Indoor climate: A comparison of residential units in Tjärna Ängar, Borlänge before and after retrofitting

Master Level Thesis

Energy Efficient Built Environment

No.12, Jun 2018

Indoor climate,

A comparison of residential units

in Tjärna Ängar, Borlänge before

and after retrofitting

Master thesis 15 credits, 2018

Energy Efficient Built Environment

Author:

Iuri Abreu Saraiva Freitas

Supervisor:

Amir Sattari

Examiner:

Csilla Gal

Course Code: EG3020

Examination date: 2018-06-05

K

Dalarna University

Energy Engineering

Abstract

This study try to understand which aspects were fundamental to indoor climate and how to

obtain them in order to provide the best possible experience in the thermal comfort of

individuals. Thus, arose the studies of Fanger, which was the seed for a new era of

discoveries in the area and founded the knowledge our society have today in this globally

used standards and norms. Referring to these fundamental aspects of the indoor comfort,

data collection was taken in situ to show in details what was happening. This study was

executed in order to demonstrate the differences between the data previous and after a

process of retrofitting in dwellings built in the 60s and 70s of the century past, in the district

of Tjärna Ängar, Borlänge, Sweden. The comparative results using criteria such as Predicted

Mean Vote (PMV), Predicted Percentage Dissatisfied (PPD), Draft Rate (DR), air velocity,

Mean Radiant Temperature (MRT), Relative Humidity (RH) and air temperature, showed an

improvement in 6 of the 8 parameters analyzed. Confirming the expectation that through

the retrofitting the residents will be more satisfied, obtain better quality of indoor climate

comfort and also increase occupied area in these dwellings.

Contents

1 Introduction ... 1

Background ... 1

Aims & Objectives ... 1

2 Theory ... 2

Heat transfer and human body ... 2

2.1.1. Convection ... 2

2.1.2. Thermal radiation ... 2

2.1.3. Evaporation ... 3

Factors in human comfort ... 3

2.2.1. Metabolic rate ... 3

2.2.2. Clothing ... 4

2.2.3. Air temperature ... 7

2.2.4. Mean radiant temperature ... 8

2.2.5. Air velocity and draft ... 9

2.2.6. Relative humidity ... 10

PMV index ... 12

PPD index ... 14

3 Methodology ... 14

Testo 480 and sensors ... 14

Measurement sites and retrofitting changes ... 17

Occupied zone ... 17

Measurement procedure ... 18

Measurement period ... 19

Reference data ... 20

Standardization of data ... 20

Calculation of PMV and PPD ... 20

Calculation of draft rates ... 20

External climate data ... 21

Daily means and their comparison ... 22

4 Results and discussion ... 23

Air temperature results ... 23

Air velocity results ... 24

Mean radiant temperature results ... 25

Relative humidity results ... 26

Predicted Mean Vote results ... 27

Predicted Percentage Dissatisfied results ... 28

Draft rate results ... 29

Errors ... 31

Limitations of study ... 31

Recommendations for future work ... 33

5 Conclusions ... 32

6 References ... 36

Appendices ... 35

Abbreviations

Abbreviation Description

AIS

Artificial Intelligence Systems

ANSI

American National Standards Institute

ASHRAE

American Society of Heating, Refrigerating, and Air-Conditioning

Engineers

BBR

Boverkets Byggregler

BFS

Boverkets Författningssamling

DR

Draft Rate

DVUT

Dimensionerande Vinterutetemperatur

EAT

Ergonomics and Aerosol Technology

EN

European Standard

HBI

Heat Balance Index

HVAC

Heating, ventilation, and air conditioning

IoT

Internet of Things

ISO

International Organization for Standardization

LTD

Local Thermal Discomfort

LTH

Lunds Tekniska Högskola

MRT

Mean Radiant Temperature

MRT

Mean Radiant Temperature

PD

Percentage dissatisfied

PMV

Predicted Mean Vote

PPD

Predicted Percentage Dissatisfied

PPM

Parts Per Million

RA

Radiant Asymmetry

RH

Relative Humidity

RT

Radiant Temperature

SIS

Swedish Standards Institute

SMHI

Swedish Meteorological and Hydrological Institute

SS

Swedish Standards

WBGT

Wet-Bulb Globe Temperature

Nomenclature

Symbol

Description

Unit

!̅

r

Mean radiant temperature

ºC

#̅

Mean air velocity

m/s

#̅

a,l

Local mean air velocity

m/s

#̅

a,l

Mean air velocity

m/s

clo

Thermal insulation

m²·ºC/W

f

cl

Clothing surface area factor

h

c

Convective heat transfer coefficient

W/m

2

·K

I

cl

Clothing insulation

clo

I

clu

Clothing insulation united

clo

M

Metabolic energy production

W/m

2

met

Metabolic rate

W/m

2

P

a

Water vapor partial pressure

Pa

t

a

Air temperature

ºC

t

a,l

Local air temperature

ºC

t

cl

Clothing surface temperature

ºC

t

pr

Plane radiant temperature

ºC

T

s

Surface temperature

ºC

T

u

Turbulence intensity

%

U

Thermal transmittance

W/m

2

_·K

V

a

Average air speed

m/s

v

ar

Relative air velocity

m/s

W

Effective mechanical power

W/m

2

_·K

Δt

Temperature variation

ºC

Δt

pr

Radiant temperature asymmetry

ºC

1 Introduction

From the beginning of time, humans have been are looking for comfortable environments

that can protect from severe weather and at the same time provide with comfort. The

humankind have lived in caves, through small settlements, small villages until start to live in

modern cities. Throughout this journey, and especially after the industrial revolution, aspects

that make up the spectrum of internal climate were increasingly highlighted and became

necessary. Nowadays, in modern buildings with many walls, enclosed and

compartmentalized environments, achieving a very high level of comfort has become a

challenge for professionals in the area. Today, a good indoor environment is a basic

requirement for a building, whose purpose is to protect residents from external influences

and create a good and healthy environment to live and work in. To achieve a good indoor

environment, it is needed to consider many parameters such as air quality, water quality,

hygiene, moisture safety, fire safety, air tightness, thermal comfort, activities, nutrition, radon

presence, sound and acoustics and light environments. Many of these areas are linked

directly or indirectly to the theme of this study and will be further explored throughout the

chapters in this text. However, even with so many variables and challenges, new

technologies, new studies and new scientific instruments are increasingly revealing the details

of how indoor climate can be achieved.

