Windows and Ventilation in Building

Windows

Window is the opening in the building. Window is a switch used for light, ventilation and visual connection usually between the outside and the inside. These are not meant for access. It rests on sill of a wall and are usually topped by lintel. It is made of different materials including Timber, Aluminum, Steel, PVC, etc. The sizes vary according to purpose and use.

Elements of Window(Terminology)

1. Frame   - It is the vertical member/ post fixed on the wall with the help of holdfast (125X75). 
2. Shutter – It is the movable part of the door which is hinged with the frame.
3. Holdfast – It is the metallic anchorage which holds the door frame against the wall.
4. Post/ jamb - Vertical member/ face of the frame/ wall, which receives the holdfast.
5. Head - The horizontal member at the top of the frame.
6. Rails – They are the horizontal members of a shutter. They are termed as the Bottom, Lock (middle), Top rail according to their location in the shutter.
7. Stile – The vertical member of shutter, which frames the shutter.
8. Panel - Block or board to seal the void of a shutter.
9. Mullion-  The vertical member lying between two shutters.
10. Sill-  the lower part of window frame.
11. Horn-  parts of window or door frame left for proper anchorage.

Types of Window

Casement/ordinary windows

A casement window is a window that is attached to its frame by one or more hinges. It usually comes in combination with fixed and ventilator portion.

Glazed/sash windows

It is the most common type of window. The window section is of glass panel. It is of two types: Single glazed, Double glazed:

Singal glazed :- It is the general practice in our locality.

Double glazed :- It is done for special purpose, such as insulation of heat and sound. Almost all glazed door and windows are double is Europe and other cold region. This in not familiar in our Himalayan region.

Louvered windows

The section is fixed with louvered. It has blind or shutter with horizontal slats that are angled to admit

light and air, but to keep out rain, direct sunshine, and noise. The angle of the slats may be adjustable. It is suitable where ventilation is desired without visual connection. 

Pivoted windows

The frame is pivoted up and down or may be horizontally or vertically pivoted along the center as per need.

Corner window

The section is fixed at the corner in two direction. It is placed at the corner, whose portion extends into both the wall.

Double hung window

The section slides vertically with in grooves in frame. It occupies less space.

Gable window

This is ordinary window. It is positioned at the gable end of the roof.

Dormer window

A dormer is a structural element of a building that protrudes from the plane of a sloping roof surface. It is placed on the roof (slope) to bring light and ventilation inside the room/attic. Dormer windows are source of light and ventilation for top floors.

Bay windows

A bay window is a window space projecting outward from the main walls of a building. It is a multi-

panel window with at least three panels set at different angles. The angles most commonly used on the inside corners of the bay are 90, 135 and 150 degrees. They are projected outside usually with low sill.

Clerestory window

It is the window just below the roof or ceiling. It is placed over the slab of a room to serve the room inside with high ceiling. Clerestory refers to any high windows above eye level. The purpose is to bring outside light, fresh air, or both into the inner space.

Lantern window

A roof lantern is a multi-paned glass structure a small building, built on a roof for day or moon light. The sections are placed horizontally on the flat roof for the purpose of light.

Sky light window

The sections are provided in a sloped surface. They are used for daylighting. The thermal performance of skylights is affected. During warm seasons, skylights with transparent glazing will cause internal heat problems.

Sliding window

In this type of window, the section slides in sideways or horizontally. It is popular in aluminum, steel and U-PVC.

Steel (metal) window 

This type of window comes in angle section/rectangular pipe section which are used as frames.

French window

This type of window has one or more panes of glass set into the whole length.

Ventilation

Ventilator is narrow opening with small height provided near the roof or slab in the building. The main purpose of the ventilation is to facilitate ventilation in the building. The shape and size of the ventilator is similar to the window sections. The shutter of the ventilator is pivoted and can be opened or closed. These shutters are side hung or top hung. They are also found as part of the door or window.

