Condensation on windows — it’s a sight familiar to many New Zealanders over the colder months. Waking up to windows laden with beads of water and having to dry off sills and glass is the norm for many Kiwis, but what causes condensation? And why is condensation such an issue for Kiwi homes?

There are many reasons your home could be experiencing condensation. Below you’ll find useful information to understand why it happens and some condensation tips so you can combat it over the winter season. 

What is Condensation? 

Before you can begin tackling the issue of reducing it, it’s important to understand what causes condensation in the first place. So what is condensation and why does it mostly appear on your windows?

Condensation is a process that occurs when warm, humid air comes into contact with a cool surface — often a window, though it can be walls. Because the air contains water vapour, when it hits the cold surface it converts to liquid, taking the form of the familiar water droplets. Warm air can hold more moisture than cold air, so when it condenses it becomes noticeable on windows and walls.

An example of condensation is when you breathe warm air on a cool window or mirror. The result is the air condensing into tiny droplets of water which fog up the surface.

Boy drawing on a window with condensation.

The reason condensation is more prevalent during the winter months is because of the stark temperature difference between the cosy interior of your home (and warm air) and the coldness outside which chills your windows. 

While condensation can easily be seen on windows, the moisture can also be absorbed by your carpets, curtains, rugs and furnishings, which can leave them feeling damp. And, if damp is left to fester, it can cause mould and odour problems. 

What Causes Condensation? 

Along with understanding what condensation is, it’s also important to know what causes condensation by identifying the biggest sources of water vapour in your home. There are a lot of everyday household activities that produce water vapour but knowing what areas of the home might be more prone to condensation can help you work to prevent it.

Within your home, you’re probably well aware that the bathroom is a hot spot for condensation. This is because it’s a space that sees a lot of water in both liquid and vapour (steam) form, thanks to showers, baths and sinks. In fact, keeping ourselves clean produces around 1.5 litres of moisture per person, per day.

Another area that sees a lot of moisture is the kitchen, creating three litres of moisture per day thanks to all the cooking and one litre per day due to the cleaning of the dishes. Your laundry can also be a big contributor to moisture-laden air, with five litres of moisture per load being released into your home if you dry your clothes in an unvented room[1].

Pot on stove creating moisture

But it’s not just household activities and chores producing all this moisture, as we touched on earlier, us humans are moisture-producing machines as well. People can each produce 0.2 litres of moisture per hour when awake, and 0.02 litres while we sleep. And, if you add perspiration to the mix, it’s an additional 0.03 litres per hour, per person! This means a four-person home could produce around 11 litres of moisture through breathing in just a 24 hour period[1]!

While all of these causes of condensation can be fairly easy to identify in your home and day-to-day life, there are other reasons you could be getting condensation on windows and general dampness in your home. Water leakage from blocked, broken or leaky pipes or guttering could also be contributing. It’s not always easy to spot this issue, but checking that water is flowing correctly through gutters and pipes and draining away during heavy rain is a good idea. Additionally, if you notice particularly damp rooms, take precautions to make sure you don’t have a leaky pipe hidden out of sight behind a wall.

Damp ground underneath your home could also be a cause of excess moisture contributing to condensation. Energywise recommends all homes have vents on all sides of the house in the subfloor walls to allow ventilation so excess moisture doesn’t build up. Additionally, you can also have thick polythene sheeting installed as a ground moisture barrier to make sure the air between the ground and your home’s floor doesn’t get damp.

Another cause of moisture that you may not have considered is moisture that has been retained in your home’s building materials, such as timber framing, concrete floors and plaster. New houses can experience high internal moisture levels for up to two years after construction.

Ways to Prevent Condensation 

Even though condensation seems untameable, there are definite ways that you can prevent it plaguing your home this winter. There are two ways that condensation can be controlled: reducing humidity and reducing the chance of warm air reaching cold surfaces.

In order to reduce humidity as much as possible you need to ensure your home is well ventilated[2]. You can start by setting aside five to ten minutes per day to open windows and doors and air out your house. Ventilating like this allows stale, moisture-laden air to escape and fresh, dry air to enter. However, areas such as the kitchen and bathroom need extra ventilation, so making use of extractor fans or rangehoods is good practice. 

Person insulating home to prevent dampness

Having a well-insulated home is the best way to reduce the likelihood of warm air reaching cold surfaces. By insulating ceilings, floors and walls of a home, the internal temperature of your house will be raised. This means cold surfaces where condensation may have previously occurred will be warmed up, preventing the process from happening. Windows are also more likely to have condensation on them if a home isn’t properly insulated. Double glazed windows can help to prevent this, but a cheaper option is always good thermal curtains, along with effective ventilation. 

Short vs Long-term Solutions for Preventing Condensation and Damp 

Condensation and damp can be annoying issues for homes and there are various short and long-term ways you can deal with this problem. 

Now that you can identify major moisture-producing areas of the home, work to minimise how much will escape into your home. This can be achieved by drying clothing outdoors as much as possible, cooking with lids on pots and pans, and opening doors and windows daily to ventilate your home. Do note that these methods aren’t likely to totally reduce the moisture in your home and shouldn’t be considered long-term solutions. 

For a more long-term approach, making some modifications to your home will mean that you won’t have to make as many lifestyle changes to achieve a condensation and damp-free abode. Fitting your bathroom and kitchen with an appropriately sized extractor fan (or rangehood in the kitchen) will help remove a lot of the excess moisture during times when water or water vapour is being produced. 

Another permanent option is having a home ventilation system installed to help reduce or prevent condensation. A ventilation system will keep your home constantly ventilated so that stale, moisture-heavy air can’t settle and potentially cause mould. HRV ventilation systems are installed in your home’s roof cavity and work to draw in fresh air that is forced into of your home through a series of ducts. As this new air is pushed in, the stale air is forced out and reduces the dampness that causes mould, mildew and condensation build ups.

What Will the Healthy Homes Guarantee Act Mean for Ventilation and Insulation in Homes? 

With the introduction of the Healthy Homes Guarantee Act, rental homes must now meet a standard set out by the government in a push to make sure homes are warmer and drier for residents. While the standards are not mandatory for those living in a home they own, they can still be useful in learning what the baseline for a dwelling should be.

The insulation standard (which must have been met by 1 July 2019) states that a home should have both ceiling and underfloor insulation with a minimum thickness of 120mm in order to lower heat loss and make homes more efficient to heat. 

The ventilation standard for homes says that a house must have openable windows or doors in the living room, dining room, kitchen and bedrooms. Additionally, there must also be an extractor fan in rooms with a bath or shower, as well as in rooms with a cooktop.

From 1 July 2021, private landlords must ensure that rental properties comply with all standards within 90 days of a new tenancy. Failure to adhere with the new standards could result in the Tenancy Tribunal ordering a landlord to undertake work, or even financially penalising them up to $4000, payable to the tenant. So, it’s well within the best interests of all involved to meet the deadline on time.

It’s important to note that HRV might not be right for all homes, as in some cases we can’t install our solutions as needed. If you’re interested in exploring your ventilation options to reduce condensation, we’d be happy to help. Get in touch with the HRV team today to book a free home assessment with one of our knowledgeable professionals. The team will let you know whether HRV can help and if so, which solutions will be best for your home and family!