Background

During the 1960s and 1970s, Sweden implemented a large-scale housing program that

became known as the "million-program". One of the projects that were built within this

program was the Tjärna Ängar, constructed by Tunabyggen company, is located northwest

of Högskola Dalarna in the town of Borlänge. Comprising more than 20 blocks of up to 4

floors.

After more than 50 years since the construction period, housing estates of this period are

now undergoing serious retrofitting needs to avoid possible damages to the structures and

the residents, as well as to adapt the social needs of our time. The demands for quality,

comfort, material excellence and low energy consumption make these retrofitting extremely

necessary.

This demonstrates the necessity of retrofitting processes as soon as possible in the country.

Due to this situation, this study will show the changes in the indoor climate as a result of the

interventions aimed at renovating the property. Using scientific equipment to measure

changes in air temperature, radiant temperature, air velocity and humidity for short and long

periods in order to collect sufficient data to assist in the evaluation of the quality of the

thermal comfort. The reason is to determine if the residents will benefit from a dwelling

within the established standards.

According to Fanger's studies dating from the late 1960s on the predicted mean vote (PMV)

model of thermal comfort, still used today as the basis for studies in the area, both in the

standards presented by ANSI/ASHRAE Standard 55-2013 and SS-EN ISO 7730: 2006. In

addition, many other current studies, basic concepts such as heat balance, sweat rate for

comfort and mean skin temperature for comfort, should be understood previously before

going further. Other important parameters are related to areas such as air velocity, mean

radiant temperature, relative humidity, air temperature, metabolic rate and clothing

insulation. These parameters will be fundamental to better understanding the bases that

support the calculations presented throughout this work in the area of Predicted Mean Vote

(PMV), Predicted Percentage Dissatisfied (PPD) and Draft Rate (DR).

Aims & Objectives

The aim of this study is to demonstrate through scientific data collected in situ the impacts

of a retrofitting process regarding indoor climate and occupied comfort zone.

2 Theory

Research on thesis and scientific articles that dealt with aligned themes were compiled and

studied bringing more scientific weight to the present study. Subjects such as definition of

thermal comfort, variation of thermal comfort, scope of variation (or ranges) of comfort,

reflections on retrofitting/revitalization services, modernization processes, study of subjects,

among many other subjects were analyzed prior or during process of developing this thesis.

The SS-EN ISO 7730: 2006 [1] and the ANSI/ASHRAE Standard 55-2013 [2] was

fundamental for this study because it provided explanations, formulas, definitions and other

points essential to this analysis. As well as Fanger's studies on internal comfort, comfort

scale definitions, use of PMV and PPD to define situations, and categorize numerical and

scientific measurement of the data collected.

As part of the proposal of this thesis it was also necessary to have previous data regarding

apartments with the same physical characteristics as those used in the present study. Thus,

data collected by Amir Sattari prior to retrofitting were also utilized in this study.

Heat transfer and human body

Heat transfer occurs when energy and entropy are transmitted from one location to another

[3]. Thermal equilibrium is a natural state of the laws of physics. If there is a difference

between temperatures between two bodies, they tend to equate over time until both have

the same temperature. Three are the phenomena connected to heat transfer: conduction,

convection and radiation [3]. However, “in the case of the human body, the heat transfer by

conduction is limited to the body parts in contact with solid surfaces, which are generally

restricted to a few, namely to the feet, and thus usually neglected. Therefore, the heat is

transferred mainly by convection and radiation” [4].

For this study, will be followed the line of reasoning that being disregarded the transfer of

heat by the conduction due to its insignificant portion in front of the total, it will be more

relevant to consider the portion of heat exchange due to the evaporation of the human body

through the skin. In this way, the article dealing with the Heat Balance Index (HBI) has in

its methodology the considerations for calculating the HBI [5]. According to the statement,

“the comfortable heat balance of the body is given by the algebraic sum of the metabolic

heat production and the heat transfer between the body and the surrounding given by the

mechanisms of radiation, convection and evaporation” [5]. Thus, there are three ways to

exchange heat between the human body and the environment which will have their

definitions presented below: convection, thermal radiation and evaporation.

2.1.1. Convection

Convection “involves movement of a heated fluid, such as air, usually a fairly rapid process”

[3]. The process of convective heat removal occurs when air presents body temperature and

the body transfers heat through the contact with the surrounding cold air. Heating the air

causes it to move ascensional as hot air rises, cold air takes its place, thus occurs convection

cycle. If the air temperature is exactly the same as the surface temperature of the body, there

will be no thermal exchange through this process. If the air temperature is higher than that

of the surface of the body, the air will yield heat to the body by reversing the mechanism [3].

2.1.2. Thermal radiation

“Radiation refers to the transmission of energy as electromagnetic radiation from its

emission at a heated surface to its absorption on another surface, a process requiring no

medium to convey the energy” [3]. It is the process by which radiant energy is transmitted

from the hot surface to the cold by means of electromagnetic waves that, upon reaching the

surface cold, they become heat. Radiant energy is emitted continuously by all the bodies that

are at a temperature above zero absolute. This is equivalent to saying that a person in an

environment is continuously emitting and receiving radiant energy, and the differential

between the received and emitted energy is that it defines whether the body is heated, or

radiation cooled. Consequently, if the temperature of the walls of an environment is lower

than that of a man's skin, this person will lose heat radiation. If the walls are warmer than

the skin, the temperature of the body will increase as a result of radiation. Thermal radiation

does not rely on air or any other means to propagate, and the amount of radiant energy

emitted by a body depends on its surface temperature [3].

2.1.3. Evaporation

When the ambient conditions cause the heat losses of the human body by convection and

radiation are not sufficient to regulate the its internal temperature, the organism intensifies

the activity of the glands perspiration and loses heat by evaporating the moisture (sweat) that

forms in the skin [2]. The explanation is simple: simultaneously to the sweating occurs to

the evaporation of sweat, this is an endothermic phenomenon, that is, to occur accurately

of heat from the body. In a simplified way, it can be said that a liquid evaporating on a hot

surface draws heat from that surface, cooling it down [2].

