The most efficient roof insulation for any building is good quality insulation batts installed with proper care in the ceiling. Insulation batts come in a choice of three materials – Glasswool, Polyester, and various blends of Sheep’s wool. Since the latter two are nearly twice the price of glasswool batts for the same R-value, we only supply polyester and sheep’s wool insulation where they are specifically requested.
Roof Insulation Products we use and recommend are AGI Big Batts, BRADFORD Gold Batts and KNAUF Earthwool Batts. All three are latest generation glasswool products with excellent insulating and non-allergenic properties, and all three are of the highest quality. All three also possess very good acoustic properties.
R-value is simply a standard of measurement for thermal insulation, and the higher the number attached, the greater the ability of the product is to impede the transfer of heat between its exposed surfaces. In Adelaide, the recommended R-value for ceiling insulation is R-3.5. Some homes in the Adelaide Hills will decidedly benefit from R-4.0 insulation in their roof. However, for the great majority of ceilings in the Metropolitan Area, R-3.5 batts of a good quality brand are quite adequate – and all the more so when the insulation is installed with the requisite care and precision.
The Performance and usefulness of any roof insulation is determined by two factors: the quality of the insulation product, and the quality of its installation. Both are important, and the insulation is not worth having if there is a deficiency in either.
The Quality of Insulation is partly a function of the material it is made of, and partly a function of its manufacturer. Loose-fill materials will inevitably compact with time and their usefulness can rapidly decline within a few years of installation. Some earlier insulation materials also had a tendency to crumble and disintegrate with age, and many homes of older vintage will find this to be both a major cause of high utility bills and a major source of dust in their living and sleeping areas. Ceiling batts in use today are almost exclusively made of recycled glass with insulating properties and a lifespan that are greatly superior to loose-fill and earlier insulation materials. The best of these modern batts will retain their efficiency almost indefinitely – they will not compact, crumble, shed fibres or disintegrate – and the products we use carry a manufacturer’s warranty on the retention of the stated R-value for a minimum of 50 years.
The Quality of Installation is solely determined by the patience and competence of the installer(s). Insulation installation is not an unduly complex task. However, when done with the requisite care and precision, it is a time-consuming process. The time needed to insulate the ceiling of a three bedroom home is 6 to 8 hours for two good installers. It can also be done over a weekend as a DIY project by anyone with a sharp knife, good balance, and a measure of manual dexterity. The main points of installation are these: (1) Where the batts need to be cut to shape, the cuts should be precise to achieve a snug fit; (2) Adequate clearances should be left around such ceiling fixtures as downlights, vents and flue pipes; and (3) No electrical cable should be covered over by insulation.