ASI2 ‐ Prof. Richard de Dear ‐ Part 2 11/01/2016

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Urban Thermal Comfort Counterpoint and alliesthesia

• Richard de Dear

• Professor - Building Science

• The University of Sydney Lecturer’s Photo

Outline of this lecture:

• Since the invention of air conditioning early in the 20th Century we've witnessed a gradual tightening of indoor temperature control around a theoretically optimum, ‘neutral’ temperature on the assumption that that's what is most desirable. The aim of this talk is to question the relevance of this basic assumption to outdoor urban bioclimates.  

• In 1979 Lisa Heschong wrote ‘Thermal Delight in Architecture,’ a book about the phenomenology of indoor climate.  Heschong’s premise was that “neutral”thermal environments inside buildings are not necessarily ideal.  Many of the most memorable and significant spaces in our lives are anything but neutral… they are layered with affect, emotion, even delight.   

• In this talk I will provide a thermo‐physiological explanation of “thermal delight.” Positive allisethesia is based on contrasting combinations of skin and core temperature trends. A given thermal stimulus can be subjectively experienced as either pleasant or unpleasant, depending on whether it is likely to restore or perturb the milieu interior to its set‐point temperature.

• The lecture finishes with various outdoor microclimatic examples where positive thermal delight occurs. 

ASI2 ‐ Prof. Richard de Dear ‐ Part 2 11/01/2016

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“subtractive” definition of thermal comfort

+3 Hot

+2 Warm

+1 Slightly warm

0 Neutral

- 1 Slightly cool

-2 Cool

-3 Cold

• In practice the operational definition of thermal comfort interprets comfort as the absence of thermal sensation

• In effect it is a subtractive definition neutral = neither warm nor cool

• But “neutral” says nothing about like or dislike or satisfaction

PMV/PPD model represents the regulatory expression of tight temperature control

The PPD logic underpins the trend to tighten temperature uniformity

within buildings with HVAC.

Buildings are judged on their imperceptibility. Comfort

performance is being measured in terms of the absence of sensation

ISO (2005) Moderate Thermal Environments – Determination of the PMV and PPD and Specification of Conditions for Thermal Comfort –ISO 7730 (Geneva; International Organization for Standardization)

Class PMV range Predicted Mean Vote

Temperature dead-band

(K)

Acceptability

(PPD)

A -0.2 < PMV < +0.2 2 <6%

B -0.5 < PMV < +0.5 4 <10%

C -0.7 < PMV < +0.7 6 <15%

ASI2 ‐ Prof. Richard de Dear ‐ Part 2 11/01/2016

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Field studies of comfortDependent variable:large samples of “right‐here‐right‐now” thermal comfort ratings on questionnaires

http://graphics8.nytim

es.com/images/2011/04/25/w

orld/

Kim

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Independent variable:detailed measurements 

or estimates of all six input variables for 

PMV/PPD predictions

ASHRAE-sponsored field testing the validity of the PPD part of Fanger’s comfort theory (1990s)

OfficeISO-7730

Rating

PredictedAcceptability(100% - PPD)

Townsville Australia

Hot/Humid Season

Townsville Australia

Warm/Dry Season

KalgoorlieAustraliaHot/DrySeason

KalgoorlieAustralia

Warm/DrySeason

Class A2K deadband >94%

80% accept

77% accept

84 % accept

84% accept

Class B4K deadband >90%

78% accept

79% accept

86 % accept

83% accept

Class C6K deadband >85%

78% accept

77% accept

86 % accept

84% accept

Arens, Humphreys, de Dear & Zhang 2010 “Are ‘class A’ temperature requirements realistic or desirable?” Building and Environment, V 45(1), 4‐10

ASI2 ‐ Prof. Richard de Dear ‐ Part 2 11/01/2016

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+3 Hot

+2 Warm

+1 Slightly warm

0 Neutral

-1 Slightly cool

-2 Cool

-3 Cold

• Lisa Heschong’s 1979 book “Thermal Delight in Architecture” contends that it’s actually desirable to experience thermal sensations

• Many examples of delightful spaces having pronounced thermal character (anything but neutral)

• Rather than thinking of the outdoor urban thermal environment in purely negative terms (i.e. a source of dissatisfaction), as engineers do, Heschong recognises its positive attributes, and sees it as another expressive of design element to work with

So is neutrality really what we want?

• Imagine this scenario: Sydney in August (that’s the coldest month of our year Downunder!)

• ta = 18oC

• tr = 32oC

• rh = 30%

• v = 0.70 m.s-1

• clo = 0.9

• metabolic rate = 58.2 W.m-2 or 1 met

• The heat-balance models for steady-state exposure under these conditions say I should feel cool (PMV= -1.5).

• The subject says it feels delightful!

So is neutrality really what we want?

ASI2 ‐ Prof. Richard de Dear ‐ Part 2 11/01/2016

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ASI2 ‐ Prof. Richard de Dear ‐ Part 2 11/01/2016

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Thermal masochism?

