Building Science Lecture Notes PDF

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Building Science Lecture Notes. Final Exam Preparation...

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Building Science Lecture Notes Week 1 – Introduction       

Building science is scientific knowledge that focuses on how buildings interact with the natural environment. It includes the analysis of all physical phenomena that affect buildings. Building physics, architectural science, material science and applied physics are terms used for the information that overlaps with building science. Buildings are subject to many forces from weather events such as storms, wind, heat and cold. Building science includes the study of indoor environments of buildings that maintain healthy indoor conditions. Thermal, acoustic, light and indoor air quality are essential components for comfortable living spaces. Building science also looks at resource use, including energy and building materials.

Assessments

Reading Materials There are two recommended eBooks available from the library that are referred to in this subject. o Allen, E & Iano, J 2019, Fundamentals of Building Construction: Materials and Methods, 7th edn, John Wiley & Sons  https://west-sydneyprimo.hosted.exlibrisgroup.com/permalink/f/1vt0uuc/UWSALMA51261120300001571 o Newark. Virdi, S & Waters, R 2017, Construction Science and Materials, 2nd edn, John Wiley & Sons, Somerset. (First addition is available and anticipate second addition will be added later in semester.)  https://ebookcentral.proquest.com/lib/uwsau/detail.action?docID=860819

Week 2 – Introduction to Scientific Units and Measurement • • •

Measurement is the process of obtaining the magnitude of a quantity relative to an agreed standard. The science of weights and measures is called metrology. Metrology is the scientific study of measurement.

Australian Connection -

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The National Measurement Laboratory was identified as a National Facility within CSIRO in December 1996. The National Measurement Institute (NMI) is responsible for establishing and maintaining Australia’s units and standards of measurement and for coordinating Australia’s national measurement system. Internationally there are agreed constants that define measurement. Measurement of any quantity involves comparison with some precisely defined unit value of the quantity. For example a kilogram of copper has the same mass all over the surface of the Earth, it is an unchanging property of nature.

Revising the SI -

The SI was revised in May 2019. Four of the base units – kilogram, ampere, kelvin and mole – were redefined. They now join the second, metre and candela as being defined by physical constants. This event likely happened without much notice from the general public – there was no disruption to our daily lives. For metrologists, however, it was an unprecedented event. Never before have so many base units been revised at one time.

SI Units -

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International System of Units is defined as: u a system of physical units ( SI units ) based on the metre, kilogram, second, ampere, kelvin, candela, and mole, together with a set of prefixes to indicate multiplication or division by a power of ten. SI Units are necessary to ensure that our everyday measurements remain comparable and consistent worldwide. Standardising such measurements not only helps to keep them consistent and accurate, but also helps society have confidence in information. For instance, mass is measured every day, and having agreement on the definition of the kilogram means that builders can trust that the concrete supplier is really providing the mass in tonnes they require for a slab. Equally, having reliable information on climate conditions, quantities of materials and strength of materials is important to the construction industry and builds trust and allows effective decisions to be made.

Multiples of 10 -

SI units are measured in multiples of 10 We are familiar with the common ones Measurement of length millimetres, metres and kilometres Measurement of mass, grams, kilograms and tonnes

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Electricity in watts and kilowatts The SI system uses arabic numerals describe the quantity. A quantity is then paired with a unit symbol, often with a prefix symbol that modifies unit magnitude.

Large Values

Small Values

Prefxi es

Density -

The density of common building materials is an important property Water 1000 Kg/m3 Steel 7874 Kg/m3 Copper 8950 Kg/m3 Aluminium 2710 Kg/m3 Concrete range 2400 – 2500 Kg/m3 Timber range 485 – 965 Kg/m3 This relates to how we design buildings to consider weight on structural stability and also how much material we need to order

Concrete -

You are required to order concrete for a slab that is 5 metres long, 4 metres wide and 150 mm deep. The concrete to give the desired strength has a density of 2450 Kg/m3 The area is the length times the width that gives 20 square metres. The depth is 150 mm, that converts to 0.15 metres. The volume is 3 cubic metres Multiply this by 2.450 and you get 7.35 tonnes of concrete

