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The representation is made on a temperature-relative humidity, instead of a standard psychrometric chart. The comfort zone in blue represents the 90% of acceptability, which means the conditions between -0.5 and +0.5 PMV, or PPD < 10%.
The recommended level of indoor humidity is in the range of 30–60% in air conditioned buildings, [34] [35] but new standards such as the adaptive model allow lower and higher humidity, depending on the other factors involved in thermal comfort. Recently, the effects of low relative humidity and high air velocity were tested on humans after ...
For example, in the range of normal temperatures, air at 68 °F (20 °C) and 50% relative humidity will become saturated if cooled to 50 °F (10 °C), its dew point, and 41 °F (5 °C) air at 80% relative humidity warmed to 68 °F (20 °C) will have a relative humidity of only 29% and feel dry.
For humidity ratios above 0.012 kg H 2 O/kg dry air (0.012 lb H 2 O/lb dry air), or for metabolic rates up to 2.0 met, the analytical model must be used to determine thermal comfort sensation. Also based on the PMV model, this method uses tools such as the ASHRAE Thermal Comfort Tool or the online CBE Thermal Comfort Tool for ASHRAE 55 [ 2 ] to ...
[citation needed] However, high humidity outdoors creates the need for careful attention to humidity levels indoors. High humidity give rise to mold growth and moisture indoors is associated with a higher prevalence of occupant respiratory problems. [citation needed] The "dew point temperature" is an absolute measure of the moisture in air ...
An indoor relative humidity of less than 51% resulted in significant reductions in mite and allergen levels. [9] Overuse of a humidifier can raise the relative humidity to excessive levels, promoting the growth of dust mites and mold, and can also cause hypersensitivity pneumonitis (humidifier lung). [10]
In the recent past, it was common for house temperatures to be kept below the comfort level; a 1978 UK study found average indoor home temperatures to be 15.8 °C (60.4 °F) while Japan in 1980 had median home temperatures of 13 °C (55 °F) to 15 °C (59 °F). [12]
Humidity occurs in indoor environments due to building related causes. Porous walls, rising damp, and leaks in the building are determinants for structural dampness due to elevated humidity levels. [4]: 185–187 The construction of the building can also lead to humidity and unwanted moisture in the indoor environment. [15]