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15 May 2024

Why is my house damp? 

We are heading into winter, and for many New Zealanders that means that they’ll start seeing condensation on the windows in the mornings, an unwelcomed guest during the winter months. It makes our homes feel cold and damp, which is a real problem in one in five Kiwi homes according to Stats NZ. So what is dampness, and where does it come from? We decided to get down to the nitty gritty to explain what is happening and why. 

It starts with moisture 

Simply put, dampness is caused by excess moisture. And so what is moisture, you may ask, and where does it come from in our home? Let's get down to the basics. 

Moisture refers to the presence of a liquid, especially water. Water in liquid form is puddles, rivers and oceans for example, but it also exists as gas in the air. When water is a gas, it is called water vapour, and this is the kind of moisture that we are interested in when we’re talking about healthy homes. 

You will be aware of water vapour when you breathe out on cold mornings or see a ‘mist’ on a river or lake. It also appears as clouds when you look up into the sky. Water vapour is what is created in your bathroom when you’re showering – but not to be confused with ‘steam’ which is water vapour at 100 degrees Celsius – like when it escapes out of a boiling kettle. 

Water vapour in the air is measured by humidity, a term that indicates the likelihood of precipitation (rain), dew, or fog. Warm air can hold more water than cold air, which is why it is often more humid in warmer climates than colder climates. There are three main measurements of humidity: absolute, relative and specific. 

Absolute humidity is the measure of water vapour in the air, regardless of temperature. 

Relative humidity is the amount of water vapour present in air expressed as a percentage of the amount needed for saturation at the same temperature or in simpler terms; how much humidity is present in the air, compared to how much there could be. 

Specific humidity refers to the mass of water vapour in a unit mass of moist air. It is usually expressed as grams of vapour per kilogram of air (or in air conditioning as grains per pound), and often used in meteorology. 

What is condensation? 

Water vapour in the air is invisible until it condenses, so when you breathe out on a cold morning, the warm moist air from your lungs hits the cool air outside and condenses to become visible. The vapour on a river exists because the temperature of the water is warmer than the air temperature so again, visible vapour is formed. This is the same effect in your bathroom shower. Warm moisture laden air rises up in the shower to join the cooler air in the bathroom. That becomes visible water vapour (not steam, unless you’re having a boiling shower!) – which then turn into condensation when it hits cooler surfaces like tiles, mirrors or windows. 

Water vapor and moisture exists in your home always. The average Kiwi family creates 8 litres of moisture every day by activities like breathing, cooking, drying laundry and showering. This is normal, and can be managed with proper insulation, sufficient heating when required and good ventilation – the three elements of the healthy home triangle. If not properly managed however, the moisture in the warm air condenses back to liquid on windows and walls. This is why our windows are weeping in the mornings after a cold night, and this is why it’s more common in winter. 

Moisture from the air can also get into drapes, carpets, bedding and clothing, and make them damp. Dampness can appear in any area that has an excess of moisture for any other reason as well, like dripping taps, broken pipes, even different kinds of building materials and much more. 

And if your home is left damp for too long, it can start to grow mould and mildew, something that is currently happening in a third of Kiwi homes. Not only can this cause serious health concerns for you and your family, but it is also damaging to your home – which often is a very large investment. 

What are signs of dampness? 

You’ll notice if your home is damp from signs like; 

  • Your clothes, carpets and curtains might feel damp or be mouldy 
  • Musty smells throughout the house, specific areas of the house or under the house 
  • Mould behind furniture, pictures, mirrors or on the walls 
  • Rotting wood in the structure of the house and window frames 

There are several different things you can do to tackle dampness, but making sure your home has all three elements of the healthy home triangle is fundamental. Proper insulation will make the heating process more efficient (and therefore cheaper!), and a well-insulated and heated home will improve ventilation effectiveness. Effective ventilation will bring in fresh, dry air into your home, which in turn is easier (and again cheaper!) to heat than damp air. 

There are different types of ventilation systems that can help improve the health of your home. Using a continuous extraction system with trickle vent will ensure all the stale air is pushed out  and replaced by fresh air that enters through trickle vent. There are balanced Ventilation system options as well that can be installed in new or existing homes therefore preventing the build-up of moist air that leads to mould and mildew and ensuring the house is well ventilated. 

Hometech’s range of ventilation systems covers all your ventilation needs, whether it be whole house ventilation or extraction ventilation for your bathroom, kitchen or roof space. 

Looking after your home is an easy way to make sure that you look after your family and stay healthy. If you want to know more about how ventilation, Hometech can help! Don't hesitate to give us a call on 0800 466 383


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