Know your insulation – one size doesn’t fit all

by Tania Wannenburg
Know your insulation one size doesnt fit all

Insulation comes in many different shapes and sizes – understanding each material’s benefits is necessary to select the most appropriate one for the application.

Choosing an insulation material to insulate a building is an important decision that will impact the building’s energy efficiency and thermal comfort for building occupants. With many different kinds of materials available on the market today, each material’s effectiveness in diverse applications should be considered in order to select the appropriate material for the intended use.

Not all types of insulation can be used in exactly the same way with the same result, as is explained in the Thermal Insulation Products and Systems Association of South Africa’s (TIPSASA’s) TiPS guidebook. Specifiers need to consider a wide range of factors such as climate, building design, R-values, resistance against moisture and air leakage, acoustics, combustibility, weight, installation requirements, cost and more, to decide what type of insulation is best for the intended space and requirements.

WALLS & ROOFS asked various industry professionals to clarify the benefits of the different types of insulation within their ideal applications.

Bulk: Fibreglass blanket
Also known as glass wool, this type of insulation is commonly known for application in ceilings of residential buildings.

However, Karlien Delport, brand and communications manager at Saint-Gobain Isover, points out that glass-wool insulation products can also be used for insulating walls, HVAC and air-conditioning systems, pipes, suspended ceilings, industrial roofs and serve as top-up roof insulation. Thanks to good soundproofing performance, many glass-wool products are also specified for acoustic applications.

“Glass-wool insulation comes in either rolls or batts, and is easy to install over ceilings, in cavity and dry walls, or within grid systems,” she says.

Paul Araujo, architectural specifier at Africa Thermal Insulations, explains that in commercial applications, glass wool is installed above purlin using straining wires for support. In residential applications, if not installed above the purlin, it can be loose laid above ceiling board. “Foil-faced blankets are ideal for climates with a high humidity to protect fibreglass form water or condensation damage,” he adds.

Glass wool is lightweight, non-toxic, non-corrosive, non-combustible and can withstand temperatures up to 300°C. It also reduces noise and dust penetration, and does not promote mould growth or vermin infestation.

Bulk: Mineral fibre blanket
Mineral wool comes in rolls or blankets, and is easy to install due to it being lightweight. In some instances it is also shot-free, which allows it to bend around curves and fit into irregular shaped spaces,” says Delport.

While it is similar in texture and appearance to glass wool, the material is denser and therefore has a higher R-value per unit thickness. With excellent thermal conductivity values, it is ideal for high-temperature environments such as industrial ducts, vessels, boilers, locomotives, solar panels, batteries, process plants, ovens and around pipes to protect against burning.

Bulk: Polyester fibre blanket
Available in convenient rolls, polyester fibre ceiling insulation is made from polyester fibre, including recycled polyethylene terephthalate (PET) bottles, providing an insulation that is light, yet strong and resilient, safe and thermally efficient, according to Rolinda Swart from D&D Roof Insulations.

“It is a cost-effective option that is suitable for use in roofs, ceilings and walls of commercial, industrial and residential buildings to provide both thermal and acoustic insulation,” she states.

Polyester fibre blankets are non-toxic, non-carcinogenic and don’t attract rodents. Its maximum limited operating temperature is 150°C and when exposed to a direct flame, the product would melt and shrink away from the flame.

Loose fill: Cellulose fibre
Cellulose Fibre insulation is made from finely shredded recycled paper that is milled into a light fibrous matrix, which is chemically treated to resist fire and fungal growth. Due to the small size of the particles, cellulose can flow around obstructions such as nails, electrical wires, trusses and more, to give a uniform fill. If the insulation is not blown to the manufacturer’s recommended density and thickness it can settle over time, and the intended R-value will not be achieved and maintained.

Where downlights that penetrates the ceiling are used, care must be taken not to have direct contact with insulation or to have the transformers underneath the insulation. For safety reasons, it is a requirement that clearances should be left around hot objects such as flues from fire places, recessed down lights and their transformers.

Rigid board: Expanded polystyrene (EPS)
This expanded polystyrene foam insulation comprises of polystyrene beads, trapping small amounts of pentane gas, which expands in heat to create closed cells. “EPS is supplied in compressed sheets in various thicknesses or in beads that can be mixed into cement. The sheets can be easily cut with conventional hand tools,” says Delport.

Thanks to its low mass and thermal efficiency, it is used in mortars for basements, under slabs and floor insulations, in cavity walls, over waterproofing on flat concrete roofs, on steel decks and for perimeter foundations. EPS can also be used in insulated panels.

According to Lammie de Beer, managing director of Technopol, EPS is often installed in external thermal insulation composite systems (ETICS) in combination with cladding materials like steel, magnesium oxide board, silica fibre board, cement fibre board and cement-based plaster systems and specialised concrete applications.

EPS is CFC- and HCFC-free, resistant to vibration, aging, mildew, bacteria and rot, and can be recycled. The limited surface operating temperature is 100°C.

