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CHAPTER 1 Functional Requirements of Buildings

1.1 Buildings and their types
Any structure for whatsoever purpose and of whatsoever materials constructed and every part thereof whether
used as human habitation or not and includes foundation, plinth, walls, floors, roofs, chimneys, plumbing and
building services, fixed platforms, verandah, balcony, cornice or projection, part of a building or anything affixed
thereto or any wall enclosing or intended to enclose any land or space and signs and outdoor display structures is
known as building.

Buildings are classified according to the occupancy into the following types:

Group(A) Residential buildings-are those buildings in which the sleeping accommodation is provided for
normal residential purposes, with or without cooking or dining or both facilities, except any building classified
under category C.

Group(B) Educational – are those building used for school, college, or day care purposes for more than 8 hours
per week.

Group(C) Institutional-these include any building which is used for purposes such a medical or other treatment
or care of persons suffering from any physical or mental illness. Institutional buildings generally provide
accommodation for the occupants.

Group(D) Assembly-these include any building where group of people gather for recreation, social, religious,
travel and similar purposes.

Group(E) Business-these include any building used for business transaction, for keeping of accounts and
records, lunch counters for less than 100 people, beauty parlor etc.

Group(F) Mercantile-these include any building which is used for shops, stores, markets, for display and sale of
merchandise.

Group(G) Industrial buildings are those where products of materials of all kinds and properties are fabricated,
assembled or processed.

Group(H) Storage are those building used for storage of any goods, wares or merchandise except highly
combustible materials.

Group(I) Hazardous-buildings used for the storage, handling, manufacture or processing of highly combustible
or explosive materials or products.

1.2 Heat phenomena in Building (thermal performance of building components, thermal comfort, thermal
design)
Thermal performance of building components:
For a non-conditioned building, it calculates temperature variation inside the building over a specified time and
helps one to estimate the duration of uncomfortable periods.

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Various heat exchange processes are possible between a building and the external environment. Heat flows by
conduction through various building elements such as walls, roof, ceiling, floor, etc. Heat transfer also takes place
from different surfaces by convection and radiation. Besides, solar radiation is transmitted through transparent
windows and is absorbed by the internal surfaces of the building. There may be evaporation of water resulting in a
cooling effect.

Heat exchange process between a building and the external environment

Heat is also added to the space due to the presence of human occupants and the use of lights and equipments. The
interaction between a human body and the indoor environment is shown in Fig above. Due to metabolic activities,
the body continuously produces heat, part of which is used as work, while the rest is dissipated into the
environment for maintaining body temperature. The body exchanges heat with its surroundings by convection,
radiation, evaporation and conduction. If heat is lost, one feels cool. In case of heat gain from surroundings, one
feels hot and begins to perspire. Movement of air affects the rate of perspiration, which in turn affects body
comfort.

The thermal performance of a building depends on a large number of factors. They can be summarised as :
(i) Design variables (geometrical dimensions of building elements such as walls, roof and windows, orientation,
shading devices, etc.);
(ii) Material properties (density, specific heat, thermal conductivity, transmissivity, etc.);

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(iii) Weather data (solar radiation, ambient temperature, wind speed, humidity, etc.); and
(iv) A building’s usage data (internal gains due to occupants, lighting and equipment, air exchanges, etc.).

 Thermal comfort
State of heat balance of the human body is thermal comfort. The fluctuations of this heat balance causes
discomfort. The metabolism that generates heat in the body depends on the daily life cycle of human being-state of
activities, fatigue and recovery. Unfavorable climatic conditions affects daily life cycle resulting stress on body and
mind causes discomfort, loss of efficiency and may eventually lead to a breakdown of health. Human response to
the thermal environment depends to a great extent on the ease with which the body is able to regulate the heat
balance in such a way that the internal body temperature is maintained constant at 37.4°C.

