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Category: Ward Self Assembled Insulated Roofing Panels Water Absorption Insulated Material Bonding

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Ward Insulated Panels
Ward Insulated Panels

Long Term Thermal Performance:

Site Assembled Multi-Part Cladding Systems
Site assembled multi-part cladding systems employ materials which may be subject to degradation under certain conditions. These systems rely on high quality site workmanship to ensure effective performance. In addition there are certain weaknesses which reduce the overall system efficiency. The above concerns can be summarised as follows:

• Insulation placement difficulties, gaps & tearing.
• Moisture accumulation (interstitial condensation) within the assembly.
• Air movement within, over & around insulant degrades performance.
• Compaction, slippage & displacement of insulant.

Effects of Moisture & Air:

General
The thermal insulating characteristics and performance of an insulant can be significantly affected by air movement and the presence of moisture. The effects of each of the three states of moisture ie vapour, liquid and ice on the insulant must be considered.

Main Moisture & Air ‘Drivers’

There are two main transport mechanisms for moisture vapour through an assembly. These are air leakage and vapour diffusion.
Where open structured insulants allow vapour diffusion to occur it must be recognised that the quantity of vapour transported will be very significantly compounded by air leakage where discontinuities exist in the air barrier system. The ratio of moisture transported by air leakage in comparison to that by vapour diffusion can be 100:1 or greater.

This highlights the critical need to address the effective control of air leakage if extensive water vapour transport through an assembly is to be avoided.

Thermal Conductivity of Water & Ice

Since water has thermal conductivity of 0.58 W/mK and ice 2.3 W/mK, both of which are significantly higher than any typical insulant, their uncontrolled entry into an insulant even in small volumes, can create serious thermal failures. This must be considered when assessing the ‘dry’ thermal conductivity values
provided by insulation manufacturers. Where an insulant is subject to wetting the actual performance will be compromised and will fail to meet the manufacturers specified level.

Effects of Moisture & Air on Thermal Performance:

Ward Factory Insulated Panels
Ward factory insulated panels are metal faced with a closed cell insulant They provide an impervious barrier to both liquid water and water vapour and are not subject to any deterioration in their thermal performance due to moisture.

The dry thermal conductivity values provided for the panels reflect the actual performance achieved on site. The cores of the panels are protected from the effects of air movement by the metal faces and the closed cell nature of the inner core. This ensures that the specified thermal performance levels are achieved and maintained throughout the life of the building.

Non-Hygroscopic

Ward factory insulated panels do not absorb liquid water or water vapour due to both the impervious metal faces and the highly resistant closed cell core.
Water has no impact on the insulant since none is absorbed. This results in a stable thermal performance.

Freezing Conditions & Thermal Performance

Ward insulated panels provide impervious faces and well sealed joints. Their effective control of moisture movement through the fabric means that even under freezing temperature conditions, frost or ice formation will not occur within the panel.

Air Intrusion Resistance

Ward insulated panel systems are highly resistant to air intrusion as a result of the materials used in their construction.

• Metal faces - impervious to air
• Closed cell insulation core - low air permeability
• Joint seals - prevent mass air transfer
• Primary junctions can be easily sealed
  
  These aspects of the assembly mean that air intrusion does not occur and has no impact on the thermal performance of the system.

Mass Air Transfer Resistance

Ward insulated panels inherently limit mass air transfer. The provision of adequate seals and due care when constructing primary junctions prevents air transfer through the completed envelope. This eliminates the thermal degradation associated with such mechanisms.

Air Convection Resistance

The uniformity of Ward insulated panels eliminates the potential thermal degradation which air convection can induce. The continuous bond between the insulation core and the metal faces prevent any air movement between the materials while the closed cell nature of the insulant itself prevents convection
currents within its structure.

The side joints have integral seals and so prevent air currents circulating at these locations.

Boundary Layer Washing Effects

The impermeable metal faces of the panels prevent air reaching the insulation core. The adhesion of the faces to the closed cell insulation structure ensures that no disturbance of the insulation boundary layers can occur.

Moisture & Insulant Material Bond Integrity

The protection given to the insulant by the metal faces and the closed cell nature of the material prevents the absorption of water into the panel core. Integrity is maintained even during extreme conditions. Since no breakdown of the material occurs, the full core bond with the metal face is maintained. The
cell structure containing the blowing agents is retained unaffected and provides stable thermal performance over the life of the panel.

Effects of Moisture & Air on Thermal Performance:

Site Assembled Multi-Part Cladding Systems
Site assembled multi-part cladding systems can be subject to significant degradation when air and moisture flows occur.

Thermal Conductivity

Manufacturers published ‘dry’ values are inappropriate where the MMMF insulant is subject to the effects of water or ice penetration. Where moisture is absorbed by the open structured insulant the value can rise dramatically.
Research has shown that a 1% water content by volume in man made mineral fibre insulation can lead to an increase of up to 86% in the materials thermal conductivity value.

Water Absorption

As water permeates the open structure of an mineral fibre insulant substantial weight is added to the material. As this occurs the fibre matrix may undergo a progressive collapse, increasing its density, reducing the insulative air spaces and thereby seriously degrading the overall thermal performance of the material.

Effects of Freezing

Where water is present as frost or ice, the thermal performance of the insulant is affected in two ways. The value of ice is some 58 times greater than that of mineral fibre and its presence will significantly compromise the overall thermal performance of the material.

In addition the freezing process may also disrupt the material structure by causing expansion within the insulant resulting in the breakage of the fibre bonds. This can result in a degree of settlement which will reduce the long term thermal performance of the material.

Air Intrusion

MMMF insulants may be subject to air intrusion due to the ventilation required in ‘cold’ roof assemblies. This may disturb the still, insulating air within the insulant matrix and reduces the thermal performance of the material.

Air Transfer

Low density mineral fibre insulants allow free air transfer through their structure producing similar degradation to that caused by air intrusion.

Air Convection

Since free air movement can occur within the MMMF structure convection currents may be supported which will degrade the thermal performance by increasing the heat transfer from the interior surfaces. Convection currents will occur where discontinuities exist at any joints or at areas where poor placement has left gaps between the insulant and the liner sheet. These defects will reduce the overall thermal efficiency of the assembly.

Boundary Layer Washing Effects

Where mineral fibre insulation is subjected to air washing over its surface its actual insulating ability can be reduced due to the disturbance caused to the ‘trapped’ air within the outer layers of the structure.

Information associated with: Ward Insulated Panels

Email this company

Ward Insulated Panels Ltd
Sherburn
Malton
North Yorkshire
YO17 8PQ

Tel: 01944 710591
Fax: 01944 710777

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