Humidity is the amount of water vapour in the air. People and pets produce moisture when we breath or perspire. Even indoor plants produce moisture. We add water vapour to indoor air through routine household activities like cooking, showering, bathing washing etc. More moisture can enter our homes from the surrounding soils through basement or crawl space.
The humidity of air is a measure of the amount of moisture present in it. The usual term used to express humidity is relative humidity (RH), which gives a direct indication of the evaporation potential. Relative Humidity, a function of temperature, is defined by the expression:
RH = AH / SH * 100%
AH = the Absolute Humidity, defined as the amount of moisture present in unit mass or unit volume of air, in terms of grams per kilogram (g/kg) or grams per cubic meter (g/m3).
SH = Saturation Point Humidity, which is the maximum amount of moisture that a unit mass or volume of air can hold at that temperature.
Humidity is usually measured by noting the wet and dry bulb temperatures. The wet bulb temperature is measured in the same way as the dry bulb temperature, but the bulb- or- sensor- in this case is covered with gauze or a wick, which is kept wet. The evaporation of moisture cools the temperature that is always lower than the dry bulb temperature, except at a relative humidity of 100%, when the wet or dry bulb temperatures show identical readings. From the recorded observation of the wet bulb temperature (WBT) and dry bulb temperature (DBT) one can read the value of the relative humidity on the psychrometric chart. Humidity is usually measured in degrees Celsius (ºC) and is measure by a wet and dry bulb thermometer.
Noise can be extremely distracting and can prevent concentrated mental work. In some cases, it can also result in physical disorders. The way noise is measured is by a sound level meter and the units sound is taken in are decibels (dB). Noise can be characterised in two ways, direct and indirect. A direct noise is determined by the intensity of the source and the distance from the ears. Reflected noise is dependent on the reflection factors of the floor, walls, ceiling, etc., and on the position of these surfaces. Direct noise should be suppressed by placing covers over impact printers or by isolating sources of noise from the rest of the work area. A distinction should also be made between meaningful noise and general background noise. Most working environments will have some background noise. However, this noise can become uncomfortable if it is irregular, such as a malfunctioning machine. Reflected noise can be reduced by introducing sound absorbing materials into the work place. Often the actual source of noise and / or the technique for controlling it is not readily apparent. As workstations continue to migrate from the computer room to the quiet office, acoustical noise becomes an increasingly important concern to both users and designers alike. Acoustical noise is considered a human comfort factor because it affects factors such as workers comfort, job satisfaction and performance. Noise has several adverse effects on human beings. On the physiological side, these effects include hearing damage and hearing loss. On the psychological side, they include interference with speech communication, impairment of performance and annoyance. Fortunately, however, the noise levels of modern workstations designed for office or laboratory environments are relatively low, much lower than those of typical data processing equipment found in computer room installations. Noise control engineers are striving to lower noise levels of workstations, while at the same time studying and identifying the psycho acoustical aspects of particular noises that most contribute to annoyance.
Another human comfort factor is lighting. Light is measured in lumens (lm), the level of luminance is measured in lux (lx) and the instrument to take the light reading is called a light meter. Lighting is one of the most important factors in considering good environment for people. For many years, the ideal lighting environment has been considered from the viewpoint of visibility. Recently, however, many researchers have realized that there are other important human factors related to light, for example, alertness (central nervous activity), autonomic nervous activity, circadian rhythm, and so on. They also found that the quality of light, for example, colour temperature and the spectrum of light, are as important as its intensity in the effect of light on those human factors. Consequently, lighting design for humans has turned out to be very complicated. Moreover, it has affected social trends as well. Some lighting companies have designed lighting fixtures to make use of those kinds of physiological effects, so we can say that lighting plays a greater role than ever.
The quality of an internal environment can be different for different people, some people like to be warmer than others, some people like a higher level of humidity etc, so there can never be one environment that is going to suit everybody’s needs. Even though we cannot create a perfect internal environment for everyone we can use general figures for temperature, lighting level etc which are close to everyone’s needs.
For a quality internal environment to be achievable there are a number of factors which need to be taken into account, for example; clothing level, noise level, lighting level, air speed and the list goes on. Each factor has to be taken into account to make sure people do not feel uncomfortable carrying out whichever task is proposed for each room. I.e. there would need to be a much lower temperature in a sports hall, where a lot of running etc takes place, than in an office, where little or no physical tasks take place, this is because when you do a lot of running or something similar you get very hot so your body requires a cool place to be in to cool down adequately, and vice versa in the office. There are also factors like light to take into account because you would need more light in a classroom where you need to read and write etc than you would in a corridor.
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