1.3 Ventilation (requirements, standards, design) & air conditioning

Ventilation may be defined as supply of fresh outside air into an enclosed space or the removal of all the vitiated air
from the enclosed space. Ventilation is necessary for the following reasons:-
 Creation of air movement
 Prevention of undue accumulation of carbon dioxide
 Prevention of flammable concentration of gas vapor
 Prevention of accumulation of dust and bacteria-carrying particles.
 Prevention of odour caused by decomposition of building material.
 Removal of smoke, odour and foul smell generated /liberated by the occupants.
 Removal of body heat generated/liberated by the occupants.
 Prevention of condensation or deposition of moisture on wall surfaces.
 Prevention of suffocation conditions in conference rooms, committee halls, cinema halls big rooms etc.
Requirements of ventilation
1. Air changes or air movement 3. Quality of air
2. Humidity 4. Temperature
Systems of ventilation
1. Natural ventilation: It is the type in which ventilation is done by careful design of doors, windows, ventilators
and sky lights. It is considered suitable for residential buildings and small houses. In this the rate of ventilation
depends upon wind effect and stack effect.

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2. Mechanical or artificial ventilation is the one in which some mechanical arrangements are mad to increase
the rate of air flow. The system is more useful for large buildings.

General rules of natural ventilation:

1. Inlet openings in the buildings should be well distributed and should be located on the windward side at a low
level and outlet openings should be located on the leeward side near the top so that incoming air stream is passed
over the occupants.
2. Inlet openings should not be obstructed by nearby buildings.
3. Inlet and outlet should be of the same size.
4. If wind direction is variable, place the inlet openings equal in all directions.
5. Windows of living rooms should open on the open side.

Air conditioning
Air conditioning may be defined as the process of treating air so as to control simultaneously its temperature,
humidity, purity and distribution to meet the requirements of the conditioned space. The various requirements of a
conditioned space may be comfort and health of human beings, needs of certain industrial processes, efficient
working of commercial premises etc.

Purpose:-
 It helps in preserving of maintaining health, comfort and convenience of occupants of residential building.
 It helps in improving the quality of products in certain industrial processes such as artificial silk, cotton cloth
etc. In other cases of industries, it provides comfortable working conditions for the workers, resulting in the
increase of the production.
 It helps in making the commercial premises such as shops, banks, offices etc, more active and efficient.
 It provides more comfortable entertainment in theatres etc.

From Functional requirements points of view:

1. Comfort air conditioning
2. Industrial air conditioning

Essentials of comfort air conditioning

1. Temperature control 3. Air velocity control
2. Humidity control 4. Air quality control

Essentials of air conditioning system

1. Filtration 4. Humidification
2. Heating(in winter season) 5. Dehumidification
3. Cooling( in summer season) 6. Air circulation or distribution

1.4 Lighting (illumination requirements, daylight, artificial lighting)

Light is required in various quantities to perform work. Each task has a specific recommendation for illumination
levels.

Definitions
Luminous Flux () : Luminous energy emitted per second Unit: lumen (lm)
Luminous intensity ( I ) : Luminous flux per unit solid angle Unit: lm / Sr
Solid angle (w): cone of radiation Unit: steradian (Sr)
Relation : I = /w

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Candela (cd) Practical unit for luminous intensity of 1/60 sq. m. of the surface of a black body at temp. of freezing
platinum under 101323 Newton / sq.m. pressure Relation : 1 lm = 1 cd x sr
Iluminance ( E )
Functions Illumination level Limiting glare Luminous flux per
(lux) index
Offices unit area reflected
Drawing studio 500 19 from a surface Unit:
General 500 16
Lux ( Lx ) or lm /
Boards 750 16
Auditorium & Foyer 100 sq.m.
Shops 500 19 Luminance ( L )
Living spaces
General 50 Luminous flux per
Reading 150 unit area coming from
Sewing 300
a source Unit : cd /
sq.m.
Glare: A condition of vision of discomfort to see object due to an unsuitable distribution or range of luminance

Natural Light
Sun is the sole source of natural lighting and heating. Depending on the different seasons, time of day and weather
conditions, sun light may be harsh, hazy or subdued. How it enters the rooms depends on type, size & placement of
windows and orientation of the building.

Lighting Requirements
 The source of light should be steady
 Glare should be avoided
 Inconvenient shadow should be avoided by proper shading at the source
 Light color on wall and ceiling

Day-lighting
The sun is the source of day light, however how and in what intensity it reaches a room depends on various
components;
a. Diffused light/ skylight
b. Light reflected on external surfaces
c. Light reflected in the internal surfaces
d. Direct sunlight
Climatic conditions greatly influence the quantity and the quality of the above components.