Factors in human comfort

For thermal comfort to be possible in humans, many factors can influence. According to

the American National Standards Institute (ANSI) and the American Society of Heating,

Refrigerating, and Air-Conditioning Engineers (ASHRAE) in the document

ANSI/ASHRAE Standard 55-2013, "thermal comfort is that condition of mind that

expresses satisfaction with the thermal environment" [2]. The same way the International

Organization for Standardization (ISO) in his publication ISO 7730:2005 and on his Swedish

version (SS-EN ISO 7730: 2006) define that “the thermal sensation of a human being is

mainly related to the thermal balance of his body as a whole” [1]. However, this definition

is not so easy to apply in practice.

Therefore, it is possible to affirm that psychological and physiological variations, which are

different for each individual, make the definition of a pattern very complex. In order to

avoid a relativized pattern that depends on so many hypotheses, it was necessary to develop

scientific methods to more fully measure the definition of the term thermal comfort.

Through laboratory studies and surveys that collected statistical data, specific conditions

were defined for some primary factors that directly influence our thermal sensation [2].

These factors are:

1. Metabolic rate;

2. Clothing insulation;

3. Air temperature;

4. Radiant temperature;

5. Air speed;

6. Humidity.

The factors could be divided between personal and environmental. The personal factors are

metabolic rate and clothing insulation, while those dealing with environmental factors are

air temperature, radiant temperature, air speed, and relative humidity.

2.2.1. Metabolic rate

The metabolic rate can be defined as the energy generated from the human body and its unit

of measure can be known as “met”. In ANSI/ASHRAE Standard 55-2013 it is quoted that

“the metabolic rates increase above 1.0 met, the evaporation of sweat becomes an

increasingly important factor for thermal comfort” [2]. However, the PMV method does not

consider this factor as a whole, it is not feasible to apply this method to a situation where

the metabolic rate is greater than 2.0 met [1].

This table is present in SS-EN ISO 7730: 2006, identified as Annex B, showing the metabolic

rates of different activities, as seen in the Table 1:

Table 1: Table “Annex B.1” of metabolic rates from SS-EN ISO 7730:2006 [1].

Activity

Metabolic rate

W/m²

met

Reclining

46

0.8

Seated, relaxed

58

1.0

Sedentary activity (office, dwelling, school, laboratory)

70

1.2

Standing, light activity (shopping, laboratory, light industry)

93

1.6

Standing, medium activity (shop assistant, domestic work, machine

work)

116

2.0

Walking on level ground:

2 km/h

110

1.9

3 km/h

140

2.4

4 km/h

165

2.8

5 km/h

200

3.4

The table above explains that depending on the position of the body and/or where this body

is located there is a variation of the metabolic rate. This rate becomes higher due to positions

and environments that demand greater physical effort [1].

For criterion of future calculations, this study considered in all its measurements a metabolic

rate of 65 W/m² or approximately 1.1 met, meaning, absolute rest of an individual. Regarding

to rate of mechanical work, in this study the standard adopted was 0.0 W/m². These

definitions will be important within the methodology process.

2.2.2. Clothing

Clothing can be defined as the amount of thermal insulation the person is wearing, but as in

other cases, this criterion may have different definitions. For this study it will be used the

same definition used in ANSI/ASHRAE Standard 55-2013, the clothing insulation (I

cl

) of

an ensemble expressed as a value is used.

The insulation protection can be determined in many ways, according to the aforementioned

standard. There are four possible methods described in the standard that can be used to

estimate the clothing insulation each of them considering different situations. These are

named as metabolic rate, rate determination, time-weighted averaging and high metabolic

rates [2].

Also, postures such as standing or sitting can result in differences between values, because

of the decreased thermal insulation due to the compressed air layers in the clothing, as seen

at ANSI/ASHRAE Standard 55-201, “Table 5.2.1.2 Metabolic Rates for Typical Tasks” [2].

Other considerations can also be seen in the examples of clothing insulation provided by a

chair, tables and other objects in the same place. Openings in fabrics, dressing styles,

different types of fabrics with density and/or different materials, even objects such as the

bed where someone is lying down, the sex of the person used for the study, and the amount

of objects or people with different values of clothing insulation are other of the many

variables described in the norm of standardization [2].

In Tables 2 and 3, it is possible to understand the information described above in a clearer

manner. There are two ways to analyze clothing insulation (I

cl

):

1) Directly from the values that make up Table 2 if it is necessary to combine more

than one clothing item (the values are for static thermal insulation),

2) Indirectly, when all the items that make up the clothing of the individual as a whole

are added together (I

clu

), as shown in Table 2 [1].

Table 2: “Table C.1” of thermal insulation for typical combinations of garments from SS-EN ISO

7730:2006 [1].

Work clothing

I

cl

Daily wear clothing

I

cl

clo

m²·K/W

clo m²·K/W

Underpants, boiler suit,

socks shoes

0.70

0.110

Panties, T-shirt, shorts,

light socks, sandals

0.30

0.050

Underpants,

shirt,

boiler suit, socks, shoes 0.80 0.125

Underpants, shirt with

short sleeves, light

trousers, light socks,

shoes

0.50

0.080

Underpants,

shirt,

trousers, smock, shoes

0.90

0.140

stockings, dress, shoes

Panties, petticoat,

0.70

0.105

Underwear with short

sleeves and legs, shirt,

trousers, jacket, socks,

shoes

1.00

0.155

Underwear shirt, trousers,

socks, shoes

_0.70

_0.110

Underwear with long

legs

and

sleeves,

thermo-jacket, socks,

shoes

1.20

0.185

Panties, shirt, trousers,

jacket, socks, shoes

_1.00

_0.155

Underwear with short

sleeves and legs, shirt,

trousers, jacket, heavy

quilted outer jacket and

overalls, socks, shoes,

cap, gloves

1.40

0.220

Panties, stockings, blouse,

long skirt, jacket, shoes

1.10

0.170

Underwear with short

sleeves and legs, shirt,

trousers, jacket, heavy

quilted outer jacket and

overalls, socks, shoes

2.00

0.310

Underwear with long

sleeves and legs, shirt,

trousers, V-neck sweater,

jacket, socks, shoes

1.30

0.200

Underwear with long

legs

and

sleeves,

thermo-jacket

and

trousers, parka with

heavy quitting, overalls

with heavy quilting,

socks,

shoes,

cap,

gloves

2.55

0.395

Underwear with short

sleeves and legs, shirt,

trousers, vest, jacket,

coat, socks, shoes

_1.50

_0.230

Table 3 shows how certain pieces of clothing of various types can be combined to change

