Underneath the Microscope

16 November 2016 Kingspan Insulation Middle East
Closed cell vs Open Cell Phenolic Ductwork Insulation

It is important to distinguish between ‘open cell’ and ‘closed cell’ structures, as their respective performance characteristics vary widely.

Open cell vs Closed Cell Phenolic Insulation

The release of the SMACNA Phenolic Duct Construction Standard (PDCS) has seen the popularity of phenolic pre-insulated ductwork panels increase. The new Standard requires a pre-insulated phenolic duct system to have a variety of attributes, such as to be UL listed as a Class 1 Air Duct to Standard for Safety UL 181.

In order for an HVAC Ductwork system to become UL Listed, the pre-insulated panels are extensively tested for their safety in areas such as corrosion, erosion, burning and flame penetration. However, the test does not require the panels to be closed cell, which is a common misconception.
 
Closed Cell Vs Open Cell Phenolic Insulation_frontcover

Open Cell Vs Closed Cell Insulation Technical Bulletin

Open Cell Insulation

Open Cell Insulation
During the manufacture of cellular insulation, ‘blowing agents’ are used to fill the cells within the insulation with a low thermal conductivity gas, instead of using air. The effect of replacing the air with a blowing agent will reduce the measured thermal conductivity of the material.
 
In an open cell Insulation, the blowing agent forms irregular pockets that are linked together into a continuous interconnected capillary network. The pockets, or cells, are open and so the blowing agent can quickly dissipate into the atmosphere after manufacture. This could be damaging to the ozone layer, should the blowing agent used be classed as an Ozone Depleting Substance (ODS), such as a CFC or HCFC blowing agent variety.
 
Immediate transfer of air or water vapour is enabled through the ‘open’ or ‘porous’ interconnected material structure, just like a sponge. Therefore, an example of an open cell foam is the bath sponge where water can easily flow through the entire structure, displacing the air. By the same token, an open cell insulation has a structure that allows moisture and vapour to permeate through it.
 

Closed Cell Insulation

Pool-Noodles
Closed cell materials are much more complex. They feature millions of unconnected microscopic and intact bubbles, which effectively contain the blowing agent over a long period of time. Consequently, the thermal performance of a closed cell rigid insulation can be maintained over the lifetime of the product.
 
Closed cell insulation materials also have higher dimensional stability and low moisture absorption coefficients, when compared with open cell insulation. Pool noodles are an example of a closed cell foam, the gas pockets are sealed from each other, so the noodles do not allow moisture ingress. The absence of moisture ingress through an insulation material will enable the insulation to effectively resist heat transmission, as water is a good conductor of heat.

The Impact on Thermal Performance

Closed cell vs Open Cell Insulation
For closed cell phenolic insulation, the thermal conductivity, also known as the lambda value, of the insulation is directly related to the lambda value of the blowing agent that is used during the manufacture of the insulation, and that sits inside the cells. The retention of this blowing agent, in a closed cell structure, is what delivers a high thermal performance.
 
In open cell phenolic insulation, blowing agents leak out of the porous material, being replaced by air. The degree of movement through the body of the material is dependent on a range of factors, including the size and density of the cells, moisture ingress, as well as the chemical composition of the material itself. This can have the effect of reducing the thermal performance of the product by around 50%.
 

Our Closed Cell Insulation Products

Contact Information

Kingspan Insulation Middle East

Kingspan Insulation operates across the Middle East, Africa and Indian Subcontinent. Contact us to find your local representative. For any inquiries send an email to info@kingspaninsulation.ae

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P.O. Box 113826, Dubai Investment Park 2

Dubai, U.A.E.

Tel: +971 4 889 1000

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