Overcast Sky
Direct rays from the sun is achieved under clear sky condition, however in practice cloud covered sky (overcast) is
taken into account in design. The illumination received from the sky varies greatly with different sky conditions
and the time of the day. A complete overcast sky is assumed as the standard for day lighting analysis. The total
illumination at the ground level is approximately taken as 5000 lux.

Day-light factor

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The ratio of indoor illumination to the simultaneous outdoor illumination is taken as constant. The percentage ratio is

Room Daylight factor Penetration Daylight area

Kitchen 2% Cooking,
Ei washing
is the indoor and preparation
illumination, taken at 50% of the area(Min. 5 M2 )
a point
Living room 1% Half of the depth 7.5
Eo is the outdoor illumination from an unobstructedM 2
sky
Bedroom 0.5 % ¾ depth 6 M2
Office 1% 4 Meters
Drawing studio 5% Over whole of the area

DF = SC + ERC + IRC
termed as the day light factor (DF);

DF = Ei X 100 (%)
Eo

The day light factor concept is valid only under overcast conditions. Three major factors contribute to the daylight
factor;
1 Sky component (SC)
2 Externally reflected component (ERC)
3 Internally reflected component (IRC)

Controlling day lighting

Design stage: layout of structures, proper orientation of the Building and controlled light penetration
Construction stage: Use of windows/ fenestrations of proper size and at suitable locations
Use of roof lighting
Use of courtyard / atriums
Minimum day lighting standards

1.3.4 Artificial light

In conditions where natural lights cannot reach; inner rooms & lobbies, after sunset or where special lightings are
required artificial lighting system is used. It is generally static and steady. However with dimmer or track light
mechanism the brightness can be controlled.

Various electric lighting sources

1. Incandescent bulb ( filament lamp ) 4. Sodium vapor lamp , High pressure lamp
2. Fluorescent lamp ( discharge tube ) 5. Induction lighting
3. Halogen lamp, Low voltage lamp 6. Illuminating optical fiber

Method of increasing the electrical lighting system efficiency

1. Selection of luminaries with high luminous efficiency
2. Selection of internal surface finishing of high reflectance value
3. Adjusting luminaries height as per the work plane level
4. Regular maintenance of the system
5. Functional positioning / proper layout of the luminaries

1.5 Sound and Acoustics (sound & noise, acoustic defects, sound insulation)
Acoustic is the science of sound, which deals with the origin, propagation and auditory sensation of sound and also
with design and construction of different building units to set optimum conditions for producing and listening
speech, music etc.
Sound
Anything that can be heard is sound. It is the sensation caused by a vibrating medium acting on the air. Source of
sound is most often vibrating solid body. The medium conveying sound to ear can be gas, liquid or solid.
It is transmitted as the longitudinal wave motion. Wave length determines pitch of sound. Higher the frequency
higher would be the pitch (frequency is the waves per unit time).
Generally sound can be divided into air borne sound and impact sound. Airborne sound is transmitted through air
and travels direct to the ear of the person. Impact sound is transmitted first through the structures such as noise of
footsteps, furniture movement, dropping of utensils etc.
Noise

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The sound which causes annoyance, interference with speech, damage to hearing and results in reduction in
efficiency of work performance is called noise.
Magnitude of noise level

Types of sounds Noise level (dB) Effects

Light road traffic 60 – 70 Physiological effect (annoyance)

Medium road traffics 70 – 80 Physiological effect (annoyance)

Heavy road traffics 80 – 90 Prolonged exposure causes permanent hearing loss

Rail traffics 90 – 100 Prolonged exposure causes damage to auditory organ

Air traffics 100 – 130 Causes pain

>130 Instantaneous loss of hearing

Effects of Noise:
 Annoyance -irritation  Interface or disturbing conversation
 Disturbance to sleep  Damage of ear

Echoes:
When a reflecting surface is so far away from the surface that the sound is reflected back as a distinct repetition of
the direct sound, the reflected sound is called an echo. Echoes are produced, when the time interval between the
direct and the reflected sound waves is about 1/15 th of a second. This defect is particularly common when the
reflecting surface is curved in shape. To minimize this defect in curved walls, the walls are covered with highly
absorbent materials on the face work.

