--the natural logarithm. Mathematically, the natural logarithm is the functional inverse of the exponential, as its graph makes clear: the logarithm is the mirror image, reflected across a diagonal, of the exponential. The logarithm cannot only help us find our place in the universe, but seems the right way to describe how human beings evaluate data coming in through the various sensory channels. Also, according to eminent physicists, logarithms may help further the understanding of quantum mechanics.

Like the exponential function, the logarithm always rises. But whereas the exponential roars unchecked to infinity at an ever-increasing rate of slope, the rise of the logarithmic function is accompanied by a slope that gets continuously flatter. And whereas the exponential approaches the horizontal axis to the left of the origin, the logarithm plunges precipitously through the horizontal axis to negative infinity, hugging the vertical axis ever more closely, though never quite reaching it. At their extremities, the exponential and logarithmic curves diverge dramatically, but near the origin they approach each other, even running in parallel. Together they resemble the graceful outline of an hourglass.

The usefulness of the logarithm is its ability to represent numerical excesses in comprehensible terms. To see how it works, consider the logarithm to the base 10, the so-called decadal logarithm (log natural = 2.302585 log decadal). For multiples of ten, the log simply counts zeros, recording them as positive when they appear in the numerator, and negative when they appear in the denominator.

Thus, the log of 1000 is 3, whereas the log of 1/100 is -2. A plot of the log has remarkable properties. On a sheet of graph paper that is divided into one-centimeter squares, a point on the curve that is a mere eleven centimeters, or half a page, above the horizontal axis lies 100 billion centimeters to the right, reaching past the orbit of the moon. Conversely, eight centimeters bellow the origin, the curve has moved to within one 100-millionth of a centimeter, or an atom's diameter, from the vertical axis.

Scientists long ago made use of the "powers of ten" notation. One hundred billion is written 1011, one 100-millionth, [10.sup.-8.] The superscripts, of course, are just the logs of the original numbers. At first, the powers of ten notation appears to be more of a shorthand; albeit a marvelously convenient one. It prevents errors and saves space. Imagine just writing out in full the values of the Planck constant ([10.sup.-43] second) and Planck length ([10.sup.-35] meter) with their combined total seventy-six zeros after the decimal point--a virtually impossible feat of patience and care. Computations are further simplified because multiplication and division by ten amounts to simply adding and subtracting powers.

But the logarithmic function has more profound implications. It is an effective analytical tool for understanding the world, a way of looking at things that might be called "logarithmic thinking" or, simply, "power thinking."

Power thinking began in the second century BC, when the Greek astronomer Hipparchus divided the stars into six categories of brightness. The giant star Antares, for instance, was bright enough to be classified within the first magnitude of brightness. Polaris, visibly dimmer, but not by much, was deemed to be a second-magnitude star. And so on. (The modern scale of visual stellar magnitudes has been extended another 30 steps in one direction to include the sun, and 24 in the opposite direction to capture the faintest object recorded by the Hubble space telescope.) Of course, Hipparchus had no way of determining brightness objectively, but his subjective classification turned out to be intrinsically logarithmic: as recorded by a detector that measures the intensity of light, Antares is 2.5 times as bright as Polaris, which is 2.5 times bright as a third magnitude star.

Hipparchus's scale illustrates an old phenomenon: the human senses perceive the world in a roughly logarithmic way. The eye, for example, cannot distinguish much more then six degrees of brightness. The range covered by six degrees is 2.5 x 2.5 x 2.5 x 2.5 x 2.5, as for human perceptions.

The ear, too, perceives approximately logarithmically. The physical intensity of sound, in terms of energy carried through the air, varies by a factor of one trillion ([10.sup.12]), from the barely audible to the threshold of pain. But because neither the ear nor the brain can resolve equal differences equally across so immense a gamut, they convert the unimaginable multiplicative factors into a comprehensive additive scale. The ear, in other words, relays the physical intensity of the sound as logarithmic ratios of loudness. Thus, a normal conversation may seem three times as loud as a whisper, whereas its measured intensity is actually 1000 ([10.sup.3]) times greater. It is no coincidence that the loudness scale invented by the telephone pioneer Alexander Graham Bell is logarithmic: a noise that registers as 80 decibels is 100 times louder than a 60-decibel sound.

If the sensory perceptions of brightness and loudness both interpret physical stimuli logarithmically, do they hint at some deeper, more fundamental law? For a century-and-a-half, that question has been at the frontier of psychophysics, the science in which psychology and physics overlap. One of the founders of the discipline was the 19th-century German biologist and physicist Gustav Theodor Fechner. Fechner had grappled for some time with the relation between stimulus and response, and while still in bed on the morning of October 22, 1850 (or so the story goes), he came up with a solution to the conundrum.

The Weber-Fechner law allows to define criteria that characterize the interaction of a man's psychological state and his environment, i.e., the impact of individual constituents on his psychology so enabling to describe the feelings produced by the given component.


