DESIGNING FOR DESIGNING FOR COMFORTCOMFORT

Richard B. Hayter, Ph.D., P.E.Richard B. Hayter, Ph.D., P.E.

Kansas State UniversityKansas State University

Manhattan, KS, USAManhattan, KS, USA

Annual Operating Costs in U.S.Annual Operating Costs in U.S.

Energy: $2.00 to $4.00/ft2

Annual Operating Costs in U.S.Annual Operating Costs in U.S.

Energy: $2.00 to $4.00/ftEnergy: $2.00 to $4.00/ft22

Maintenance: $2.00 to $4.00/ftMaintenance: $2.00 to $4.00/ft22

Annual Operating Costs in U.S.Annual Operating Costs in U.S.

Energy: $2.00 to $4.00/ftEnergy: $2.00 to $4.00/ft22

Maintenance: $2.00 to $4.00/ftMaintenance: $2.00 to $4.00/ft22

Owning or Leasing: $10.00 to Owning or Leasing: $10.00 to $40.00/ft$40.00/ft22

Annual Operating Costs in U.S.Annual Operating Costs in U.S.

Energy: $2.00 to $4.00/ft2

Maintenance: $2.00 to $4.00/ft2

Owning or Leasing: $10.00 to $40.00/ft2

Personnel: $200.00 to $400.00/ft2

Optimizing Environmental Optimizing Environmental Control Control MayMay

Minimize operating cost including Minimize operating cost including energyenergy

Optimizing Environmental Optimizing Environmental Control Control MayMay

Minimize operating cost including energy

Improve productivity

Evolution of ControllersEvolution of Controllers

On/Off Proportional Control Dead Band Comfort Controllers Fuzzy Logic

Indoor Design ConditionsIndoor Design Conditions

2003 ASHRAE Applications 2003 ASHRAE Applications HandbookHandbook - Office Buildings, - Office Buildings, SummerSummer

7474ooF (23F (23ooC) - 78C) - 78ooF (26F (26ooC)C)

50 - 60% rh50 - 60% rh

Indoor Design ConditionsIndoor Design Conditions

2003 ASHRAE Applications Handbook2003 ASHRAE Applications Handbook - - Office Buildings, SummerOffice Buildings, Summer

7474ooF (23F (23ooC) - 78C) - 78ooF (26F (26ooC)C)

50 - 60% rh50 - 60% rh

Footnote: “This table ... should not be used Footnote: “This table ... should not be used as the sole source for design criteria.”as the sole source for design criteria.”

Indoor Design ConditionsIndoor Design Conditions

ASHRAE/IES 90.1-2001ASHRAE/IES 90.1-2001::

““6.2.2 Load Calculations. Heating and cooling 6.2.2 Load Calculations. Heating and cooling system design loads for the purpose of sizing system design loads for the purpose of sizing systems and equipment shall be determined in systems and equipment shall be determined in accordance with generally accepted engineering accordance with generally accepted engineering standards and handbooks acceptable to the standards and handbooks acceptable to the adopting authority (for example, adopting authority (for example, ASHRAE ASHRAE Handbook Handbook – Fundamentals).– Fundamentals).””

Fundamentals of Thermal Fundamentals of Thermal ComfortComfort

““Thermal Comfort:Thermal Comfort: That condition of mind which That condition of mind which expresses satisfaction with the expresses satisfaction with the

thermal environment and is thermal environment and is assessed by subjective evaluation.”assessed by subjective evaluation.”

Principles of Heat TransferPrinciples of Heat Transfer

Humans transfer sensible heat by Humans transfer sensible heat by conduction, convection and radiation.conduction, convection and radiation.

Humans transfer latent heat by Humans transfer latent heat by evaporation from the skin evaporation from the skin (evaporation of perspiration) and (evaporation of perspiration) and through respiration.through respiration.

MetabolismMetabolism

Ranges from approximately 340 Btu/Hr Ranges from approximately 340 Btu/Hr (sedentary) to 3400 Btu/Hr (strenuous).(sedentary) to 3400 Btu/Hr (strenuous).

Metabolic capacity of trained athlete can Metabolic capacity of trained athlete can reach 20 times their sedentary rate.reach 20 times their sedentary rate.

More typical maximum is 12 times More typical maximum is 12 times sedentary for age 20 and 7 times sedentary for age 20 and 7 times sedentary for age 70.sedentary for age 70.