Week 3 - ENERGY, MASS, FORCE, VELOCITY, ACCELERATION AND NEWTONS LAWS -

Energy is the capacity for doing work. It may exist in potential, kinetic, thermal, electrical, chemical, mechanical, nuclear, or other various forms. An example is the energy from petrol that is combusted in a piston and converts to mechanical energy. Mass is a measure of how much matter is in an object. Mass is commonly measured by how much something weighs. But weight is caused by gravity, so your weight on the Moon is less than here on Earth, while the mass stays the same.

Force -

Force is a push or pull upon an object resulting from the object's interaction with another object. - Whenever there is an interaction between two objects, there is a force upon each of the objects. - When the interaction ceases, the two objects no longer experience the force. - Forces only exist as a result of an interaction.

Velocity -

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Velocity of an object can be defined as the rate of change of the object's position with respect to a frame of reference and time. Velocity is basically speeding in a specific direction. Technically it is a vector quantity, which means we need both magnitude (speed) and direction to define velocity. - A vector, in physics, is a quantity that has both magnitude and direction. Velocity is generally referred to as metres per second

Acceleration • • • • • •

Acceleration is a vector quantity that is defined as the rate at which an object changes its velocity. Accelerations are vector quantities; in that they have magnitude and direction. An object is accelerating if it is changing its velocity. - For example, when you are driving faster you are accelerating your speed Acceleration is the change in velocity over time Mathematically acceleration (a) is the change in velocity (Δv) over the change in time (Δt), represented by the equation a = Δv/Δt. This allows you to measure how fast velocity changes in meters per second squared (m/s 2).

Sir Isaac Newton and the Apple • •

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Legend has it that a young Isaac Newton witnessed an apple fall from a tree and that lead to his development of the three laws of motion. He commenced study at Cambridge University in 1661. Four years later, following an outbreak of the bubonic plague, the University temporarily closed, forcing Newton to move back to his childhood home, Woolsthorpe Manor. It was during this period that he was in the orchard there and witnessed an apple drop from a tree. The tree was blown down in 1820, however its root base remained and the tree has regrown.

Introduction to the Laws of thermodynamics • •

Newton’s laws of motion are three physical laws that gave the foundation for classical mechanics. These laws describe the relationship between a body and the forces acting upon it, and its motion in response to those forces. - Newton's first law states that every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force. - The second law explains how the velocity of an object changes when it is subjected to an external force. The law defines a force to be equal to change in momentum (mass times velocity) per change in time. Force = mass x acceleration - The third law states that for every action (force) in nature there is an equal and opposite reaction.

Week 4 – Science of Materials -

Materials science includes durability, materials engineering, forensics and failure analysis. Materials are best understood when they are grouped into categories with common properties

Common Material Properties -

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Metals u Conductive, ductile, reliable mechanical properties, corrode, recyclable Ceramics u Brittle, hard, resist high temperatures, statistical variation in strength, high stiffness, opportunities for recycling Organics u Carbon based, combust, melt, soften or degrade with heat, moderate to low stiffness, timber offers re-use/recycling. Plastics are type specific in recycling

Ceramics: Tiles, Bricks, Pavers, Glass and Concrete -

One of the oldest and also newest building material Clay based: clay is shaped and sintered in a furnace. Glass: oxides are melted to form clear glass Cement: clay/limestone blend is heated at high temperatures (used in concrete)

Ceramics -

Ceramics are made from naturally occurring minerals such as clay, limestone and sand. Processed by heat from natural gas Impact of mining/extraction processes, release of gases etc and energy in manufacture Opportunity to use waste from other industries such as fly ash from coal burning

Metal: Ferrous and Non-Ferrous -

Metals are extracted from naturally occurring minerals Mineral deposits are limited Considerable energy is required to purify minerals from a mineral to a metal Require substantial energy to produce a metal producing significant carbon dioxide