Reverberation
When the sound waves get reflected, a part of the sound energy is converted into heat energy by friction and is
absorbed by the walls. Subsequently the reflected waves get inter-reflected from one surface to another until they
gradually fade and become inaudible. This phenomenon of undue prolongation of sound by successive reflections
from surrounding surfaces after the source sound has ceased is termed as reverberation. A certain amount of
reverberation is necessary to enhance the sound. However, excessive reverberation is damaging to clarity.

Sound insulation of buildings:

Control of noise transmission is essential to minimize the disturbing effect of sound passing from one room to
another, through walls, partitions and floors or ceilings.

General consideration
1. Isolate sound source
2. Proper orientation of building , i.e. no opening towards noise
3. Properly planned rooms in building
4. Furnishing materials in room helps sound absorption
5. Partitions – Ridge and Movable
6. Control of impact sound i.e. sue of resilient materials as carpets in floor
7. Discontinuing the path of vibration by using sound absorbing materials
8. Use of headphones and air plugs in case of high sound.

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The constructional measures to be adopted for noise control and sound insulation are briefly discussed below:

Wall construction:
The sound insulation rating of a wall is generally governed by the net sound transmission loss it provides and also
the efficiency with which it serves as a barrio for speed sound. Weight of walls is the governing factor in wall is the
governing factor is wall insulation. It is seen that a solid one brick wall plastered on both sides, proves quite
effective as a sound insulation partition wall. It has an average reduction of 50dB. A cavity wall type of construction
can be made to have increased insulation value by filling the cavity with some resilient material.

Floors:

Transmission of sound takes place more easily through floors. This is on account of the fact that the sound
producing source has actual contact with floor. Hence the floor serves as the most common path for the
transmission of impact noise. The ordinary R.C.C. floor weighing less than 220kg/sq.m has a sound reduction of
only 45dB. Thus bare concrete and timber floors do not function effectively as barrier against impact sound. A
floating floor resting on a resilient material like glass wool, mineral wool, quilt, hairfelt etc., has an increased rating
for impact sound insulation.

1.6 Orientation & planning of buildings

(principles, site-selection, economy, setting-out)

Orientation of building is a very important factor

which is directly connected to the standards of
thermal comfort and ventilation within building. It is
guided by natural elements like sunlight and its
intensity, direction of the wind, seasons of the year
and temperature variations. Orientation is determined
by climatic factors of wind and solar radiation.

The building orientation can have an impact on

heating, lighting and cooling costs. By maximizing
southern exposure, for example, one can take optimal

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advantage of the sun for daylight and passive solar heating. Minimizing western exposures will result in lower
cooling costs, where it's most difficult to provide shade from the sun.

1. Hot climatic zones:

The buildings should be oriented from solar point of view so that as a whole it should receive the maximum solar
radiation in winter and the minimum in summer. Longer walls of building should face north & south. Non-habitat
rooms can be located on outer faces to act as thermal barrier. Preferably, the kitchen should be located on leeward
side of the building to avoid circulation of hot air and smell from the kitchen.
 Large openings with heavy shutters should be provided on northern and western faces as light coming from north
is always diffused and indirect.
 Thick walls are preferred to act as insulating barrier.
 Should be built up with good insulating material having slope in windward direction. False ceiling can be used to
improve thermal performance of building.
 Large shady trees whose roots do not strain foundation and basement should be planted near external walls to
provide shade

2. Warm and humid climatic zone:

Orientation of buildings in this zone should be preferably in North-South direction for habitable rooms i.e. longer
walls should face north & south so that shorter sides are exposed to direct sunlight.
 Proper cross ventilation of building is of extreme importance; therefore large openings should be positioned on
windward and leeward direction. However, openings should be provided with suitable protection like sunshades,
chhajjas etc. from Sun and rain.
 Walls of Low thermal capacity material should be used in construction and walls can be thinner as temperatures
are not very high.
 Roofs: should have large overhangs to avoid rainwater hitting the wall. Roof should be finished with materials of
low thermal conductivity.
 Shrubs of medium height which do not act as wind barriers are recommended.
 Good rain-water drainage is essential.