Thermal EquilibriumThermal Equilibrium

Is achieved when the metabolic Is achieved when the metabolic rate equals rate of heat loss less rate equals rate of heat loss less work.work.

Physiological ResponsesPhysiological Responses Sweating = Increased Evaporation Sweating = Increased Evaporation

(little benefit from dripping sweat)(little benefit from dripping sweat) Note: If heat production is greater than Note: If heat production is greater than

heat loss, first mechanism is vasodilatation heat loss, first mechanism is vasodilatation which can double or triple heat loss. which can double or triple heat loss. Conditioned athletes sweat a higher Conditioned athletes sweat a higher proportion of water to oil.proportion of water to oil.

Shivering = Increases Metabolism.Shivering = Increases Metabolism.

Thermal NeutralityThermal Neutrality

That condition where no physiological That condition where no physiological response is needed other than response is needed other than vasomotion to maintain a normal vasomotion to maintain a normal body temperature.body temperature.

Normally achieved between TNormally achieved between Too = 73 = 73ooF F to 81to 81ooF for clothed sedentary and 84F for clothed sedentary and 84ooF F to 88to 88ooF unclothed.F unclothed.

Individual DifferencesIndividual Differences Elderly prefer same condition as young. Lower

metabolic rate of elderly is compensated by lower latent loss from body. Preference for warmer thermostats is because of lower activity levels.

Elderly are more susceptible to extremes.

No difference between sexes in the unclothed condition. Clothed females may prefer warmer temperature because of lighter clothing.

DiscomfortDiscomfort

Localized discomfort will overshadow Localized discomfort will overshadow comfort even under conditions of comfort even under conditions of thermal neutrality.thermal neutrality.

Causes of localized discomfort include Causes of localized discomfort include asymmetric radiation, drafts, contact asymmetric radiation, drafts, contact with cold or hot floors, vertical with cold or hot floors, vertical temperature differences.temperature differences.

Discomfort ContinuedDiscomfort Continued

Drafts have a disproportionate effect on comfort based on heat transfer.

Dissatisfaction with the environment grows exponentially as air turbulence increases.

Comfort = Productivity(?)Comfort = Productivity(?)

Motivation more dominant than Motivation more dominant than comfort.comfort.

Comfort = Productivity(?)Comfort = Productivity(?)

Motivation more dominant than comfort.

Productivity = f (1/discomfort)

Variables Affecting ComfortVariables Affecting Comfort

Typical Controlled VariablesTypical Controlled Variables

Dry Bulb Temperature

Relative Humidity (Water Vapor Pressure)

Air Velocity

Possible Controlled VariablesPossible Controlled Variables Mean Radiant Temperature Radiant Asymmetry Drafts Vertical Temperature Stratification Floor/Ceiling Temperature Non Steady State Conditions

– Rate of Change– Amplitude and Basal Temperature

Possible Non Thermal Possible Non Thermal Controlled VariablesControlled Variables

Noise Noise

Air QualityAir Quality

LightingLighting

Typical Uncontrolled VariablesTypical Uncontrolled Variables

Activity Level of Occupants

Clothing

Operative Temperature (tOperative Temperature (too))

“The uniform temperature of an imaginary black enclosure in which an occupant would exchange the same amount of heat by radiation plus convection as in the actual nonuniform environment.”

Operative Temperature Cont.Operative Temperature Cont.

““Operative temperature is Operative temperature is numerically the average of the numerically the average of the air temperature and mean air temperature and mean radiant temperature weighted by radiant temperature weighted by their respective heat transfer their respective heat transfer coefficients.”coefficients.”

Operative Temperature Cont.Operative Temperature Cont.

The operative temperature equals the dry bulb temperature in spaces where the temperatures of the surfaces surrounding the occupant and the dry bulb temperature are approximately the same.

Operative Temperature Cont.Operative Temperature Cont.

Environmental control systems Environmental control systems must have some way to must have some way to compensate when the surface compensate when the surface temperatures are considerably temperatures are considerably different than the dry bulb different than the dry bulb temperature.temperature.

Thermal Comfort StandardsThermal Comfort Standards

ForwardForward

The standard is intended for use in design, commissioning, and testing of buildings and other occupied spaces and their HVAC systems and for the evaluation of thermal environments.

