Ceiling insulation

Heat rises so, for most homes, making it easier and cheaper to heat properly starts with good ceiling insulation. Fortunately, ceiling insulation is relatively cheap and easy to have done in houses with accessible roof spaces.

Before you start

Here are some things to look at before getting started on your ceiling insulation.

Are you eligible for funding? If your house was built before 2000, you are eligible for funding to get your insulation installed - find out more about Warm Up New Zealand: Heat Smart funding.

Does your house have a ceiling space? If not, putting in insulation in your skillion roof or cathedral ceiling may still be possible - find out more about insulating a skillion roof/cathedral ceiling.

Check your insulation. A quick look in your roof space will tell you if you have any. If there is, you'll still want to check what state it's in - find out how to check if your ceiling insulation is adequate.

Get leaks and electrical issues sorted first. Check your roof and plumbing services in the roof space for leaks, and check that your electrical wiring and installations look in safe condition - you should sort any issues before you start insulating.

Consider using a qualified professional. This is the simplest way to get a good insulation solution, installed correctly and safely - find out more about using a qualified professional.

Is your home multi-storey? Only the upper ceiling between your home and the outside needs to be insulated. You don't need to insulate the ceiling between floors except above or below unheated rooms like laundries, workshops or garages. You may, however, want to insulate ceilings between floors with acoustic insulation.

Building a new house or addition? It's much easier to get your insulation done properly at the outset than fix it up afterwards. There are some specific considerations - find out more about designing to keep in the heat.

How much insulation?

How much insulation you need in your ceiling depends on how cold it gets in your area and on the thickness and condition of any existing ceiling insulation.

‘R-value' - the higher, the better

The R-value is a measurement of the insulation's effectiveness - the higher the R-value, the more effective it is at preventing heat loss.

The table below lists recommended minimum R-values for retrofitting ceiling insulation into existing homes. EECA recommends going higher if you can.

Notes:

• Ceiling insulation alone won't prevent all heat loss from your home - so don't forget about things like your underfloor insulation, blocking up draughts and getting good thermal curtains for your windows. Your home will also be cheaper and easier to heat with good heating.

• If you do have some existing insulation, check if the insulation is adequate.

Which insulation product?

There are two common types of ceiling insulation: bulk, which fits between or rolls over ceiling joists, and loose-fill, which is blown in. Loose-fill is not used in EECA's insulation programme as its performance can be variable.

Checklist for choosing a bulk insulation product

To get a suitable, effective ceiling insulation product, choose one that is:

• Fit for purpose. It should be intended for installation in roofs or ceilings.
• A high R-value. R-value is a measurement of the insulation's effectiveness - the higher the R-value the better.
• The right width. You need the correct width for the spacing of ceiling joists, roof trusses or rafters, if the insulation is to. be installed between these.
• For skillion roofs, the right thickness. You need to keep a 25mm gap between the insulation and the roof underlay.
• Compliant with Standard AS/NZS 4859.1. Look for the Standard AS/NZS 4859.1 compliance statement on the insulation packaging.

You may also want to check:

• Performance guarantees offered by insulation manufacturers on their products.
• The manufacturer's instructions for safely and correctly handling and installing the insulation, if you are thinking of doing it yourself.

>> Download the list of specific insulation products accepted for use under the Warm Up New Zealand: Heat Smart programme.

About bulk insulation

Bulk ceiling insulation comes in two types - segments, which fit between the joists above your ceiling, and blankets, designed to be rolled out across the top of the ceiling and the joists.

Blanket insulation that covers ceiling joists prevents extra heat loss through the timber joists. If you install segments between joists, you need to put in higher R-value insulation to make up for the heat that gets lost through the timber joists - this is reflected in the table of minimum recommended R-values for existing homes above.

When topping up existing insulation, it can be easier to install blanket insulation than segments where the existing insulation leaves insufficient room to properly fit segments between timber framing.

About loose-fill insulation

Loose-fill insulation is blown onto the ceiling. It can be an option for roof spaces where there is insufficient space to move around and install bulk insulation.

Be aware though that the safety, effectiveness and durability of the loose-fill insulation installation are very dependent on the quality of the insulation material, the installer's equipment and experience. Loose-fill insulation can settle or move around over time which reduces its performance and can create moisture problems if the insulation gets into contact with the roof or roof underlay along the edges of the roof space. Rigid open-ended collars must be installed around heat sources such as downlight fittings, chimneys, flues and unducted extractor fans to maintain required safety gaps and avoid a fire hazard.

Loose-fill products do not meet EECA's requirements for specific insulation products accepted for use under the Warm Up New Zealand: Heat Smart programme.

Installing ceiling insulation

Correct installation is absolutely critical if ceiling insulation is to perform properly and safely over its life.

Using a qualified professional

EECA recommends using a qualified professional, especially if you are unsure of how to access and safely work in a roof space. Look for an installer who:

• is competent with the New Zealand insulation installation standard NZS 4246; and
• has completed the insulation installer training of the Insulation Association of New Zealand (IAONZ) - see a list of graduates on the IAONZ website.

If your house was built before 2000, check out ENERGYWISE funding for ceiling and underfloor insulation - all installations under this programme are required to meet strict quality and safety requirements.

Doing it yourself

If you are considering the DIY approach, there is some good information available to help you install your insulation correctly and safely.

>> Find out more about installing insulation.

>> Learn about fire safety clearances for ceiling heat sources (downlights, chimneys and extractor fans).