INCORPORATING COLD CHAIN
FEATURE
• Polyisocyanurate and polyurethane insulation is manufactured by chemical reactions between poly-alcohols and isocyanurates creating or forming tiny air cells . The cells contain refrigerant gases instead of air . The boards must be protected from prolonged exposure to water and sunlight , and if used on the interior must be covered with a fireresistant material .
• Rockwool insulation refers to a type of material that is derived from actual rocks and minerals . It also goes by the names of stone wool insulation , mineral wool insulation , or slag wool insulation . A wide range of products can be made from rockwool due to its excellent ability to block sound as well as heat . This type of insulation is commonly used in applications that require the best resistance to fire risk . Although it is a product that can withstand 1000-degree heat , without a supporting structure to match , it is a brittle structural material .
Information about the technical differences between open and closed cell technology is available from manufacturers but in simple terms it involves weight , density and permeability properties of air / vapours which impact thermal resistance of insulation material that is manufactured using chemical reactions .
INSULATION PERFORMANCE AND MEASUREMENTS The thermal performance of all components and systems , except windows and doors , is expressed in terms of an “ R-value ”. For windows and doors , performance is expressed in terms of U-value .
What is an R-value ? Insulation materials are rated for their performance in restricting heat transfer . This is expressed as the R-value , also known as thermal resistance . The R-value is a guide to performance as an insulator — the higher
Panel World
A custom installation of insulated panels for a high traffic zone area .
the R-value , the better the insulation or resistance to heat flow that the material provides . R-values are expressed using the metric unit ’ s m ². K / W , where :
• M 2 refers to one metre squared of the material of a specified thickness ;
• K refers to a one-degree temperature difference ( Kelvin or Celsius ) across the material ;
• W refers to the amount of heat flow across the material in watts .
• Use the nominal R-values as listed by the manufacturer to determine the performance .
Products which have the same R-value will provide exactly the same insulating effect , provided they are correctly installed . Products must be installed in accordance with the manufacturer ’ s specifications and guidelines .
Material R-values refer to the thermal resistance values of bulk / mass type insulation are measured on the product alone according to international standards . System R-values indicate the thermal resistance value of reflective insulation is calculated based on international standards and depend on the product being installed as specified in accordance to the manufacturer ’ s specifications . This is known as a system R-value which incorporates air spaces . Composite R-values are the thermal resistance values of composite insulation products are measured by testing the composite product as a unit according to international standards .
Direction of heat flow effect R-values can differ depending on the direction of heat flow through the product . The difference is generally marginal for bulk insulation but can be pronounced for reflective insulation .
• Up R-values describe resistance to heat flow upwards ( sometimes known as ‘ winter ’ R-values ).
• Down R-values describe resistance to heat flow downwards ( sometimes known as ‘ summer ’ R- values ).
What is a U-value ? Sometimes insulation or systems are rated in terms of their thermal transmittance
( U-value ), rather than R-value . The U-value measures the transfer of heat through a material or a building element ( thermal transmittance ), whereas the R-value measures the resistance to heat transfer . U-values are often used in technical literature , especially to indicate the thermal properties of glass and to calculate heat losses and gains .
The U-value is the reciprocal of the R-value , R = 1 / U or U = 1 / R . For example , with an R-value of 2.0 , the U-value is 1 / 2 or 0.5 .
The U-value is expressed using the metric units ( W / m ². K ) where :
• W refers to the amount of heat transmitted across the face or through the material in watts ;
• m ² refers to one metre squared of the material of a specified thickness ; and
• K or ‘ degree Kelvin ’ refers to each ° C temperature difference across the face of the materials or through the material .
A smaller U-value results in lower heat flow , and therefore less heat loss . Higher U-values mean greater heat loss .
What is an overall and total R-value ? The overall R-value is the total resistance of a building element or system combination . It takes into account resistance provided by construction materials used in a walls or ceilings , internal air spaces , thermal bridging , insulation materials and air films adjacent to solid materials . Each of these components has its own inherent R-value , the sum of which provides the overall R-value .
The intervention added R-value or added thermal resistance is the value of the insulating material alone . This is the term most used when buying thermal insulation . Some products will have a higher R-value for a specified thickness . For example , a 70 mm thick extruded polystyrene board and 100 mm thick glass wool blanket may have the same apparent R-value .
The R-value is the material thermal resistance , ie product only , whereas the total R-value describes the total thermal resistance of the system to heat flow provided by a roof and ceiling assembly ( inclusive of all materials and air films ), a wall or a floor . These values are calculated from the resistance of each component , including the insulation . Total R-values are the best indicator of performance , as they show how insulation performs within the envelope .
Thermal bridging is the transfer of heat across building elements , which have less thermal resistance than the added insulation . This decreases the overall R-value . Wall frames and ceiling beams are examples of thermal bridges , having a lower R-value than the insulating material placed between them . Because of this , the overall R-value of a typical ceiling and / or wall is reduced .
Rigifoam
Ceiling boards are another common application in the cold chain for insulated panels – particularly in warehouses and distribution centres .
Precool Manufacturing
A facility in South Africa that has 22m high walls - completely fitted with local product .
WHAT ELEMENTS FORM PART OF DECIDING ON THE RIGHT INSULATION PRODUCT ? Having so many options of product to consider , you may wonder what aspects you need to keep in mind when doing your evaluations or generating the project specifications . As you would be aware , each room or facility for that matter usually involves customer or process-specific designs to suit . Some of the items that need to be included are :
COLD LINK AFRICA • June 2022 www . coldlinkafrica . co . za 21