2- INTD409 Interion Environmental Technology University of Nizwa Faculty of Engineering and Architecture Dept. of Architecture & Innterior 2- INTD409 Interion Environmental Technology Thermal comfort zone Dr. Mamdouh I. Zaky

THERMAL COMFORT

Why Worry About Thermal Comfort? Designers have an ethical responsibility to cause no harm – my personal opinion Gripes about thermal comfort are consistently the number one complaint heard by building managers/owners Comfort decisions can have substantial energy and resource consumption implications Comfort is the basis for a substantial investment (in a climate control system) Green design demands (sort of ) thermal comfort

Two Ways to Look at Thermal Comfort As a psychological phenomenon As a physical phenomenon Both views are valid, both must be tempered by statistics, and both views are important to building design efforts

What is Thermal Comfort? “That condition of mind which expresses satisfaction with the thermal environment and is assessed by subjective evaluation.” ASHRAE Standard 55-2010 Thermal Environmental Conditions for Human Occupancy

Subjective Evaluation (Asking) 1. The traditional 7-point “status” scale: cold | cool | slightly cool | neutral | slightly warm | warm | hot 2. An alternative “action” scale: Would you prefer: to be warmer | no change | to be cooler

Thermal Comfort Chart comfort zone(s)

Physical Context of Thermal Comfort -- dishealth conditions the body’s response

Physical Basis of Thermal Comfort Fundamentally, comfort involves a heat balance (a thermal equilibrium) … where: heat in ≈ heat out where “heat in” is provided by metabolism, radiation, conduction, convection where “heat out” is via radiation, conduction, convection, evaporation

Heat Flow Mechanisms

Heat Flow to/from Human Body Sensible Heat Flows via conduction, radiation, and convection Flow rate is generally related to space temperatures Latent Heat Flows via evaporation Flow rate is generally related to space humidity Total Heat Flow = sensible + latent flows

Heat Flow to/from Human Body Conduction (sensible) Convection (sensible) Radiation (sensible) Evaporation/Condensation (latent)

Conduction The flow of heat between two adjacent and touching solids (or from one part to another part within an object) by direct interaction between molecules example: walking on a beach in your bare feet for comfort, the key environmental variable is: SURFACE TEMPERATURE

Convection The flow of heat from the surface of a material to/from a surrounding fluid (usually air); the free motion of molecules of the fluid is very important in promoting heat flow example: fanning yourself with a newspaper for comfort, the key environmental variables are: AIR TEMPERATURE | AIR SPEED

Radiation The flow of heat between objects that are not in direct contact—but that can “see” each other via electromagnetic radiation; the objects may be a few inches or a million miles apart example: warming yourself in front of a fireplace for comfort, the key environmental variable is: SURFACE TEMPERATURE

Evaporation The flow of heat that must be provided as a material changes state (from a liquid to a gas); this heat represents the energy required to break molecular bonds (called the latent heat of vaporization) example: feeling cool coming out of a swimming pool on a breezy day for comfort, the key environmental variables are: RELATIVE HUMIDITY | AIR SPEED

Environmental Comfort Factors Air temperature (dry bulb – deg F) Relative humidity (%) Air speed (ft per min) Radiant conditions Mean radiant temperature [MRT] in deg F or other radiation value in Btuh per sf These factors are controllable through design – a passive system should control all four factors; an active (HVAC) system is expected to control the first three (with “architecture” controlling the fourth)

Measuring Environmental Factors data logging air temperature, RH, wind speed air speed surface temperature

The Designer’s Job Understand the physical basis of thermal comfort and related variables Appreciate the influence of the psychological aspects of thermal comfort Use this understanding and appreciation to design spaces that building users will decide are thermally comfortable

QUESTIONS?

2- INTD409 Interior Environmental Technology University of Nizwa Faculty of Engineering and Architecture Dept. of Architecture & Innterior 2- INTD409 Interior Environmental Technology Green Design Controls Dr. Mamdouh I. Zaky

Green Design Controls Process Recommendations Select experienced and innovative design team Include performance goals in SOW Develop quantifiable goals Document in Owner’s Project Requirements / Basis of Design Hire a Commissioning Agent prior to design Use an integrated design approach Owners, Cx Agents, all design disciplines, end-users involved in all phases of design Energy modeling to optimize energy efficiency Plan for preventive maintenance (PM) Train facility operators and occupants

Green Design Controls Cooperative environment for decision makers Intense effort to identify and address issues in a short time Listen and understand needs and limitations Envision realistic and creative solutions Record ideas as they are introduced Effectively express ideas in a plan to serve as a vehicle to move the process forward Owner well-defined goals (OPR)

Green Design Controls Optimize daylighting to full possible extent Building orientation, photocell controls with dimmable ballasts Reduces lighting and cooling loads Daylight glass and view glass are not the same Efficient lighting design Lighting Power Density < 1 W/ft2 Pendant direct/indirect Occupancy sensors, auto night shut-off Dedicated outdoor air treatment Energy Recovery Ventilator or Demand-Controlled Ventilation Centralize exhaust zones for energy recovery

Green Design Controls Efficient, tight envelope Appropriate, well-installed insulation Low-e, low- Solar Heat Gain Coefficient (SHGC) windows (esp. east/west facing) Shading for south facing windows Light colored roof High efficiency HVAC with optimized control system Balance with maintenance concerns Size properly, incorporate strategies for variable loads Energy star appliances and office equipment Use energy modeling iteratively to identify and reduce loads, and optimize efficiency of design