3. Cold climatic zone:

Cold climate occurs in mountainous regions and plateaus 800 to 1200 meters above sea level.
 Orientation should preferably be in north – south direction i.e. longer walls should face north & south to receive
more solar heat during winter months.
 Glazing windows upto 25% floor area may be provided. Double glazing is preferable to avoid heat losses during
winter nights.
 Thin walls with insulation from inner side (2.5cm thick insulation) are preferable.
 Roofs should be preferably made of asbestos cement or G.I. sheets backed by false ceiling of wood, 2.5cm wood-
wool board or equivalent material.
 The roof should have sufficient slope for quick drainage of rainwater and snow.
 Provision for heating of building should be kept like fire places etc.

Factors affecting orientation:

Sensory
 Thermal—solar exposure, wind direction, temperature
 Visual—varying daylight qualities in different locations and at different times of day
 Acoustical—direction of objectionable noises
 Environmental—smoke, dust, odors
Psychological
 Views
 Privacy
 Street activity
Local development patterns
 Street direction
 Spatial organization, land use, urban design
 Zoning
Accessibility requirements—main/secondary entrances, parking

Other considerations
 Aesthetic

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 Direction of storms
 Site conditions—topography, geotechnical, wetlands
 Site vegetation—mature trees
 View corridors, scenic easements

Orientation principles:

1. Slope and soil Considerations

Consider both long term storm water and short term erosion impacts during construction. Avoid very steep slopes.
2. Site Plan
Bioclimatic design, Slopes to the south allow for plenty of solar access, while north facing slopes will provide good
shading opportunities.
3. for Rectangular Buildings
They should be oriented with the long axis running east west .In this configuration; east and west walls receive
less direct sun in summer. So, unwanted heat gain is reduced. Same configuration works well for buildings in cold
climates where passive solar heat gain on the south side during the winter is desired.
A long narrow building plan also facilitates daylighting and natural ventilation.
4. Solar Energy: Both a friend and a foe
5. Proximity of trees to building
Growth rate, life span of nearby trees should be considered
6. Account prevailing winds
7. Driving and parking lots should be located on the east or north side of the building in summer season (hot climate)
and in cold climates, they should be kept on south and west to melt snow.

Planning of buildings:

The basic objective of planning of buildings is to arrange all the units of building on all floors and at level
according to their functional requirements making best use of the space available for a building.
The shape of a plan is governed by several factors such as climatic conditions, site location, accommodation
requirements, local bye-laws, surrounding environment etc.

Factors considered in planning:

1. Aspect: aspect means peculiarly of the arrangement of doors and windows in the external walls of a building
which allows the occupants to enjoy the natural gifts such as sunshine, breeze, scenery etc. this consideration
includes good view of nature or scenes according to the uses of space such a kitchen in east direction for early
U-V ray, a reading rooms, class rooms in north direction for diffused light of the evening etc.

2. Prospect: is the impressions that house is likely to make on person who looks it from the outside. Hence, it
includes the attainment of pleasing appearance by the use of natural beauties, disposition of doors and
windows.
3. Privacy: it is one of the important principles in the planning of buildings of residential type.
4. Grouping: grouping means the disposition of various rooms in the layout in a typical fashion so that the rooms
are placed in proper correlation of their functions and in proximity with each other. Services must be nearer to
and independently accessible from every bed-room. Bathroom and toilets must be far away from the kitchen
and dining rooms.
5. Sanitation: sanitation includes cleaning facilities, sanitation services, providing sufficient ventilation etc.
6. Circulation: it may vertical or horizontal circulation.
7. Economy: economy of the construction and operation of the building should be planned in advance.
8. Practical considerations: although different structural, financial and other considerations are discussed,
practical possibility is the most considerable factor in planning of a building.

Setting out a building:

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This is the process of obtaining the positions of the structural parts of a building in the geometrical construction.
The positions of the structural parts of a building can be obtained by detailed structural drawings. These data has
to be transferred to the field to start the geometrical construction with sufficient accuracy; enabling independent
checks for readily detecting of any errors.
The first step in building setting out is to identify a base line according to the site layout plan. We can establish the
base line considering the permanent structures and the relevant distances to structural parts from them as given in
the drawings.