Patrick Bellew – Atelia Ten (Gardens by the Bay, Singapore)

ASI2 ‐ Prof. Richard de Dear ‐ Part 2 11/01/2016

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Thermal hedonism?

Definitely thermal hedonism!

ASI2 ‐ Prof. Richard de Dear ‐ Part 2 11/01/2016

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The hearth

ASI2 ‐ Prof. Richard de Dear ‐ Part 2 11/01/2016

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The Persian Garden

“The classical Persian garden is intended to provide the antidote to

both the lethargy and the exhaustion of the senses. There is the liveliness of the fountains and

the overhanging vines with their fluttering leaves that create a

dappled light. And there are also areas of still water and large stone pavilions that create a deep, quiet

shade. One is free to move among these different elements and to

choose the place where the balance of liveliness and quietude are just right. The Persian garden

offers an amazing richness and variety of sensory experiences which all serve to reinforce the pervasive sense of Coolness.”

(Heschong, 1979, p.27)

Golestan Palace, Tehran.

ASI2 ‐ Prof. Richard de Dear ‐ Part 2 11/01/2016

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ASI2 ‐ Prof. Richard de Dear ‐ Part 2 11/01/2016

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ASI2 ‐ Prof. Richard de Dear ‐ Part 2 11/01/2016

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Example:‘Miroir d’eau’, Bordeaux, France

Images:http://ourfrenchgarden.blogspot.com/2012/08/le‐miroir‐deau‐bordeaux.html

Architect: Michel Courajoud

ASI2 ‐ Prof. Richard de Dear ‐ Part 2 11/01/2016

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• People rarely achieve steady-state with the outdoor bioclimatic environment so, to me, much of the conventional science of thermal comfort seems irrelevant to the question at hand.

• Temporal transients in those heat-balance parameters due to temporal variations (subject moving from one microclimate to another)

• Spatial inhomogeneities in those heat-balance parameters due

Non-steady-state or non-isothermal exposures to the Outdoor Urban Climate: Alliesthesia

Instead of regarding thermal variance as “discomfort” could it be a positive attribute?

•Rather than defining comfort in the engineer’s subtractive way i.e. the absence of thermal sensation (neutrality), surely there’s a more meaningful framework for understanding our experience of outdoor urban micrtoclimates?

•An alliesthesial phenomenology of bio-climate prompts a new lexicon of thermal comfort; - “thermal texture” describes spatial thermal variation- “thermal counterpoint” describes temporal thermal variation- “thermal polarity” describes the relationship between…

(a) the sign of the local thermal stimulus (warming or cooling), and(b) the sign of the whole-body thermal sensation (warm or cool)

de Dear, R

. (2011) “R

evisiting an

 old hypothesis o

f human

 therm

al perce

ptio

n: A

lliesthesia”. 

Building R

esearch

 and Inform

ation 39, (2

): 108‐117.

ASI2 ‐ Prof. Richard de Dear ‐ Part 2 11/01/2016

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Thermal alliesthesiaIn a classic 1971 paper in Science titled “The physiological role of pleasure,”Cabanac coined the term alliesthesia to explain how the internal state of the body determines the hedonic tone of environmental stimuli. 

For our thermal sense this leads to two scenarios…* positive alliesthesia:  a stimulus feels pleasant if it has the potential  to restore internal temperature to its normal (setpoint) value e.g. if core temp is higher than setpoint, peripheral cooling delivers thermal delight, reinforcing behavioral thermoregulation

* negative alliesthesia:  stimulus is unpleasant when behavioral avoidance restores internal temperature to its normal value  e.g. if core temp is lower than setpoint, peripheral convective cooling is experienced as draft, or worse, windchill

For example alliesthesia explains how identical rates of air movement be perceived as: 

•an unpleasant draft in one context, and •a pleasant breeze in a different setting

Experimentally induced thermal alliesthesia

Mower, G

. D. (1

976). P

erce

ived Inten

sity of P

erip

heral Th

erm

al Stim

uli is In

dependent o

f Intern

al Body Te

mperatu

re. Jo

urnal of 

Comparative a

nd Physio

logica

l Psych

ology, 9

0(2), 1

152–1155.

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Temporal and spatial variants of thermal alliesthesiaThe term “alliesthesia” came from the physiological sciences where the focus is traditionally on thermal-environmental extremities of this diagram where discomfort is clear and behavioral thermoregulation carries obvious biological significance

The alliesthesia hypothesis begs the question; Is discomfort a pre-requisite for thermal pleasure?

This got us interested in exploring alliesthesia within the region of adaptive thermal acceptability (what the physiologists call the “thermo-neutral zone”)

Tom Parkin

son (P

hD research

 project at U

niversity o

f Sydney) 

Temporal dimensions of thermal alliesthesia

Plan of different alliesthesia experiments in climate chamber

Tom Parkinson (PhD research project at University of Sydney)

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Relationship between thermal pleasure and preceding thermal discomfort

1 minute prior transient

1 minute post transient

* p<0.05

Tom Parkinson (PhD research project at University of Sydney) 

Summary of temporal alliesthesia

• Alliesthesia can occur within the region of adaptive thermal acceptability(i.e. thermoneutral region of vasomotor regulation). 

