Insulation
- Since they do not decrease heat flow, heavy materials are not good thermal insulators. However, where there are significant differences in temperture between day and night they do slow heat passage throught the building fabric
- Bulk and reflective insulation is more effective. Because of its thermal mass brick is better put to use as an interior surface to stabilise temperatures. Other than for the appearance it serves little purpose as an exterior finish since it is not impervious to moisture. Drip grooves allow any moisture that does penetrate the wall to be shed.
- Adding insulation to one part of a home won't increase the heat losses through other parts. Although windows can be areas of great heat loss and gain, all insulation makes a difference by reducing heat flow. Insulated surfaces stay at a temperature closer to the indoor air temperature and therefore create a more comfortable environment.
- Contrary to popular belief plastic pipes are not an insulator and do require insulation.
- Insulation is often the most cost effective way to reduce heating and cooling
DRAUGHT SEALING
- Air leakage accounts for 15 to 25 percent of winter heat loss in buildings.
- Using airtight construction, controlling ventilation and installing well sealed windows and doors is your best way to reduce heat loss thought air leaks.
- Improve the performance of existing windows and doors by using draught-proofing strips. Use between the door and frame, at the door base and between the openable sash of the window and the frame.
- Seal gaps between the window/door frame and the wall.
- Avoid using light fixtures that create gaps in the ceiling insulation.
- Whenever an exhaust fan is installed makes sure that there is a non return baffle in place.
- Insulate the underside of wooden floors.
INSULATION
- Ceilings and roof spaces account for 25 to 35 percent of winter heat loss and must be well insulated. To prevent heat loss, locate most of the insulation next to the ceiling as this is where the greatest temperature control is required.
- Floors account for 10 to 20 percent of winter heat loss. In cool climates insulate the underside of suspended timber floors and suspended concrete slabs. Insulate the edges of ground slabs but do not insulate under ground slabs unless groundwater is present.
- Walls account for 15 to 25 percent of winter heat loss. Insulation levels in walls are often limited by cavity or frame width. In cold climates, alternative wall construction systems that allow higher insulation levels
are recommended.
- In high mass walls, thermal lag slows heat flow on a day/night basis. Insulation is still required in most instances.
CHOOSING INSULATION- WHERE TO START
- Insulation products come in 2 main categories - bulk and reflective. These are sometimes combined into a composite material. There are many different products available.
- For purposes of comparison look at the R- value of insulation materials because it is this measurement that indicates resistance to heat flow. The higher the r- value the better the insulation level. Some products require professional installation in order to achieve optimum performance. Weigh all the costs involved against the performance guarantees to determine what is best for you. The builiding envelope and heating /cooling systems are not taken into consideration in the r-value. It is strictly a measure of the material itself.
- Compare the environmental benefits of different products. Ask about recycled content and how easily the product can be recycled after use. Currently some brands of polyester insulation contain up to 80 percent recycled PET (the plastic commonly used in drink bottles). Some brands of cellulose fibre contain 100 percent recycled paper. Glass fibre insulation contains between 25 to 60 percent recycled glass.
- 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 (sometimes known as 'winter' R values).
- Down R values describe resistance to heat flow downwards (sometimes known as 'summer' R values).
- Up and down R values should be quoted when installing insulation in roofs, ceilings and floors.
INSULATION TYPES & THEIR APPLICATIONS
- Bulk insulation 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 fibre, wool, cellulose fibre, polyester and polystyrene. All products come with one material R-value for a given thickness.
- Reflective insulation mainly resists radiant heat flow due to its high reflectivity and low emissivity (ability to re-radiate heat). 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.
- Dust settling on the reflective surface will greatly reduce performance. Face reflective surfaces downwards or keep them vertical. The 'anti-glare' surface of single sided foil sarking should always face up.
- The system R values for reflective insulation are supplied as up and down values. System values depend on where and how the reflective insulation is installed. Ensure system values provided by the manufacturer relate to your particular installation situation.