Managing condensation – an insulation and ventilation issue

by | Jul 14, 2022

Condensation continues to be an increasing problem in homes and can often cause mould growth which leads to damp, rotting walls and window frames, while also destroying furniture and personal items.

In response to this on-going problem the National Construction Code (NCC) was updated in 2019 with a new section of the code implemented – titled ‘Condensation Management’. The updated code remains of significant interest to the hardware and building industry because of ongoing implications when installing both insulation and ventilation products.


What is condensation?
Air holds water and when air cools it has a reduced capacity to hold water as vapour. This is when the vapour can drop out and form liquid on surfaces.

Why is condensation an increasing problem?
The activities that are conducted within the house daily, including cooking, washing—and even breathing—cause condensation. Houses are more airtight than ever before which is why water vapour build up is on the rise. This is particularly an issue in the southern states of Australia.

What are the Condensation Management provisions trying to achieve?
The new provisions are attempting to achieve several things including having buildings constructed dry, resisting rain and groundwater, managing water vapour in the house—and ensuring any water can dry out quickly.

What problems are created by condensation?
Condensation can form on building materials and cause mould or rot. High humidity can cause many health problems including increasing microbial infestations (such as dust mites), affecting asthmatics and increasing allergic reactions.

While recent changes to insulation requirements (under clause 3.8.7.2) are generally well understood and complied within the different climate zones, it seems that changes to ventilation requirements (clauses 3.8.7.3&4) are probably less understood. In essence, new ventilation requirements entail exhaust fans from bathrooms, toilets and laundries to be vented externally.

If vented into the roof cavity, there are some significant additional requirements around venting out the roof cavity, depending on the pitch of the roof, according to the new requirements.

3.8.7.3 Flow rate and discharge of exhaust systems 
(b) Exhaust from a bathroom, sanitary compartment, or laundry must be discharged— 
(i) directly or via a shaft or duct to outdoor air; or 
(ii) a roof space that is ventilated in accordance with 3.8.7.4. 

3.8.7.4 Ventilation of roof spaces 
(a) Where an exhaust system covered by 3.8.7.3 discharges into a roof space, the roof space must be ventilated to outdoor air through evenly distributed openings. 
(b) Openings required by (a) must have a total unobstructed area of 1/300 of the respective ceiling area if the roof pitch is more than 22°, or 1/150 of the respective ceiling area if the roof pitch is not more than 22°. 
(c) 30 per cent of the total unobstructed area required by (b) must be located not more than 900 millimetres below the ridge or highest point of the roof space, measured vertically, with the remaining required area provided by eave vents.

The 2022 changes are yet to be finalised, however earlier drafts suggest that the Australian Building Code Board (ACBC) is probably likely to tighten these provisions further.

AHJ recently spoke with Rohan Harry, Managing Director of Partner Pacific. Since 2009, Partner Pacific has been providing residential HVAC solutions under several brands including Accord, Pacific Air, McMaster Ventilation and Alpine Ventilation. 

While it is currently still allowable to discharge fans into the roof cavity and then ventilate the roof cavity out, according to Mr Harry, in reality this is rarely now done. 

“The requirement for openings totalling 1/150th of the roof space area in most homes creates a time, cost and aesthetics problem that is usually best avoided by directly venting out fans via the roof, wall or eave,” Mr Harry said.

The new requirements are now causing extra headaches for builders because they have had to source different products from different supply channels including plumbing, electrical and hardware, Mr Harry says many are finding it challenging. 

“We believe that the hardware and builders supply channel is the natural location for builders to look to find a complete solution in one place. However until recently the channel has mainly had access to DIY type products only—and have not had the range to compete,” he said.

Partner Pacific has now addressed these challenges by putting together a complete solution under the Alpine Ventilation brand for roof, wall and eave vents, ducting and accessories. 

“When developing the new solutions, Partner Pacific’s focus has been on developing a product range that is Bushfire Attack Level rated (BAL), easy to install, aesthetically pleasing, clearly packaged—and is cost-competitive. This solution works equally well for both exhaust fans and rangehoods which also require external air extraction. It also suits most DIYer needs,” Mr Harry said.

Since the new solution was launched last year, the range is now available on chargeback at the Independent Hardware Group (IHG) and is also gaining momentum at Hardware and Building Traders (HBT) and NatBuild.

Whilst these condensation management provisions can be challenging for the builder, Mr Harry says this is also an opportunity for retailers to help solve an issue and strengthen builder relationships.  

“It can also help businesses grow—as we estimate the average cost of compliance to these provisions is approximately $500 per new home. In these challenging conditions, any opportunity to grow is critical,” he said.