thermal comfort

define thermal comfort

the state of mind which expresses satisfaction with the thermal environment

define thermal neutrality

the condition in which a person is not feeling too hot or too cold

• can assume they are feeling thermal comfort

describe the factors that affect thermal comfort

• indoor environment

• personal variables

• weather conditions

• design and type of space

• personal control over space - adaption

define inside air temperature (t_a)

average temperature of the bulk air in a room

define mean radiant temperature (t_r)

average temperature of the surfaces that surround a particular point in a room

define operative temperature (t_op)

average of the air temperature AND mean radiant temperature (weighted by respective heat transfer)

what is operative temperature affected by?

convection and radiation

how is mean radiant temperature (t_r) calculated?

how is operative temperature (t_op) calculated?

what assumption is made?

assume air speed < 0.1m/s and calculating dry resultant temperature

what is operative temperature t_op also known as ?

dry resultant temperature OR

inside environmental temperature (t_ei)

how can we assess thermal comfort?

PMV/PPD INDEX

ADAPTIVE THERMAL COMFORT MODEL

what does PMV and PPD stand for?

PMV - predicted mean vote

PPD - percentage of people dissatisfied

how was the PMV/PPD index developed?

• took a group of people of different ages, genders etc

• placed them in environmentally controlled chambers

• altered state of undress OR

  • one other of 6 environmental/personal variables

• find PPD from measured PMV

what are the 6 environmental/personal variables in PMV/PPD index?

• air temp

• radiant temp

• air velocity

• humidity

• clothing

• metabolic heat

define the adaptive thermal comfort model

if a change occurs and produces discomfort, people react in ways that restore their discomfort

who conducted studies in adaptive thermal comfort?

humphreys and nicol

what does the adaptive thermal comfort model demonstrate?

• thermal comfort is affected by heat balance of human body AND OTHER FACTORS

• people are NOT passive recipients of thermal environment

  • play active role in creating thermal environment through physical/behavioural responses

how does acclimatisation impact the adaptive thermal comfort model?

• modifies people’s thermal expectations and preferences

• causes people to have different reactions

• have different ideas of thermal comfort

physical/behavioural responses to cold

• shivering

• huddling

• exercise

• alter thermostat/turn on heating

• put on more clothes/warmer clothes

physical/behavioural responses to heat

• sweating

• open windows

• wear less/cooler clothes

• turn on fans/ac

how does the adaptive thermal comfort model explain the relation between occupants and the building?

comfort is achieved by occupants adapting to the building AND adapting the building to them

• within reasonable context → should be supported by conditions allowing occupants to control their environment

factors to consider when designing thermally comfortable buildings

• outside climate

• building’s context and form

• building services

• occupants

how can buildings be designed to achieve thermally comfortable indoor environments?

• activities & clothing levels of occupants

• effective planning of spaces

• expectation and experience of occupants

• buffer spaces

• provision of local control/adaption opportunities

• enable movement to space where most comfortable

• educate occupants on adaptions to maintain thermal comfort

purpose of buffer spaces

protect against extreme thermal exposure to maintain comfortable interior

who ran the PMV/PPD index?

fanger

who ran the SET (standard effective temperature) model

gagge

how did PMV/PPD index classify their data?

a 7 point scale

resulting number is called comfort vote

+3 is hot, -3 is cold

why was the PMV/PPD index criticised?

doesn’t consider

• age

• gender

• number of occupants

• acclimatisation

assumes people to be totally passive to thermal environment

how does humidity impact perception of temperature?

higher humidity levels - seems warmer

lower humidity levels - seems colder

humidity > 80% - unable to cool by perspiration

optimum average room temperature range

what must it not fall below?

optimum: 21-23C

must not fall below 18C

equation for human body heat balance