 Types of ventilators

1. Side hung

1. Bottom hung

1. Horizontally pivoted

1. Vertical pivoted

1. Top hung

1. Vertical sliding etc.

Fixing method

 According to material use, fixing of door and window frames are done simultaneously at the time of wall construction. Holdfasts of required numbers are nailed. Frame is carried to position and set with the help of ropes and poles. Frame is then put to plumb (frame should be perfectly vertical). Once the frame is set and leveled, the holdfasts are fixed in wall, cement, concrete etc. Final checking of plumb is done, if required corrections are applied.

Doors and its types in buildings

Door 

A door is a movable structure used to close off an entrance. When opened, they admit ventilation and light. It typically consists of a panel that swings on hinges or that slides or rotates inside a space. Door has essentially two parts: Frame and shutter. The door is used to control the physical atmosphere, noise, etc. Doors also have an aesthetic role in creating an impression.

Elements of Door (Terminology)

1. Frame  - It is the vertical member/post fixed on the wall with the help of holdfast (125X5). It receives the  door shutter.
2. Shutter – It is the movable part of the door which is hinged with the frame.
3. Holdfast – It is the metallic anchorage which holds the door frame against the wall.
4. Post/jamb - It is the vertical member/face of the frame/wall, which receives the holdfast.
5. Head - It is the horizontal member at the top of the frame.
6. Rails – They are the horizontal members of a shutter. They are termed as the Bottom, Lock (middle), Top rail according to their location in the shutter.
7. Stile – It is the vertical member of shutter, which frames the shutter.
8. Panel - It is the block or board to seal the void of a shutter.
9. Batten – They are the planks used for the face of a shutter. (traditional door)
10. Ledge - It is the horizontal member used in battened & ledged door. (traditional door)
11. Brace - It is the inclined member used in battened ledged & braced door. (traditional door)

Types of Door

1. Battened door
2. Paneled door
3. Glazed door 
4. Flush door
5. Sliding door
6. Revolving door
7. Collapsible door
8. Rolling shutter door
9. Swing door
10. Solid core door
11. Nuwood door

Battened door

It consists of series of battens  with tongue & groove joint. The battens hold the planks together. Sometimes a long diagonal slat or two are also implemented to prevent the door from skewing. In some doors, the battens are replaced with iron bars. 

Paneled door

Panel doors, also called stile and rail doors, are built with frame and panel construction: They consist of a frame made up of stiles, a top rail, a bottom rail, and sometimes an intermediate rail. Into this framework a plywood panel is fitted. This panel may fit into a groove or a rebate. This door is used as external door.

Glazed door 

They are similar to Panels door except Panels are in glass. They are normally made up of timber and used as internal door.

Flush door

These types include many modern doors, including most interior doors. They are joint-less; the rails and frame are hidden. Normally the frame is made up of  timber. They are used as internal doors.

Sliding door

A sliding door is a type of door which opens horizontally by sliding. Panels are fixed with wheels on their top & bottom. The wheels run over the iron or hardwood. The panel slide across saving space. They are common in aluminum and steel.

Revolving door

The revolving door is the movement of personnel between roles as legislators and regulators. It helps to maintain thermal condition inside the room. It is found in the entrance of public buildings. 

Collapsible door

They are fabricated from mild steel. They have scissor joints and collapse on sides and save space.

Roller shutters

Roller shutters are closures where the door leaf rolls up above the doorway. Panel coils up on the top. They are used mostly in shops and stores.

Swing door

It can be opened on either side (double/top hinged). It is found in restaurants and public spaces.

Solid core door

It is laminated door section. Fame is made of timber. Hardwood or pressed wood may be used for core of the frame.

Nuwood door

Nuwood is the artificial wood. It gives fine finishing. The wood is cut to desired shape & size. Nuwood can be used to form solid core.

