Xci Archives - Hunter Panels

Real World Factors Affecting Insulating Power

QUESTION:

What real world factors can affect a product’s insulating power?

ANSWER:

R-value is a reliable measurement of how materials will perform in a static test environment, however real world application will differ from laboratory circumstances. The insulation used in an exterior wall will be part of the overall building envelope, not used in isolation. Factors such as moisture, air infiltration, and convective flows within the wall all can play a part in the overall thermal efficiency of a wall system.

QUESTION:

How do products obtain their R-value?

ANSWER:

Air

Closed-cell foam insulations derive their R-value from the blowing agents/gases contained within the cells. The blowing agents for different types of foam plastics will vary, but all are selected for their ability to enhance the thermal performance of the foam. Because of their closedcell composition, all closed-cell foam products provide excellent resistance to moisture and air intrusion along with thermal performance.
Fibrous materials derive their R-value from air trapped within pockets between the fibers. Air and/or water movement through fibrous insulation products will reduce the insulating power, which is why fibrous insulations have traditionally been used within interior stud cavities with barriers (walls) which restrict air & water movement on all 6 sides of the cavity.

To illustrate how fibrous insulations work and how air or water can impact insulating power, think of a person who wears a sweater outside on a cool day to keep warm. On a calm, cool day the sweater does a nice job keeping them warm. If the wind picks up, the air penetrates the fibers and the sweater no longer insulates the way it did when the air was not moving, in fact they may put a wind breaker over the sweater to try to keep warm. If it rains, the sweater gets wet as water penetrates the fibers, again impacting the insulating ability. When the sweater dries out, it will insulate well again, but how long does it take to dry and how quickly will that person want to put it back on? What happens if the weather is consistently wet or there is a significant amount of wind? Would a sweater be your first choice to keep you warm in such conditions?

Moisture

Both bulk water and water vapor should be considered when making choices for continuous insulation or “ci”. There are a number of tests utilized to measure water resistance of various building materials, and it is important to understand what they measure and how those measurements apply to various product applications.

The ASTM C209 and ASTM C272 are most frequently utilized for products used in an exterior environment where the presence of water is likely. ASTM C272 has been predominantly used when focusing on below-grade application. ASTM C209 has been more closely associated with above grade exterior walls due to the inclusion of a drainage period. ASTM C1104 is a test created specifically for mineral fiber insulations that does not include the presence of bulk water.

Independent tests performed on Hunter Xci polyiso and a leading dual density mineral fiber board product yielded telling results. Both materials were subjected to identical test procedures at accredited independent facilities. R-value measurements used were taken at both 75°F and 40°F mean reference temperatures

In the dry state, the measured average R-values were in line with published R-values for both the 2″ ISO (R-13) and 3″ dual-density mineral fiber (R-12.9). In the wet state, test averages resulted in the polyiso product performing within 3% of published R-values. In the same wet state, test averages resulted in the mineral fiber product R-values being diminished by 70% from published Rvalue.

In the dry state, the measured average R-values were in line with published R-values for both the 2″ ISO (R-13) and 3″ Dual-Density Mineral Fiber (R-12.9). In the wet state, test averages again resulted in the polyiso product performing within percentage points of published R-values. In the same wet state, test averages resulted in the mineral fiber product R-values being diminished by 62% from published R-value.

Closed cell foam insulation products have excellent moisture resistance, while fibrous materials do not. Tech bulletins or FAQ from fibrous insulation manufacturers state that when product is wet, R-value will be reduced, but they do not typically reference how much reduction will be seen. The above results show the R-value reduction to be substantial, even when drainage opportunity is provided.

CONCLUSION:

Polyiso insulation performs better in retaining R-value in wet environments, such as exterior wall cavities, than mineral fiber. Consideration should be given to such factors when selecting insulation materials.

How Does ASTM C 1289 Classify Foam Insulation?

Question:

How does ASTM C 1289 classify foam insulation?

Answer:

ASTM C 1289 is a standard developed by ASTM members that classifies the design requirements for a specific material, product, system and service. All faced rigid polyisocyanurate manufacturers are required to manufacture and test to the standards of ASTM C1289. This standard classifies faced polyiso panels by type, class, and grade.

Type

Refers to the facer material that is bonded to the foam. Below is a list of common types of facers used in the commercial wall market.

Type	Description
I	Foil Facer
II	Glass Mat Faced
V	Plywood or OSB on one side, Fibrous Felt or Glass Mat on the other side.

CLASS FOR TYPE I MATERIALS

For foil faced polyiso the “Class” designation refers to whether or not the foam core is glass fiber reinforced.

Class	Description
1	Non-Reinforced Foam Core
2	Glass Fiber Reinforced Foam Core or Non-Reinforced Foam Core

CLASS FOR TYPE II MATERIALS

For glass mat faced polyiso the “Class” designation refers to the material used in conjunction with the glass mat. Currently, all Type II polyiso products for commercial wall applications fall into the Class 2 category.