the thermal insulation of the individual as a whole (I

clu

) and quantify the respective Change

Table 2 “gives the corresponding change in the optimum operative temperature necessary

to maintain thermal sensation at neutral when a garment is added or removed at light mainly

sedentary activity (1.2 met)” [1]. In other words, Table 2 shows how the use of certain clothes

can change the thermal insulation and as a result of this a change in the thermal sensation

of the users. The greater the clothing insulation (I

cl

) the greater the thermal insulation and

consequently the greater capacity to retain heat the laundry will have. This table also shows

that work clothes generally have higher I

cl

than daily wear.

Table 3: “Table C.2” of thermal insulation for garments and changes of optimum operative temperature

from SS-EN ISO 7730:2006 [1].

Garment

I

clu

optimum operative

Change of

temperature, °C

clo

m²·K/W

Underwear

Panties

0.03

0.005

0.2

Underpants with long legs

0.10

0.016

0.6

Singlet

0.04

0.006

0.3

T-shirt

0.09

0.014

0.6

Shirt with long sleeves

0.12

0.019

0.8

Panties and bra

0.03

0.005

0.2

Shirts/Blouses

Short sleeves

0.15

0.023

0.9

Light-weight, long sleeves

0.20

0.031

1.3

Normal, long sleeves

0.25

0.039

1.6

Flannel shirt, long sleeves

0.30

0.047

1.9

Light-weight blouse, long sleeves

0.15

0.023

0.9

Trousers

Shorts

0.06

0.009

0.4

Light weight

0.20

0.031

1.3

Normal

0.25

0.039

1.6

Flannel

0.28

0.043

1.7

Dresses/skirts

Light skirts (summer)

0.15

0.023

0.39

Heavy skirt (winter)

0.25

0.039

1.6

Light dress, short sleeves

0.20

0.031

1.3

Winter dress, long sleeves

0.40

0.062

2.5

Boiler suit

0.55

0.085

3.4

Sweaters

Sleeveless vest

0.12

0.019

0.8

Thins sweater

0.20

0.031

1.3

Sweater

0.28

0.043

1.7

Thick sweater

0.35

0.054

2.2

Jackets

Jacket

0.35

0.054

2.2

Smock

0.30

0.047

1.9

High-insulative, fiber-pelt

Boiler suit

0.90

0.140

5.6

Trousers

0.35

0.054

2.2

Jacket

0.40

0.062

2.5

Vest

0.20

0.031

1.3

Outdoor clothing

Coat

0.60

0.093

3.7

Down jacket

0.55

0.085

3.4

Parka

0.70

0.109

4.3

Fiber-pelt overalls

0.55

0.085

3.4

Sundries

Socks

0.02

0.003

0.1

Thick, ankle socks

0.05

0.006

0.3

Thick, long socks

0.10

0.016

0.6

Nylon stockings

0.03

0.005

0.2

Shoes (thin soled)

0.02

0.003

0.1

Shoes (thick soled)

0.04

0.006

0.3

Boots

0.10

0.016

0.6

Gloves

0.05

0.008

0.3

Table 4 shows the additional insulation values generated by the chair in cases for sedentary

people. These values can range from 0.0 to 0.4 clo [1], but in Table 4 only shows values

between 0.00 clo and 0.15 clo.

Table 4: “Table C.3” of thermal insulation values for chairs from SS-EN ISO 7730:2006

[1].

Type of chair

I

clu

clo

m²·K/W

Net/metal chair

0.00

0.00

Wooden stool

0.01

0.002

Standard office chair

0.1

0.016

Executive chair

0.15

0.023

2.2.3. Air temperature

Defined as temperature of the air surrounding the occupant, air temperature is one of the

aspects that can most directly influence the thermal sensation of an individual and

consequently his thermal comfort. Together with the mean radiant temperature, the smallest

variations are already capable of influencing factors such as PMV and PPD, according to the

calculations performed for this study which will be shown later with data and graphs [2].

When the air temperature is lower than that of the skin, the removal of heat by convection

will be all the greater the lower the air temperature. If the air is at a higher temperature than

the skin, it will give heat to the body by convection. As for evaporation, the influence of air

temperature will depend on relative humidity and air velocity [2].

It should be remembered that some Swedish regulations define minimum temperatures so

that the thermal comfort of its users is possible. In the case of the Swedish National Board

of Health and Welfare (in Swedish: Socialstyrelsen) the minimum temperatures so that the

thermal comfort should not be below 20 °C [7]. According to other organizations such as

"Boverket's building regulations - mandatory provisions and general recommendations, BBR

", at Boverkets Författningssamling (BFS) 2011: 6, with amendments up to BFS 2016: 6,

similarly the Public Health Agency of Sweden (in Swedish: Folkhälsomyndigheten) as well

the Swedish Work Environment Authority (in Swedish: Arbetsmiljöverket) declare also have

rules pertaining to indoor temperature [8]. In BFS 2015:3, section 6:42 [9] it is stated that in

order to have thermal comfort in the space intended to be used, it is first necessary to ensure

that the construction shall be designed in agreement to the point of at least reaching normal

operating conditions. In this way the outdoor design condition, as the term is defined in

ANSI/ASHRAE Standard 55-2013 [2], (in Swedish: dimensionerande vinterutetemperatur,

DVUT) must be calculated to “ensure the lowest directed operative temperature in the

occupied zone is estimated to be 18 °C in residential and workrooms and 20 °C in sanitary

rooms and healthcare facilities and in rooms for children in preschools and for the elderly

in service buildings and similar establishments”, as translated [9].

