Glossary of Common Terms (F – Q)
PIR, PUR and PU insulation – what’s the difference?
This week’s glossary provides a helpful definition of each, as well as explaining other common industry terms beginning with letters F through Q. Don’t forget to take a look at last week’s blog post, Glossary of Common Terms (A – E), and remember to check back next week for the final part in the series.
If you think we’ve missed something important, please do leave a comment and we will do our best to help.
Hint: Use CTRL + F to search for a specific term!
Facing – The surface element of an insulation board. Rigid and semi–rigid insulation boards often have a foil facing which lowers the emissivity of the insulation element.
Fibrous Insulation – An insulation material made up of fibres rather than cells.
Fully Bonded – Typically used in reference to flat roofing, and refers to where a bond between two materials is considered to cover the whole surface. As a full bond covers a greater proportion of the roof area, these systems can generally provide greater restraint against wind uplift than partially bonded systems.
Geotextile Membrane – A non–woven geo–synthetic membrane used in a variety of applications within the construction industry to act as separation and filtration membranes.
GWP – Global Warming Potential is a relative measure of how much heat a greenhouse gas traps in the atmosphere, and in turn how much the product is estimated to contribute towards global warming. It compares the amount of heat trapped by a certain mass of the gas in question to the amount of heat trapped by a similar mass of carbon dioxide. A GWP is calculated over a specific time interval, commonly 20, 100 or 500 years.
Green Guide Rating – The 2008 Green Guide Rating system uses data from Environmental Profiles to classify performance of construction materials in a number of areas to award a summary rating on a scale of E (worst) up to A+ (best).
HTB or Transmission heat transfer coefficient associated with non–repeating thermal bridges – The HTB is the overall sum of heat–loss / gain from each junction multiplied by that junction’s length.
ISO – International Standardisation Organisation is a certification body that provides assessments such as 9001- quality management, 14001- environmental management, 18001- Occupational Health and Safety (OHSAS), and 50001- energy management.
IWI – Internal Wall Insulation, insulation on the inside or warm side of a wall.
Kappa Value – This relates to the thermal mass of a construction. It is the measure of how much heat will be stored per metre squared of a building and represents ‘k’ in the unit of measure kJ/m2K. ‘k’, or the heat capacity of a building, can be calculated using the following equation:
k = 10 – 6 x Ʃ (dj rj cj)
dj = thickness of layer (mm)
rj = density of layer (kg/m3)
cj = specific heat capacity of layer (J/kg·K)
The calculation is over all layers in the element, starting at the inside surface and stopping at whichever of the following conditions is encountered first (which may mean part way through a layer):
- The total thickness of the layers exceeds 100mm
- The midpoint of the construction is reached
- An insulation layer is reached (defined as thermal conductivity ≤ 0.08 W/m.K)
Lambda Value – Sometimes called the ‘k–value’ or ‘ʎ–value’, this measures the thermal conductivity of a material. k–value is shown in units of W/mK where ‘m’ represents the thickness of the material in metres. Insulants have a low thermal conductivity meaning heat cannot pass through them easily. The k–value shows the general performance of a material with regards to thermal conductivity and does not relate to the material’s thickness.
LCA – Life Cycle Assessment is how the environmental impact of a building is assessed from raw materials to disposal or recycling.
Loose Fill Insulation – For example, cellulose or mineral insulations that are typically installed in the air cavities of buildings through a gap or drilled hole in the building element.
Moisture Ingress – The act of water entering something. In construction terminology the term is typically used in reference to external moisture (i.e. ground moisture or precipitation) entering a construction.
MVHR – Mechanical Ventilation with Heat Recovery: A system that ventilates a space by removing indoor air, recovering the heat from that indoor air, and using it to pre–heat fresh air from outside.
Open Cell Insulation – This insulation has a structure that allows moisture and vapour to permeate through it.
OSB – Oriented Strand Board, also known as OSB, Sterling board or Exterior board, is an engineered wood product formed by layering strands (flakes) of wood in specific orientations set within a resin to form a rigid board. The product is typically available in differing thickness from 6–25mm, and comes in differing grades from 1–4. Grades 2–4 are most common, with grade 3 or 4 generally being used in structural applications. A common application for boards of this type is as a structural sheathing to timber frames where they enhance the bending and racking strength of the frame.
P/A Ratio – The perimeter / area ratio is worked out by dividing the exposed perimeter given by the floor area. This will calculate how much floor insulation is need. The exposed perimeter refers only to the walls that connect to an unheated space, so this will mainly be an outside space or areas such as a garage. The smaller the P/A figure the smaller the amount of insulation that is required, for example, a large area with a small exposed perimeter will have less heat loss and, therefore, will require less insulation.
Partial Bonding – Typically used in reference to flat roofing and relates to the method of bonding various components to the substrates beneath. When using a partial bond only a proportion of the two adjacent layers are bonded to one another, this can be to allow for a degree of differential movement, the release of gas during installation, or just due to discontinuity in the substrate, i.e. such as in the case of a profiled metal deck. When referring to built–up bituminous felt partially bonded systems are generally achieved by using a 3G perforated felt, which is loose laid above the substrate (i.e. deck or insulation) and the next layer of felt is then partially bonded to the substrate at the points of the perforations in the 3G layer.
Passivhaus or Passive House Standard – ‘A Passivhaus is a building, for which thermal comfort can be achieved solely by post–heating or post–cooling of the fresh air mass, which is required to achieve sufficient indoor air quality conditions – without the need for additional recirculation of air.’ The Passivhaus standard is a very high standard of energy efficiency by reducing levels of heat loss through high levels of insulation and preventing air loss, the building is heated passively through the sun, human occupants and household appliances with the remaining heat being supplied through heating or cooling of air in a mechanical ventilation system.
Phenolic Foam (PF) – An insulant such as Kingspan Kooltherm rigid phenolic boards. It has a high compressive strength and a closed cell structure. The thermal conductivity of phenolic foam is lower than that of rigid polyurethane or extruded polystyrene.
Plenum – In ductwork, a plenum is a space above a ceiling that allows the collection of air in order to let it move between different spaces in the building.
PIR – Polyisocyanurate foam is a rigid polymeric foam insulation, for example Kingspan Thermapitch that has a thermal conductivity of 0.022 W/m·K.
Psi Value or Ψ Value – The measure of heat loss per K shown in units of W/m·K where ‘m’ details the length of a junction in metres. It is used to estimate the potential for non–repeating thermal bridges.
PU – A family of rigid cellular thermoset polymeric foam with a close cell structure that forms both PIR and PUR based polymer forms. Kingspan’s Therma range is made up of PU rigid urethane insulants.
PUR – Polyurethane foam is a rigid polymeric foam insulation with a high thermal resistance and low thermal conductivity. It can be used on its own or to seal air gaps between existing insulation elements.
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