How can I avoid condensation on my windows and building structure?

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There are ways in which we can alleviate condensation in our homes. 

In essence, we have to lower our dew point, the temperature at which the water in our cup starts to overflow. We can do this by reducing the relative humidity or by warming-up our building itself, though often both are required in cold damp homes. Research by BRANZ has clearly pointed out that our homes are not cold because they are damp, they are damp because they are cold. By heating up the test spaces to a minimum of 18 degrees Celsius, in less than 1% of the time high relative humidity was an issue in that study. Meaning that proper heating of spaces eliminated 99% of the humidity issues in homes (1).

 

Different climates, materials and living stiles require different products for best results. Get in touch for a free consultation- we help you find what works best for you according to science, not a marketing message.

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1. Reduce the relative humidity

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Reducing the relative humidity in our indoor air to a healthy level (between 40% and 60%) is an important step. It reduces our heating bills, keeps us and the building healthy and decreases the dew point. We can lower the relative humidity in several ways:

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• Use more natural building materials and finishes that buffer moisture: they take it in during times of high humidity and release the moisture again during the daytime, as the relative humidity in the room lowers. Examples of such products are sheep wool or wood fiber insulation, sheep wool rugs, solid wood furniture or clay based plaster. Different studies have found that homes with lots of moisture buffering materials can save you up to 25-30% of your energy costs.

• Get more plants that minimize moisture in the air. Using plants like the Boston Fern, English Ivy, or the Peace Lily will help lower the amount of moisture in your air.

• Get a ventilation system. A ventilation system will replace the stale air, which has high relative humidity, with fresh air and reduce relative humidity. Please ensure a ventilation system with a heat exchanger to be selected for this. While it is very common in NZ to have a ventilation system that draws air out of the roof cavity, those systems do not comply with regulations for the NZ ventilation standard for indoor air quality.

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Let us be clear, to put 1 plant in a bedroom will not do the job, further it does not replace the need to either regularly open your windows or use a ventilation system. Using buffering materials just lessens the need for ventilation, which is particularly handy overnight if you do not have a ventilation system.

 

2. Warm-up your building

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A different way and often used in conjunction with lowering the relative humidity is to warm up your building surfaces. In double glazing, for example, the cold temperature is blocked at the outer glass, keeping the inner glass pane warmer and often above the dew point (though there are cases where the condensation still happens due to very high RH or on the aluminium window frame). Another way to decrease condensation on windows are exterior shutters- shutting out radiant cooling from the sky and keeping the temperature of the windows higher.

 

Warming up our building envelope is a way to reduce or eliminate condensation in our walls. It is important though that the water vapour has a chance to escape the building and will not get stuck and absorbed within the structure to cause structural and health issues. Many natural building materials like magnesium oxide wall boards, natural paints and insulation will do this. 

 

Insulating our walls will keep the parts inside the wall warmer; this is especially important with steel framing as steel gets much colder than, for example, timber. You should also consider to use more efficient heating sources that heat surfaces, drying those out and reflecting the heat into the air. They will often save you on running costs and also create higher comfort in our homes. See here for more info.

 

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