Another concept to be presented is the average air temperature, which according to

ANSI/ASHRAE Standard 55-2013 is the average of the temperature values that compose

the scenery around an individual (or measurement instrument) at a specific location and time

[2].

2.2.4. Mean radiant temperature

It is also necessary to introduce the concept of mean radiant temperature (MRT) that is “the

temperature of a uniform, black enclosure that exchanges the same amount of heat by

radiation with the occupant as the actual enclosure. It is a single value for the entire body

expressed as a spatial average of the temperature of surfaces surrounding the occupant

weighted by their view factors with respect to the occupant” [2]. MRT can be obtained from

globe thermometer measurements. However, while a spherical sensor represents the human

body in seated position, an ellipsoid-shaped one can represents it in either standing or sitting

position [2].

The principle of calculating mean radiant temperature (MRT) is that the globe being in

equilibrium with the environment, then the heat exchanged for radiation between the globe

and the surrounding surfaces is equal to the convective heat exchanged between the globe

and air [2]. As the thickness of the globe is small, the temperature of the confined air in it is

approximately equal to the surface temperature of the globe. Knowing this surface

temperature of the globe it is possible to determine the MRT.

One problem that arises from MRT is Radiant Asymmetry (RA). This problem is caused

when phenomena of warm or cool ceilings, walls/windows occur [1], or due to direct

sunlight [2]. With more detail this problem occurs when there is a difference between the

plane radiant temperature (t

pr

) in opposite directions. It can occur horizontally or vertically,

as explained by ANSI/ASHRAE Standard 55-2013: "The vertical radiant temperature

asymmetry is with plane radiant temperatures in the upward and downward directions. The

horizontal radiant temperature asymmetry is the maximum radiant temperature asymmetry

for all horizontal directions" [2]. Generally, this problem can cause local discomfort as well

as decrease the area of thermal satisfactoriness of the studied location, with people being

more easily affected by the hot ceiling than by other hot or cold delimiting vertical surfaces

[2] as can be seen in Figure 1 below, where vertically is the percentage dissatisfied (PD) in

percentage and horizontally is radiant temperature asymmetry (RA) measure in Celsius

degrees. Through the relation between these two axes is show how much a warm ceiling (1),

a cool wall (2), a cool ceiling (3) and a warm wall (4) can affect PD creating Local Thermal

Discomfort (LTD). Unlike the PMV and the PPD that express warm and cold depletion in

relation to the whole body, LTD refers only to the dissatisfaction caused by unwanted

cooling or heating of one particular part of the body [10].

Figure 1: Local thermal discomfort caused by radiant temperature (RA) asymmetry [1].

In case of LTD, those most affected are people with little or no physical activity (M = 70

W/m

2

_{), that is, considered to be sedentary. In these cases, because of the resting state, the}

body tends to equalize the temperature with that of the external environment, leaving the

thermal sensation near the neutral [1]. On the other hand, for people with high levels of

activity the perception of thermal discomfort becomes practically insignificant considering

that they become less thermally sensitive and therefore less vulnerable to the LTD [2].

2.2.5. Air velocity and draft

Air velocity is one of the aspects that most directly influence human comfort since it is

directly connected to air temperature, thermal sensation, evaporation (sweat), PPD among

other factors [1] [2]. Its occurrence

that changes our thermal sensation and our thermal

corporal comfort

a

llowing convective heat exchange between our body and the environment

expressed by PMV and PPD index and local thermal discomfort

[

1].

According to SS-EN ISO 7730: 2006 there is no minimum air velocity required for thermal

comfort, but empirically it is a fact that increasing the air velocity can serve to reduce the

sensation of heat, leaving the environment more refreshed, even if there is an increase in

temperature [1]. In situations of overheating, openings such as windows and doors can help

control the feeling of heat in the environment due to increased ventilation. In other cases,

mechanical ventilation can also achieve the same effects and benefits. With devices such as

doors, windows and other openings, it is possible to allow a temperature increase without

generating thermal discomfort in the local users.

To determine how much it will be possible to increase or decrease the temperature in an

environment through ventilation (air movement and dissipation) it is necessary to

understand how our body behaves in these hypothetical scenarios. SS-EN ISO 7730: 2006

define reference temperature of 26 °C and 0.20 m/s for air velocity [1]. To achieve benefits

of increased air velocity it is necessary to check other aspects such as clothing, physical

activity level and difference between surface temperature of clothing/skin and air

temperature.

Draft is defined as “unwanted local cooling of the body caused by air movement” [1], their

perception is correlated with factors such as air temperature, level of activity and the clothes

used by the person [2].

Regarding the last factor, the lower the coverage, the greater the person's perception of draft

rate [2]. The parts of the body that are most sensitive are the “head region comprising the

head, neck, and shoulders and the leg region comprising the ankles, feet, and legs” [2]. For

the calculation of DR, Equation 1 is to be used:

Equation 1: Draft formula from SS-EN ISO 7730:2006 [1]

$% = (34 − !

,,.

)(#̅

,,.

− 0,05)

2,34

(0,37 · #̅

,,.

· 7

8

+ 3,14)

Conditions:

For #̅

,,.

< 0.05 m/s: use #̅

,,.

= 0.05 m/s

For DR > 100 %: use DR = 100 %

Where:

!

_,,.

is the local air temperature, in degrees Celsius, 20 °C to 26 °C;

#̅

_,,.

is the local mean air velocity, in meters per second, < 0.5 m/s;

7

₈

is the local turbulence intensity, in percent, 10 % to 60 % (if

unknown, 40 % may be used).

In order to reach plausible values, the DR formula follows the considerations that the air

velocity cannot be equal to or less than 0.05 m/s, otherwise the second part of the equation

would be zero.

Some recommendations are made at SS-EN ISO 7730:2006 explaining this formula applies

to people with little or no physical activity (sedentary) therefore having a body temperature

close to the environment as well as to predict the draft at neck area [1]. In the same way as

in the height of the arms and feet this formula may overestimate the DR predicted [1]. The

higher the index of bodily physical activity the less will be the sensation of DR and based on

activities above 1.2 met in the same way as for people who feel warmer than neutral [1].

