How to properly insulate your home for winter
Monday 10 April 2007
With winter rapidly approaching, it is time to start thinking about heating our homes as efficiently as we can. The first step to doing this is making sure they are properly insulated.
The benefits of insulation are widely known - energy savings, and improved health and comfort for example - but many people do not realise that the way that insulation is installed has a major impact on its performance.
Poor installation, such as gaps as small as 2 mm, can reduce the performance by as much as 50%.
In New Zealand, there are about 900,000 homes built before insulation became mandatory in 1978. Many homeowners have installed insulation, but that could be up to 25 years old, so it pays to check it over to make sure it is doing what it should be.
An uninsulated house can result in significant heat loss with up to 35% of heat escaping through the ceiling, 25% through the walls, 26% through the windows, and 14% through the floor.
Here are some things to think about when installing insulation that will ensure you will get all the benefits.
Choosing the right product
The ability of insulation to stop heat escaping is measured as its thermal resistance or R value. The R value depends on the type of material and how thick it is. The higher the R value the more effective the insulation.
The R value you need depends on how cold it gets where you live. As a general rule
Zone 1 & 2 - North Island excluding the Central Plateau
| Roof | Walls | Floor | |
| Minimum | R1.9 | R1.5 | R1.3 |
| Average | R2.6 | R2.1 | R1.9 |
| Best (EECA recommended) | R3.3 | R2.6 | R3.1 |
Zone 3 - South Island and the North Island Central Plateau
| Roof | Walls | Floor | |
| Minimum | R2.5 | R1.9 | R1.3 |
| Average | R3.1 | R2.1 | R1.9 |
| Best (EECA recommended) | R3.5 | R2.6 | R3.1 |
Products available
There are many different products available, so choose the one that best fits your situation and matches your required R value:
- Fiberglass (glasswool) - this product is made from recycled glass, use protective clothing when installing.
- Polyester and wool - usually in blanket form. This product is easier to handle than fiberglass.
- Mineral wool - made from inorganic oxides or minerals, rock or slag.
- Expanded polystyrene - this comes in rigid foam sheets and can be used to insulate floors, walls and ceilings.
- Loose fill - insulation that is in the form of small particles or fibres that are blown into place. This can only be installed by professionals
- Reflective foil - can be used underfloors, but not in walls or ceilings as it does not meet the Building Code requirements for these applications.
Checking existing insulation
If you have existing insulation, check to see if it is damp. If it is, you need to remove it and start again.
Also, check that the insulation is flush with the joists – sometimes insulation that has been in place for many years looses its thickness. You can add more insulation over the top of existing layers, as long as there is no damp.
Older houses sometimes have loose fill insulation in the ceiling. Draughts can blow loose fill around over time. Have a look to see if it is uneven. If it is, level it out and add another layer of blanket insulation over the top.
General tips
- In walls, make sure that the cavity is large enough to allow the insulation to sit at its designed thickness. Don’t squash more in as this will reduce the overall R value. Insulation needs the air spaces in between the fibres to prevent the heat escaping.
- Allow a 150 mm gap around recessed light fittings, such as halogen down lights. This will reduce the overall performance of the insulation, but is necessary because of fire risk. It is a good idea to choose insulation with a higher R value to compensate.
- Before installing insulation in wall cavities make sure that you have underlay (for example building paper) in place. This stops the insulation being damaged by condensation.
- Make sure there are no folds or creases or gaps between pieces.
- Do not ‘tuck’ the edges in as the compression reduces the performance of the insulation
- Use off-cuts to fill small gaps around doors and windows.
- For ceiling insulation, leave a clear space of at least 25mm between the insulation material and the roof underlay, or the roof cladding so that any condensation that may occur will not be absorbed by the insulation material.
For more information on insulating your house visit : www.energywise.org.nz
Insulation standard
A new standard - NZS4246 : 2006 ‘Energy Efficiency – Installing insulation in residential buildings’ has recently been published by Standards New Zealand and is an industry first in New Zealand on how to install insulation.
Copies of NZS4246 : 2006 Energy Efficiency – Installing insulation in residential buildings can be purchased from Standards New Zealand. Visit www.standards.co.nz for more information.
ENDS
For further information contact EECA's Marketing and Communications Advisor, on 04 495 8255 or 021 941 140.