Home Ventilation Systems Assessment

My Comments on the

Home Ventilation Systems Assessment

Report done for the EECA in January 2009

Firstly I welcome and look forward to comments made from all sides. The EECA and associated people, or any members of the public, who want to ask questions, or who have there own experiences to comment on.

One thing I have found is that people without actual experience of a well specified ventilation system, often have understandings that are based on theoretical information rather than actual experience.

I believe that it is about time that this discussion started, as it will help more people understand what the benefits are of installing a correctly specified ventilation system that is best for both the specific home in question, how the home is heated and the area in New Zealand where the home is situated.

Over the next few weeks I will comment on various parts of the ‘Home Ventilation Systems Assessment’ and look forward to seeing the discussions that continue.

This report covers many good explanations and comments:

For example, section 2.1:

“The need for ventilation to maintain indoor air quality

It has long been recognised that houses require a periodic refreshing

of air in order to maintain air quality, reduce moisture, control

moulds etc. Minimum ventilation rates of one complete air change

every 2-3 hours (i.e. 0.3-0.5 air changes per hour (ac/h)) have generally

been accepted as international norms, with higher rates necessary

where houses have open flame combustion appliances.”

This is why we need to ventilate our homes the minimum requirements to maintain Indoor Air Quality, not removing excess moisture built up over years and/or to give some warmth when available.

What has been happening over the last number of years (your home has existed for many years, possibly 40 years or more) is that many homes have been getting damper and damper as successive people have lived in them. Each family has done their best to try to keep the heat in, with the cold and the damp drafts out, (Sometimes when you open your windows the ‘fresh air’ entering your home is colder and damper than what you have inside).

Each family of 4 people will put between 30 and 60 liters of moisture (depending on the study or website you read) into the home each day, the home then has to either absorb or remove this water. Let’s assume that on average, the home manages to remove most of this water and ultimately absorbs only 5 Liters of moisture each day.

This means that in just 1 year, the home could absorb about 1780 Litres of water. This occurs in such small quantities that we do not even know it is happening. Therefore over 10 years the home could have absorbed about 17600 Liters. I know even this may be an extreme example, so how about this, over time your home had an extra 100 Litres of water to heat before it could heat you. Firstly it is going to take longer to heat the home to make you feel comfortable, secondly it’s going to cost you a lot more to heat it, thirdly it is going to be a cold damp home. This is without the mould, condensation and illnesses.

Consequently, the moisture levels in most homes have increased dramatically over the years, making our homes harder to heat and keep dry especially in the winter, and then hard to keep cool (ie, not humid) and comfortable in the summer.

That covers the homes built before we started to insulate them let alone seal these homes to stop drafts and keep the heat in, and even more recently added the requirement to double glaze all new homes.

Sealing, Insulating and Double Glazing, has reduced the natural air changes per hour down to less than 0.20 ac/h in some cases, especially homes being closed up for longer periods of time as they are these days, and with this the Indoor Air Quality (IAQ) is getting worse and therefore the moisture content increasing.

I’ve been in some very cold damp homes that are less than 1 year old. All that was needed was a positive pressure ventilation system which improved the comfort levels for the owners, improved the condition of the home and resulted in lower energy bills.

This is where a well controlled, correctly designed, forced (positive pressure) ventilation system is an advantage they work well in either the older style of home the newer homes as this then enable’s the home to be correctly ventilated in a cost effective manner.

With the New Zealand Government implementing funding to insulate house’s built prior to the year 2000 we will find more homes becoming far more air airtight than they have ever been and they in turn will need a quality, correctly specified home ventilation system to keep the home fresh and remove excess moisture.

Can you remember the homes that had wooden window frames replaced by aluminium and then the condensation problems got worse?

Download a copy of the EECA Home Ventilation Report and have a read, don’t make any specific decisions but do think through what the report says. Hopefully I’ll explain many of the relevant aspects of the report over the next few weeks.

Please read the following pages and if you want ask questions or make comment use my easier ventilation blog.

The Need for Ventilation to maintain indoor air quality

The New Zealand Situation

Moisture control, airflows and ventilation