Setting out is done based on the principle of “Whole to part”. According to this principle the largest possible
rectangle of the building is found and set up first. Then it is further divided into small parts completing the major
setting out for the building.
It is very important that setting out process is done in a horizontal plane. When the ground profile is not horizontal
proper care must be paid to establish the setting out profiles in a one level. For simple applications a tube filled
with water can be used to obtain the levels.
Main instruments involved in this process are Theodolite, Steel and Linen Tapes, Arrows, Wooden pegs, Wire nails
and Nylon threads.
After establishing the base line, the main rectangle is set up using the pegs and theodolite. Arrows are used as
temporary pegs and wooden pegs are driven for permanent pegs .90° angle is taken by the theodolite and
Pythagoras rule is also commonly used for the process. When using the Pythagoras rule proper care must be paid
to obtain the largest possible combination of triangles for higher accuracy. Steel tape must be used to measure long
distances and it must be tightly stretched when taking the readings.
Wooden pegs atop by a wire nail are driven to establish the grid lines of the building. These pegs are driven at
places such that they won’t be disturbed by field work
etc. Usually they are driven with a distance of 1.5 meter
from the grid line.
The diagonals of the main rectangle are checked to
determine its accuracy. Accurately set up main
rectangle is then subdivided to obtain the consisting
gridlines. These are obtained by the using structural
drawings, Theodolite and steel tape. Nylon threads are
stretched between the pegs to obtain the gridlines
when necessary.
Usually apart from the pegs depicting the main grid
lines, pegs which show the 500mm off sets are also
established during the setting out process to facilitate
the construction that follows.

1.7 Moisture & its movement through building components and damp proofing
Moisture or damp is water particles that appear on the surface of the materials. If we talk this in the building, it is
one of the most important elements affecting the living
condition inside and deteriorating the strength and
durability of the building components. Damp appears in
any surface of the building on the ceiling on the wall, on
the floor and on the other surfaces inside or outside.
Sources of Moisture

Fundamentally, the sources of moisture may be noted as

follows:
 Rainwater
 Ground water
 Water from condensation

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Phenomenon of Condensation

The air that exists everywhere in the atmosphere is a mixture of dry gases and water vapour. Therefore, moisture
is present normally in the atmosphere in the form of water vapour. This water vapour exists in the form of finely
divided particles of superheated steam at the given air temperature (dry-bulb temperature). The amount of water
vapour that a given quantity of air can hold increases with the temperature. If the air temperature is increased, it
would take more water particles and if the air temperature is lowered the water particles diffuse each other and at
a definite temperature, the air can go longer hold water molecules in vapour state. When air at any particular
temperature contains as much as water vapour as it can hold, the air is said to be saturated and the condition of air
is said to be moisture saturation state. The particular temperature at which the air is at the state of moisture
saturation is known as its dew point. If the temperature of air is decreased from dew point, the excess vapour can
no longer be held by the air and will be deposited on the surface as condensation.
Surface condensation and interstitial condensation:

When the temperature of any surface within a building is at temperature below the dew point of the adjacent air,
some of the water particles in the air will condense on that surface, this is called surface condensation. Depending
on the nature of the surface, the condensed moisture may either be absorbed by the material perhaps remaining
unnoticeable or it may appear as liquid water on the surface.
Surface condensation will not occur if,
 The temperature of the surface is kept above the dew point of the adjacent air by adequate heating or by sufficient
insulation behind the surface.
 The humidity of the air is limited so that its dew point is below the temperature of the surface.
With the occasional or intermittent surface condensation, an absorbent surface is advantageous, as it can retain a
limited quantity of moisture until conditions change and re-evaporation can take place.
Condensation in building is not necessarily confined to exposed surfaces, but may under certain conditions occur
within a material or on a surface within the thickness of a wall, roof or floor construction. This is called interstitial
condensation.

Vapour diffusion: The flow of water vapour through a porous building material or composite slab is analogous to
the flow of heat through the structure. Convection current transfers heat and moisture at the fluid solid boundary.
Conduction heat transfers is similar to vapour diffusion through a porous material and is resistance to moisture
flow varies with density as thermal resistance does but in the opposite sense.