 Retaining Wall and Water Proofing

Retaining Wall:

A retaining wall is a structure designed and constructed to resist the lateral pressure of soil. Retaining walls are built in order to hold back ground. Lateral earth pressures are zero at the top of the wall & a maximum value at the lowest depth. Earth pressures will push the wall forward or overturn it if not properly addressed. The basement wall is thus one form of retaining wall. Most often used to refer to a cantilever retaining wall which is a freestanding structure without lateral support at its top.

Function of retaining wall

• Strength stability & durability
• Resistance to overturn
• Resistance to horizontal slide
• Resistance to overstress in the materials of construction
• Resistance to overstress in the soil on which the wall rest

Design Consideration:

Retaining wall must be ensure that;

1. Overturning does not occur
2. Sliding does not occur
3. The soil beneath the wall is not overloaded
4. The materials in the wall are not overstressed

Forces acting on Retaining walls

The effect of 2 forms of earth pressure need to be considered during the process of designing the retaining wall that is:

1. Active Earth Pressure

     “ It is the pressure that at all times are tending to move or overturn the retaining wall”

2. Passive Earth Pressure

     “It is reactionary pressures that will react in the form of a resistance to movement of the wall"

Angle of repose

It is the natural slope taken up by any soil; It is given in terms of the angle to the horizontal base line. It varies from 45-0̊ for wet soil but for most soil this angle of repose is 30̊

Wedge of soil

This is the soil resting on the upper plane of the angle of repose

Surcharge

This is the additional mass of soil above the top surface of wall

Factors affecting strength, stability & durability 

• Nature and type of soil
• Height of water table
• Sub-soil water movements
• Types of wall
• Materials used in the wall

Types of retaining walls

1. Gravity or mass retaining wall
2. Cantilever or L-shaped retaining wall
3. Sheet piling retaining wall
4. Anchored retaining wall
   
   
   

1. Gravity or mass retaining wall

Gravity walls depend on the weight of their mass (stone, concrete or other heavy material) to resist pressures from behind. With of the base is usually H/4 to H/2 ,where H is the height of wall. For efficiency the wall is sloped in front face. Reinforced to avoid cracking. Height is usually limited to 1.8 to 2 m.

2. Cantilever or L-shaped retaining wall

Cantilevered retaining walls are made from an internal stem of steel-reinforced. These wall have much thinner stem and utilize the weight of the backfill soil to provide most  of the resistance to sliding and overturning, less expensive than mass gravity walls, most common type of earth retaining structure.

3. Sheet piling retaining wall

Retaining properties and water proofing of basements

• Damp Proofing Course (DPC) for basement
• Provided on outside surface of wall and underside of floor of basement
• DPC must withstand the water pressure from underside
• Basement must have sufficient dimension
• Base concrete (PCC) of sufficient thickness to be provided with minimum projection of 15cm beyond outer wall as a protective before DPC
• RCC wall and slab be provided after DPC course
• Asphalt layer is best DPC in basement and it should be continuous
• There must be proper lapping of DPC in joints and cracks
  
  
  

Methods of water proofing

1. Membrane water proofing -rater repelling substance like bituminous felt,  asphalt, silicon etc.

2. Integral waterproofing -adding certain waterproofing compounds into the concrete mix.

3. Surface treatment -Filling up the pores of the surface subjected to dampness-paint, cement slurry etc.

4. Pressure grouting 

5. Cavity of construction

Foundation/Footing and Its Types (Deep)

B) Deep Foundation

 This is preferred where the soil strata at the surface are not very good. The foundation is driven deep into the ground till it reaches a hard strata or compacted soil. Deep foundation can be classified as;

1. Pile foundation 

 Piles are generally used in buildings. Piles are driven into the ground to strengthen the strength of the soil below. 