At operative temperatures below 22.5 °C, average air speed (V

a

) caused by the building, its

fenestration, and its HVAC system shall not exceed 0.15 m/s. This limit does not require

consideration of air movement produced by office equipment or occupants. As exception

the higher average air speeds (V

a

) that are permitted by Section 5.3.3 of ANSI/ASHRAE

Standard 55-2013 [2].

2.2.6. Relative humidity

In a short, relative humidity (RH) provides the relation of the maximum amount of moisture

the air may hold for a particular temperature [11]. In more scientific terms, the relative

humidity of the air at a given temperature is the ratio of the number of grams of water vapor

present in 1 m

3

_{of air to the maximum amount of grams of water vapor that 1 m}

3

_{of air may}

contain when saturated in that.

As relative humidity varies with air temperature, there are better means for quantifying the

amount of water diluted in the air. Such measure is for example the absolute humidity. It

expresses the water mass per unit volume (grams of water per cubic meter) or per unit mass

of air (grams of water per kilogram of air) as seen in Figure 2. Nevertheless, this study will

rely on the measure of relative humidity.

Figure 2: Relationship between saturation vapor content (g/m

3

_{) and temperature (ºC) according to absolute}

humidity definition [12].

In relation to human thermal comfort, the ANSI/ASHRAE Standard 55-2013 does not

establish lower limits to humidity. However, there are recommended lower limits established

on the basis of human well-being, such as dry skin, irritation of mucous areas, dry eyes and

generation of static electricity [2]. Low RH, especially during the winter period when low air

temperature reduces absolute humidity, can have serious consequences. "70 % of the staff

at Swedish offices, schools and kindergartens experiences that the air is too dry during the

winter season" [12], says a study conducted in Sweden between the months of December

2013 and March 2014. If possible, RH should be maintained around 40 % to 70 % so that

the risk of viruses and bacteria is reduced [12], as shows Figure 3.

Figure 3: Description of optimum zone of RH to lower risks of viruses and bacteria [12].

Mechanical (artificial) ventilation system have a tendency to reduce RH by 10 %, compared

to natural ventilation [12]. This is demonstrated by the study analyzing the mean indoor RH

and air temperature data in several Swedish regions. The results of this study is presented in

Figure 4. Data from the six different regions are sorted into three groups according to the

measured RH value ranges: (1) high values, (2) median values, and (3) low values [12].

Figure 4: Comparison in six different Swedish locations between RH values for constructions with

mechanical ventilation and natural ventilation between the period from January 3

rd

_{to March 7}

th

_{, 2014}

[12].

According to the ANSI/ASHRAE Standard 55-2013, the influence of RH on the heat

balance in moderate temperatures (below 26 °C) and at moderate activity levels (less than 2

met) is limited [2]. It is also stated that a 10 % increase may generate an increase in the thermal

sensation of 0.3 °C in the operative temperature. So, the more the ambient temperature

and/or the level of physical activity increases, the greater the impact the relative humidity of

the air will have on thermal comfort [2].

PMV index

Predicted Mean Vote (PMV) is “an index that predicts the mean value of the thermal

sensation votes (self-reported perceptions)”, been determined for a large group of people

using a seven point thermal sensation scale [2]. The thermal sensation of individuals is

expressed with the help of a seven point thermal sensation scale, which varies from “cold”

(-3), “cool” (-2), “slightly cool” (-1), “neutral” (0), “slightly warm” (+1), “warm” (+2) until

“hot” (+3) [2]. According to the standard, the recommend range of PMV is between -0.5

and +0.5 [2].

Table 5: Fanger's definition of thermal sensation scale described as “Seven-point thermal sensation scale”

at SS-EN ISO 7730:2006 [1].

Seven-point thermal sensation scale

Hot

+3

Warm

+2

Slightly warm

+1

Neutral

0

Slightly cool

-1

Cool

-2

Cold

-3

Since the human thermal balance is the function of the previously discussed environmental

and personal factors, it is possible to estimate the thermal sensation of occupants using the

PMV formula (see Equation 2.) [1].

Equation 1: Formula to calculate Predicted Mean Vote (PMV) from SS-EN ISO 7730:2006 [1]

;<=>?=<!@ !ℎ@ BCD ?EFGH @I?<!FJGE (1) !J (4):

(1) BCD = [0.303 · exp(−0.036 · C) + 0.028] · {(C − V) − 3.05 · 10

WX

· [5733 − 6.99 · (C − V) − Z

_,

] − 0.42 · [(C − V) − 58.15 − 1.7

· 10

W[

_{· C · (5867 − Z}

,

) − 0.0014 · C · (34 − !

,

) − 3.96 · 10

W\

· ]

^.

· [(!

_^.

+ 273)

_

_{− (!̅}

`

+ 273)

_

] − ]

^.

· ℎ

^

· (!

^.

− !

,

)

(2) !

_^.

= 35.7 − 0.028 · (C − V) − a

_^.

· {3.96 · 10

W\

_{· ]}

^.

· [(!

^.

+ 273)

_

− (!̅

_`

+ 273)

_

_{] + ]}

^.

· ℎ

^

· (!

^.

− !

,

)}

(3) ℎ

^

= c

2.38 · |!

_^.

− !

_,

|

2,4[

_{]Je 2.38 · |!}

^.

− !

,

|

2,4[

> 12.1 · g#

,`

12.1 · g#

,`

]Je 2.38 · |!

^.

− !

,

|

2,4[

< 12.1 · g#

,`

(4) ]

_^.

= i

1.00 + 1.290 =

^.

]Je =

^.

≤ 0.078 k² · m/V

1.05 + 0.645 =

^.

]Je =

^.

> 0.078 k² · m/V

Where:

M is the metabolic rate, in watts per square meters (W/m²);

W is the effective mechanical power, in watts per square meters (W/m²);

a

^.

is the clothing insulation, in square meters kelvin per watt (m²·K/W);

!

_,

is the air temperature, in degrees Celsius (°C);

!̅

_`

is the mean radiant temperature, in degrees Celsius (°C);

#

_,`

is the relative air velocity, in meters per second (m/s);

Z

_,

is the water vapor pressure, in pascals (Pa);

ℎ

_^

is the convective heat transfer coefficient, in watts per square meters kelvin

[(W/(m²·K)];

!