The sources of water vapour in an occupied building are as follows:

1. Transpiration
2. Cooking
3. Washing, bathing, and drying clothes.
4. Humidifiers and open water surfaces
5. Combustion of paraffin oil. (complete combustion of 1kg of C2H20 produces 1.41 kg of water vapor)

The effects of Moisture

1. Efflorescence (disintegration of bricks, stones, tiles etc to powder like material)

2. Softening and crumbling of plaster.
3. Bleaching and flaking of paints with formation of patches.
4. Warping, buckling and rotting of timber.
5. Corrosion of metals (particularly ferrous metals)
6. Damage of electrical fittings.
7. Growth of fungus and termites.
8. Unhygienic condition to occupant in the building.
9. Damaging sound and thermal insulation.

Movement of Moisture: Almost all construction materials used in the building absorb water to some extent. There
are definite phenomena for the absorption and movement of this water in the building components. Followings are
different forces governing the movement of moisture through the building components.

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1. Capillary action 5. Air pressure

2. wind loads (Momentum of water particles) 6. Diffusion ( occurs due to difference in vapor
3. Surface tension of the building component pressure)
4. Gravity forces

Moisture control

 Ground water control-The ground water and rain water percolating in to the ground causes great problem to the
buildings. This is very sensitive work and due to the attention has to be paid to control the entry of moisture.
Besides, condensation is also quite frequent in ground floor and basements.

Followings are the methods of moisture control in the substructure of the building.

1. Damp proofing
2. Water proofing
3. Subsurface drainage

Under damp proofing, it is meant by the application of simple damp proofing paints or membrane to control the
capillary infiltration.

The requirements of an ideal material for damp proofing are:

1. It should be impervious. 5. It should be durable.

2. It should be flexible. 6. It should resist the load safely.
3. It should be easy to carry out leak proofing 7. It should not contain sulphates, chloride and
joints. nitrates.
4. It should be stable. 8. It should be cheap.

Various methods of damp proofing are as given below:

1. Providing D.P.C. course 4. Integral treatment
2. Providing cavity walls 5. Guniting and
3. Surface treatment 6. Pressure grouting.

Under water proofing, it is meant by deliberate application of impervious layer under all adverse weather
condition.

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Subsurface drainage is the method of diverting underground water away from the foundation and basement.
Depending upon the condition of the ground, the perforated underground drain may be directed towards the low
land or a drywell of adequate capacity. Subsurface drainage can also be directed to sump pump and water collected
may be pumped out. After this, there must be proper water proofing treatment in the foundation and walls of the
basement.

 Rain control
Rain is the most important factor to control in order to construct a durable building. Rain may enter in the building
in many ways. Rain is more dependent on the climate and varies from place to place. It is difficult to forecast the
intensity of rain in time and place. A general idea could be drawn from the amount of annual rainfall. Besides, the
wind has substantial effect on the intensity, strength and direction of rain.

Rain protection into and through building surfaces is governed by capillary action, momentum, surface tension,
gravity forces and air pressure. Capillary forces draw water into rain water into pores and tiny cracks, while the
remaining forces direct rain water into larger openings.

Followings are the means of rain penetration control in practice:

1. Capillary breaks 4. Use of flashings
2. Obstruction of horizontal openings 5. Creation of pressure equalization
3. Drip edge or kerfs on horizontal openings

 Vapor control
Water vapor moves in two ways, by vapor diffusion and by air transport. The mechanism differs for both the cases.
If may happen that the means of effective control of the vapor diffusion may not be effective for air transport.
Vapor diffusion is the movement of moisture in the vapor state through a material as a result of vapor pressure
difference (concentration gradient) or a temperature difference (thermal gradient). It is not the movement of
moisture as a result of air movement. Vapor diffusion moves moisture form an area of higher vapor pressure to an
area of lower vapor pressure as well as form the warm side of the building component to the cold side. Therefore,
the moisture will migrate by diffusion from where there is more to where there is less. The movement of the
moisture from warm side to the cold side of the building component is called ‘thermally driven diffusion’. The
moisture condenses on cold surfaces acting as dehumidifiers pulling more moisture towards them.The air
transport is the process of movement of moisture present in the air from the area of higher air pressure to a area of
lower air pressure.

A lecture note on building technology by Kishor Thapa,HCOE