GLOSSARY

 
Mineral Fiber insulation principally made of fibers manufactured from rock, slag or glass, with or without binders.

 

Insulations forms

Roll

A relatively flat and flexible insulationin coherent sheet form furnished in units of substantial area.

Board Semirigid insulation preformed into rectangular units having a degree of suppleness particularly related to their geometrical dimensions.
Loose fill Insulation in granular, nodular, fibrous, powdery, or similar form designed to be installed by pouring, blowing, or hand placement.
Pipe Insulation in a form suitable for application to cylindrical surfaces.
Reflective insulation
Insulation depending for its performance upon reduction of radiant heat transfer across air spaces by use of one or more surfaces of high reflectance and low emittance.

 

Thermal Insulation: properties

Thermal conductivity, λ o k 

The time rate of steady state heat flow through a unit area of a homogeneous material induced by a unit temperature gradient in a direction perpendicular to that unit area. ( λ or k in SI units: W/mK)

Thermal resistance, R

The quantity determined by the temperature difference, at steady state, between two defined surfaces of a material or construction that induces a unit heat flow rate through a unit area.  R = thickness/λ   (R in SI units: m²K/W) 

Thermal conductance, C

The time rate of steady state heat flow through a unit area of a material or construction induced by a unit temperature difference between the body surfaces. Thermal resistance and thermal conductance are reciprocals of one another. (C in SI units: W/m2K) 

Water vapor diffusion The process by which water vapor spreads or moves through permeable materials caused by a difference in water vapor pressure.
Water vapor permeability

The time rate of water vapor transmission through unit area of flat material of unit thickness induced by unit vapor pressure difference between two specific surfaces, under specified temperature and humidity conditions. Permeability is the arithmetic product of permeance and thickness. SI units: kg/(m s Pa) 

Water vapor permeance

The time rate of water vapor transmission through unit area of flat material or construction induced by unit vapor pressure difference between two specific surfaces, under specified temperature and humidity conditions. SI units: kg/(m² h Pa)

Water vapor resistance  Vapor resistance is the reciprocal of vapor permeance. It is the arithmetic product of the resistivity and thickness.
Water vapor pressure The pressure of water vapor at a given temperature; also the component of atmospheric pressure contributed by the presence of water vapor.
Water vapour diffusion

It is a measure of the material’s relative reluctance to let water vapour (steam/condensation) pass through, and is measure in comparison to the properties of air.  The lower the m-value, the more breathable the material.  It is a property of the material itself and independent of the thickness of the material in a particular construction.

Thermal insulation: general definitions

Dewpoint temperature   

The temperature at which condensation of water vapor in a space begins for a given state of humidity and pressure as the vapor temperature is reduced;the temperature corresponding to saturation (100 % relative humidity) for a given absolute humidity at constant pressure.

Absolute humidity The mass of water vapor per unit volume.
Relative humidity

A given volume of air is able to hold a small amount of water vapour and this (maximum) amount of water vapour depends upon the air temperature. The air will not always hold the maximum possible quantity of water vapour so that it is usual to express the amount of water vapour present as a percentage of the maximum:

Relative humidity = actual amount of water vapor present/maximum amount of water vapor that may be held at a particular temperature

or

Relative humidity = actual partial pressure of water vapour/saturated vapour pressure

Facing A protective or decorative (or both) surface applied as the outermost layers of an insulation system.
Water vapor retarder (barrier)

A material or system that adequately impedes the transmission of water vapor under specified conditions.

FSK (foil scrim kraft)

A glass scrim reinforced vapor retarder laminate of aluminum foil and kraft paper bonded together with a fire retardant adhesive. The foil side faces outward to present a neat metallic surface finish.

Heat flow rate, Q

The quantity of heat transferred to or from a system in unit time. (Q in SI units: W)

heat flux, q

The heat flow rate through a surface of unit area perpendicular to the direction of heat flow. (q in SI units: W/m²)

Specific heat

The quantity of heat required to change the temperature of a unit mass of a substance one degree, measured as the average quantity over the temperature range specified. (In SI units: J/kg K)

Thermal capacity

The quantity of heat required to change the temperature of the body one degree. For a homogeneous body, it is the product of mass and specific heat. For a nonhomogeneous body, it is the sum of the products of mass and specific heat of the individual constituents. (In SI units: J/K)

Thermal insulation

A material or assembly of materials used to provide resistance to heat flow.
Thermal insulation system Applied or installed thermal insulation complete with any accessories, vapor retarder, and facing required.
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