Rigid board: Extruded polystyrene (XPS)
XPS is a high-density polystyrene foam board with a complete closed cell structure. It is commonly used for slab-edge and cavity brick wall insulation, but is also often installed to insulate ceilings and roofs under soffit, over purlins and trusses, or in-between rafters.

The inverted roof concept, also known as protected membrane or upside down roofing, ensures insulating both the waterproofing membrane and the reinforced concrete slab from extreme thermal stress. This is achieved by placing the extruded polystyrene insulation board above, instead of below the waterproofing membrane.

The inverted roof installation can be installed either as new or retrofit insulation above waterproofing membranes on flat topped buildings or balconies, in retail or office developments, flats, hospitals, airports, hotels and in residential housing.

Rigid board: Polyurethane and polyisocyanurate (PIR)
Ideal for areas which require a high R-value, polyurethane and polyisocyanurate (PIR) boards are produced by chemical reactions between poly-alcohols and isocyanurates, which create tiny air cells containing fluorocarbons instead of air. Polyisocyanurate is a thermoset material that doesn’t soften or melt under high temperatures.

PIR boards need to be protected from prolonged exposure to water and sunlight, and if used on the interior must be covered with a fire-resistant material, such as drywall.

Polyisocyanurate boards can be installed as ceilings, over purlin, under soffit, under screed, as vertical cladding as well as in cavity walls.

External thermal insulation composite systems (ETICS)
Carol-Anne Curtis, Weber product manager for ETICS and facades at Saint-Gobain, describes ETICS (External Thermal Insulation Composite System) as an alternative building technology with many benefits such as lightweight for design flexibility and proven thermal ratings for building thermal comfort to name a few. ETICS is utilised for construction of new buildings or to refresh the exterior facades as part of a retrofit. “All materials in the system have a measure of thermal conductivity, when used together they increase the thermal rating of the building,” she explains.

De Beer points out that EPS boards, for example, can form part of an ETICS solution to dramatically improve a building’s thermal performance. “These boards can be chemically and mechanically fixed to an external facade, and plastered to ensure fire resistance and withstand environmental conditions,” he states.

Being lightweight and flexible, ETICS inspire new exterior design possibilities and since it is applied to the outside of the building, no internal space is lost and disruption is minimal during installation.

Spray-on: Polyurethane foam
Polyurethane foam is closed cell foam that can be used for a variety of spray applications to insulate roofs, ceilings, walls and floors.

The mixed material expands to form a unified membrane that seals surfaces and acts as an air barrier. Single-component foam is available in spray cans for small applications such as sealing around windows and doors. The foam should be protected from prolonged exposure to sunlight and when used in a building interior, it must be covered with a fire-resistant material such as drywall.

Reflective foil membranes
These membranes act predominantly as radiant heat barriers that reflect heat using a shiny surface. Small percentages of the heat is let through and absorbed.

To ensure optimal effectivity, reflective foil membranes need to be installed next to an air gap, which will help to reduce the absorption and lower the emittance of heat through the membrane. It is also important that the bright surface facing the air space remains clean as dust build-up reduces the R-value.

Another important consideration, as stated in TIPSASA’s TiPS guidebook, is that “reflective insulation is more effective at reducing summer heat gain than slowing heat losses in winter”. Reflective foil is often used in combination with bulk insulation for optimum performance.

Polyethylene and aluminium foil
“Foil products radiate up to 95% of radiant summer heat away from the building and act as a vapour, conductive and radiant barrier all in one,” states Araujo.

“In a commercial or residential application using steel trusses, straining wires are used to support the insulation, when installed over purlin. However, when timber trusses are used, no straining wires are necessary when installed over purlin, as the trusses are spaced adequately to support the insulation. The product can also be retrofitted to an existing residential roof system with minimal disruption during installation,” he explains.

According to Araujo, foil products are easy to install, are ultraviolet (UV) protected, do not discolour or delaminate, and reduce dust penetration into the roof space. It contains no fibres, is non-toxic, non-carcinogenic and does not attract rodents.

Final advice
When selecting insulation, ensure that the material:
1.    Is in compliance with relevant South African National Standard i.e. product standard;
2.    Is appropriate for the intended occupancy class in accordance with SANS 10400 Part A;
3.    Complies with the fire safety requirements given in SANS 10400 Part T and SANS 428; and
4.    Complies with the recommended R-value for the relevant climatic zones in accordance with SANS 10400 Part XA and SANS 204.

Full thanks and acknowledgement are given to D&D Roof Insulations,Saint-Gobain Isover, Weber Saint-Gobain, Technopol, Africa Thermal Insulations, TIPSASA for the information given to write this article.

In summary
This article looks at various types of insulating materials:
•    Bulk: Fibreglass blanket.
•    Bulk: Mineral fibre blanket.
•    Bulk: Polyester fibre blanket.
•    Loose fill: Cellulose fibre.
•    Rigid board: Expanded polystyrene (EPS).
•    Rigid board: Extruded polystyrene (XPS).
•    Rigid board: Polyurethane and polyisocyanurate (PIR).
•    External thermal insulation composite systems (ETICS).
•    Spray-on: Polyurethane.
•    Reflective foil membranes.
•    Polyethylene and aluminium foil.

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