According to their use they can be classified as,

•  Bearing pile
•  Friction pile
•  Sheet pile
•  Anchor pile
•  Compaction pile
•  Fender pile
•  Batter pile

According to the material used, piles are classified as;

a. Timber piles

b. Concrete piles i. Precast        ii. Cast- in-situ

c. Steel piles

d. Composite piles

2. Well foundation

This foundation is mostly used in black cotton soil which is good for agriculture & bad for structure. This type of soil has high shrinkage value due to change in moisture content and volume varies as 20-30% of original volume. It develops very wide & deep cracks due to excessive shrinkage and is problematic for foundation.

Precaution for foundation in black cotton soil 

•  Foundation depth be enough below from cracks to hard strata
• Prevent foundation from direct contact with black cotton soil
• If thickness of black cotton soil is high,foundation is to be laid on piles
• Raft foundation is the choice in this condition
• Tie-beam in plinth is important

Bearing capacity of soil

It is the ability of soil to support the load coming over it. Bearing capacity of soil depends upon the types of soil.

Methods of improving bearing capacity of the soil

1. Compacting the soil
2. Increasing depth of the foundation
3. Drainage of soil
4. Grouting 
5. Chemical treatment
6. Driving sand piles

Some Common Problem with existing foundation

1. Causes of foundation settlement
2. Consolidation of soil particles
3. Reduction of moisture content
4. General earth movement

Effects of unequal settlement

• Distortion of structure fabrics
• Failure of structure

Prevention of undue unequal settlement

• Proper foundation design
• Proper soil investigation

Causes of foundation failure

• Unequal settlement of sub-soil
• Unequal load distribution
• Horizontal movement of soil adjoining structure
• Lateral pressure tending overturn
• Shrinkage due to withdrawal of moisture from soil
• Atmospheric action
• Lateral escape of soil below foundation
• Nearby building construction
• Trees etc.

Foundation/Footing and Its Types (Shallow)

A building is divided into two parts;

i.   Sub-structure (portion below the Plinth level)
ii. Super-structure (portion above the Plinth level)

 Foundation is the lowest part of the structure below plinth level, which provides base for super structure. It does not take up the load of the structure by itself, it only transfers superimposed load to the soil below.

Objective of foundation

•  To provide a leveled base for the superstructure
•  To transmit all superimposed loads of the structure to the soil
•  To increase stability; prevent tilting or overturning of the structure
•  To prevent unequal settlement 

Types of Foundation 

A) Shallow foundation             B) Deep foundation

A) Shallow Foundation (Wide foundation)

 It is placed immediately beneath the lowest part of the super structure. It is spread more horizontal than vertical. The depth is less than or equal to its width. It transfers the loads to subsoil at a shallow depth, close to the ground level.

Types:
1. Spread Footing: 

The base is made wider than the top so as to distribute the load from the superstructure over a large area.

a) Wall (Strip) Footing

 It is generally used for ordinary building with load bearing walls. The successive increment in the width is achieved by providing 5 cm (1/2 brick) offset at both sides.

b) Reinforced Concrete Footing

 In case of heavy loading, R.C.C. footing proves to be economical over brick footing.

c) Inverted Arch Footing

 It is used where the bearing capacity of the soil is very poor and load of the structure is concentrated over the columns.

d) Column Footing

 It is also known as independent/ isolated footing. It may be constructed using bricks, R.C.C. or stones.

2. Grillage Foundation 

 It is used where the load of the structure is excessive and the bearing capacity of the soil is poor. It is recommended where deep foundation is not possible. Steel and timber grillage foundation are generally used.

3. Combined Footings

 In this footing two or more columns are supported by a single base. They can be Rectangular or Trapezoidal in shape.

4. Raft or Mat Foundation

 Generally this type of foundation is used where the load of the structure is excessive and the bearing capacity of the soil is poor or where basement space is desired and pile is very expensive.

Lighting Design in Building and Energy Conscious

Lighting Design in Building

Light is the band of electromagnetic radiation of wave length-380-780 nm (1nm=10-9 m). Lighting is the desirable effect in the building envelope. It is the most important communication channel of man with environment and it is the prerequisite of seeing. Good lighting is necessary to enable work with efficiency.