The impact of the environment on man's physiology is described by a differential equation; for full details see Jokl (1974, 1989). In its simplest form it can be expressed as

di[nu][psi] = -([d[rho] * ]/dt), (2)


[PSI] = N/(A * t)([a * [m.sup.-2] * [s.sup.-1]]) agent flow intensity;

N = agent, homogenous component of the physical reality creating flows (e.g., warmth) and directly or potentially exposing the subject, a;

A = area perpendicular to the agent flow direction, [m.sup.2] ([in.sup.2]);

T = time, s;

[rho] * = N/V (a [m.sup.-3] [a [in.sup.-3]]) agent concentration, density; and

V = volume of transfer field, [m.sup.3] ([in.sup.3]).

This differential equation makes it possible to estimate physical criteria characterizing the interaction between man's physiology and his environment, e.g., hygrothermal, odor, and acoustic.

Applied to the hygrothermal constituent (for heat energy expressed by enthalpy) we get

[psi](a * [m.sup.-3] [a * [in.sup.-3]]) = [rho] * h (J * [m.sup.-3] [Btu.[in.sup.-3]])

= [rho] * [c.sub.p] * [T.sub.o] (J * [m.sup.-3] [Btu * [in.sup.-3]]), (3)


h = [c.sub.p] * [] = enthalpy, J * [kg.sup.-1] (Btu [lb.sup.-1];

[c.sub.b] = specific heat at constant pressure, J * [kg.sup.-1] * [degrees][C.sup.-1] (Btu * [lb.sup.-1] * [degrees][F.sup.-1]);

To = operative temperature, [degrees]C ([degrees]F); and

[rho] = specific mass of heat transfer field, kg * [m.sup.-3] (lb * [in.sup.3]).

The physical criterion of the interaction between a man's physiology and hygrothermal constituents is the product of enthalpy and specific mass. If specific mass is constant, enthalpy remains the sole criterion. If specific heat is constant, then only operative temperature remains as the criterion.

Applied to the acoustic constituent (dimensional analysis applied), we get the following:

[psi](a * [m.sup.-3] [a * in.sup.-3]) = (J * [m.sup.-3] [Btu * [in.sup.-3]])

= (N * m * [m.sup.-3] [lb * in * [in.sup.-3]]) = (N * [m.sup.-2] [lb * [in.sup.-2]]) (4)

The physical criterion of interaction between a man's physiology and the acoustic constituent is the acoustic pressure.


It is evident from the theoretical discussion that two criteria for an evaluation of the environment are necessary: psychological, expressed by a physical value, and physiological, also expressed by a physical value.

The criteria are summed up in Table 1.
Table 1. An Overview of Criteria Physical-Physiological and

Constituent Physical-Physiological Physical-Psychological

Acoustic acoustic pressure decibel (dB) *

Hygrothermal enthalpy x specific mass decitherm (dTh) **

Odor odor concentration deciodor (dOd) **

 * unit in common use
 ** unit proposed

While for the acoustic constituent, the criteria are established and in common use, for the hygrothermal and odor constituent, the criteria are the subject of this paper.

The discussion of the hygrothermal microclimate constituents is the subject of Part 2 of this paper and contains five sections:

1. Hygrothermal microclimate evaluation based on human physiology.

2. Hygrothermal microclimate evaluation based on human psychology.

3. Admissible ranges of optimal operative temperatures.

4 Optimal interior air humidity.

5. Appraisal of a non-uniform hygrothermal microclimate (in preparation).

The odor microclimate-constituent is the subject of Part 3: Odor microclimate evaluation based on human physiology and psychology.


A = area perpendicular to the agent flow direction

[c.sub.p] = specific heat at constant pressure

h = [cp.sub.p] * [T.sub.o] = enthalpy

N = agent, homogenous component of the physical reality creating flows (e.g., warmth) and directly or potentially exposing the subject

t = time

V = volume of transfer field

[rho] = specific mass of heat transfer field

[rho] * = N/(A * t) agent concentration (density)

[PSI] = N/(A * t) agent flow intensity


This study was funded by the European grant FP 6 AEROSPACE, Code AST4-CT-2005-516131, ICE (Ideal Cabin Environment). The author greatly appreciates the efforts of Dr. Erhard Mayer, outstanding researcher of the Fraunhofer Institute for Building Physics, Holzkirchen, Germany, who allowed my participation with the mentioned European grant. The author also greatly appreciates the efforts of Professor Dusan Nevrala (UK), who edited my manuscript so conscientiously and prepared it for publication.


Jokl, M.V. 1974. Some natural laws about harmful agents in the human environment. Journal of Theoretical Biology 48:1-9.

Jokl, M.V. 1989. The Theory and Practice of Indoor Climate. Illinois: Thomas.

Rohles, F.H. 1971. The ecosystem complex: A new approach in specifying the man-environment relationship. Journal of Environmental Systems 1(4):321-28.

Selye, H. 1974. Stress without Distress. Philadelphia and New York: J.B. Lippincott Company.

von Baeyer, H. Ch. 2000 Power tool. The Sciences, Sept./Oct., pp. 12-15.

Weber, J.H. 1995. Sick building syndrome--Dangerous game with spread characters. Air Infiltration Review 16:12-13.

Miloslav V. Jokl, PhD, DSc

Miloslav V. Jokl is a full-time professor in the Department of Microenvironmental and Building Services Engineering, Czech Technical University, Prague, Czechia.
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Author:Jokl, Miloslav V.
Publication:ASHRAE Transactions
Article Type:Report
Geographic Code:1USA
Date:Jan 1, 2011
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