_^.

is the clothing surface temperature, in degrees Celsius (°C).

NOTE: 1 metabolic unit = 1 met = 58.2 W/m²; 1 clothing unit = 1 clo = 0.155 m²·°C/W.

The SS-EN ISO 7730: 2006 standard states that this index should only be used when the

PMV values are within the range of -2 and +2, and when the six main parameters are within

the following ranges [1]:

M 46 W/m² to 232 W/m² (0.8 met to 4 met);

a

_^.

0 m²·K/W to 0.310 m²·K/W (0 clo to 2 clo);

!

,

10 °C to 30 °C;

!̅

`

10 °C to 40 °C;

#

_,`

0 m/s to 1 m/s;

Z

_,

0 Pa to 2700 Pa;

NOTE: in respect of #

,`

, during light, mainly sedentary, activity, a mean velocity within

this range can be felt as a draft.

T

hose are ranges for the six main parameters according SS-EN ISO 7730: 2006 to use the

PMV calculation formula described in Equation 2[1].

Also, according to the standard, there are three different ways to derive the PMV: a)

Computing it according to Equation 2. with the use of numerical models; b) Determining it

via tables provided in the Annex E of the standard, if environmental and personal factors

are know; and c) Obtaining it from the direct measurement of the necessary environmental

factors [1].

PPD index

The Predicted Percentage Dissatisfied (PPD), which is calculated from PMV, attempts to

predict the percentage of people dissatisfied by a given thermal [1] [2]. The formula

presented in SS-EN ISO 7730: 2006 is as follows:

Equation 3: PPD formula from ANSI/ASHRAE Standard 55-2013 [2]

BB$ = 100 − 95 · exp(−0.03353 · BCD

_

_{− 0.2179 · BCD}

4

₎

The SS-EN ISO 7730: 2006 affirms that it is impossible to obtain in an environment

combination of comfort variables that fully satisfies all the members of a large group, there

will always be dissatisfied person inside the group who would like the place be warmer or

colder [1] [2]. Still, ANSI/ASHRAE Standard 55-2013 considers a thermally comfortable

environment when it satisfies at least 80 % of its occupants [2].

The relationship between PPD and PMV is illustrated in Figure 5:

Figure 5: Predicted Percentage Dissatisfied (PPD) variation as a function of Predicted Mean Vote

(PMV) in percentage (%) [1].

As Figure 5 indicates, the majority of the people satisfied with the thermal environment are

close to the value of PMV = 0. The PPD values are always displayed in percentage, this

means that their maximum value is 100.

Over the past decades, several criticisms emerged regarding the thermal comfort ranges

derived by Fanger. According to these studies the influence of parameters, such as gender

or age, have not been considered by the PMV/PPD index [13].

3 Methodology

In this section describes the equipment and methods used in data collection and analysis in

this study.

Testo 480 and sensors

Testo 480, instrument for measuring indoor climate, was utilized during the field

measurements (Figure 6.A). The instrument features a high-precision digital temperature,

humidity and air flow probes and a data logger. The device and the probes are shown in

Figure 6.B. [14].

Figures 6.A and 6.B: Images from Testo 480 (A) and some accessories (B) that could be combined. These

images are from their official website (Testo SE & Co.) [14]

The probes used in this study are:

a) Comfort probe for turbulence measurement in accordance with EN 13779;

b) IAQ probe for analyzing Indoor Air Quality, CO

2

, absolute pressure measurement;

c) Globe thermometer (TC type K) for the measurement of radiant heat.

Is a globe thermometer with 150 millimeters of diameter (Ø 150 mm) with a

thermocouple type K at its center for measuring the temperature with 1.45 m fixed

cable. [14]

Figure 7.A, 7.B and 7.C: Comfort probe for turbulence measurement (A), IAQ probe for analyzing

Indoor Air Quality, CO

2

, absolute pressure measurement (B) and Globe thermometer (TC type K) for the

measurement of radiant heat (C). (Testo SE & Co.) [14]

The figure 7.A is showing a comfort level probe. His technical data is described below:

(B)

Table 6: technical data from comfort level probe [14].

Temperature - NTC

Measuring range

32° to 122 °F / 0 to +50 °C

Accuracy

±0.9 °F / ±0.5 °C

Resolution

0.1 °F / 0.1 °C

Absolute Pressure

Measuring range

+280 to +440 InH₂O / +700 to +1100 hPa

Accuracy

±1 InH₂O / ±3 hPa

Resolution

0.1 InH₂O / 0.1 hPa

Velocity - Hot wire anemometer

Measuring range

0 to +984 fpm / 0 to +5 m/s

Accuracy

±(5.91 fpm + 4 % of mv) / ±(0.03 m/s + 4 % of mv)

Resolution

0.01 fpm / 0.01 m/s

General technical data

Length probe

12.992 in. / 330 mm

Probe head diameter

3.543 in. / 90 mm

Standards

EN 13779

The figure 7.B is showing an IAQ probe. His technical data is described below:

Table 8: technical data from IAQ probe [14].

Temperature - NTC

Measuring range

32° to 122 °F / 0 to +50 °C

Accuracy

±0.9 °F / ±0.5 °C

Resolution

0.1 °F / 0.1 °C

Humidity - Capacitive

Measuring range

0 to +100 % RH

Accuracy

±(1.8 % RH + 0.7 % of mv)

Resolution

0.1 % RH

Ambient CO₂

Measuring range

0 to +10000 ppm

Accuracy

±(75 ppm + 3 % of mv)

0 to +5000 ppm

±(150 ppm + 5 % of mv)

5001 to +10000 ppm

Resolution

1 ppm

General technical data

Diameter probe shaft 0.8 in. / 21 mm

Length probe

12 in. / 305 mm

Table 9: technical data from globe probe [14].

Temperature - Type K TC

Measuring range

32.0° to 248.0 °F / 0 to +120 °C

Accuracy

Class 1

General technical data

Cable length

4.8 ft. / 1.45 m

Emissivity

0,95

Probe head diameter

5.9 in. / 150 mm

Measurement sites and retrofitting changes

Two apartments in Tjärn Ängar were chosen for this study. Apartment 32 in Klöverstigen

26D and apartment 22 in Kornstigen 25B. The apartments were unfurnished and without

residents during the period of the measurements. Outdoor temperature values

corresponding to indoor measurement periods were obtained from the Swedish

Meteorological and Hydrological Institute’s (SMHI) online database [15].

