Suffering from condensation frustration? Do you wake up to windows laden with beads of water? Sick of wiping down your sills and glass every winter morning?

You’re not alone in your frustration. Damp windows are a familiar sight to many Kiwis, especially when the temperature starts to cool off. Condensation can be as light as a faint misting on the bottom edges of your window, or as severe as drops of water that run down the window and frame. Left untreated, this kind of moisture buildup can cause mould on aluminium windows and rot on wooden ones.  It’s typically caused by excessive moisture in the house, as a result of:

  • Poor indoor ventilation
  • Inadequate insulation 
  • Sub-par heating
  • Or a combination of all three!

Let’s crack the condensation code once and for all. Keep reading to learn about the six common culprits that cause damp windows, and how you can prevent them this winter. 

First things first, what causes condensation?

To you, condensation is the pool of water you’re forced to wipe down every morning.  But, in actual fact – there’s a more scientific reason condensation exists. 

Condensation is the process of water vapour in the air changing into liquid water. When warm, humid air (which contains water vapour) comes into contact with a cold, solid surface like a cold window, it converts into a liquid form, which then trickles down your window. Warm air usually holds more water than cold air, so when it condenses it becomes more noticeable on your windows. 

You may notice that in the winter, condensation cranks up a gear. This is because of the temperature difference between the cosy interior of your home, and the coldness outside which chills your windows. 

Water vapour can come from a range of sources. The top moisture makers in your home include:

  • Cooking
  • Hot showers
  • Drying clothes
  • Unflued gas heaters
  • Rising damp from floors

Thankfully, the moisture levels inside your home can be managed by insulating, heating and ventilating (more on this later!)

So, what are the common causes of condensation, and more importantly, how can you prevent it?


1. Your home has poor insulation 

The mysterious moisture on your windows could be caused by a lack of insulation in your walls, ceilings and floors. This is often a common cause of condensation in older properties. In fact, houses built before 1978 are unlikely to have any insulation at all. 

A properly insulated home is less prone to dampness, and is, therefore, drier and easier to heat. The recently introduced insulation standard states that a home should have both ceiling and underfloor insulation with a minimum thickness of 120mm in order to lower heat loss, reduce dampness and make homes more livable and heat efficient. 

So, make sure your roof’s insulation is more than 120mm thick, and sufficiently covers your ceiling lining and framing. If you’ve got suspended floors, look into installing insulation between the joists, or consider laying a ground sheet under the house to soak up excess moisture. If you’re up for a major refit, insulate your walls with a blown-in insulation solution or bulk insulation. 

We said ‘insulation’ a lot in the last paragraph – and for good reason! Proper ceiling, floors and wall insulation will raise the internal temperature of your house. Those cold surfaces where condensation was collecting? They’ll be warmed up in the process, reducing the chances of condensation build up. 

2. Your house’s orientation is off

Your home’s positioning might be why your windows are looking woeful this winter. If your property is positioned for optimal sunshine and breezy airflow, you’ll reduce the likelihood that condensation occurs on your windows.

According to Smarter Homes, an ideal home orientation means:

  • You strike the right balance of sun – especially in the winter or cooler climates
  • You’re sheltered from strong, chilly wind, but can take advantage of breezes to cool your home when it’s too warm 
  • Your home is built to make the most of natural light 

Well-placed, well-sized windows make the most of sunshine hours and allow for natural cross-flow ventilation. This lessens the temperature imbalance that causes condensation. 

We appreciate that it’s near impossible to change your home’s orientation unless you are building a property from scratch (in which case, your property’s positioning should be your primary consideration). Not to worry, we’ll cover some easy-to-implement condensation hacks next!

3. Your plant life is perpetuating the problem 

This one might surprise you – outdoor plant life near your windows can kick off a process called reverse condensation. This reverse condensation usually happens when it is hot and humid outside. When the air is cooler inside your home, it makes the surface of the glass cooler than the dew point. Plants release moisture into the air, and can therefore increase the chances of reverse condensation.

Indoor plant life can also contribute to condensation build up on your windows. If damp patches start to appear on your walls, or you start to notice more surface condensation on your windows near to your house plants then it might time to rehome them – ideally, somewhere away from your windows, both inside and out!

4. Your windows aren’t double glazed 

While older New Zealand homes usually have single glazed windows, these days, most new houses require double glazing windows to comply with the New Zealand Building Code. Given approx 21-31% of heat escapes through windows, it’s no wonder double glazing is a must.  Not to mention, if a window only has single glazing, the cool temperature on the outside transfers easily to the inside and condensation occurs rapidly.

Using two layers of glass panes, and a pocket of gas between the panes, double glazed windows reduce the rate of heat loss from inside the house. With less heat able to move through the tight air pocket, the room stays warmer for longer, and your windows stay dry, too. The warmer the glass surface, the less chance of condensation. 

If you’re after a budget-friendly alternative to double glazing, consider investing in double-lined, thermal curtains. But remember – make sure to open your curtains regularly. This will allow air to circulate against the windows, which dries out any excess moisture and ultimately prevents condensation from forming. 


5. Your indoor activities are increasing the moisture levels in your home

So, it turns out we all have a part to play when it comes to condensation. According to Energy Wise NZ, the average New Zealand family produces up to 8 litres of moisture in the home each day from activities like cooking and showering. That’s a whole lot of moisture, which can contribute to a whole lot of condensation on your windows!

Here’s our top tips for reducing the moisture levels inside your home: 

  • Eliminate moisture – where possible, dry washing outdoors rather than indoors.
  • Extract moisture by using extraction fans in typically damp rooms like the kitchen, bathroom and laundry.
  • Air out your home often – open doors and windows to create a cross draft, or use a ventilation system (we’ll dive into this deeper next)
  • Keep the home warm – insulation and heating reduces dampness, and lessens the risk of mould growth on cold surfaces.

6. Your home lacks ventilation.

The easiest way to control condensation is by reducing the chance of warm, humid air reaching cold surfaces. To do this, you’ll need to make sure your home is well ventilated. Ventilation allows stale, moisture-laden air to escape and fresh, dry air to enter.

According to Energywise, one simple way to reduce window condensation is to open multiple windows in your home for a short time period, every day. Plus, the ventilation standard for Kiwi homes says that a house must have openable windows or doors in the living room, dining room, kitchen and bedrooms.  

But, in the middle of an icy cold winter, ventilation can seem pretty-counter intuitive. After all, why would you willingly let cold air seep into your home, when you’re struggling to keep warm as it is? If you limit opening your windows in the winter so you don’t lose all your precious heat, you can prevent air circulating. Then, the damp air you end up with is much harder to heat. What a catch 22 indeed!

A positive pressure ventilation system is one way to solve this conundrum. A positive pressure system is a roof ventilation unit, installed in your ceiling space and ducted throughout your entire home. 

The unit in the ceiling space draws in the fresher, drier air from the roof. A fan then pushes the air out to the ducts and into the rooms of your home. As this fresh air is fed into your home, the movement forces the stale, damp indoor air out of the room. Because of this, the damp air isn’t able to settle on cooler surfaces like windows and has no time to convert into moisture. This reduces the chances of mould, mildew and condensation build up on your windows. 

7. Kick condensation to the curb, once and for all

Don’t let weeping windows dampen your mood this winter. If you’re concerned about the condensation build up on your windows, why not book a Free Home Assessment? An experienced HRV team member will take your needs and the needs of your home into account, giving you a total home solution that will keep your home dry and warm and rid your windows of condensation, too!