Page 293 - Mechanical Engineers' Handbook (Volume 4)

282 Energy Auditing

Table 3 Range of Illuminances Appropriate for Various Types of Activities and Weighting Factors
a
for Choosing the Footcandle Level within a Range of Illuminance 6
Range of Illuminances
Category (footcandles) Type of Activity
A 2–3–5 Public areas with dark surroundings
B 5–7.5–10 Simple orientation for short temporary visits
C 10–15–20 Working spaces where visual tasks are only occasionally
performed
D 20–30–50 Performance of visual tasks of high contrast or large size:
for example, reading printed material, typed originals,
handwriting in ink and good xerography; rough bench
and machine work; ordinary inspection; rough
assembly
E 50–75–100 Performance of visual tasks of medium contrast or small
size: for example, reading medium-pencil handwriting,
poorly printed or reproduced material; medium bench
and machine work; difficult inspection; medium
assembly
F 100–150–200 Performance of visual tasks of low contrast or very small
size: for example, reading handwriting in hard pencil or
very poorly reproduced material; very difficult
inspection
G 200–300–500 Performance of visual tasks of low contrast and very
small size over a prolonged period: for example, fine
assembly; very difficult inspection; fine bench and
machine work
H 500–750–1000 Performance of very prolonged and exacting visual tasks:
for example, the most difficult inspection; extra-fine
bench and machine work; extrafine assembly
I 1000–1500–2000 Performance of very special visual tasks of extremely low
contrast and small size: for example, surgical
procedures
Weighting Factors
Worker or task charactristics 1 0 1
Worker’s age Under 40 40–65 Over 65
Speed and/or accuracy Not important Important Critical
Reflectance of task background Greater than 70% 30–70% Less than 30%
a To determine a footcandle level within a range of illuminance, find the weighting factor for each worker or task
characteristic and sum the weighting factors to obtain a score. If the score is 3or 2, use the lowest footcandle level;
if 1, 0, or 1, use the middle footcandle level; if 2 or 3, use the highest level.

Analysis of HVAC systems in a commercial building is generally more complicated and
requires more time and effort than lighting systems. However, the approach is similar in that
the auditor will usually begin by examining operating and maintenance practices and then
proceed to measure system performance.
Determining the fraction of a building’s energy consumption that is devoted to the
operation of its HVAC systems can be difficult. The approaches to this problem can be
classified as either deterministic or statistical. In the deterministic approaches an effort is