About ventilation and heating systems, before retrofitting process there was an exhaust

ventilation system (a fan runs continuously to suck the air). The fresh air comes from a small

ventil (duct) over the windows and a water-borne radiator as a heating system. This duct was

located above the window and had no heating process attached. In this case the air entered

with the average low temperature given the environment during the Swedish winter.

After retrofitting process two measurements were made. First was done a measurement in

apartment 32 in Klöverstigen 26D over 24 hours during one day. This apartment has a

balanced ventilation with heat recovery (FTX system in Swedish) and a heating system with

water-borne radiator. The second measurement was done in apartment 22 in Kornstigen

25B with more interventions, removing and sealing the duct previously found above the

window and along with this was install a new exhaust ventilation system with heat recovery

through exhaust air heat pumps (a fan runs continuously to suck the air). The fresh air now

comes from a small hole and is passed through a warm radiator to the room, then the warm

dirty air is sucked to ventilation canals, and the heat is recovered by a heat pump. The heating

system remained the same with a water-borne exhaust-radiator.

Figure 8.A and 8.B: Block of apartments in the district of Tjärn Ängar. Klöverstigen 26D (A) and

Kornstigen 25B (B).

Occupied zone

Measurement locations were selected so that all of them fall within the occupied zone. The

occupied zone is defined as the three-dimensional area comprised between heights of 0.1 m

to 2.0 m from the ground, 0.6 m from exterior walls or other external limit, and 1.0 m from

windows or doors, as shown in Figure 9. This arrangement allows to analyze how the end

user will feel when using the environment.

Figure 9: Definition of occupied zone [9].

Measurement procedure

During the measurement, access to the apartments were restricted to the researchers only.

Moving in the vicinity of the instrument were also avoided as much as possible to reduce

interference. The same applied to the operation of doors. The windows remained shut, with

their blinds or curtains fully open ensuring the entry of natural light.

The instrument was placed in the living room of each apartment. It recorded air velocity,

mean radiant temperature, CO

2

, relative humidity and air temperature data at 10-minutes

intervals during the 24-hour measurement period from 9 selected locations.

Figure 9.A and 9.B: Testo 480 (A) and used probes (B) during the measurements at Klöverstigen 26D.

The nine locations were arranged in a straight line along the middle of the living room (5.5

m x 3.6 m in size). The measurement locations spread from the window towards the back

wall of the room. In the case of points from 1 to 7, measurements were conducted at 0.60

m above the floor. The measurement points of 8 and 9 were located at the same place as 1

and 3, respectively. The only difference is that they recorded conditions at 0.20 m above the

floor. The purpose of this height variation was twofold. First, to evaluate the most accessible

(B)

(A)

area for subjects in seated positions, and second, to assess the possible draft of the air in the

environment.

Figure 10.A and 10.B: Distribution of measuring points (A) (B) on the floor of the used living room at

Kornstigen, 25B.

Figure 11: Distribution of measuring points over the floor during all measurements. Layout before

retrofitting process.

Measurement period

Based on the understanding that the winter period is more curtail from thermal comfort

point of view in Sweden, all measurements were conducted during the coldest months [16].

Several other studies that focus on indoor thermal comfort, recommend winter as the time

period for data collection [12]. In Sweden, winter is from December to March [12], with the

coldest months in Borlänge being the months of January and February [15] [16].

The data from December 18

th

_{, 2017 on the Klöverstigen 26D test unit, apartment 32 was}

collected only at reference point 3 during a complete 24-hour cycle. The data collected

during the days 15

th

_{to 19}

th

_{of February of 2018 in the test unit Kornstigen 25B, apartment}

22 were collected on all nine reference points, in cycles of 24 hours.

Reference data

The reference data of this study was collected prior to the building retrofitting by Amir

Sattari. The reference measurements were conducted between January 19

th

_{and 27}

th

_{of 2017}

at Klöverstigen 26B, utilizing an identical filed measurement approach as the current study.

Standardization of data

Both data sets, obtained before and after retrofitting the buildings, were treated and

processed in similar manner: the data were migrated to Excel, classified by type and finally,

hourly mean values were calculated. This process resulted in 21 spreadsheets.

Calculation of PMV and PPD

With the data processed and arranged in hourly averages, the next step was derive hourly

PMV and PPD via the web tool provided by the Ergonomics and Aerosol Technology of

Lunds Tekniska Högskolan [6]. In order to calculate the data using this online PMV and

PPD calculator it was necessary to set default values for metabolic energy production

(W/m

2

_{) and basic clothing insulation (1 clo = 0.155 W/m}

2

_{·K). In the first case, the value of}

65 W/m

2

_{was set as standard whereas in the second case the value of 0.7 clo was defined,}

considering that users would be wearing light clothing inside their homes. It was also

necessary to determine for a value of rate of mechanical work, which in this case was 0.0

W/m

2

_{, assuming that the inhabitants of these houses were at rest, that means no physical}

activity. Considerations were also made in relative air velocity, since in this online calculator

the possible values for this parameter ranged from 0.1 m/s to 1.0 m/s. During the

measurements, as it was already possible to see, several times the relative air velocity was

below 0.1 m/s, therefore, by necessity of PMV and PPD calculations, it was necessary to

round off values lower than 0.1 m/s for this number, allowing the use of this instrument

throughout the study.

The obtained hourly mean values of PMV and PPD were added to the previously derived

worksheets. This allowed me to evaluate their diurnal fluctuations in each measurement

location.

Figure 18: Example of a calculation with data from this research generating a value of PMV and PPD

referring to the average hourly values of data collected during one of the measurements. [6]

Calculation of draft rates

The next step was to calculate the hourly draft rate (DR) values and add them to the existing

data sheet. DR was calculated using the formula in Equation 1. Since the local turbulence

intensity in this study is unknown, was decided to rely on the 40 % value, recommended

above. As DR is a percentage value, all values higher than 100 % were rounded down to 100