Insulation “R Value” Testing Comparison

May 5, 2011Leave a reply

Insulation Material Test – ASTM C518
* Standard test for rating most insulation products
* Test uses guarded hot plate apparatus – tests insulation material sample
* Testing usually conducted at room temperature over a few hours
* Test does not consider factors such as air movement, thermal bridging, etc.

Insulation Material Test – ASTM C518
1″ P2000 = R-4.11
6″ Fiberglass = R-19

Installed Insulation Performance Test – ASTM C1363
* Test measures insulation material in installed state (as part of wall section)
* Installed testing considers factors such as thermal bridging, surface convection effects and installation deficiencies.
* While still a laboratory test, measures more real-life conditions than ASTM C518
* Replaced standard guarded hot box ASTM C236
* Measures temperature difference interior / exterior

Installed Insulation Performance Test – ASTM C1363
1″ P2000 in 2″ x 6″ frame wall = R-10.2
6″ Fiberglass in 2″ x 6″ frame wall = R-11.5

CONCLUSIONS:
1. Installed Performance tests are more relevant to real life performance.
2. Installed Insulation Performance testing showed that 1″ of P2000 Insulation performed about the same as 6″ of fiberglass insulation
3. Discrepency between fiberglass test results (material test versus installed test) confirmed by several independent studies.

ASTM C1363-05 Testing

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“Standard Test Method for Thermal Performance of Building Materials and Envelope Assemblies by Means of Hot Box Apparatus”.

The ASTM C1363-05 test measures the steady state thermal performance of building assemblies and materials at conditions typical to normal building applications.

Tests can be conducted at simulated exterior temperatures ranging from -54°F (-48°C) to 185°F (85°C), with a typical residential interior temperature of 70°F (21°C).

The test allows the thermal performance of the building assembly to be evaluated under installed temperature conditions typical to the various climate zones that exist through out the world.

Since wall assemblies are tested, the effects of thermal bridging using real world framing factors and common installation deficiencies (e.g. improper stud spacing) are also included. The test also makes provision to evaluate the effects of forced or natural convection on the faces of the system assembly.

However, the test protocol does not allow the evaluation of moisture and air infiltration, which may have a major impact on thermal performance under installed conditions.

Tests such as the ASTM C1363-05 begin to address the issues that affect the installed performance of an insulation product. To be representative of field conditions, test assemblies are required to duplicate field construction in respects to framing geometry, material composition, installation practice, and orientation.

For a more detailed description of the test scope, visit the ASTM web site by clicking on this link;

ASTM C-518-04 Testing

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“Standard Test Method for Steady-State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus”.

The ASTM C-518 test method covers the measurement of steady state thermal transmission through flat slab specimens using a heat flow meter apparatus. The heat flow meter has the following advantages:

* Simple concept
* Rapid
* Applicable to a wide range of test specimens

The heat flow meter apparatus establishes a steady state, linear heat flow through the insulation via two parallel plates which are kept at constant, but different temperatures.

The apparatus requires calibration, which is carried out using materials that are expected to exhibit similar thermal characteristics as the test specimen, creating additional uncertainty in the test results. As such, this test method is considered a secondary method of measurement.

For a more detailed description of the test scope, visit the ASTM web site at: www.astm.org/Standards/C518.htm

Understanding R-Value

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Do we really understand R-Value?

Insulation is used in both residential and commercial applications to control the transfer of heat through the building envelope and maintain an acceptable level of thermal comfort for building occupants. Heat transfer is an extremely complex topic, which is often oversimplified using linear models and test procedures. This is mainly the result of attempts to develop a system that the consumer could understand, allowing them a yardstick with which to make insulation purchasing decisions.

However, simplicity of a complex topic such as heat transfer comes at a cost, real world relevance. US DOE supported research(see link below), Wall R-Values that tell it like it is revealed that the center of cavity performance values stated on most insulation products is often misrepresented as wall performance ratings, resulting in performance being overstated by as much as 27 to 58%.
So How is Insulation Performance Currently Evaluated?

Most of the thermal performance testing completed on conventional insulations focus on their resistance to conductive heat transfer as measured by R-Value in the ASTM C518 Test.

The test is meant to provide a level playing field when comparing the thermal resistance of various types of insulations to determine the most suitable for a particular application.

However, what most people fail to consider (or realize) is that R-value is not a material property; it is a measurement under a specific set of conditions.

In reality, the R-value of a particular material is dependent on a number of environmental and installation parameters, external to the material itself.

R = ƒ(material properties, time, thickness, moisture content, system configuration, installation deficiencies, …)

If any of the properties listed in the above equation are changed, the measured R-Value of the material may also change, affecting different materials in different ways.

Current regulations require the thermal resistance of insulations to be measured at temperatures that vary significantly from installed conditions. In addition, real world factors that have been documented to affect some insulation types are not considered such as:

* Air/moisture infiltration
* Installation deficiencies
* Thermal bridging
* Extreme temperatures
* Physical and thermal degradation

This is not an exhaustive list by any means. However, inclusion of any or all of these parameters may affect the overall performance of an insulation product, resulting in a product with a high labeled R-Value performing worse than another product that would appear to be inferior from a tested R-Value perspective.

A study showing how ignoring real world, installed parameters can lead to improper insulation choices can be found here;

“Wall R-Values That Tell It Like It Is”

Clear wall, whole wall, cavity……..what do all these R-Values mean?

Refer to the link below to Oak Ridge National Laboratories website for a description of these terms as well as some useful information on interpreting R-values.

Whole-Wall Thermal Performance: R-Value

Insulation Products Thermal Testing Results

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Being a system based insulating product, P2000 is engineered to work with the other building assembly components to minimize heat loss by the key mechanisms that affect thermal performance under installed conditions. When reflective materials are incorporated in the building envelope, the combination of orientation as well as air spaces can elevate the performance of a wall, ceiling or floor assembly beyond the recognized R values of the building materials alone.

1″ P2000
R-4.1
1″ P2000 + Air Space**
R-6.8
1″ P2000 Wall Assembly
R-10.2
R-19 Fiberglass Wall Assembly
R-11.5
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