• Alliesthesial signal‐to‐noise ratio tends to be stronger when the subject is more distant from their preferred temperature.

• When core temperature cooler than its setpoint, any peripheral stimulation of cutaneous warm receptors will trigger positive alliesthesia.  Peripheral stimulation can be through any of the heat transfer modes… ‐ radiative heat gain‐ convective heat gain‐ latent heat gain‐ conductive heat gain

• When core temperature is warmer than its setpoint, any peripheral stimulation of cutaneous cold receptors will trigger positive alliesthesia. Peripheral stimulation can be through any of the heat transfer modes… ‐ radiative heat loss‐ convective heat loss‐ latent heat loss‐ conductive heat loss 

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Investigations of spatial thermal alliesthesia within the adaptive comfort zone

Summary of spatial alliesthesia

• Within the region of adaptive thermal acceptability (thermoneutralzone) we found evidence that spatial differences in skin temperature trends were correlated with alliesthesia

• Global (whole-body) thermal pleasure can be influenced by skin temperature trends at single distal sites (hands, feet)

ASI2 ‐ Prof. Richard de Dear ‐ Part 2 11/01/2016

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Topophilia and the poetics of space

• The American geographer Yi-Fu Twan uses the term “topophilia” to refer to the feelings that we associate with particular locations, and which collectively define a sense of place – our “emotional landscape.” The loved place is a repository of meanings that arise from the accumulation of the more profound emotional experiences in that space. In so many examples in Heschong’s book I see positive thermal alliesthesia having a significant role to play in creation of topophilia

• reinstating the thermal sense to the urban designer’s palette enriches our total experience of built space

• Designing urban areas for thermal pleasure leads away from… - isothermal, - constant, - imperceptible (neutral) thermal environments

• Thermal pleasure is found in variations - thermal stimulation- counterpoint of core and peripheral thermoreceptors - thermally textured environments or pathways

Thermal Texture

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• e.g. Universal Thermal Climate Index (UTCI)- UTCI is just a steady-state heat balance models- But alliesthesia implies a thermal gestalt “the whole thermal experience is more than just the sum of individual heat transfers”

• Makoto Nakayoshi (Tokyo Institute of Technology – Kanda’s lab) introduced the concept of “Lagrangian Urban Climate” relating to the thermal experiences of a subject moving through a textured, urban thermal environment.

• Lagrangian thermal comfort models will need to incorporate the dynamic characteristics of cutaneous thermoreceptors

What Does Alliesthesia Do For Outdoor Thermal Comfort Models?

Meteorological part Physiological part

Short& Long wave radiation, Heat exchange velocity(Globe anemo-radiometer)

Air temperature & Humidity sensor in the radiation shield

Data logger for physiological variables

Pulse rate

Perception of heat

Body motion(Acceleration sensor)

Data logger for micro climate variables

Nakayoshi, M., Kanda, M., Shi,R. and de Dear, R.  (2015). "Outdoor thermal physiology along human pathways: a study using a wearable measurement system.” International Journal of Biometeorology 59: 503‐515.

ASI2 ‐ Prof. Richard de Dear ‐ Part 2 11/01/2016

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Biotope area

Green spot

Reflective painted area

Commercial area

Parking lot

Observational route & pictures

27 28.5 30 31.5 33 [deg C]

Ta [8:00‐10:30] on August 24th

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33.5 34 34.5 35 35.5 [deg C]

Tskin [8:00‐10:30] on August 24th

Skin cold receptors are more sensitive to transientsthan warm receptors

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Step-wells of Gujurat

• Blending Hindu and Islamic styles of architecture, their lattice-like walls, profusely carved columns, ornamented towers, and intricate relief sculptures throughout make them exceptional architecture. For these past 500 years, step-wells have been an integral part of western Indian communities as sites for drinking, washing, and bathing, as well as for colorful festivals.

Adelaj step-well near Ahmedabad

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Adelaj step-well near Ahmedabad

The Adelaj Step-well

Descending six storeys into the earth creates a 

pronounced thermocline of at least 6~8K, from the mid‐to‐high thirties at ground level (combined with 

intense solar heat loads). 

This creates a trajectory of temporal alliethesia (thermal delight) that 

gently suffuses the visual delight of the 

step‐well 

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Negative alliesthesia = antagonism between core and peripheryPositive alliesthesia = complementarity between core and periphery

ConclusionsNo matter how precisely applied, the subtractive approach to the task of

providing thermal comfort – removal of all thermal sensation – completely

misses the point of how we perceive outdoor

bioclimatic environments

Is it time to eschew isothermal, homogenous, steady micro-climate and

start designing thermal texture and counterpoint

as potential thermal pleasure rather than local

discomfort?

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End, Thank you

Richard de DearThe University of SydneyRichard.Dedear@sydney.edu.ausydney.edu.au/architecture/research/ieq/index.shtml