Natural light:

The ultimate source of natural light is sun. Radiation (heat) with light is received from sun . Bright sun gives about 100 Klux (100000 lux). Intensity of radiation is likely to be 1 kw/m2.

Quality of sun light: It may be harsh, sparkling, hazy, sub-dared. Quality depends on length of day, weather, seasons. These are external conditions.

Day light

Source of day light is sun. The factors affecting penetration of light through openings depends upon the types, size, placement and orientation of the opening. Skylight may be direct or overcast. Overheating and glare have to be avoided. The quality of day light in rooms is proportional to the area of glass in windows relative to floor area and this is conformed by the measure of day light factor.

Day light factor

It is the ratio of internal illumination in a certain point of building with the simultaneous outdoor illumination. It is expressed in percent. Day light varies considerably in intensity both hourly and daily due to the rotation of the earth and the consequent relative position of sun. It is commonly used for artificial lighting.

DF=Ei/Eo*100

Here, Ei is indoor illumination at a point

        Eo is outdoor illumination from unobstructed sky

 This formula is valid under overcast sky condition (no direct sun). DF=SC+ERC+IRC

SC is sky component

ERC is externally reflected component 

IRC is internally reflected component

Example: Given DF = 8%

Eo=6000 lux Then,

DF=Ei / Eo *100

8 =(Ei / 6000) *100 Ei=480 lux

Good visibility depends on:

– Characteristics of work

– The sight of workers

– Speed and accuracy necessary in the performance of work

– The ease and comfort of working

Glare: It is the condition of vision in which there is discomfort or a reduction in the ability to see significant objects or both, due to an unsuitable distribution or range of illumination or to extreme contrast in space in a room

Guidance for good lighting

• Broader opening gives better distribution of light.

• Openings on two oppose sides will give greater uniformity.

• Cross lighting with openings on adjacent walls tends to increase the diffused light with in a room.

• Deep openings tend to minimize the glare.

• Openings provided with sunshades, louvers etc. excludes as far as possible the direct sun light from the room.

Artificial lighting

The primary purpose of artificial lighting system is to provide sufficient illumination for the performance of visual tasks.

• Artificial lighting requirements

– The source of light should be steady. 

– Glare should be eliminated.

– Inconvenient shadows should be avoided.

– The degree of illumination must be suitable for the particular visual task. 

– Lighting should not cause excessive heat.

Energy conscious design: renewable and non-renewable source of energy, active and passive methods of solar cooling and heating. Energy conscious design deals with: 

– Effective design,

– Effective planning,

– Reusing available resources,

– Maximum use naturally available energy

Energy conscious design is the design of buildings such that it has maximum use of renewable energy and exploitation of non-renewable sources of energy is to be minimum level.

Renewable Energy:

• It is the term used to cover energy flows, that occurs naturally and repeatedly in the environment and can be harnessed for human benefits.

• The ultimate source of renewable energy: sun, gravity force, earth’s rotation etc.

• Example: Solar energy, wind energy, wave energy, Hydroelectric energy, Bio-mass energy, Energy from wastes, Tidal power, Geo-thermal energy etc.

Non-renewable energy:

• The flow of energy that can be extracted from the elements available.

• As the source element goes on consuming while generating energy, the term used for this energy is non-renewable.

• Sources:

– Minerals

– Nuclear elements • Examples:

– Fuel energy (from minerals-petroleum products) 

– Nuclear energy,

– Electricity by fuel etc.

Active method of solar heating:

• The process of heating directly with the use of solar collectors using the heat for human comfort.

Passive method of solar heating:

 A building in which the various components are arranged in a manner that maximizes the collection of solar heat, it is stored and finally distributed in to the building space with out any expenditure of conventional form of energy (Flavin 1980). Building is designed in such a way that maximum amount of solar energy is trapped inside the building.

