Condensation is a big issue for many homes in New Zealand and a major contributor to unhealthy homes and inhabitants

The 2018 Census showed 12.6% of New Zealand homes have an A4 sheet size, or more, of mould at times while 4.3% of homes always have an A4 sheet worth of mould. That’s a total of 316,300 homes (1)

Dampness (classed as when a home feels or smells damp, or has damp patches on the wall, ceiling, floor, or window frames (1)) occurred in 18.5% of households at times, with 3% saying it’s permanent. That’s 402,394 New Zealand homes experiencing dampness!!

If we calculate based on 2.35 per dwelling (average number of people per dwelling – 2018 Census (1) a whopping 945,626 people are at risk of being adversely affected by dampness where they live.

Beacon Pathways research released in 2021 shows that “injuries and hospitalisations caused purely by cold, damp, mouldy, or dangerous housing could be costing New Zealand more than $145 million each year in ACC claims and hospitalisation costs.” (2).

How does condensation occur?

As the temperature outside drops, the air cools, causing air surrounding the glass to cool and humidity (amount of water vapour in the air) to rise. If the air is cooled enough, the ‘dew point’ (the temperature at which air is cool enough to release moisture) is reached and condensation forms.

Water vapour will appear as condensation if it touches a surface that is cooler than the air temperature. Condensation is typically worse lower down the glass, due to the convective flow of the air making the glass cooler the lower down you go. The cooler the glass, the more condensation

With a temperature inside the home of 20°C and a humidity of 70%, what temperature will it need to be outside before the glass in your home will begin to show condensation?

Single glazing – starts to show condensation when the outside temperature reaches around 8°C.

Standard double glazing – starts to show condensation at around 4°C

SuperTherm Warm™ double glazingwill need to drop to around -6°C before condensation will begin to form

Condensation triggers.

The extent of condensation is determined by 3 variables:

–  Glass temperature – how cold the glass is, affected by outside air temperature

–  Room air temperature – warmth in the room

–  Room humidity – how much moisture is held in the air within the room (consider the things causing moisture in the home)

We tend to underestimate how much impact our day-to-day tasks have on the moisture in our homes. Just look at how much moisture is produced by these activities!!

The relative humidity of a room is recommended to be in the 40–60% range so not all moisture is bad, but these everyday tasks could be producing much higher levels of moisture in the air which in turn increases the risk of condensation occurring.  To make a healthy home we need to insulate. Double-glazed windows and doors work in tandem with other solutions (e.g., ceilings, floors, and walls) to provide that insulation

Reducing condensation with double glazing.

While our comfort level increases indoors, so does the prospect of condensation.  Choosing genuine double glazing reduces the chance of condensation forming, as the amount of heat lost through the glass is reduced, the inside of your house stays warmer which in turn keeps the inner pane of the double glazing substantially warmer.

By double glazing:

–  More heat is retained inside the home longer, and the inside-pane of your double glazing stays warmer.

–  Warmer glass = less air chill (e.g., there is up to an 81% reduction in heat loss by using SuperTherm Warm™ double glazing meaning the glass temperature and room temperature will be kept much closer)

–  It is unlikely that the air will chill to dew point (the point at which it condenses)

–  Cold draughts are eliminated

Reduce the impact of condensation in your home by choosing high-performingSuperTherm Warm™ Low E double glazing with argon

Other considerations.

While changing from single glazing to double-glazing will make a significant difference, there are other things to consider that impact the likelihood of condensation occurring.

There are three important factors to consider:

1. How much moisture is within a home and how is it ventilated

So many things within our homes produce moisture so it is wise to ensure regular ventilation is provided. Opening windows for even 15 minutes a day may be all you need to keep your home at a healthy humidity level.

2. Joinery Type

Timber windows and doors will naturally be less likely to have condensation form on them, whereas aluminium frames are likely to have condensation still occur (on the metal frames).

3. Dew on the Outside

Better insulating glass can result in dew occurring on the outside glass pane. This occurs in mild conditions where there is no breeze due to the outside glass being cooler than the outside air temperature. Dew on the outside demonstrates that the double glazing is doing an excellent job of retaining the heat within the home and it will clear quickly as the heat outside begins to rise.

Keeping your home well-ventilated.

What is the best approach when it comes to ventilation? Beacon Pathway recommends: (3)

–  Remove unhealthy moisture-producing items, e.g., unflued gas heating etc.

–  Insulate

–  Activate ventilation in key moisture-producing zones (e.g., bathrooms, kitchens with extractor fans)

–  Activate passive ventilation in other areas (e.g., have a window slightly open in bedrooms)

Dehumidifiers also draw in moisture-laden air, extract the water, and recycle the dry air back into the environment.

Positive pressure ventilation systems.

Positive Pressure Ventilation Systems are often considered a healthy and effective means to ventilate the home and keep an ambient temperature throughout. Beacon Pathways explains that “These systems bring filtered air from the roof space into the house through a single, or multiple, ceiling vents. The pressure forces the stale air to leak out through gaps, windows, and doors.” (4)

To be truly effective, air should be sourced from the outside, not from the roof space, as it’s not proven that home ventilation system filters effectively reduce the contaminants in the roof.

The New Zealand Building Code requires homes to ventilate using outdoor air to maintain air purity. Ventilation systems that draw air from the roof space and not directly from outside do not comply with ventilation standard NZS4303:1990 “Ventilation for acceptable indoor air quality” and therefore cannot be used to comply with the Building Code Acceptable Solution for ventilation.