Thermal:

Q: What is an R-value?

An R-Value (thermal resistance) indicates the insulating power of an insulation material. The higher the R-value, the greater the insulating power i.e  more energy savings.

Fire:

Q:  I need to build a wall that is rated to 1 hour.  Which building insulation product will achieve this rating?

Fire Rating of walls, floors, columns, and other building members under fire exposure conditions are tested in accordance to ASTM E-119. The fire resistive ratings are expressed in hours. The fire ratings of these assemblies are largely dependent upon the thickness of the gypsum board /Steel sheet and not the insulation. The insulation is usually an optional item in the assembly and should not have a negative impact on the hourly fire rating.

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Acoustic:

Q:  What is Reverberation time?

Reverberation time is the time taken for the sound pressure level to drop by 60 dB after the generated noise has been stopped.

Areas with a long reverberation time are referred to as being 'live', e.g. cathedrals and churches. Those with a short reverberation time are referred to as being 'dead', e.g. offices with thick carpets and absorbent ceilings.

A reduction of 60 dB in the sound pressure level is equivalent to the reduction of acoustic energy by a factor of one million. As a rough guide, the reverberation time of a room is approximately equal to the time it takes for loud clapping to become inaudible.

Q:  What is STC value?

STC (Sound Transmission Class) value is a single number rating to specify the reduction in sound levels that the partition provides. The sound transmission loss performance of a partition is measured using ASTM E 90 "Standard Test Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements" and calculated according to ASTM E 413 "Classification for Rating Sound Insulation." As a general rule, the higher the STC rating, the better the partition's acoustical performance.

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Q:  What are CAC ratings?

Ceiling Attenuation Class (CAC) ratings are used to determine the sound transmission loss through an acoustical or dropped ceiling. A CAC rating is determined by ASTM test method E 1414 "Standard Test Method for Airborne Sound Attenuation Between Rooms Sharing a Common Ceiling Plenum" and provides a value that is equivalent to an STC value

Q:  What are IIC ratings?

An IIC (Impact Isolation Class) rating describes the impact noise that is transmitted through a floor/ceiling assembly. The rating is determined by ASTM E 492 "Standard Test Method for Laboratory Measurement of Impact Sound transmission Through Floor-Ceiling Assemblies Using the Tapping Machine." High ratings indicate that impact noise is reduced substantially.

Q:  Are there advantages to using steel studs over wood studs?

Twenty five gauge steel studs provide superior sound control performance to wood studs with the same dimensions. The flexibility of the studs allows the partition to provide performance equivalent to a wood stud construction with resilient channels.

Q:  What are resilient channels and where are they sold?

Resilient channels are strips of metal with an offset that spaces the drywall approximately ½" away from the framing. They are typically installed 24 inches on center perpendicular to the studs. The use of resilient channels dramatically reduces the amount of sound that is conducted though the structure.

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Health:

Q:  Do Rockwool products contain asbestos?

No, Rockwool does not use Asbestos as a raw ingredient in manufacturing of any of its products.

Q:  Do Rockwool products cause Cancer?

No.

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Water Vapor:

Q:  What is  Dew Point?

Dew Point is the temperature at which condensations forms.

Q:  What is Condensation?

Air is composed of many gases.   One of these is water in a gaseous from, called water vapor.  The amount of water vapor that air can hold is a function of temperature.  When the air comes in contact with an object at a temperature where water vapor will change to a liquid.  This process is called condensation.

Q:  What is perm?

Perm is a traditional unit of water vapor permeability, that is, the ability of a material to permit the passage of water vapor. If we want to keep things dry, we wrap them in something having low permeability. A material has a permeability of one perm if it allows transmission of one grain of water vapor per square foot of area per inch of mercury (in Hg) of pressure difference per hour. The value depends somewhat on temperature, however. At 0 °C, one perm equals about 5.721 x 10-11 kilograms per square meter per pascal per second (kg/(m2*Pa*s)) or about 0.2060 mg/(m2*Pa*h); at room temperature the equivalent is about 5.745 x 10-11 kg/(m2•Pa•s). [The SI unit, kg/(m2*Pa*s), simplifies to seconds per meter (s/m).] The lower the perm value, the better the vapor barrier.

Q:  What is perm inch?

Perm inch is a traditional unit of water vapor permeance. The perm value (see above) does not depend on the thickness of the material used as a water barrier. The permeance is the product of the perm value and the thickness, measured in inches. One perm inch equals about 1.453 x 10-12 kg/(m*Pa*s) at 0 °C or about 1.459 x 10-12 kg/(m*Pa*s) at room temperature. The SI unit kg/(m*Pa*s) actually simplifies to seconds (s).

Q:  What is Water Vapor Transmission?

The amount of water vapor passing through a given area of a plastic sheet or film in a given time, when the sheet or film is maintained at a constant temperature and when its faces are exposed to certain different relative humidities. The result is usually expressed as grams per 24 hours per square meter (g/24 hr•m2).

Q: What is the difference between permeance and permeability?

Permeability is the water vapor transmission of a homogeneous material under unit vapor pressure difference between two specific surfaces, per unit thickness. An acceptable unit of permeability is perms-inch: grain-in/h*ft2*in*Hg. Permeability is important for specifying insulation materials.

Permeance is the water vapor transmission of a specific sample under unit vapor pressure difference between two specific surfaces. An acceptable unit of permeance is perm: grain/h*ft2*in*Hg. Permeance is important for specifying vapor retarders.

It is important to ONLY use permeance when specifying vapor retarders. The industry standard requirements for vapor retarder permeance in mechanical systems are typically 0.02 perms for below 32°F service temperature and 0.03 to 0.05 perms for above 32°F service temperatures. When selecting a vapor retarder, make sure that permeance meets these requirements. Saran* 540 and 560 vapor retarder films easily meet the more stringent of these two requirements (0.02 perms). This makes them suitable for use at service temperatures from ambient down to cryogenic temperatures.

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Q:  Which side do I install the vapor retarder on?

It depends on your geographical location. In cold climates, the vapor retarder should be installed on the inside (warm in winter) of the structure. In hot and humid climates the vapor retarder should be installed on the outside (warm side). Vapor retarders play an integral role in moisture control. Since climates are rarely cold or hot all the time, the vapor retarder should be placed to the side of the structure that is the predominately warm side. This is because heat flows from warmer to cooler in attempt to reach equilibrium. The warmer air can hold a higher amount of water vapor. As air cools, it can reach the dew point. This is the point at which the relative humidity reaches 100% and water vapor condenses from the vapor phase to the liquid phase. Therefore, the vapor retarder should be placed to the predominately warm side to prevent the moisture from migrating with the heat flow to the cold side, reaching the dew point, and creating a liquid moisture problem.

General:

Q:  Which way does the foil face (reflective side) on the AP foil faced insulation need to face?

In most cases it doesn't matter. Both sides have the same perm rating (0.05 perms). The reflective side will give an increased R-value when used behind an exterior brick veneer. This is called a reflective air space. Sometimes the non-reflective side is installed towards the outside to reduce glare from the sun or to eliminate any concerns about too much heat build up behind vinyl siding.