Organic Materials -

Plastics are manufactured from petroleum and other organic sources Plastics are long chains of carbon molecules Defined as either thermoplastic or thermoset Use valuable oil resources

Materials families

Common materials

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Energy to convert basic organic compounds to plastics is detrimental to our environment Processing and addition of additives produce harmful materials such as plasticisers Problems with disposal and by-products during manufacture, use and disposal

Composite Materials •

Several examples in construction are; • Concrete (cement and aggregates) • Reinforced concrete (concrete and steel reinforcement) • Aluminium Composite Cladding • Fibreglass Property Example Physical

mass, response to heat, insulation, optical, acoustic

Mechanical

strength, stiffness, fatigue and

Chemical

reaction to water, corrosion of metals, response to acids and alkalis

creep

What Causes the different properties? -

All materials are made of atoms Properties of materials are the result of the type of atom, mixture of atoms and how these atoms are bonded together.

Atomic Structure Atomic structure - Atoms are the basic building blocks of all materials - Atoms have three subatomic particles: u protons, neutrons, and electrons - Atoms bond to each other in several ways by joining through electrons - The type of bond influences the properties of a material - Primary Bonds: forms when atoms attach to each other by interchanging or sharing electrons to fill the outer electron shell. Types: Covalent Bond -

Covalent bonding is a form of chemical bonding between two non metallic atoms which is characterized by the sharing of pairs of electrons between atoms and other covalent bonds.

Metallic Bond • • •

Atoms share electrons with many neighbouring atoms Strong and allows ductility in metals Electrons • free to move between atoms • good conductor of heat and electricity

Secondary Bonds 1. 2. 3. 4. 5.

Attraction between atoms. There is no sharing of electrons to form a strong structure. Weaker than primary bonds. Bond type in thermoplastics It is what keeps water together

Bonding Type Summary • •

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In ceramics the atoms and electrons are locked in place • This gives stiffness, brittleness and low conductivity In metals atoms can “slip” and electrons can move • This gives strength and conduction • Free movement of electrons in metals is why metals corrode In most plastics the chains are held together by covalent bonds between carbon atoms. The chains are either joined by secondary bonds or covalent bonds.

Properties of Bonding Type Bonds between atoms determine properties such as: - Density - Compressibility - Strength - Thermal coefficient of expansion (changes in bond length with temperature) - Thermal conductivity - Melting point - Electrical conductivity Week 5 – Concrete -

Concrete is the most used material in construction. Properties of concrete are influenced by its mix design and how concrete is used. In this module we will cover the science of cement and concrete. Chapter 13 of the online text book by Allen from pages 496 – 507 should be reviewed

What is Concrete? -

Concrete is the most used material in construction. Concrete is a mixture of cement, sand, aggregate, water, air and additives In this module well will look at each of the additives used in concrete

Cementitious Materials -

Portland cement (Cementitious Material) is the basic binder used in concrete Supplementary Cementitious Materials (SCM) are waste products from other industries - Fly ash - Slag (ground granulated blast furnace slag) - Amorphous silica (silica fume)

Cementitious Products • • •

cement + water = paste or grout paste + fine aggregate = mortar or render mortar + coarse aggregate = concrete

MANUFACTURE OF PORTLAND CLINKER & CEMENT A two-stage production process: - Clinker: Produced when limestone and clay (or similar) are burnt together - Portland Cement: Produced by grinding clinker and adding small amount of gypsum (set regulator to slow reaction) Module 10 – Control of Heat in Buildings Thermal Comfort -

The primary function of a building is to keep occupants cool in summer and warm in winter. The passage of heat to and from the body must be balanced to attain thermal comfort. Heat is produced by the body as it converts food into useful energy, known as Metabolism. The conversion process is not very efficient; only 20% of the chemical energy in food is converted to useful purposes. The other 80% must be dissipated as heat.

