Insulators

The characteristics of a thermal insulation are mainly determined by it's composition. For that reaon thermal insulatins are divided into Five major types., although in many instances particular insulations are hybrids of these types.

Vaccum is the best insulation - Otherwise it is the entraped air molucule that causes the Insulation.

1. FLAKE

Is composed of small particles or flakes which finely divide the air space.
These flakes may or may not be bonded together,Vermiculite,or expanded
Mica is commonly used for flake insulation.

2. FIBROUS

Fibrous insulation is composed of small diameter fibers which finely divide the air space.These fibers may be organic or inorganic and may or may not be bonded together. Organic fibers may be - hair,wood,cane,wool, or synthetic.Inorganic fibers may be Glass,Rock wool,Slag wool,aluminica silica,asbestos, or carbon.

3. GRANULAR

Is composed of small nodules which contain voids or hollow spaces.It is not considered a true cellular material since gas can be transferred between the individual spaces. The material may be Magnesia,Calcium Silicate, diatomaceous earth and vegetable cork.,Thermocole.

4. CELLULAR

Is composed of small individual cells sealed from each other,It is produced of Glass,rubber,and plastic.

5. REFLECTIVE
Is composed of parallel thin sheets or foil of high thermal reflectance and spaced to reflect radiant heat back towards it's source.The spacing also is designed to provide restricted air(or gas) spaces.The restricted air space reduces heat transfer caused by convection and conduction.

Insulations are further classified in five types depending upon its temperature of use and applications.

1) HIGH TEMPERATURE INSULATION 800º C AND ABOVE 2000 º C

2) MIDDLE RANGE TEMPERATURE INSULATIN AMBIENT -60 º C TO 800 º C

3) COLD INSULATION AMBIENT TO MINUS 30 º C

4) CRYOGENIC INSULATION MINUS 33 º C TO MINUS 273 ºC

5) ACOUSTIC INSULATION MAINLY USED FOR SOUND ABSORPTION.

6) THE DESIGN SELECTION OF MATERIAL AND ITS INSULATION THICKNESS ARE DECIDED

Based on Property of the Insulation material such as;(parameters for selection of material) Abrasion resistance,Alkalinity,Breaking load,Capilirity,Chemical reaction,Coefficient of Expansion, Shrinkage, combustibility,9flash point,flame point,self ignition point,burning rate,Rate of flame travel, heat contribution,Expolosion index,Auto internal heating.Toxicity of products of combustion, Smoke density, Melting point, Compressive strength,corrosion to substrates,Density, Dimentional stability. Emittance, Flexural strength,Hardness, Hygroscopicity,Incidence of craking,Reflectance,Resistance to acids,Resistance to caustics,Resistance to solvents,shear strength.specific gravity (aperent+real), specific heat Temperature limits, Temperature rise- self internal heating,Tensile strength, Thermal Conductivity, Thermal diffusivity,Thermal resistance,Thermal shock resistance, Vapour migration, vapour permeability, vibration resistance warpage ,water absorption, Resistance to Air or Gas velocity, etc.

Of the above catorigies of Applications , the High Temperature Furnaces , Cryogenic Applications and Acoustic Insulation need a high degree of Expertise .

Many people offen think that Insulation does not need maintenance,which is absolutely wrong.Periodic
Maintenance is a must.( A stitch in time saves nine)

There are new developments in this field and Maintenance frendly Insulations are available .The
Equoiments which need often opening can be fitted to removable insulation.

Reflective coatings can improve Insulation of many substrates.and give good saving

Introduction

Electricity bills, oil bills, gas bills--all homeowners pay for one or more of these utilities, and wish they paid less. Often many of us do not really know how to control or reduce our utility bills. We resign ourselves to high bills because we think that is the price we have to pay for a comfortable home. We encourage our children to turn off the lights and appliances, but may not recognize the benefits of insulating the attic.

Why Should You Insulate?

Heating and cooling ("space conditioning") account for 50 to 70% of the energy used in the average American home. About 20% goes for heating water. On the other hand, lighting and appliances and everything else account for only 10 to 30% of the energy used in most residences. It makes good sense to turn lights and appliances off when they are not needed, and you'll save even more on your energy costs if your reduce the amount of energy needed for heating and cooling.

Unless your home was constructed with special attention to energy efficiency, adding insulation will probably reduce your utility bills. Much of the existing housing stock in the United States is not insulated to the best level. Older homes are likely to use more energy than newer homes, leading to very high heating and air-conditioning bills. Even if you own a new home, adding insulation may save enough money in reduced utility bills to pay for itself within a few years, continue to save you money for as long as you own the home, and increase the resale value of your house.

The Crucial Role of Thermal Insulation

Inadequate insulation and air leakage are leading causes of energy waste in most homes. Insulation saves money and our nation's limited energy resources. It can also make your house more comfortable by helping to maintain a uniform temperature throughout the house. Walls, ceilings, and floors will be warmer in the winter and cooler in the summer. Insulation can also act as a sound absorber or barrier, keeping noise levels down.

It is possible to add insulation to almost any house. You may be able to do the job yourself if the structural framing is accessible--for instance, in unfinished attics or under the floor over an unheated space. Or, you may prefer to hire an insulation contractor. In either case, it is important to choose and install the insulation correctly.