Purpose:Purpose:

““... ... to specify the combinations of indoor thermal environmental factors and personal factors that will produce thermal environmental conditions acceptable to a majority of the occupants within the space.”.”

Six Factors for ComfortSix Factors for Comfort

1. Metabolic rate2. Clothing insulation3. Air temperature4. Radiant temperature5. Air speed6. Humidity

Conditions for Acceptable Conditions for Acceptable Thermal Environment Cont.Thermal Environment Cont.

Assumes sedentary activity. (Includes provisions for adjustment.)

Assumes similarity in clothing for season. (Includes provisions for adjustment.)

For 80% occupant acceptability

Other Criteria-Air VelocityOther Criteria-Air Velocity No minimum specified. Temperature may No minimum specified. Temperature may

exceed upper limit of zone if compensated exceed upper limit of zone if compensated with elevated air velocities.with elevated air velocities.

For sendentary occupants, temperature For sendentary occupants, temperature cannot exceed comfort zone by more than cannot exceed comfort zone by more than 33ooC(5.4C(5.4ooF) nor compensating air velocity F) nor compensating air velocity greater than 0.8m/s(160fpm).greater than 0.8m/s(160fpm).

Elevated air velocities must be under the Elevated air velocities must be under the control of the occupant.control of the occupant.

DiscomfortDiscomfort

The local thermal discomfort caused by a vertical air temperature difference between the feet and the head by an asymmetric radiant field, by local convective cooling (draft), or by contact with a hot or cold floor must be considered in determining conditions for acceptable thermal comfort.

Other Criteria-Non Steady Other Criteria-Non Steady StateState

No restrictions on rate of change of cyclic No restrictions on rate of change of cyclic temperatures if peak-to-peak difference temperatures if peak-to-peak difference is less than 1.1is less than 1.1ooC (2C (2ooF).F).

Temperature drifts and controlled ramp Temperature drifts and controlled ramp changes are acceptable under specified changes are acceptable under specified conditions and can exceed comfort zone conditions and can exceed comfort zone within limits. (Such as night setback.)within limits. (Such as night setback.)

Other Criteria-NonuniformityOther Criteria-Nonuniformity

Limits on vertical temperature gradients within Limits on vertical temperature gradients within the occupied zone are specified.the occupied zone are specified.

Radiant asymmetry in the vertical direction Radiant asymmetry in the vertical direction shall be less than 5shall be less than 5ooC (9C (9ooF) under a warm F) under a warm ceiling and less than 10ceiling and less than 10ooC (18C (18ooF) in the F) in the horizontal direction from a cool wall.horizontal direction from a cool wall.

Floor surface temperatures shall be between Floor surface temperatures shall be between 1919ooC (66C (66ooF) and 29F) and 29ooC (84C (84ooF).F).

Evaluation of Thermal Evaluation of Thermal EnvironmentEnvironment

1. Measuring Device Criteria

2. Measurement Positions

3. Measurement Periods

4. Measuring Conditions

5. Mechanical Equipment Operating Conditions

6. Validating the Thermal Environment

International StandardsInternational Standards

ISO StandardsISO Standards

“This standard (55-2004) is in close agreement with ISO Standards 77261 and 7730.2”

CEN 156 Proposed Prestandard CEN 156 Proposed Prestandard (never adopted)(never adopted)

“Ventilation for Buildings Design Criteria for the Indoor Environment”

Proposed CEN Standard Scope:Proposed CEN Standard Scope:

““...The indoor environment comprises ...The indoor environment comprises the thermal environment, the air the thermal environment, the air quality and the acoustic quality and the acoustic environment.”environment.”

The FutureThe Future

Greater application of multivariate controllers including fuzzy logic will provide comfort at minimum energy use.

The FutureThe Future

Greater application of multivariate Greater application of multivariate controllers including fuzzy logic controllers including fuzzy logic will provide comfort at minimum will provide comfort at minimum energy use.energy use.

Introduction of convenient Introduction of convenient design tools.design tools.

The FutureThe Future Greater application of multivariate Greater application of multivariate

controllers including fuzzy logic will controllers including fuzzy logic will provide comfort at minimum energy use.provide comfort at minimum energy use.

Introduction of convenient design tools.Introduction of convenient design tools.

Revisions to comfort standards.Revisions to comfort standards.

Thanks for listening!Thanks for listening!