Moisture control, air flows and ventilation:

Moisture control, air flows and ventilation:

To enable a home to be cost effective to maintain, dry and heat, you need to be aware of the effects on your family and your home in relationship to Moisture control, air flows and ventilation.

The good thing about this section of the report is that each paragraph has positive comment to make about the Positive Pressure systems that were tested in both NZ and the UK, The comments are made in relation to both the condition of the house and the well being of the occupants.

The homes in the UK had both a lower relative humidity (R/H) as well as lower absolute humidity levels in relationship to outside. Bare in mind during cold weather the UK generally has a lower outside humidity (or dampness) than we do in New Zealand, and less sunshine hours to warm the roof cavity.

Comments made in the NZ – EECA report:


“However, Stephen noted that the occupants were more enthusiastic about the effectiveness of input ventilation than the results would suggest. Those who previously had the highest humidity in their houses were the most impressed”


“Nevertheless, the study found that without exception, all participants felt that condensation within their houses was either significantly reduced or had disappeared entirely after the installation of the ventilation system.”

Both sections make comment on the general well being of the occupants.


“Some occupants also claimed relief from severe respiratory illness”


There was also a strong reduction in self reported health symptoms”

Many of the comments made in the Home Ventilation Report for the NZ – EECA report are talking about ‘Fresh Air’ being brought into your home. Often this ‘Fresh Air’ is polluted, full of dust, pollens, is cold and very often full of wind blown moisture.

If your existing ventilation system or ventilating process includes opening windows, uses a constant speed fan or manually variable control, does not have a filter or is a low quality filter, then you are very likely getting the wrong volumes of the worst quality air available. IE, to much cold air at night and or not enough warm dry air during the day, and or full of what you do not need or want.

“Description of Fresh Air”

Oxygen 20.94% – Carbon Dioxide 0.03% – Nitrogen and other inert Gases 79.03%

To “Ventilate a Home” in the simplest form, means opening windows, this brings in outside air which we hope will replace the stale moisture laden inside air.

By doing this we are hoping that the outside air is warmer and drier than inside (very unlikely) and this uncontrolled cold damp air will get into all parts of our home (again very unlikely).

Lets look at this again:

When we open our windows we bring in

What we need

–Air – Oxygen, Nitrogen, a little carbon dioxide and other gases

And what we do not want or need.

Use a ventilation System to Remove

–Dampness – wet wind
–Coldness – outside air temp


Why do we bring these unwanted pollutants in when we do not need them (generally it’s habit, a lack of knowledge, we haven’t thought it through, we don’t know how to keep them out or we can’t afford to do anything else).

Each one of these ‘pollutants’ cost us in one way or another – our time – our money – our energy – our health – a devaluing home or other resources to either kill them, remove them, dry them out or let our bodies cope with them in one way or another.

Ideally we only need clean fresh, dry and warm air to come into our homes – this will replace the stale, damp, polluted, air that we have manufactured just by living in your home.

The easiest way to do this is to install a well designed Positive Pressure home ventilation system this will give you fresh, dry, filtered, clean and warmed (when possible) healthy air for your family and your home.

“Hot Air is capable of holding more moisture than cold air”

That statement is correct, now think of this:

If the Air and the room are dry before they are heated they

will be cheaper to heat and

will become ‘a warm dry room’ not ‘a humid moist warm room’

When we have warm air holding water we end up with condensation on our windows then we generally see the condensationas the problem and we tend to stick to one thought and that is to remove the condensation. We could wipe it off, we could install a heat pump or we could install Double glazing. All these thoughts only mask the condensation problem they do not remove the moisture in your home which is causing the condensation.

What we forget is that this moisture (condensation) is everywhere in our homes, our carpets, our curtains, out timber, our beds etc. Our cold bed in winter is our hot sticky bed in summer, to remove and keep removing household moisture a ventilation system needs to run all year round to give you the best benefits.

The Need for Ventilation to maintain indoor air quality

The New Zealand Situation