An Introduction to Insulation
What is Insulation?
Insulation is a material that blocks or resists energy transfer through it. Insulation can reduce the transfer of heat, sound or electricity between objects with different properties. In building construction insulation is typically used to reduce heat transfer between the inside and outside of your home, and is important for your roof, walls and flooring.
Insulation can be made from materials including fibreglass, cellulose, foam and mineral wool and can be installed in a variety of ways. The effectiveness of insulation is measured in R-values, indicating the resistance to heat transfer. The higher the R value the more effective the insulation is. Your need for insulation and how much of it will be dependent on the climate your home is built in.
Why is Insulation Important?
Insulation is a critical factor in improving the energy efficiency of your home. Insulation reduces heat loss or prevents heat from entering your home when trying to keep it cool. This is critical for the passive heating and cooling design of your home. A passive house will reduce the need to artificially heat and cool your home, which in turn can reduce energy bills and lower greenhouse gas emissions. It also links to the comfort of your home as a consistent indoor temperature will improve liveability.
Insulation can also help with noise reduction by reducing the transmission of sound, improving privacy and reducing noise pollution. Some insulation types will assist with moisture control to prevent the buildup of moisture in walls and roofing which can reduce the chances of mould growth. Some insulation types are also helpful in reducing the spread of flames in the event of a fire, as again it reduces the transfer of energy through it.
Total R-values
The total R-value is a value given to a housing component (roof, wall, floor) to describe the total resistance to heat flow. The total R-value is the sum of the R values of each material component making up that wall, roof, or floor. This R-value encompasses the performance of the insulation acting within the building component along with all other materials, for whatever insulative properties they add.
Insulation types
Bulk Insulation
Bulk Insulation is a material that works by holding air in tiny pockets. This air slows down the conduction (and convection) of heat through the space taken by the material.
Some common materials for bulk insulation, in batts, rolls, fill or boards include:
- glass wool
- wool
- cellulose fibre
- polyester
- polystyrene, expanded (EPS) or extruded (XPS)
- polyisocyanurate (PIR)
- polyurethane (PUR).
Bulk insulation also generally has one R-value for a given thickness of that material.
Reflective Insulation
Reflective insulation is a material that works by reflecting radiant heat away from the building. This is most effective for climates where heat transfers primarily from this radiant heat. A minimum space of 25mm of air is needed above the reflective layer to allow the insulation to work efficiently.
Reflective materials include aluminium foils laminated onto a sheet of concertina-type batts and multi-cell batts (think accordion or crinkle style).
The total R-value for reflective insulation in ceilings, roofing and flooring will be accompanied by an ‘up’ or ‘down’ classifier. This describes the direction of resistance for that value, and so two values are provided for roofing, ceilings and flooring.
Composite Insulation
Of course, a combination of the two insulations can be used in different areas of the home, or hybrid forms including foil blankets can be used.