Class	Description
2	Polymer Bonded Glass Fiber Mat both sides, Coated Glass
3	Glass Mat Only

GRADE

Refers to the product’s compressive strength for permeable faced products. Compressive strength is reported in terms of PSI. Several polyiso products are available in multiple grades

Grade	Description
1	16psi min
2	20psi min (Standard for most Xci products
3	25psi min

Testing for R-Value

Question:

How does the test method work for determining R-value of a building product?

Answer:

R-value is the most commonly used measurement tool used in the building and construction industry to evaluate resistance to heat flow. The higher the product’s R-value measurement, the greater the insulating power. Measuring R-value, or resistance to heat flow, is accomplished by placing the material to be tested between two plates of different temperatures. ASTM C518 utilizes both hot and cold plates that are air-impermeable, directly in contact with the sample being tested. Heat flow is then measured across the sample as temperatures of the plates are maintained. One plate would be considered the “cold side” and the other would be considered the “warm side”. The mean temperature is the average between the temperatures on both sides of the test mechanism (Temp of cold side + Temp of warm side/2).

Question:

Temperature and R-values, what are the important facts to understand?

Answer:

Thermal resistance of materials can vary with temperature, so the FTC has established published requirements for R-value to be measured at 75 degree mean temperature creating a uniform standard across materials. Attempts to redirect conversation toward R-values at different mean temperatures are often misleading or confusing, which is why the FTC established the 75 degree mean temperature requirement. It is important to note, mean temperature is not synonymous with ambient temperature, or outdoor temperature. Mean temperature in terms of R-value would be the average between the temperature on the cold side of the wall and the temperature on the warm side of the wall.

Assuming the indoor temperature of a building to be 68 degrees year round, that temperature could serve as either the warm side or the cold side. Assuming the indoor temperature of a building to be 68 degrees year round, that temperature could serve as either the warm side or the cold side.

Evaluating the information nationally, the average mean low temperatures for major metropolitan areas across the US are above 50 degrees mean, and the average mean high temperatures range from above 60 degrees mean into the upper 70’s depending on geographic region. Thusly, it is important to understand the definition of mean temperature in terms of R-value calculation. Redirection of conversation away from FTC mandated R-value measurement is a deliberate attempt to mislead and confuse which could result in improperly insulated buildings.

Does Lower ASTM E84 Value Equal Better Fire Performance?

Question:

Explain why there may be differences in ASTM E84 flame spread and smoke developed values of foam insulations. Does a lower ASTM E84 value always convey better fire performance?

Answer:

Some insulation products may have a lower flame spread, but this does not necessarily imply that the product is more fire-resistant. It is important to understand the dynamics of the testing standard and how certain products behave during the test. The ASTM E84 test is a tunnel test where a single layer of the product to be tested is installed horizontally to the ceiling of the tunnel, and then subjected to flame on one end. Temperature and smoke development performance values are then gathered as the flame travels. Testing of materials that melt, drip, or delaminate to such a degree that the continuity of the flame front is destroyed results in low flame spread indices that do not directly relate to indices obtained by testing materials that remain in place. This is a common occurrence for thermoplastic insulations (e.g. XPS or EPS) during the ASTM E84 test. Thermoplastics tend to soften at temperatures nearing 165 degrees and melt/drip approaching 200 degrees. The test is then terminated because the product ceases to exist, and a flame spread measurement is then assigned.

From ASTM E84 Test Procedure:

X4.7.7 Some materials, such as cellular plastics and thermoplastic materials, can be difficult to evaluate. Thermoplastic materials not mechanically fastened will often fall to the floor of the tunnel. Accordingly, these materials as well as thermosetting cellular plastics can also receive relatively low fsi. (8,9) If supported on wire screen, rods, or other supports, some plastic materials can be completely engulfed in flame and a questionable comparison would result between the flame spread indices and smoke developed indices of these materials and those of materials that are unsupported.

X4.7.8 The materials described above, that is those that drip, melt, delaminate, draw away from the fire, or require artificial support present unique problems and require careful interpretation of the test results. Some of these materials that are assigned a low fsi based on this method may exhibit an increasing intensity of the fire exposure. The result, therefore, may not be indicative of their performance if evaluated under large-scale test procedures. Alternative means of testing may be necessary to fully evaluate some of these materials

UL now notes via footnote that the results for thermoplastics testing were evaluated while material remained in the initial test position. The footnote then references measured flame spread and smoke developed values for molten residue that dripped to the floor of the test apparatus. These additional noted details result in values that are significantly higher than published ASTM E84 test values for the same material.

Flame Spread and smoke developed recorded while material remained in the original test position. Ignition of molten residue on the furnace floor resulted in flame travel equivalent to calculated flame spread Classification of 110 and smoke developed Classification of over 500.

Polyiso, by its thermoset nature, has superior fire performance properties over thermoplastic insulations. Thermosets can withstand a high temperature without losing physical properties and physical integrity. During the ASTM E84 test, polyiso stays intact and performs per the standard minimum value of <450 smoke developed and <25 or <75 flame spread depending on the product.