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Reflective Insulation,
Radiant Barriers
and
Raidant Control Coatings
Text Box: Understanding and Using






























Compiled by

 

REFLECTIVE INSULATION MANUFACTURERS ASSOCIATION

April 1999
TABLE OF CONTENTS

1.       ABOUT RIMA............................................................................................................................................................................

2.       INTRODUCTION......................................................................................................................................................................

3.       OBJECTIVES.............................................................................................................................................................................

4.       COMMENTS ON HEAT TRANSFER...................................................................................................................................

4.1          Conduction

4.2          Convection

4.3          Radiation

5.       THE NEED FOR INSULATION.............................................................................................................................................

6.       REFLECTIVE INSULATION..................................................................................................................................................

6.1      Concept of Reflective Insulation.................................................................................................................................

6.2      Understanding a Reflective Insulation System.........................................................................................................

6.3      Types of Reflective Insulation Materials....................................................................................................................

6.4      Applications for Reflective Insulation Materials.......................................................................................................

6.5      Installing Reflective Insulation Systems.....................................................................................................................

7.     RADIANT BARRIERS.............................................................................................................................................................

        7.1      Physics of Radiant Barriers..........................................................................................................................................

        7.2      Radiant Barrier Systems (RBS)...................................................................................................................................

        7.3      Types of Radiant Barrier Material...............................................................................................................................

        7.4      Installing Radiant Barriers............................................................................................................................................

7.4.1           Attics.................................................................................................................................................................

7.4.2           Walls.................................................................................................................................................................

7.4.3           Floors...............................................................................................................................................................

8.     INTERIOR RADIATION CONTROL COATINGS (IRCC)...............................................................................................

        8.1      Definition of an IRCC.....................................................................................................................................................

        8.2      Physics on an IRCC.......................................................................................................................................................

        8.3      Definition on an Interior Radiation Control System (IRCC)....................................................................................

        8.4      Advantages of an IRCC.................................................................................................................................................

        8.5      Installation Methods for an IRCC................................................................................................................................

        8.6      Typical Installations of Andiation Control System (IRCC)......................................................................................

                    8.6.1       Under Roof......................................................................................................................................................

                    8.6.2       Interior Side Walls..........................................................................................................................................

                    8.6.3       Exterior Side Walls........................................................................................................................................

8.6.4           Other Possible Uses – Construction..........................................................................................................

        8.7      Other Possible Uses of an IRCC.................................................................................................................................

9.       GLOSSARY OF TERMS.........................................................................................................................................................

10.    REFERENCES...........................................................................................................................................................................................                

10.1    Reviews

10.2    Technical Papers..........................................................................................................................................................

10.3    Documents......................................................................................................................................................................

            10.3.1     ASHRAE Handbook......................................................................................................................................

            10.3.2     Federal Trade Commission.........................................................................................................................

            10.3.3     International Conference of Building Officials (ICBO)............................................................................

            10.3.4     U.S. Department of Energy...........................................................................................................................

10.4    ASTM Standards............................................................................................................................................................

11.    APPENDIX – INTRODUCTORY COMMENTS ON ESTIMATING THERMAL RESISTANCES FOR

      REFLECTIVE INSULATION SYSTEMS..............................................................................................................................


About RIMA

 

The Reflective Insulation Manufacturers Association (RIMA) is the only trade association representing the reflective insulation, radiant barrier and radiant control coatings industries.  RIMA activities are guided by an active board of industry members that participate on national and local levels of building code organizations and governmental agencies.

 

RIMA’s objective is to further the understanding and acceptance of reflective insulation, radiant control coatings, and radiant barriers.  Toward this, RIMA members have contributed many articles that have appeared in magazines and newsletters such as:

 

Builders Magazine, Journal of Light Construction, Popular Mechanics, Popular Science, Architecture Magazine, RSI, Energy Design Update, Contractor’s Guide, Practical Homeowner, Rural Builder, Frame Builder Professional, Metal Construction News, Metal Architecture.

 

RIMA has also contributed technical papers to various conferences and workshops sponsored by the Department of Energy, ASHRAE, TVA, ASTM, and Oak Ridge National Laboratory.  RIMA members meet twice a year at the ASTM C-16 Committee meetings to discuss current technical issues and establish standards that promote the best use of reflective insulation, radiant control coatings, and radiant barrier products.  RIMA’s members come from a variety of backgrounds including engineers, scientists, manufacturers, marketers, and academicians.                 

 

The RIMA Handbook aims to provide a simple yet comprehensive guide elaborating on the fundamentals of heat transfer and the concept of reflective insulation and radiant barriers.

 

 

INTRODUCTION

The key to maintaining a comfortable temperature in a building is to reduce the heat transfer out of the building in the winter and reduce heat transfer into the building in the summer.

