INSULATION COMPRESSIVE STRENGTH FORMULA
Insulation ability to resist deformation or maintain shape is often called compression strength. Compressive strength declarations are provided by insulation manufacturers and are established in accordance with recognized test standards. These values serve as a basis for comparing different insulation products or brands. Compressive strength can vary among insulants depending on its material properties.
When identifying the compressive capabilities of an insulation material, it undergoes two tests:
1. 10% Short term testing (Compressive Behaviour BS EN 826:2013)
2. 2% Long term testing (Compressive Creep BS EN 1606:2013)
10% SHORT TERM TESTING (COMPRESSIVE BEHAVIOUR BS EN 826:2013)
The compressive strength of thermal insulation is measured by a method described in the formal test standard EN 826 “Thermal insulating products for building applications – determination of compression behaviour.”
The European standard BS EN 826 outlines the guidelines for the apparatus and methodologies employed in assessing the compressive characteristics of rigid insulation test specimens. This involves gauging the force needed to deform the material by 10%. A successful outcome indicates that the insulation has passed the test, provided no failures are observed during the evaluation process.
For instance, XPS 500 insulation is rated at 500 kPa when tested to BS EN 826 (500 Kilopascals is equivalent to 50 tonnes per square metre).
EN 826 is clear that its test method is employed to obtain ‘reference values’ that allow appropriate loading calculations to be carried out by a structural engineer.
HOW INSULATION COMPRESSIVE BEHAVIOUR TEST LOOK LIKE?
A load is applied to the insulation sample being tested. Machine tests insulation compressive strength. A result is declared when either the material reaches the limit of elastic behaviour (i.e. it fails), in which case the result is the load ‘at yield’, or the insulation compresses by 10% relative to the original sample thickness.
Pic. 1 Behaviour insulation test
2% LONG TERM TESTING (COMPRESSIVE CREEP BS EN 1606:2013)
To check how well insulation can handle weight, there's a key test called BS EN 1606. This test is conducted to determine how the insulation product will perform in long term intervals, for example, over a 10, 25 or 50 year period and figures out the maximum safe weight it can bear without losing more than 2% of its thickness.
A 2% margin is way stricter than the 10% deformation limit in BS EN 826. The contrast in results can greatly influence the correct specifications for a product.
Therefore, when evaluating material for a floor build, it's crucial to rely on BS EN 1606 as a safe assessment, while recognizing that BS EN 826 is solely a destructive test.
HOW THE INSULATION COMPRESSIVE CREEP TEST LOOK LIKE?
During this test, the insulating material undergoes a continuous load in specific temperature and humidity conditions, with repeated measurements of material deformation. Usually, three samples are subjected to three different loads, each with different weights compared to the short-term test. The idea is to make sure the material doesn't bend too much, staying within a 2% change over a period of 20 to 50 years.
Pic. 2 Compressive creep insulation test
WHAT IS COMPRESSIVE STRENGTH OF INSULATION?
There are situations in which insulation compressive strength is rarely considered, such as insulating the roof between rafters or filling partition walls within a room. However, there are places where compressive strength cannot be overlooked, such as in car parks, industrial units, and cold stores.
All insulation products should clearly state their compressive strength, measured in kilopascals (kPa), which tells you the maximum load the material can take.
Phenolic insulation boards are usually good for standard floors with a compressive strength of around 120 kPa. For tougher jobs, like heavy-duty applications, Extruded Polystyrene (XPS) boards work well, offering compressive strengths up to 300 kPa. Popular PIR rigid boards known as a Celotex or Unilin fall in the range of 120-150 kPa for compressive strength. On the flip side, Expanded Polystyrene has the lowest compressive strength at about 70 kPa, so it's not suitable for insulating floors.
WHAT IS THE MINIMUM COMPRESSIVE STRENGTH OF INSULATION?
When we talk about how strong insulation needs to be, especially for floors in garages or homes, you should look for a material that can handle heavy loads without getting squished. So, what's the minimum strength it should have?
Well, for insulating floors, yous should use insulation material with at least 100 kPa compressive strength. That means it can support around 10 tons of weight per square metre.
If you use insulation material with lower strength, in the best-case scenario, it might slightly lower the floor by 10%, but in the worst-case scenario, it could cause the floor surface to crack due to the insulation material underneath getting squeezed.
That's why you should follow safety standards and go for boards with a minimum compressive strength rating of 120 kPa.
WHICH INSULATING MATERIAL HAS A HIGH COMPRESSIVE STRENGTH?
When comparing insulation product densities, XPS stands out with greater compressive strength than EPS, PIR/PUR, or Phenolic foam. In the market of insulation materials, there are no options more resistant to compression than XPS (extruded polystyrene). This is attributed to its manufacturing process. Thanks to the way XPS is made, it can withstand loads of up to 700 kPa, which means it can handle a remarkable 70 tons per square meter. Therefore, extruded polystyrene is considered among the insulation with the highest compressive strength and is frequently chosen for industrial projects like car parks or heavy load applications.
WHAT IS THE COMPRESSIVE STRENGTH OF KINGSPAN?
The company Kingspan is one of the most recognized brands manufacturing insulation materials in the UK. Its popularity is attributed, among other things, to the range of insulation types used for various applications, be it external walls, floors, or walls in general.
In general, the compressive strength of Kingspan insulation products varies, starting at 100 kPa and reaching up to 700 kPa. The specific compressive strength depends on the intended application and looks as follows:
- Kingspan K112 Framing Board - 100kPa
- Kingspan K103 Kooltherm Floorboard - 120kPa
- Kingspan GreenGuard XPS Insulation GG300 – 300kPa
- Kingspan GreenGuard XPS Insulation GG500 – 500kPa
- Kingspan GreenGuard XPS Insulation GG700 – 700kPa
Related:
DIFFERENCE BETWEEN EPS AND XPS INSULATION BOARDS
BEST FLOOR INSULATION - THE COMPLETE GUIDE
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