Thermal Insulation

THERMAL INSULATION AND ITS BENEFITS

Definition

It is a provision to resist the flow of heat to and from a body or building. It is also a material that reduces the rate of heat flow between the body and its surroundings.

It is the reduction of heat transfer between objects in thermal contact or in range of radiative influence.

1. General principles of thermal Insulation

• The thermal resistance of an insulating material is directly proportional to its thickness.

• The provision of an air gap is a very important insulating agent.

• The thermal resistance of a building depends on its 1910 orientation also.

• Heat energy that flows from one region to another is due to the difference in temperature between the two regions.

• The heat is transferred by conduction, convection, or radiation, or combination of any of them.

2. Thermal Insulating Materials

The materials which are used for thermal insulation are known as thermal insulating materials . They are classified as

(a) Organic materials

(b) Inorganic materials

(a) Organic materials:

Examples:

Cattle hair,Silk, Wool, Wood-pulp, Corkboard, Sawdust, Sugar-cane fiber, Cardboard, Paper, Leather.

(b) Inorganic insulating materials:

Examples:

Still air, Mineral wool, Slag-wool, Glass wool, Charcoal, Gypsum powder slag, Coke power, Asbestos.

3. Methods of thermal insulation

The methods of thermal insulation are given below:

•  Use of materials with low thermal conductivity

Materials with low thermal conductivity (hollow bricks and tiles) should be used for walls and roofs.

•  Thickness of walls and roofs

Thicker the wall or roof, lesser is the heat transfer. Hence, the external walls or roofs should be thicker to ensure thermal insulation.

• Provision of air spaces

Air spaces in walls and roof increase thermal insulation. Hence, the use of hollow bricks, cavity walls, etc., improves thermal insulation.

• Heat insulation by orientation

The building should be so oriented that there is minimum transfer of heat during summer and maximum transfer of heat in winter.

• Thermal insulation by shadings

Providing sunshades (to doors and windows) and raising parapet wall heights improve thermal insulation to some extent.

• Providing sufficient height of the ceiling

The intensity of longwave radiations emitted by the ceiling decreases as it travels downwards. However, it is not significant beyond 1-1.3 m. Hence, the ceiling should be provided at a height of about 1-1.3 m above the height of the occupant.

• Using thermal insulating materials

Thermal insulating materials can be used to get good thermal insulation.

The thermal insulation of roofs, external walls, doors and windows are discussed below:

(i) Thermal insulation of roofs

Thermal insulating materials may be kept over the roofs, but a waterproof course is essential below them.

Providing a 25 mm thick concrete mixed with coconut pith is one such method of thermal insulation.

For external insulation, Asbestos Cement (AC) sheets on bricks are used. (Figure 1.13). Fixing shiny and reflective materials to the top surface can also ensure thermal insulation.

A false ceiling of insulating material may be provided to leave an air gap between the roof and ceiling.

 (ii) Thermal insulation of walls

The following treatments may be used for thermal insulation of walls.

• Fixing thermal insulating materials on inside and outside of the walls.

• Applying light coloured whitewash or distemper on the wall. Homer m001

• Creating air space in partition walls by fixing the sheathing of hardboards and battens as shown in fig. 1.14.

• The suitable thickness of wall may be provided.

• The hollow wall or cavity wall construction may be used.

• Weathersheds, projections, curtains, etc. may be provided on the exposed doors and windows.

(iii) Insulating doors and windows

Heat transmission through doors and windows may be reduced by:

• Providing sunshades

• Using louvered shutters

• Using venetian blinds and curtains with heavy folds

• Using insulating glass or double glass femted between them

Benefits of Thermal Insulation

The benefits of thermal insulation are:

• By thermal insulation, the room remains cooler in summer and warmer in winter than outside.

Hence, a room provided with thermal insulation gives good comfort both in summer and winter.

• Energy Saving: Thermal insulation decreases the bear ed en oljeruan transfer of heat between inside and outside of the room. This results in less quantity of energy required for maintaining the desired temperature in the room.

• Thermal insulation reduces thermal stresses of roof decks tend to crack.

• No heat absorption and subsequent dissipation.

• Expansion joints can be avoided.

• Temperature drop of 5°C to 10°C depending on outside temperature.