Insulation

Whether you are building or renovating, take the opportunity to choose the right insulation for your home – it will help you maintain the best ambient temperatures for health and comfort.

Fitting insulation when building is the most effective way of ensuring your house stays warm and saves on heating bills. Cold damp homes can affect your family’s health.

How insulation works

Insulation works by reducing the transfer of heat by means of a barrier. The measure of insulation is expressed as an R-value, which is a product’s resistance to heat flow. The higher the R-value the more effective the insulation is in resisting heat transfer.

The most common R-value in new homes for walls and roofs is between R1.9 and 3.3, depending where you live. You can ask for higher R-values in your insulation for more comfort and savings on heating. The extra cost of installing better insulation may be offset by savings in energy costs.

Research shows that older, uninsulated homes typically lose 30-35% of heat through the roof, 18-25% through walls, 6-9% air leakage, 21-31% from windows and 12-14% through the floor.

Energy efficient houses benefit New Zealand by reducing energy consumption, reducing greenhouse gas emissions and improving people’s health.

Insulation can also help to limit internal condensation.

Insulation needs complete coverage

Insulation is most effective when achieves unbroken coverage around the building. If there are any breaks in the insulating material, heat can escape.

If you are putting in insulation in an exsisting house, for example when you are renovating, be conscious that any gaps or interruptions in the insulating material will significantly reduce its insulating qualities.

Legal requirements for insulation

The Building Code in Clause H1 has requirements for the energy efficiency of new houses and for alterations. One way of complying with Clause H1 is to use the Acceptable Solution, H1/AS1, which has tables setting out R values for roofs, walls, floors and windows. These tables apply only when the window area is less than 30% of the total wall area. When the window area is greater than 30%, heat loss through the windows – even if double glazed – will be significant and other methods of complying with Clause H1 are available.

The H1 Acceptable Solution can be viewed here.

Note that the R values specified in the tables in the H1 Acceptable Solution are construction R values, not the R values of the insulation that must be provided. For example, the construction R value for timber-framed walls takes into account the thermal resistance of the lining, the timber framing, the insulation material and the external cladding. Consequently, the R value of the insulation material itself will need to be higher than the R value specified in the tables. Information on construction R values is contained in the BRANZ ‘House Insulation Guide’ that may be purchased from BRANZ.

Types of insulation

Generally the thicker the product, the greater the insulation effect. Insulation is provided by a variety of materials, some of which are better for different areas of the house. Examples are:

Wool
Glass wool
Rock wool
Polyester blanket
Polystyrene sheet

When choosing, consider products which:

Are non-combustible/fire resistant
Are vermin resistant
Stay mould-free/will not rot
Perform over time
Continue to perform over time (e.g. will not sag)
Are independently verified or tested
Are easy to fit if you are doing it yourself
Are non-toxic/non-irritant

For more information about different types of insulation, go to consumer.org.nz. Note: you need to be a member to access this information.

Further information

BRANZ has a range of guides and information to help you make a new or existing home energy efficient. BRANZ can be contacted on 04 237 1170 or through www.branz.org.nz.

The BRANZ Annual Loss Factor (ALF) software programme can be useful for designers in evaluating the effects of different types of construction and of large glazing areas on the energy performance of a house. You can access ALF at http://alf.branz.co.nz/.

The Energy Efficiency and Conservation Authority also has information on how to improve the energy efficiency of existing homes on its EnergyWise website.

The Home Energy Advice Centre is an independent, not-for-profit service providing free, impartial advice tailored to suit the individual home owner. The Centre can be contacted on 0800 388 588.

Eco Design Advisors also provide independent advice about sustainability features such as insulation. They can be contacted at www.ecodesignadvisor.org.nz.

Funding for insulation and heating

You can get ENERGYWISE™ funding to help insulate your house, and install clean and efficient heating under the government's Warm Up New Zealand: Heat Smart Programme. Homeowners with houses built before 2000 are eligible.

Funding can be used to install:

Ceiling and underfloor insulation, up to a required standard (please note, if you can access the space, you have to get both ceiling and underfloor insulation done to qualify for funding).
A clean, efficient heating device in the primary living space, if it does not already have a heating device that meets current standards (please note, you are only eligible for funding towards a heater if you have proper insulation first - your service provider will be able to tell you if you qualify).
The following energy efficiency measures where necessary: a hot water cylinder wrap, pipe lagging, draught-stopping, and a ground moisture barrier.

Thermal control

Linda recently extended her kitchen/dining area. As the area lost the sun at 2.15pm in the winter she chose the following features:

Concrete floor with large tiles. The walls and high ceiling are all lined with higher grade insulation, outer walls are brick which were recycled from removing the original outer wall.
Bi-fold doors on the west-facing wall, opening out onto a paved semi-enclosed patio.
Windows on the northern wall 600mm above floor level for more sun. Also, fixed glass windows in the roof line on the same wall.
An ordinary window on the east wall for low rise morning sun.
All windows double glazed except the east wall which has a thermal-lined Roman Blind.

Linda commented that:

The flooring retains any heat from the sun for a long time. On sunny days the bi-folds can be opened to trap any heat from the patio as well as the floor. Washing dries overnight on a washing rack in winter.
The double glazing is fantastic, windows never fog up, it’s not cold to touch and good for sound proofing.
In summer, with the sun being higher in the sky the room does not get too hot because doors and windows can be opened.