406 Energy Project Financing: Resources and Strategies for Success
an increase of skin moisture. The upper humidity limits of ASHRAE s
thermal comfort zone vary with temperature from approximately 60%
RH at 26°C to 80% RH at 20°C.
Air temperature and humidity also influence perceptions of the
quality of indoor air and the level of complaints about non-specific
building-related health symptoms (often called sick building syndrome
symptoms). Higher air temperature has been associated with increased
health symptom prevalences in several studies (Skov et al. 1989, Jaak-
kola et al. 1991, Wyon 1992, Menzies et al. 1993). Occupants perceived
acceptability of air quality has been shown to decrease as temperature
and humidity increase in the range between 18°C, 30% RH and 28°C,
70% RH (Fang et al. 1997, Molhave et al. 1993).
4.3 INDOOR LIGHTING
The quality of the indoor environment depends significantly on
several aspects of lighting (JES 1993, Veitch and Newsham 1998) includ-
ing the illuminance (intensity of light that impinges upon a surface), the
amount of glare, and the spectrum of the light^1. There is evidence that
a decrease in the amount of flicker in light, i.e., the magnitude of the
rapid cyclic change in illuminance over time, may be associated with
a decrease in headache and eyestrain (Wilkens et al. 1988) and with an
increase in worker performance (Veitch and Newsham 1997). In many
indoor spaces, the indoor environment is influenced by both daylight
and by artificial lighting. Characteristics of windows and skylights and
their shading affect the daylighting of indoors. The quality of electric
indoor lighting is a function of the types, locations, and number of lu-
minaires, and the optical characteristics of indoor surfaces such as their
spectral reflectivity and color.
The method of lighting control, such as no control, automatic dim-
ming of artificial light, and manual control of overhead or task lighting
may also influence lighting quality.
Lighting characteristics influence the quality of vision and can
have psychological influences on mood and on perceptions about the
pleasantness of a space. Because extremes in lighting have a clear im-
pact on performance, indoor lighting in commercial buildings is usually
maintained within the limits specified in guidelines or standards. The
- The evidence for effects of spectrum of light on satisfaction and perfor-
mance is mixed (e.g., Veitch 1994, Berman 1992)