Design considerations:

• Location             • Layout

• Orientation         • Shape

• External color    • Openings etc.

 Acoustical properties of building materials

Sound: Any thing that can be heard. 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 hear can be gas, liquid or solid . It is transmitted as the longitudinal wave motion, I.e. successive compression of molecules. In solid body, the transmission is by lateral wave motion. Wave length determines pitch of sound . Higher the frequency higher would be the pitch (frequency is the waves per unit time. Loudness depends on distance from / to vibrating body. Unit of loudness is dB.

• Range of hearing loudness

– Rustle of leaves, whisper 10dB. 

– Airplane, pneumatic drill 130dB.

• Ranges of hearing frequency 

– Low 20 Hz/s.

– High 20000 Hz/s.

This range changes with age and other subjective factors.

Reaction produced by sound 

1. Reflection- from walls, floors, ceiling etc.

2. Absorption- by walls, by floors, by ceiling, by furniture etc. 

3. Transmission- to adjacent rooms.

Sound classification

1. Air borne sound- sound through air to air

2. Impact or structure borne sound- sound through direct contact; such as footsteps, hammering or vibration etc. it is very sharp and troublesome.

Acoustics

Acoustic is the science of sound. It assures the optimum conditions for producing and listening to speech and music. The panning of acoustical design has to provide for dissipation of noise and insulation against sound.

Noise and its effect: Noise is the undesired or unwanted sound. It has following effects;

1.      Annoyance- irritation 

2.      Disturbance of sleep

3. Interface or disturbing conversation 

4. Damage of ear

Measurement of annoyance is subjective attitude and depends on mental and physical well being of listeners with their experience.

Magnitude of Noise level

Types of sound Noise level (dB) Effects

Light road traffics         60-70 Physiological effect (annoyance)

Medium road traffics 70-80 Physiological effect (annoyance)

Heavy road traffics         80-90 Prolonged exposure cause permanent hearing loss

Rail traffics         90-100 Prolonged exposure cause damage to auditory organ

Air traffics         100-130 Causes pain

                >130 Instantaneous loss of hearing

Defects due to reflected sound

1. Echoes is the reflected sound and heard just after the produced sound as a repetition.

2. Reverberation is continuous reflection of produced sound waves 9reflection, inter-reflection etc.) until they are gradually faded out. Certain amount of reverberation is necessary to enhance the sound, but excessive is damaging to clarity. Reverberation time: It is the time taken for sound to decay by below annoyance level (60dB) after the sound source has stopped. It depends on; volume of room, absorption in walls, roofs, and floors etc. it has to be minimized using sound absorbing materials.

Sound insulation

1.Sound absorption (prevention of reflection) 

2.Sound insulation (prevention of transmission)

Sound absorbents 

1. Porous materials

2. Resonant panels 

3. Cavity resonators 

4. Composite types

• In porous materials, the sound waves on striking its surface enter to the pores, vibrate inside and die-out there . Normally, these materials are soft and have large pores with interconnected channels. Porous materials may also be put in the gap between boards . It is suitable for low frequency waves.
• Resonant panels are semi-hard in the form of porous fiber boards than acts as sound absorbent. These boards are fixed on timber frame with air gap between and also with wall backing . In the resonant panels, the sound pressure waves cause vibration and this vibration is absorbed by air gap (space) called damping.
• Cavity resonators are the chambers with the narrow openings. The absorption of sound absorption of sound takes place in this case by the resonance of air.
• Composite types are the perforated panels fixed with air space containing porous absorbents. The panels may be of metal, plywood, hard board, plaster boards etc. The perforation should be at least 10 percent of area high frequency sounds are absorbed in this perforated panel.

Noise control and constructional precautions to reduce noise

General consideration

1.Isolate sound source

2.Proper orientation of building, I.e. no opening towards noise 

3.Properly planed rooms in building

4.Furnishing materials in room helps sound absorption 

5.Partitions- rigid and movable

6.Control of impact sound, I.e. use 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

Constructional measures

1.Walls/partitions: Absorbents in the walls/partitions act as the barriers to air borne sound transmission.

