Thermal Insulations

Prof. Dr. Saiful HuqueInstitute of Renewable Energy

University of Dhaka 19-11-2013

What is thermal Insulation

Thermal insulation are material or

combination of materials that help retard the flow of heat energy by conductive, convective or radiation mode of heat

Types of thermal insulation

They can be of several typesFibrousParticulateFilmBlockAnd composites of these materials

Application of thermal insulation

Conserve energy by reducing heat loss and gain of structure and ducts Control surface temperature of structure for comfortPrevent vapor condensation on surfaces having temperature below the point temperature of the surrounding atmosphere

Application of thermal insulation

Reduce temperature fluctuation within an enclosure when required heating or cooling is not available

Reduce temperature variations within a conditioned space for increased personal Comfort

Thermal insulation can serve extra

Add structural strength to wall ceiling or floor

Provide support to surface finish

Impede water vapor transmission and air Infiltration

Reduce noise and vibration

Limiting material of thermal insulation

The own survival temperature is considered as second selection criteria after primary criteriaLike consideration of low thermal conductivity

Based on origin thermal insulation material can be

categorized into three categories1

inorganic or fibrous or cellularlike glass wool, rock wool, slag

wool, calcium silicate bonded perlite, Vermicular or ceramic products

Category of thermal insulation

2 Organic fibrous material like cellulose, cotton,

animal hair, wood pulp, cane or synthetic fibers and organic cellular materials such as cork, foamed rubber, polystyrene, polyurethane and other polymers

Category of thermal insulation

3

Metallic or metallic organic reflective membrane.

These surfaces must face an air, gas filled or evacuated space to be effective.

Properties of Insulating materialsPhysical properties:Loose fill insulationInsulating cementFlexible and semi rigid insulationRigid materialReflective materialFoam-in-place insulation Accessory materials

Properties of Insulating materials

Thermal properties:Thermal resistance and insulationThermal conductivityThe R-value:Conductance of a material C = k/L where k and

L are thermal conductivity and thickness of insulating material.

Properties of Insulating materials

The R value of the insulation is defined as R = 1/C = L/k it means for obtaining a higher R-

value of insulation, either more thickness of insulating material or a material of low conductance should be used.

Names like R11, R-12 represent ratio of thickness and thermal conductivity in BTU system of units

Properties of Insulating materials

Mechanical properties:Some insulation materials have sufficient structural strength to act as load bearing members. Mechanical properties vary with basic composition such as density, composition, cell size, fiber diameter and orientation, type and amount of binder and temperature

Properties of Insulating materials

Health and safety:Most thermal insulations have good resistance to potential risk to health, such as fire, vermin, rot, objectionable odors and vapors.Potential risks from insulation material can be

put into two categories :Risk related to storage, handling and installationRisks that can occur after installation e.g. Aging

Properties of Insulating materials

Health and safety:Potential health effects range from temporary Irritation to serious changes in body functions.

Manufactures recommendations and government codes must be concerned beforeusing insulating materials.

Properties of Insulating materials

Acoustics:Some thermal insulation materials can also serve purpose of acoustic control.Acoustic efficiency depends upon physical structure of the material. Materials with open porous surfaces have sound absorption capability. Sound absorption insulation material are installed on interior surfaces.

Factors Affecting Thermal Performance Of Insulation Materials

Physical ParametersEnvironmental parametersSurface conductanceAir Cavities For Insulation

Insulation practices

Selection of insulation in buildings is based upon thermal properties of materials, space availability, compatibility of materials withadjacent materials and interior and exterior climatic conditions.Insulation practices differ from the type of basicconstruction

Insulating materials

Wood Frame

Steel Frame

Concrete block

Fire brick

Insulation can reduce operating cost and size of the cooling system significantly

Thank you