Insulation
Around 900,000 New Zealand homes have substandard insulation. [1] Good quality, well installed insulation can significantly reduce the rate of heat loss in your home. This makes your house easier and cheaper to heat properly than without insulation.
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Benefits of insulation in your home
Good insulation means a significant reduction in the rate of heat loss in your house via ceilings, walls, floors, windows and doors. This reduced rate of heat loss makes the house easier and cheaper to heat properly. This means the house will be healthier and more comfortable to live in.
Heat loss in the home
Heat is lost from the inside of the house in two main ways:
- Air infiltration - hot air escapes from the house through cracks, gaps, holes, and open chimneys. This is replaced by cold air.
- Conductivity - hot air escapes directly through the elements of the house such as walls, ceilings, floors, windows, skylights and doors.
If your house is draughty, any insulation you install won’t be able to do its job properly. It’s important to minimise the amount of air leakage from your house at the same time as you improve the insulation.
Heat always finds the easiest path out of a house. If you insulate one part of your house, the ceiling for example, you reduce the rate at which heat is lost through the ceiling. But the rate at which it escapes through other parts of the house increases. To get best results you need increase the insulation for all of the outside building elements of your house.
What to insulate?
The following is the sensible order in which to install insulation:
- Insulate your ceiling first. Heat rises. In an uninsulated house the majority of heat is lost through the ceiling
- Next, insulate under your floor. If the floor is cold, you feel cold.
- Walls and windows are both relatively difficult and expensive to insulate in an existing house. These are jobs normally left for when individual rooms or a whole house is being renovated. If you need to remove wall lining in your house, you can install wall insulation.
- Insulate, too, when replacing windows.
Effectiveness of insulation
Three key factors determine how well insulation works in your house:
- Thermal resistance (r value) of the product installed - the product should be fit for purpose
- Quality of the insulation products
- How well the insulation is installed in your house.
R value
The effectiveness of insulation is measured by its thermal resistance, or R value. The higher the R value on an insulation product, the more it slows down the transfer of heat. For a fixed insulation density, the R value of insulation gets higher as the product gets thicker.
For example an R3.0 product has greater thickness than a R1.0 product of the same type.
Be careful not to use the thickness of insulation to compare different products, always use the R-values, that way you are comparing like for like.
Note: Reflective foils do not have an R value. The foil helps increase the R value of your floor by trapping air between the floor joists.
How much insulation?
The R-value you need depends on how cold it gets where you live. The table below gives recommended minimum R-values for existing homes - it's good to install more if you can.
| MINIMUM RECOMMENDED R-VALUES FOR EXISTING HOMES | ||
| North Island (excluding Central Plateau) | South Island and Central Plateau | |
| Ceilings with 0-75mm of existing insulation | R2.8 blanket or R3.4 segment insulation | R3.2 blanket or R4.0 segment insulation |
| Ceilings with 75-120mm of existing insulation | R1.8 blanket insulation | R2.4 blanket insulation |
| Underfloor | R1.4 bulk insulation | R1.4 bulk insulation |
| Walls | Check the thickness of your wall cavity and find the highest R-value product at that thickness | |
Insulation quality
Well-made insulation is more likely to do its job and remain effective for years to come.
Check what sort of performance guarantees the insulation manufacturers offer on their products. The minimum you should consider is 20 years, but some products come with 50 year performance guarantees.
EECA recommends products tested to the AS/NZS 4859.1 Standard, ‘Materials for the thermal insulation of buildings. Part 1: General criteria and technical provisions’.
These products have been through a series of tests for thermal performance. By choosing insulation products tested to the standard, you know you are getting exactly what you are paying for. Look for a AS/NZS 4859.1 compliance statement on the insulation packaging.
Compliance with the standard is now mandatory for all insulation products used in new houses.
Insulation also loses its effectiveness if it gets damp. It is therefore important to fix any moisture or dampness problems in areas where you are going to install insulation.
Check your phone directory for a company near you or contact an ENERGYWISE™ Warm Up New Zealand: Heat Smart provider who installs insulation.
Installation quality
For insulation to work well it is essential that it’s installed properly.
Ensure that there are no gaps between insulation pieces, plus no folds or tucked in areas.
Consider professional installation or download the NZ Standard on installing insulation in residential buildings NZS 4246. The Standard provides good advice on how to install insulation well.
Types of insulation products
A variety of insulation products are available on the market. It’s important to understand which types of product are best suited for different applications.
Insulation such as fibreglass, cellulose, polyester, polystyrene or wool fibre traps air in small pockets, providing a barrier to warm air escaping. In the past, reflective foil was often used under floors. Better products are now commonly used.
Bulk insulation is available in different forms such as:
- Biscuit – pre-cut pieces
- Blanket – long rolls
- Loose fill – where loose material is pumped in
- Foam insulation - that is pumped into existing walls.
EECA does not recommend the use of pumped foam insulation for a number of reasons.
Climate zones - what do they mean?
New Zealand is divided into three different climate zones based on temperatures common within those areas. These zones help determine the amount of insulation required.
Climate Zone 1
All areas north of, and including, Franklin District. Thames-Coromandel is also part of Climate Zone 1.
Climate Zone 2
All North Island areas not covered by Climate Zones 1 and 3.
Climate Zone 3
All of South Island and North Island Central Plateau (Taupo and Ruapehu Districts, and north of Rangitikei District).
Note: The above is an abbreviated summary of the climate zones set out in the New Zealand Building Code. For the exact definitions, please refer to the Building Code.
Insulation product labelling
EECA recommends that insulation products are tested to the AS/NZS 4859.1 standard.
If the insulation has been tested to this standard there will be a compliance statement on the label. Look for the AS/NZS 4859.1 standard: ‘Materials for the thermal insulation of buildings. Part 1: General criteria and technical provisions’ on the Standards New Zealand website.
Take action
Find out if you are eligible for ENERGYWISE™ insulation funding.
More information
- For home heating and energy options for New Zealanders see Consumer online
- For comprehensive information on insulation, download the Department of Building and Housing booklet: Your Guide To Smarter Insulation.
- For a comprehensive discussion on insulation see the Smarter Homes website
Product certification
- For a background to how products are certified, go to the Consumer Build website
- Check with the Department of Building and Housing for changes to the Building code.
- Download a copy of ‘The Building Code Compliance Document Clause H1 Energy’
Building Resources
- For Green Building resources and design innovation, see the inhabit website.
- To view a case study of successful ventilation and double glazing, go to Waitakere NOW Home website
- You can find a checklist for regular maintenance of windows and doors on the Consumer Build website
- For independent and unbiased research, testing, consultancy and information resource for the building and construction industry, visit the BRANZ website.
Notes:
[1]Clark, S.J., Jones, M. & Page, I.C. 2005. New Zealand 2005 House Condition Survey. Wellington: BRANZ
[2] Standards New Zealand, 2006, NZS 4246:2006 Energy Efficiency - Installing Insulation in Residential Buildings, Wellington: Standards New Zealand.