Types:

•Rigid and homogeneous partitions: Insulation in this case depends on the weight of thee partition per unit area and increases with thickness

• Partition of porous material Insulation increases to 10% or higher. Material may be rigid of flexible.

• Hollow and composite partition Cavity is better: Filling of cavity with resilient material is preferred.

Following table illustrates the insulation properties for different walls;

S.No. Types of wall     Approx. wt. of wall kg/m2     Average sound reduction, dB

1 One brick wall, plastered in both side         490             50

2 One and half brick wall plastered in both side 710             53

3 Cavity (50mm) with half brick in both leaves 490             50-53

4 Half brick or concrete with plaster both side     170             45

5 200mm concrete wall                 185             45

6 Gypsum board partition on timber frame 70             45

7 75mm hallow clay block with plaster both side 110             36

Hard reflecting surface outside partition increases insulation

 Constructional measures

1. Floors/Ceilings

These are the horizontal barrier to noise. They act as barrier to air borne and impact sounds, but offer poor insulation for insulation for structure borne or impact sounds. Insulation in floor; resilient surface materials, floating floors. 

• Resilient surface materials on floors: Cotton/wooden carpets, asphalt/mastics, pvc carpets, corks etc. Softer the material used greater would be the insulation value.

• Floating floor construction: Provides insulation from any other parts of structure. It is made to rest or float over existing floor by means of resilient materials such as glass wool, quilt, hair felt, cork rubber etc. Impact sound do not transmits. It can be adopted in all floors. On concrete floor, partition is constructed off the structural floor and it is independent

Types of floating floors:

• Concrete floor with floating concrete screed: It is the PCC of 1:1.5:3 on resilient materials above concrete floor.

• Concrete floor with floating wooden raft: It is wooden boarding nailed to battens forming raft on resilient quilt (20mm).

• Heavy concrete floor with soft floor (resilient) finish or covering. 

Wooden floors: It has the problem of impact sound.

2. Windows and doors: 

It should be,

•Air tight

•Double glazed

•Thickness of glass to be increased 

•Increased weight of shutter

3. Insulating sanitary fitting

•WC be insulated, pan to rest upon thin pad of felt, PVC, corks, rubber etc.

•Cisterns not on wall of bed rooms, brackets be fixed with insulating materials (clips)

4. Machine mounting and insulation of machinery

Machines resting on the resilient materials as steel spring, rubber, corks etc.

Thermal performance of building sections and insulation

Thermal performance of building sections

A thermal performance of building sections depends upon thermal properties, outside surface finish, orientation and climatic conditions. These properties are represented in two categories.

a)Thermal characteristics of the building section

b)Thermal performance index.

The U-value of the building sections can be computed with a knowledge of thermal conductivities of building sections, their thickness and surface resistance. Although there will be slight variation in the U-values for difference cities due to variation in surface resistance, for all practical proposes in building design certain constant values of surface resistance are assumed in U-value calculation . The average value of inside surface conductance (fi) for building material surface is about 9.3 W/ m2 deg C for still air and for wind velocity of 8.0 km/h, outside surface conductance (fo) is 19.90 W / m2 degC.

The values of surface conductance and the surface resistance are given in the appendix.

 

Transmittance of composite wall

In the composite wall construction, the U-value of the wall of that particular composition would not be available in the given table and computation of the U-values should be processed following the formula: U=1/Ra

Here the summation of resistance (Ra) of all materials used in the wall or in any structural member is necessary. The resistance can be worked out with the values of conductivity (k) for different materials and their thickness.

The values of the conductivity (k) are given in the appendix.

