ASHRAE-Standard-55 - Page 067
Extracted Content
Table L-1 Comfort Evaluation Approaches for Various Applications
| Measurement Method | Occupant Surveys | Nature of Application | Col4 |
|---|---|---|---|
| Measurement Method | Occupant Surveys | Short-Term Long-Term | Short-Term Long-Term |
| Measurement Method | Occupant Surveys | Right-Now/Point-in-Time Survey (must survey relevant times and population): • Binning (TSENS scores) leads to % comfort exceedance during period of survey. • Needs coincident temperature to extrapolate to full range of conditions. (Used for research, problem diagnostics) | Occupant Satisfaction Survey: • Survey scores give % dissatisfied directly. (“dissatisfaction” may be interpreted to start either below –1, or below 0). • Time period of interest can be specified to survey takers. (Used for building management, commissioning, rating operators and real estate value, compliance with green building rating systems) |
| Measurement Method | Environmental Measurements | Spot Measurements, Temporary (Mobile) Sensors (must select a relevant time to measure): • Use measurements to determine PMV (Section 5.3). • Use measurements to determine compliance with adaptive model (Section 5.4). (Used for real-time operation, testing and validating system performance) | Logging Sensors over Period of Interest, or Trend Data from Permanently Installed (BAS) Sensors: • Exceedance hours: Sum of hours over PMV or adaptive model limits. • Binned exceedances may be weighted by their severity. • Instances of excessive rate-of-temperature change or of local thermal discomfort can be counted. (Used for evaluating system and operator performance over time) |
L3. EVALUATION OF COMFORT IN EXISTING SPACES
The evaluation approach depends on the intended application. The list of possible evaluation applications is extensive. They require evaluation over varying time periods, from short term (ST) to long term (LT):
a. Real-time operation of a building using comfort metrics (ST) b. Evaluating HVAC system performance (ST, LT) c. Building management decisions regarding upgrades, continuous commissioning, and rating the perfor mance of operators and service providers (LT) d. Real-estate portfolio management: rating building quality and value (LT, ST) e. Validating compliance with LEED existing-buildings requirements (ST, LT) f. Validating compliance with requirements of codes—energy, hospital, etc. (ST)
There are two main approaches to evaluating thermal comfort in operating buildings. One is to directly determine occupant thermal sensations and satisfaction through the statistical evaluation of occupant surveys. The other is to use comfort models to estimate sensations and satisfaction of the occupants from measured environmental variables. The measurements needed for each of these approaches are described in Sections L1 and L2.
Surveys and physical measurements may be used in combination with each other for the purpose of problem diagnosis and research (see Table L-1). In the short-term, point-in-time surveys are used to obtain comfort perceptions coincident with short-interval logged environmental measurements or BAS system trend data. For evaluating building performance over time, occupant satisfaction surveys results are correlated with averages of long-term measurements of environmental conditions.
L3.1 Analysis Based on Occupant Surveys. Surveys can assess comfort directly, in contrast to the indirect approach of calculating comfort through comfort models using measured environmental variables.
a. Short-Term Analyses (Using Instantaneous Comfort Determinations)
- Measures from Point-in-Time (“Right-Now”) Surveys i. Thermal acceptability votes ii. Thermal sensation (TSENS) votes (When averaged for a population, TSENS votes correspond
directly to PMV votes.) iii. Temperature preference votes and air-movement preference votes (“less”/“no change”/“more”) 2. Criteria for Passing i. –0.5 to +0.5 on the PMV scale, inclusive, is the Standard 55 criterion for passing ii. Field surveys usually consider TSENS values of –1 and +1 as representing “satisfied”; the break
along the categorical seven-point thermal sensation scale is at –1.5 and +1.5, inclusive. 3. Local Thermal Discomfort Determination i. Questions about any local thermal discomfort (e.g., ankle, neck discomfort) ii. Questions addressing solar radiation effects on comfort
ANSI/ASHRAE Standard 55-2023 65