Human Batteries

Heat Gain and Loss -

Evaporation: only produces heat loss through perspiration and respiration. Conduction: the body loses or gains heat by contact with a surface. Convection: heat is dissipated from or introduced to the body by air currents. Radiation: heat can be radiated to and from the body if the surrounding surfaces have a different temperature.

Basic Concepts of Heat -

Sensible Heat o Sensible heat is heat flow that occurs with a temperature change Latent Heat o Latent heat results from the change of state from: o solid to liquid  Heat of Fusion o liquid to gas  Heat of Vaporisation

Heat Flow through a Building -

Conduction heat flow Radiant heat flow Convective heat flow

Envelope Heat flow -

Heat Bridges o Metallic components in buildings form heat bridges that conduct heat through metal frames in double-glazed windows, lintels, brick ties, battens. o When the ground is in contact with a building, the temperature under the building remains relatively constant, except at its edge.

Radiation -

The exterior of the building is subjected to Solar radiation is generally short wave, high temperature and high-grade heat. The interior of the building is also subjected to radiant effects. Hot surfaces emit low temperature and low-grade heat. The effect of solar radiation is accounted by increasing the effective outside temperature; known as the Sol-Air Temperature.

Measurement of heat flow -

Conductivity “k” is a measure of a material’s ability to pass heat through a unit thickness of material (W / m oC) Resistivity “r” is a measure of a material’s capacity to impede heat transfer over a unit thickness (m. oC / W) (Think of insulation materials)

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Resistivity is the inverse of conductivity. r = 1 / k

Types of Insulation -

Because there are two types of heat flow through a building, there are two types of insulation: Bulk insulation resists the passage of conductive heat flow o The high thermal resistance is due to air voids that are trapped within the material. Foil resists radiant heat flow. o restricts the passage of heat by reflecting most of the heat

Periodic Heat Flow -

Steady state heat flow only applies in climates where the daily temperature fluctuations do not exceed +/- 3oC. Housing in tropical climates can be modeled using steady state conditions. Steady state heat flow conditions cannot be applied in Australia o Australia has considerable daily (diurnal) and seasonal temperature changes o Our climatic conditions allow more effective use of the Passive Solar design techniques o Passive Solar design relies on periodic heat flow in a building.

Passage of heat -

The passage of heat through the wall can be thought of as a heat wave. The flow of heat into and out of the building depends not only on the U values of the elements but also on their heat capacities. o Heat capacity, ratio of heat absorbed by a material to the temperature change o The SI unit of heat capacity is joule per kelvin.

Passive Solar Construction -

Three components are needed: o Thermal mass o Bulk insulation o Equator-facing glazing (north in Australia)

Collection and Storage of Heat -

Heat can be stored by mass construction Concrete floors Masonry walls Direct contact with mass soil

Mass Cooling -

High thermal mass remains hot long after external temperatures have cooled. At night-time, thermal mass within the building is hotter than its surroundings. Air in contact with the mass heats up and rises. Hence, cool air can be drawn into the building and hot air expelled.

Module 11 – Light in Buildings Daylighting -

Windows are the weak link in the thermal envelope. The extra electricity to light the building is more than compensated by reduced energy for cooling and heating. Daylighting provides visual interest. Windows allow occupants to stay connected with outside world. The variation of daylighting indicates passage of time, through the movement of shadows and change in the color of the light. It enhances the well-being of occupants. Fluctuations in daylighting stimulate people, while artificial lighting oppresses them.

Location -

The required daylight depends on the climate: o In temperate climates, day-lighting provides a sense of well-being o tropical climates, excessive sun-light is associated with over-heating.

Composition of Daylight

Factors Affecting Solar Intensity and Duration -

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The quantity of daylight varies with the position of the sun. The sun path varies according the season. In the southern hemisphere, the sun rises and sets; o to the north in winter o to the south in summer Cloud cover Latitudinal variations o Distance from the equator

Components of Daylight -

Yellow beams: Direct sunlight and skyli...