Applications of Different Insulation Materials

Insulation types and their applications vary depending where or what part of the house you need to install:

Bulk insulation materials

Mainly resists the transfer of conducted and convected heat, relying on pockets of trapped air within its structure. Its thermal resistance is essentially the same regardless of the direction of heat flow through it. Bulk insulation includes materials such as glass wool, wool, cellulose fibre, polyester and polystyrene. All bulk insulation products come with one material R-value for a given thickness. Bulk insulation traps air in still layers.

Reflective insulation materials

Mainly resists radiant heat flow due to its high reflectivity and low emissivity. It relies on the presence of an air layer of at least 25mm next to the shiny surface. The thermal resistance of reflective insulation varies with the direction of heat flow through it. Reflective insulation is usually shiny aluminum foil laminated onto paper or plastic and is available as sheets (sarking), concertina-type batts and multi-cell batts. Together these products are known as reflective foil laminates, or (RFL). Dust settling on the reflective surface greatly reduces performance. Face reflective surfaces downwards or keep them vertical. The anti-glare surface of single sided foil sarking should always face upwards or outwards. The total R-values for reflective insulation are supplied as ‘up’ and ‘down’ values. Total values depend on where and how the reflective insulation is installed. Make sure that system values provided by the manufacturer relate to your particular installation situation. Composite bulk and reflective materials are available that combine some features of both types. Examples include reflective foil faced blankets, foil backed batts and foil faced boards.

The building code sets out minimum requirements for the R-values of materials used in the construction of buildings. It is generally advisable to exceed these for greater comfort and energy savings. The higher the R-value, the better the thermal performance. Material R-values are supplied with bulk insulation materials and refer to the insulating value of the product alone. The higher the R-value the better the thermal performance. Total R-values are supplied with reflective insulation and depend on the product being installed as specified. R-values can differ depending on the direction of heat flow through the product. The difference is generally marginal for bulk insulation but can be pronounced for reflective insulation.

• ‘Up’ R-values describe resistance to heat flow upwards (winter R-values).
• ‘Down’ R-values describe resistance to heat flow downwards (summer R-values).

Up and down R-values should be quoted when installing reflective insulation in roofs, ceilings and floors. It is extremely important to ensure that your insulation is installed by competent, experienced professionals. Badly-installed insulation which is crammed in too tight, has gaps or gets wet will do little to protect your home, even if it's material with very high R-values. Also for using insulation materials, the walls and roof spaces also need to be constructed properly, using appropriate framing techniques, radiant barriers and other approaches to reducing heat transfer. And most importantly, insulate the foundations, basement walls and slabs, especially in colder climates.