It most certainly does however in order for roof ventilation to work very effectively you need to have a balanced system – with an inlet and outlet vent of the same volume to equalize the air flow with a pair of ventilators to each zone of a roofspace and these ventilators are best situated within the roof covering, it’s basic physics -fluid dynamics – fresh air in stale moist heated air out.

Insulating a roof without effective roof ventilation can cause any amount of problems – when the Government Insulation Program was in full swing we received many complaints from recipients of this program complaining that since installing the insulation their homes were much hotter.

We neutralised their problems with effective roof ventilation.

To give you another example for heat increase after installing insulation – a home with a corrugated metal roof without ceiling insulation or even a vapour barrier under the roof sheeting (sarking) had our ventilators installed. The ventilators made 2° difference inside the home and the hot zone during the afternoon and evening was reduced by six hours.

The same house was reroofed having ceiling insulation and sarking installed and the same roof vents re-installed – after the insulation was installed the hot zone was only reduced by 4 hours. This is a significant difference would you not agree?

I can give you many other examples of the need for effective roof ventilation. Due to over insulation without effective roof ventilation a home in the Canberra suburb of Deakin experienced massive condensation problems to every wall in the house – due to over insulation. We remedied this problem by effective ventilation to the roof – the home had 5 pavilions – 5 buildings joined together by glass walkways – 2 ventilators were installed in each roof – result no more condensation.

At this point I would direct you to a blog on this site “Warning! Read Before You Design Your Next Housing Project”. There are many other blogs on this site regarding different methods of insulation, check them out.

To give another example for over insulating – sarking of roof tiles – sarking roof tiles is only necessary if your roof pitch is 15° or lower to avoid leakage, or if it is mandated in a bushfire area, however if you are in a bushfire area I would not suggest using roof tiles at all – my recommendation would be to use corrugated colorbond – see blog on this site – “Sarking Roof Tiles”.

I would also direct you to a report from Kelly Burke – from Consumer Affairs 26 September 2009. This full report is on this site in Case Studies & Reports regarding a massive condensation problem that ensued due to over insulation of a tiled roof without effective roof ventilation.


We send our Smoothline ventilators for corrugated colorbond to every state of Australia to solve the problems of condensation in winter due to over insulated houses – however Victoria, Southern NSW and Tasmania are by far the worst states.

Due to the new BAL ratings for bushfires this has further exacerbated the problem of condensation there can be relief with effective ventilation up to BAL 40, however in Flame Zone BAL FZ protusions in the roof are not allowed. So no roof ventilators in BAL FZ – so massive condensation problems in BAL FZ.

We believe that the ceilings should have no protusions -ceiling vents, downlights and especially bathrooms and kitchens that dump into the roofspace all should be avoided. Kitchens and bathrooms should be ducted through the roof to the outside atmosphere. That the ceiling be insulated and a colorbond roof to have a vapour barrier, preferably a blanket foil combination and for the roofspace to have an effective roof ventilation system. A tiled roof has no need to be sarked unless of course it is below 15° etc. The enclosed space is the inside of the home and the ceiling should be sealed off from the roofspace. Whether a tiled roof is sarked or is not sarked you will need an effective roof ventilation system.

The problem for ceiling insulation is, 5 days after continual heat the R value is compromised somewhat, allowing heat to enter the enclosed space (the inside of the home) this is the problem for summer without effective roof ventilation.

However in winter the number one culprit is condensation moisture, as around 25% of your home heating escapes to the roofspace. You definitely do not want a heated roofspace, this is further complicated by sarking and/or blanket insulation. Just imagine what happens with all the heat trapped in the roofspace between the ceiling insulation and the vapour barrier above – it could be raining in your roof – our ventilators have solved this problem as well as the summer heat problem, in winter the heated air that rises to come in contact with the underside of the roof covering holds a percentage of water vapour, this point of contact is called the Dew Point. At this point the heated air will condense and the moisture within will disperse and become water – it could be raining in your roof.

Whilst the worst problems are within metal roofs, the report from Kelly Burke from Consumer Affairs was a sarked tiled roof.

We believe that insulation is a valuable part of home comfort as long as it’s complimented with an effective roof ventilation system, this is usually recommended by most reputable insulation companies.

Some BLOGS on this site you may be interested in.
“A Well Insulated Home”
“Condensation Problems on Underside of Metal Roofs”
“Insulation for Winter”
“Roof Ventilation Energy Savings”
“Sarking Roof Tiles”
“A Message to Victorian Builders”
“Cavity Wall Insulation”.

In conclusion you can have all the pretty graphs and pictures to try to support an untruth – however the aforementioned cases regarding over insulation without effective roofspace ventilation. These are not hypotheticals they are –


You can take it from me with almost 6 decades in the roofing industry, I have seen all the horrible truths that can happen to roofspaces of homes without effective roofspace ventilation. Even the most ineffective roof ventilator will be better than no ventilator at all and most insulation companies understand the need and recommend to use some form of roof ventilation, for an insulation company to deny this fact is nothing short of criminal.

As far back as 1999 Mr Larry Little, Chief of CSIRO Building and Construction and Engineering said “Australian homes are a major contributor to greenhouse gases and Sick Building Syndrome. Some of todays’ homes are sealed so well to keep them cool in summer and warm in winter that fresh air change may not occur, it’s time we moved back to natural ventilation.”

You could also look on our Customer Testimonials to see what real people say about effective roof ventilation.

“Face the simple fact before it comes involved. Solve the small problem before it becomes a big problem” – Lao Tzu.

We leave you with a quote we often use “A corrugated metal roof without effective roof ventilation is like playing Russian roulette with a full magazine”. The same rings true for any roofspace insulated without an effective roof ventilation system.