Are you waking up to wet windows? Condensation in homes can be a big issue, even when you can’t see it.

It can be avoided though. Learn more about what you need to know, and what you can do, here.

The topic of Condensation is getting a lot of discussion at the moment in the industry. At the time of writing this blog, there’s potential changes coming in the National Construction Code in 2021 (for NCC2022) related to Condensation, although it’s unknown exactly what they’ll be (drafts are out for comment at the moment).

However, as I’ve learned (from Andy Russell from the Proctor Group, who is doing a lot of education in this space), Condensation has been discussed as a negative factor for buildings and occupant health for many, many years (Andy brought up some information shared by the Australian Standards Board back in 1992, and some industry literature from the 1930s!)

It’s estimated that over 40% of buildings (including homes) in Australia are impacted by condensation.

It occurs because cold air can’t carry as much moisture as warm air, and when you get moisture levels that are too high meeting temperatures in building fabric that are too low, or there’s an uncontrolled flow of water vapour moving from a source to a region of cold temperature (like the shower steam meeting the bathroom mirror) then condensation can occur.

When this happens in your home, it’s often when it’s cold outside, and warmer (and more humid) inside, and you’re seeing condensation form on the inside of your windows.

You’ll be seeing it on your windows (because they’re non-porous and can’t absorb water), but it can also be happening inside the walls of your home, and in the roof space as well.

Best case scenario is that you have the correct construction, with the required barriers in your walls and roof space, and adequate ventilation to prevent the condensation, or enable this moisture to quickly dry out or drain away.

Worst case scenario, the moisture is being absorbed into your insulation, timber framing, or other building fabric, and not drying out … where it can then cause mould and general deterioration to your home (and potentially your health as well).

Given over 40% of buildings are dealing with this, you’re most likely very familiar with it. And it’s not limited to cold climates. Condensation is an issue for any climate and location.

So, how do you avoid condensation in your future home?

In Canada in the 1980s, and then New Zealand in the 1990s, leaky buildings became a huge issue in the property industry, with buildings unable to withstand weather conditions. There were large financial ramifications, and big moves were made in building codes to improve the situation.

As part of this, they developed the 4Ds of Weathertightness, and they’re a great framework for any project. The 4Ds are:

#1 Deflection

This is about how your home sheds water, through the design of the roof, the use of eaves, and gutters etc. Aim to design these things so you keep water off the walls of your home, as it will help you reduce the chance of water penetrating your home’s exterior (because cladding may not be completely waterproof). Ensure good flashings over windows etc.

#2 Drainage

Promote water to move away from the home, plus ensure conditions around the home don’t enable water to sit close to walls and foundations.
Cavities are included in your wall construction to provide space for water to drain behind cladding (and staying outside of your home’s interior). Vapour membranes and wall wraps prevent water from soaking your insulation or internal lining.

#3 Drying

Cavities in wall construction also provide an air gap that provides ventilation to evaporate water, or dry out any building elements that have absorbed water. Ventilation in roof spaces through vents in a controlled way (not whirlybirds) helps roof spaces dry and manages heat load to the home overall.

#4 Durability

Choose materials and products that are fit for purpose for the climate you’re building in and will last.

(You can read more about leaky buildings and the 4Ds in New Zealand here.)

In addition to keeping the weather out of our home, we also need to be aware that the various activities in the home can create a lot of humidity in our interiors.

We need to give that humidity a chance to dry out, otherwise it will be absorbed as vapour into our building envelope, potentially become condensation and make the inside of our walls wet.

It’s all ok if it can evaporate once in the wall cavity, or we can adequately ventilate or dehumidify our interiors. However, if you have a foil sarking on your walls that doesn’t allow vapour to escape from the interior, you could have some issues.

The volume building industry does not pay a lot of attention to condensation and its risks, such as dust mites and mould growth.

However, there are many people in our population dealing with chronic health conditions that are often dramatically improved or eliminated when their living environment is dryer and healthier.

There are houses all over Australia still being (legally) built without sarking on the roof, before metal roofing goes on. Look into those roof spaces of a morning, and you’ll see water dripping off the underside of the metal roof onto the ceiling insulation within the roof space.

Low pitch roofs that (due to the minimisation of space within them) don’t have adequate ventilation, and condensation can be a big issue in these instances if they haven’t been properly detailed.

We’re creating homes that are more airtight (which is actually good when done right).

It’s just that it’s happening in combination with a range of other factors. The increase in insulation, our huge use of air conditioning, lack of dehumidification, and not utilising natural ventilation: We’re living in big eskies, and not giving our homes the chance to dry out.

The wording of the National Construction Code provides some loop holes, and a lot of people just simply don’t understand the impact of their decisions or detailing (including industry professionals).

There are, however, many designers, architects and builders out there, who are very serious about this. And there’s products available that can seriously improve your home’s ability to minimise condensation risks as well.

Where can you get more information about Condensation?

Well, condensation is a big topic, but the 2019 “Condensation in Buildings Handbook” by the Australian Building Codes Board is an awesome place to start if you’re super keen to learn more.

A word of warning: it is a big read, but a worthwhile resource to get some nitty gritty info.

At the very least, check out the Design, Construction and Occupant Checklist information at the end of it.

You can then use it as a framework for discussions with your architect or designer and builder.

And you can work with your designer / architect and builder to check that all specifications are fit for purpose, and meet manufacturers’ requirements in how you intend to use them. And, then detail those selections (with product names / brands etc) in your specifications so that substitutions don’t occur during your build.

I will say this: it’s clear from the research I’ve been doing how important it is to choose your team well, to work with them very closely, and to be informed so you get the best outcome for your future home.

And, even before COVID, we were spending 80-90% of our time indoors. Now, that time is mostly in our homes (as opposed to our workplaces).

Condensation can seriously impact the health of our homes, and our health and well-being too.

Creating a healthy home that has a great quality indoor air environment, can dry out when it gets damp and minimises the impact of condensation, will support your health and well-being long-term.

And it will help with the durability of your home long-term too.

If you want some other resources for creating a healthy home, here’s some podcast episodes that may help …

Episode #100 | Healthy Interiors: Creating your low tox home | Interview with Melissa Wittig, Interior Designer
Episode #206 | How to Choose Greener Building Materials, with Druce Davey
Episode #96 | An Introduction to Building Biology | Interview with Narelle McDonald, Healthy Living Spaces
Episode #129 | How to create a healthy home | Interview with Kate Hamblet, Balanced Architecture
Episode #129 | Designing a sustainable new home or renovation | Interview with Kyle Macht, Macht Architecture
Episode #130 | A room by room guide to a healthy home | Interview with Kate Hamblet, Balanced Architecture
Episode #105 | What is Passive House (or Passivhaus)? | Interview with Daniel Kress of Smart Plus Homes

That was a long read, but I hope you found that helpful

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