 

Heat is transmitted across confined air spaces by radiation, convection, and conduction.  The goal of all insulation and barriers is to reduce heating and cooling loads.  Reflective insulation, radiant control coatings, and radiant barriers are products that perform this function by reducing radiant heat transfer thereby reducing the heating and cooling requirements.

 

 

OBJECTIVES

 

·         Discuss heat transfer, with an emphasis on radiant heat transfer.

 

·         Explain the underlying principles of reflective insulation and radiant barriers.

 

·         Clarify the differences between these two reflective technologies and illustrate applications best suited to each product.

 

·         Provide a working knowledge of the effective use of reflective insulation and radiant barriers.

 

The handbook does not intend to be a definitive source, but will cover some basic information.  There are a large number of excellent authoritative publications about reflective technologies and products.  They are listed in section 10, References, and are recommended for additional information and guidance.  Our purpose in this section is to inform in an easily understandable way, the virtues of the reflective products represented by RIMA members.

 

 

FUNDAMENTALS OF HEAT TRANSFER

 

Heat flows from a hot or warm medium to a cold medium in three ways:

 

·         By radiation from a warm surface to a cooler surface through an air space

·         By conduction through solid or fluid materials

·         By convection, which involves the physical movement of air

 

Conduction

 


Conduction is the direct flow of heat through a material resulting from physical contact.  The transfer of heat by conduction is caused by molecular motion in which molecules transfer their energy to adjoining molecules and increase their temperature.

                                   

A typical example of conduction would be the heat transferred from hot coffee, through the cup, to the hand holding the cup.  Another example, as shown above, the contents of the kettle boils from heat transferred from the burner to the kettle.  Also, the poker becomes hot from contact with the hot coals.

                       

Heat transfer by conduction is governed by the fundamental equation described by Fouier’s law:

 

(Rate of heat flow) = k x (Area) x (Temperature Gradient)

 

The factor k is called the thermal conductivity and is a characteristic of the material through which heat is flowing, and it varies with temperature and the degree of compaction or its density.

 


The thermal conductivity of typical building and insulation materials is listed below1:

 

 

 

 

 

Material

 

k (Btu/(h.ft2) (°F/ft)

 

Btu *in/ft2*h*°F

Sawdust

0.034

0.408

Wood Shavings

0.034

0.408

Mineral Wool

0.0217

0.260

INSULATION

Std. Fiberglass Batt

0.313

3.2

High Performance Fiberglass Batt

0.263

3.8

Loose-Fill Fiberglass

0.400

2.5

Loose-Fill Rock Wool

0.357

2.8

Loose-Fill Cellulose

0.270

3.7

Expanded Polystyrene

0.263

3.8

Extruded Polystyrene

0.208

4.8

GASES

Air

0.181

5.52

Carbon Dioxide

0.113

8.85

Helium

1.031

0.97

Methane

0.234

4.27

LIQUIDS

Ethylene Glycol

1.80

0.56

Gasoline

0.94

1.06

Water

4.19

0.24

METALS

Aluminum

1404

0.0007

Copper

2636

0.0004

Iron

468

0.0021

Lead

241

0.0041

MISCELLANEOUS BUILDING MATERIALS

Acoustical Tile

0.40

2.5

Asphalt

0.43

2.3

Concrete (D=140 pcf)

9.7

0.1

Cotton (D=6 pcf)

0.42

2.4

Glass

9.7

0.1

Soil (D=130 pcf)

3.6

0.3

Fir Lumber

0.76

1.3

Oak Lumber

1.18

0.8

Yellow Pine Lumber

1.04

1.0

Plywood

0.83

1.2

 

 

 

 

 

 

Convection

 

Convection is the transfer of heat in fluid, such as air, caused by the movement of the heated air or fluid.  In a building space, warm air rises and cold air settles to create a convection loop and is termed free convection.  Convection can also be caused mechanically, (termed forced convection), by a fan or by wind.

 

Text Box: Typical examples of heat transfer through convection:

1.	Warm air rising from register. (forced  convection)

2.	Warm air rising from all surfaces of radiator, (after air in contact with radiator has been heated by conduction).

3.	Warm air rising from chimney. (free convection)

 

In the flow of heat through a solid body to air, it was observed that the passage of heat into the air was not accomplished solely through conduction.  Instead, it occurred partly by radiation and partly by free convection.  A temperature difference existed between the hot solid and the average temperature of the air.  In this case, the resistance to heat transfer cannot be computed using the thermal conductivity of air alone.  Instead, the resistance has to be determined experimentally by measuring the surface temperature of the solid, the temperature of air, and the heat transferred from the solid to air.  The resistance computed is the combined resistance of conduction, free convection, and radiation.  This resistance, denoted by the letter “R”, ha