The amount of energy you conserve will depend on several factors: your local climate; the size, shape, and construction of your house; the living habits of your family; the type and efficiency of the heating and cooling systems; and the fuel you use. Once the energy savings have paid for the installation cost, energy conserved is money saved--and the annual savings will increase if utility rates go up.

Insulation Priorities

It is most important to:
-Insulate your attic to the recommended level, including the attic door, or hatch cover.
-Provide the recommended level of insulation under floors above unheated spaces, around walls in a heated basement or unventilated crawl space, and on the edges of slabs-on-grade.
-Use the recommended levels of insulation for exterior walls for new house construction. When remodeling or re-siding your house, consider using the levels recommended for new construction in your existing walls.

What Kind of Insulation Should You Buy?

Once you have located the areas in your house requiring insulation, and have determined what R-value is needed, you will need to decide what type to buy. Some types of insulation require professional installation, and others you can install. You should consider the several forms of insulation available, their R-values, and the thickness needed. Remember, for a given type and weight of insulation, the thicker it is, the higher its R-value. The basic forms of thermal insulation are summarized in Table 1. Here is some additional information.

Form	Method of Installation	Where Applicable	Advantages
Blankets: Batts or Rolls Fiber glass Rock wool	Fitted between studs, joists and beams	All unfinished walls, floors and ceilings	Do-it-yourself Suited for standard stud and joist spacing, which is relatively free from obstructions
Loose-Fill (blown-in) or Spray-applied Rock wool Fiber glass Cellulose Polyurethane foam	Blown into place or spray applied by special equipment	Enclosed existing wall cavities or open new wall cavities Unfinished attic floors and hard to reach places	Commonly used insulation for retrofits (adding insulation to existing finished areas) Good for irregularly shaped areas and around obstructions
Rigid Insulation Extruded polystyrene foam (XPS) Expanded polystyrene foam (EPS or beadboard) Polyurethane foam Polyisocyanurate foam	Interior applications: Must be covered with 1/2-inch gypsum board or other building-code approved material for fire safety Exterior applications: Must be covered with weather-proof facing	Basement walls Exterior walls under finishing (Some foam boards include a foil facing which will act as a vapor retarder. Please read the discussion about where to place, or not to place, a vapor retarder) Unvented low slope roofs	High insulating value for relatively little thickness Can block thermal short circuits when installed continuously over frames or joists.
Reflective Systems Foil-faced paper Foil-faced polyethylene bubbles Foil-faced plastic film Foil-faced cardboard	Foils, films, or papers: Fitted between wood-frame studs joists, and beams	Unfinished ceilings, walls, and floors	Do-it-yourself All suitable for framing at standard spacing. Bubble-form suitable if framing is irregular or if obstructions are present Effectiveness depends on spacing and heat flow direction
Loose-Fill (poured in) Vermiculite or Perlite	not currently used for home insulation, but may be found in older homes

Basic Forms of Thermal Insulation

BLANKETS, in the form of batts or rolls, are flexible products made from mineral fibers. They are available in widths suited to standard spacings of wall studs and attic or floor joists. Continuous rolls can be hand-cut and trimmed to fit. They are available with or without vapor retarder facings. Batts with a special flame-resistant facing are available in various widths for basement walls where the insulation will be left exposed.

BLOWN-IN loose-fill insulation includes loose fibers or fiber pellets that are blown into building cavities or attics using special pneumatic equipment. Another form includes fibers that are co-sprayed with an adhesive to make them resistant to settling. The blown-in material can provide additional resistance to air infiltration if the insulation is sufficiently dense.

FOAMED-IN-PLACE polyurethane foam insulation can be applied by a professional applicator using special equipment to meter, mix, and spray into place. Polyurethane foam can also help to reduce air leaks.

RIGID INSULATION is made from fibrous materials or plastic foams and is pressed or extruded into board-like forms and molded pipe-coverings. These provide thermal and acoustical insulation, strength with low weight, and coverage with few heat loss paths. Such boards may be faced with a reflective foil that reduces heat flow when next to an air space.

REFLECTIVE INSULATION SYSTEMS are fabricated from aluminum foils with a variety of backings such as kraft paper, plastic film, polyethylene bubbles, or cardboard. The resistance to heat flow depends on the heat flow direction, and this type of insulation is most effective in reducing downward heat flow. Reflective systems are typically located between roof rafters, floor joists, or wall studs. If a single reflective surface is used alone and faces an open space, such as an attic, it is called a RADIANT BARRIER. Radiant barrriers are sometimes used in buildings to reduce summer heat gain and winter heat loss. They are more effective in hot climates than in cool climates. All radiant barriers must have a low emittance (0.1 or less) and high reflectance (0.9 or more).

Typical types of residential thermal insulation material
The following types of insulation are common:

Rock Wool - blanket form and most common before 1950.

Fiberglas - most common since 1950; more resilient than rock wool.

Cellulose - made from scrap paper products.

Perlite - A loose material usually used to fill voids; inorganic, noncombustible and moisture and insect resistant.

Vermiculite - Naturally occurring mica like material that expands by heating; used as loose fill; organic, noncombustible and resists decay and insects.

Polystyrene Form - Usually in pellet form or as bead-board; inorganic polymer that is combustible but decay, moisture, and insect resistant.

Polyurethane & Polylsocyanaurate Foam - Usually in rigid board form; formable and subject to dimensional changes due to curing and aging.
Formaldehyde Foam - Inorganic foam pumped into wall cavities most common as a retrofit on older homes.