We like to keep our homes warm in winter and cool in summer. With energy efficiency star ratings being mandated in most areas of Australia, thermal insulation is increased to the point of going overboard to reach the star ratings and create a well-insulated home.

Some of today’s new homes are so over insulated to keep them warm in winter and cool in summer with the flow on ramifications for excessive condensation problems to occur within the walls and the roofspace for example –


This type of insulation usually blown in is contradictory to having a cavity at all. A cavity is there for a reason and as air is the best insulator of them all leave the cavity alone. The other concerns for cavity wall insulation are you bring the outside wall into contact with the internal wall.

The ramifications for this practice are the possibility for penetrating dampness and unfilled air pockets leaving cold spots on the inside walls. This will attract condensation. With moisture in the insulation cavity filled walls can cause corrosion of the metal ties that tie the brickwork to the timber frame.

So as a cavity is there to keep the outside wall from contact with the internal wall for the obvious reasons, unless of course you use a board type insulation and leave some cavity, leave the cavity alone – it is there for a reason.

Then you have your ceiling batt insulation with R4’s giving the best result any more is going over the top, pardon the pun.

Blown in insulation is not a good option due to it moving and bunching up. Don’t contemplate polyurethane spray foam insulation due to the possibilities for off gassing and follow on SBS, see Blog on this site “Is Polyurethane Spray Foam Insulation Safe”.

So to keep as much heat as possible in the home as you can for winter and keep as much heat out as possible in summer R4 ceiling batts are your best bet.

Whilst ceiling insulation stops the heat from the suns rays to a point from entering the home in summer and most of the heat from the home in winter, this protection is limited and the performance will at some time become compromised. Some heat will be lost to the roofspace in winter and after 5 days of constant excessive heat in summer, heat will be allowed to permeate the ceiling insulation and enter the home from the roofspace, without effective roofspace ventilation.

So what about vapour barriers under the roof coverings. With a tiled roof unless the roof is pitched at 15° sarking may have an effect for the possibility for roof leaks. However is pretty much useless and is more than likely counter productive as an insulator, as without an effective roof ventilation system the vapour barrier will more than likely cause condensation and in summer will lock heat in between the ceiling and the roof covering.

Whilst with a corrugated metal roof quite often referred to as a colourbond roof it is necessary to have a vapour barrier, the best type of insulation for a corrugated metal roof is the blanket combined foil now generically known as Anticon.


For a tiled roof have R4 ceiling batt insulation or equivalent installed on the ceiling, sarking (or vapour barrier) will only be of any use to keep outside dust from entering the ceiling space and will have a negative effect for condensation problems and hardly any value as an insulator, without an effective roof ventilation system.

For a corrugated metal roof install R4 ceiling batts or equivalent as well as at least 50mil blanket foil insulation under the roof covering.

With both of these roof coverings an effective roof ventilation system will be necessary to ward off the problems of condensation and for SBS.

So we have addressed the need for insulation in the roofspace and have covered the negativity of cavity wall insulation , so what more can we do to insulate our home.


We have addressed the need for bulk insulation what else can we do to keep warm in winter and cool in summer?

Plenty - we could start with double glazing of windows, too expensive you say. So we go onto the next best thing, heavy curtains. Most heat loss and gain are through the windows – so heavy curtains are going to help heaps. Moving onto gap leaks in the home these need to be sealed up, gaps around doors and windows – use draught snakes under doors.

Gaps in the ceiling – remove or seal up ceiling vents and seal around all protusions in the ceiling, get rid of downlights. Air leakage can cause up to 25% heat loss in winter.

A common misconception is to close internal doors in winter this can have a very negative effect for condensation problems, especially in bedroom areas. Rug up to keep yourself warm in winter and dress down for the summer.


Cover the windows. This is a necessity in summer with shutters or blinds, shutters are not as good as blinds as shutters do not shade the brickwork below the windows and are quite expensive, canvas blinds are inexpensive and work brilliantly lasting for 15 years or longer, best buying are the lighter colours white etc. These will reflect the heat away from the home make sure that they are 4 inches wider than the window either side and that they can be drawn down past the window.


Strategically plant deciduous trees facing walls where the sun lasts the longest, so the walls do not absorb significant heat within the summer months. You will therefore have good shading coefficient and with the autumn fall you will have excellent warmth with the winter sun. Planting trees strategically helps the shading of roof and wall surfaces, this is important to reduce summer heat gain. Planting ground cover plants instead of paths and pavers will help to keep the ground surface temperatures down and plant small shrubs wherever possible.

So there you have it – insulation goes beyond bulk insulation. Regarding the over insulation of homes see Blog on this site “Warning! Read Before You Design Your Next Housing Project”.

Whether you insulate or not you will need an effective roof ventilation system to remove all the nasties of the roofspace to keep you cool in summer and dry 24/7 all year round.