Closed cell foam sheets can be considered for some insulation-related work because polyethylene foam creates a low-density closed-cell layer between surfaces. All Foam's AFP30 and AFP45 technical data sheets both list insulation among typical applications, but neither publishes thermal conductivity, R-value or U-value data. That missing information sets an important limit on what can responsibly be claimed.
Quick answer
AFP30 and AFP45 can be considered as thin closed-cell insulation, separation or thermal-break layers where the project does not require an unverified thermal value. They should not be sold or specified as a complete certified building-insulation system without the exact thermal, fire and installation evidence required by that design.
What does "insulation" mean in this context?
Insulation is a broad word.
A thin foam sheet can reduce direct contact between harder surfaces and can add a layer of material with many gas-filled cells. That can be useful where a design needs local separation or a thin insulating layer.
However, an engineering or building calculation normally needs quantified thermal performance.
That is the point where the exact product data matters.
What the AFP30 and AFP45 data sheets confirm
The AFP30 grade is rigid, cross-linked and closed cell, with a nominal density of 30 kg/m3.
AFP45 is also rigid cross-linked closed-cell PE, but its nominal density is higher at 45 kg/m3.
The current data sheets list insulation-related uses, but they do not publish:
- thermal conductivity or lambda
- R-value
- U-value
- a certified system build-up
- a declared thermal resistance by thickness
Those values should not be invented or borrowed from another polyethylene foam.
Thermal conductivity, R-value and U-value are different things
These terms are often mixed together in online product descriptions.
Thermal conductivity, often written as lambda, is a material property measured under defined conditions.
R-value describes thermal resistance through a particular thickness or construction.
U-value describes heat transfer through a complete element or assembly.
A supplier publishing one of these values for a different PE foam does not make it valid for AFP30 or AFP45.
If a project needs a calculated result, use documented data for the exact material and construction.
Why density alone cannot tell you which grade insulates better
AFP45 is denser than AFP30.
AFP45 also has a higher published compression resistance at 25% deflection.
That tells us something useful about mechanical behaviour, but it does not prove that AFP45 has a better or worse thermal conductivity.
Density is one input into foam structure. It is not a substitute for measured thermal data.
Choose AFP30 or AFP45 from the full mechanical requirement, not from an unsupported thermal ranking.
Thickness matters only when the material property is known
A thicker layer usually creates a longer path for heat flow, but a responsible thermal calculation still needs the thermal conductivity of the exact material.
Without that value, it is not sound to publish a statement such as:
- 10mm gives a certain R-value
- 25mm equals a particular insulation board
- AFP45 gives a fixed percentage improvement over AFP30
All Foam does not publish those claims for these grades.
For a non-calculated protective lining, thickness may instead be chosen from space, fit and mechanical needs.
Thermal bridges can bypass the foam
A local foam layer does not automatically control every heat path.
Heat can bypass an insulating section through:
- metal fixings
- framing
- uninsulated edges
- joints
- penetrations
- compressed areas
- direct contact between structural parts
This is why a small thermal-break pad and a complete insulation system should not be described as the same thing.
The whole construction controls the result.
Compression can change the installed layer
Closed-cell foam is still compressible.
If a sheet is squeezed significantly between two parts, its installed thickness is lower than its free thickness.
That can affect both mechanical behaviour and whatever thermal separation the layer contributes.
Where the thickness is functionally important, design the joint so the foam is compressed only as intended.
Do not assume the nominal sheet thickness remains unchanged after tightening fixings or clamping components.
Condensation is a separate design question
Low water absorption does not mean a construction cannot experience condensation.
Condensation can occur when moist air reaches a sufficiently cold surface.
A foam layer may alter surface temperatures, but the complete moisture behaviour can also depend on:
- air leakage
- vapour movement
- temperature difference
- joints
- trapped cavities
- ventilation
- drainage
- adjacent materials
A closed-cell layer should therefore not be marketed as a guarantee of "no condensation".
Water resistance and thermal performance are not interchangeable
AFP30 is described in its technical data as waterproof and non-absorbent.
AFP45's current sheet records maximum water absorption at 1% by volume.
Those are useful moisture-related properties, but they do not provide a thermal conductivity figure.
Likewise, a material can provide useful thermal resistance without making a finished assembly watertight.
Keep the two specifications separate.
Fire performance must be checked independently
A material being useful for insulation does not mean it carries the fire classification required for a building, vehicle, public space or industrial installation.
Where fire performance is specified:
- identify the exact standard
- check the exact product documentation
- check whether the requirement applies to the raw foam or complete assembly
- use a product with appropriate evidence if AFP30 or AFP45 does not meet the requirement
Do not infer a fire rating from the words "closed cell" or "insulation".
Mechanical requirements can decide the grade
Sometimes the reason for using a PE foam layer is both thermal and mechanical.
The layer may also need to:
- resist crushing
- space components
- reduce hard contact
- act as a protective liner
- tolerate handling
- maintain a defined gap
In those cases, compression data may be more important to the grade choice than density alone.
AFP45 is denser and has higher published compression resistance than AFP30, so it may suit higher mechanical loads where the rest of the specification also fits.
When purpose-made insulation is the better choice
If the project requires a declared thermal conductivity, certified system build-up, building-regulation calculation or manufacturer-backed thermal performance, a purpose-made insulation product with the required documentation may be the better choice.
That is not a weakness of AFP30 or AFP45.
It is simply good specification practice: use a material whose published evidence matches the claim the project needs.
What to record before choosing closed-cell PE for insulation
A useful specification brief includes:
- what the foam is separating or lining
- available thickness
- whether a calculated thermal value is required
- operating temperature
- expected compression
- moisture exposure
- condensation risk
- fire requirement
- fixing method
- required service life
- whether the finished assembly will be tested
This keeps the material decision tied to measurable requirements.
Quick answers
Is closed cell polyethylene foam an insulator? It can be used in insulation-related applications, and AFP30 and AFP45 data sheets list insulation among typical uses. All Foam does not publish thermal conductivity or R-values for these grades.
What is the R-value of AFP30 or AFP45? All Foam does not publish an R-value for either grade, so a value should not be copied from another polyethylene product.
Does thicker closed cell PE always insulate better? Thickness affects the heat path, but quantified performance still depends on the thermal property of the exact grade and the complete construction.
Is AFP45 a better thermal insulator because it is denser? That cannot be claimed from the current data. AFP45 is denser and more compression-resistant, but comparative thermal conductivity is not published.
Can closed cell PE stop thermal bridging? It can be considered as a local separation layer, but the complete design must still account for fixings, framing, edges and other heat paths.
