Types of ceiling insulation
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.
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. When you’re topping up existing insulation, it can be easier to install blanket insulation than segments because you can just roll it over the top of what’s there already.
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 - check the table of minimum recommended R-values for existing homes.
Loose-fill insulation is blown onto the ceiling. It can be an option if there’s not enough space in your roof to move around and install bulk insulation.
Loose-fill is not used in EECA’s insulation programme as its performance can be variable. Its safety, effectiveness and durability depend on the quality of the material used as well as the installer's equipment and experience. As it can settle or move around over time, the insulation can get into contact with the roof or roof underlay and cause moisture problems.
If you install loose-fill, you also need to install rigid open-ended collars around heat sources like downlights fittings, chimneys, flues and non-ducted extractor fans to maintain required safety gaps and avoid a fire hazard.
Checklist for choosing ceiling insulation
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 you’re going to insulate in between
- the right thickness (for normal and particularly skillion roofs) - you need to keep at least a 25mm gap between the insulation and the roof underlay
- compliant with the testing Standard AS/NZS 4859.1 – so you know the product works as stated. Look for the 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.