Thermal Insulation Definition

The laws of heat transfer established that when a temperature difference between the internal and external or different parts of the building exists, this resulting in transfer of heat from the hotter to colder zones and this is referred as to thermal insulation.

This transfer of heat can take place by any of the three methods.

• Conduction.
• Convection.
• Radiation.

The rate of heat flow from one part to the other depends on the capacity of the building material or building unit such as wall, floor, roof, doors, windows etc. to transmit the same.

This property is measured by thermal transmittance denoted by ‘U’. The main objective of ‘Thermal Insulation’ is to observe a constant heat or temperature inside building, irrespective of temperature changes outside.

Advantages of Thermal Insulation

Advantages of thermal insulation are as follows:

• Thermal insulation keeps the room cool in summer and hot in winter.
• Due to thermal insulation the demand of heating in winter and refrigeration in summer, is considerably reduced. This results in lot of fuel saving and maintenance cost.
• Use of thermal insulating material inside a room results in prevention of condensation on interior walls and ceiling etc.
• The use of thermal insulating materials further reduces the risk of water freezing in case of pipes and heat loss in case of hot water systems.

List of Thermal Insulation Materials 

The various types of thermal insulation materials and some of the most important and useful are described below:

1. Slab or Block Insulation
2. Blanket Insulation
3. Loose Fill Insulation
4. Batt Insulating Materials
5. Insulating Boards
6. Reflective sheet Materials
7. Light weight Materials

Slab or Block Thermal Insulation Material :

They are known as blocks or boards, 2.5 cm thick and 60 cm x 120 cm in area. These may be made of cork board, mineral wool, verimiculite, cellular glass, cellular rubber, saw dust, asbestos cement etc. There are fixed to walls or roofs.

Blanket Insulation :

They are made up of flexible fibrous material and are available in rolls. These fibrous materials are made from mineral wool, wood fibre, cotton, animal hair etc. The blanket insulations are prepared in thicknesses of 1 to 8 cm in rolls and are directly spread an the surface of walls and ceilings.

Loose Fill Insulation :

These may consist of fibrous materials like rock wool, slag wool, cellulose or timber fibre wool etc. filled loosely in the studding space.

Batt Insulation Materials :

They are soft materials similar to blanket insulations but are smaller in size and greater in thickness usually 5 to 9 cm. They are also spread on the surface of walls and ceilings.

Insulating Boards :

These are used for interior lining of walls, and also for partition walls. Structural insulating boards is manufactured by first making a pulp of wood, cane or other materials and then pressing them in form of boards by adding suitable adhesives. They are available in different sizes and thickness.

Reflecting Sheet Materials :

Reflecting sheet materials have high reflectivity and low emission rate, thus offering high heat resistance. Solar energy striking reflective surfaces get reflected and amount of heat which may get transmitted is greatly reduced. Reflective insulations may consist of gypsum boards, steel sheet reflective materials, aluminium foils, sheet aluminium reflective material etc.

Light Weight Materials :

The cement and concrete products have lower insulation value. But with the use of light weight materials such as blast furnace slag, burnt clay aggregate, porous aggregates etc or concrete, its resistance against heat can be improved.

Different Methods of Thermal Insulation

Apart form providing thermal insulating material on walls, roofs, doors, windows etc. thermal insulation can also be achieved by the following methods:

Methods of Heat Insulation of Roofs :

(a) Heat insulating materials may be applied externally or internally to the roofs. In case of internal application, heat insulating materials may be fixed by adhesive or otherwise on the underside of roofs from within the rooms. In case of external application, heat insulating materials may be installed over the roof but below a waterproof course.

 

(b) For flat roofs, external insulation may also be done by arranging asbestos sheets or corrugated galvanised iron sheets or bricks.

Also Read : Curved Roof : Construction, Advantages; Disadvantages

Also Read : Pitched Roof : Components, Types of Pitched Roof

 

(c) Shining and reflecting materials may be fixed on the top of the roof.

(d) Roofs may be flooded with water in the form of sprays or otherwise. Loss due to evaporation may be compensated by make up arrangements.

(e) Roofs may be white washed before on-set each summer.

(f) Top exposed surface of roof may be covered by 2.5 cm thick layer of coconut pitch cement concretes. Such a concrete is prepared by mixing coconut pitch with cement and water. After laying, it is covered with an impermeable layer and then allowed to dry for 20 to 30 days.

Method of Heat Insulation of Exposed Walls :

Heat insulation of exposed walls may be achieved by the following ways:

(a) The thickness of the walls may be increased, depending upon the extent of insulation derived.

(b) Cavity walls construction may be adopted, for external walls.

(c) The walls may be constructed out of suitable heat insulating materials provided structural requirements are met.

(d) Heat insulating materials may be fixed on the inside or outside of the exposed wall, is such a way that the value of overall thermal transmittance is brought within a desired limits. In the case of external application, overall water-proofing is essential.

(e) Light coloured white-wash or distemper may be applied on the exposed surface of the wall to increase thermal insulation value.

Methods of Insulation of Exposed Windows Doors Ventilators etc :

All the windows, doors, ventilators etc. which are exposed, transmit heat to a considerable extent. In dealing with heat insulation of exposed windows and doors, suitable methods should be adopted to reduce.

(a) Reduction of Incidence of solar heat : The incidence of solar heat on exposed doors and windows can be reduced by the following means.

(i) External shading, such as louvered shutters, sun breakers chajjas and

(ii) Internal shading, such as curtains and ventilation blinds.

(b) Reduction of heat transmission : Where glazed window and doors are provided, the reduction of heat transmission may be achieved by insulating glass or double glass with air space in between or by any other suitable means.