Taking an example of a composite wall, that consists of 110 mm brick wall (1/2 brick) as a outer leaf, cavity of 50 mm then after, 110 mm inner brick wall, 2.5mm insulating layer of glass wool on the inner leaf of brick wall. There is a plaster of 12 mm after the insulation. The wall is facing west.

As a first steps to find the resistance (U) value of this wall, the values of the conductivities of the different wall section to be found referring table in the appendix;

In some cases (e.g. for the prediction of condensation) it will be necessary to know the temperature at any point with in the wall, i.e. the thermal gradient through the wall, or other constructional elements. This can be established quite simply by a graphic method .

The thermal gradient can be clearly explained with the help of the cross section of the wall considered in the above example. Assuming the temperature of inside and outside of the room to be 20ºC and 0ºC respectively.

Now, drawing a cross section of wall to a scale representing the resistance of the individual layers, instead of thickness. Say, a scale of 1mm=0.01 m2ºC/W, thus the external surface resistance is represented by 7.6 mm and the resistance of the brickwork is shown as 9.5 mm, etc. along cross-section of the wall can be drawn to a scale, say 1:10.

Establishing the temperature of outside and inside 20ºC and 0ºC points at the faces of the resistance section, and connecting them with the straight line, the intersecting points of this line with the various layers can now be projected across horizontally to the corresponding layers of the physical wall section. A line connecting the points thus derived in the wall will represent the thermal through the wall.

Types of insulation

The practical ideal insulation is a vacuum or air when kept completely motionless in a space separating two solid components. Air, however can be kept motionless even in a narrow vertical cavity (in a wall assembly). As a result of warm and colder sides of the cavity, heat transfers from warm side to cold side by radiation . The air in the cavity coming in contact with the warm side is heated by convection and this will give rise of convective currents. These convective currents can minimized by breaking up horizontally the air in the space in to tiny compartments. Thus the air will remain still and exhibits excellent insulating properties. The principal way in which thermal insulation works is the capacity of that material; to resist heat flow by forming the tortuous path through the material around voids. The more efficient insulation types are also made from materials with poor thermal conductance. i.e, Mass type insulation, Reflective insulation

 Mass type insulation

Reduces the flow of heat by preventing convection in entrapped air and also by forming a barrier to radiation. Mass type insulation may be;

1. Slab and blocks- cork board, mineral wool slabs, cellular glass or rubber slabs saw dust or cement boards.

2. Blanket insulation- flexible fibrous materials such as; glass fibers, cotton and animal hairs.

Reflective insulation

Reflective insulation is also called the radiant barriers. These types of insulation reduces the transfer of heat through air space by minimizing radiation of energy from the warmer or emitting surface of one of the components which enclose and air space to a colder or receiving surface of the other component. Emissivity of various building materials at the same surface temperature vary. The radiation across an air space between two polished aluminum surfaces will be only about 3% of that between two black surfaces . Reflective materials act as insulation, because of their low surface emissivity by reflecting incident radiation energy. It is estimated that in a cavity wall, up to 60% of heat transfer takes place by radiation.

Types of insulating materials

Organic: fibers, including cellulose fibers, thatch and wood fibers.

Inorganic: foams, including foamed glass, cellular concrete, hollow glass bead concrete, perlite and vermiculite, expanded polystyrene bead concrete etc.

Metal foils and metal foil laminated on other materials: one form combines shiny aluminum foil with flexible polyethylene foam and its manufacturer reports very favorable insulation values especially, where radiant heat is the predominant mode of heat transfer.

Insulation of building components

Organic foams including expanded polystyrene, polyurethane foam, polyisocyanurate foam and cork etc.

Composite materials combining several of the materials listed above.

Natural materials of low thermal resistance, which nevertheless, act as thermal insulators and also provide thermal storage including earth, masonry and turf. 61

 Insulation of building components

1. Perimeter and foundation insulation 

2. Basement insulation

3. Wall insulation •Masonry wall insulation •Framed wall insulation

4. Roof and attic insulation