Frequently Asked Questions
Why could indoor air quality be a problem in our homes?
Our homes and offices may be becoming ‘tighter’ with less free air movement with the outdoors. This is due to:
- Improvements in building techniques and styles (concrete slab-on-ground construction) producing ‘tighter’ buildings;
- Changes to building regulations to increase energy conservation (insulation and design regulations);
- Demand for greater comfort during very warm or cold periods;
- Need to reduce the intrusion of external noise and/or air pollution;
- Increased demand for privacy; and
- Increased demand for security.
Indoor Air Quality Facts
- The U.S. EPA. studies show that indoor air can be 2 to 5 times more polluted than outdoor air.
- “Occupants of new Australian homes may be exposed to up to 20 times the maximum allowable limits of indoor air toxics, an Australian first study has found.” (CSIRO media release)
- We require between 8,000 and 10,000 litres of air each day.
- We spend more and more of our time indoors. More than 90% according to the C.S.I.R.O.
- Moisture, a key ingredient in indoor air pollution, is generated mainly from our activities within the home. These activities include: Cooking, Washing, Bathing, Respiration and Perspiration ( adults add about 2 litres of moisture to the airstream everyday), etc.
- Outdoor pollutants (car fumes, pollen, dust,) can also enter the home and become concentrated there.
Why is it important to ventilate?
Ventilation is the key to improving indoor air quality!
“Indoor air quality is influenced by two major components: the amount and quality of outdoor air getting in, and indoor sources of emissions.”*
|Contributing factor to indoor air quality||Percentage of cases|
|Contamination from inside the building||16|
|Contaminants brought in from outside the building||10|
|Building material contamination||4|
|Cause not determined||13|
The above information comes from the Australian Government Air Toxics website.
Ventilation assists in controlling relative humidity which:
- controls dustmite and molds
- reduces lifetime of airborne viruses and bacteria
- controls off-gassing from building materials and furnishings.
Ventilation dilutes and removes harmful airborne pollutants, and
Ventilation replenishes oxygen levels:
- to provide adequate levels for occupants to breathe
- and to ensure gas fired appliances burn correctly.
Why “Natural” ventilation (using windows and doors) doesn’t always work
- The weather is unpredictable, ie. too windy, no breeze, too cold or hot,
- Poor location of doors and windows often restricts good cross ventilation,
- Indoor temperature control is lost when windows and external doors are left open,
- Windows don’t filter (dust, pollen, outdoor pollution and noise), and
- Home Security can be compromised.
What causes indoor air pollution?
Air pollution in the home is often misunderstood or underestimated.
Since the mid nineteen eighties, building scientists have had to come to grip with the terms Sick Building Syndrome and ‘Building Related Illness’. The first complaints relating to illnesses associated with the indoor environment came out of the workplace and included problems such as migraines, nausea, sinus problems or even worse.
Now, these same scientists are beginning to focus on residential buildings and they are finding even worse pollution problems right inside the home. What is supposed to be a safe haven for the family, has turned out to be an extremely unsafe environment in terms of occupant health.
Close to 250 chemicals are used in the building materials that make up a house. With the introduction of new household products like cleaners, personal care products and simple things such as ‘air fresheners’, we are building up a substantial arsenal of chemicals in our homes. Warm and humid conditions in the home allow a phenomenon known as ‘off-gassing’ to occur. Chemicals such as formaldehyde and Volatile Organic Compounds which are in many of the building products in the home leach out of the products in a gaseous form creating a toxic, chemical soup we live in, day in and day out.
To help you identify the pollutants inside your home, see the Pollution Sources List below.
|moisture|| pressed wood furniture |
|insect repellents||dry-cleaned clothes||house dust mites|
|personal care products||air fresheners||stored fuels|
|tobacco smoke||carpets||pressed-wood subflooring|
|drapery||open fireplaces||household chemicals|
|moulds and mildews||plant soil||rubbish bins|
|unvented clothes dryers||pesticides||and|
|fixed vents which allow pollen, dust, humidity, noise and other pollutants to enter from outside.|
Do moulds and fungi increase our risk to respiratory illnesses?
From ABC Radio National an interview by Rae Fry of the Health Report with the head of the Environmental Division of Finland’s National Public Health Institute – Dr Aino Nevalainen.
” Now to a subject that doesn’t get a lot of attention, probably not as much as it should. The quality of indoor air. Most of us spend 80% to 90% of our time inside, but how much do we know about the effects on our health?
A big study has just been done in Finland about fungi and mould in indoor air. And the researchers found that the rates of respiratory conditions, like sinusitis and flu are affected. It’s not older buildings with that patch of rising damp in the corner, that we’re talking about. In modern buildings, moisture can get trapped inside walls where you can’t see it; and in houses these days, there’s so much water going in and out, for showers and laundry, that leaking pipes can be a problem. ”
Why are Relative Humidity (RH) levels significant in your home?
It is accepted that the indoor relative humidity often exceeds outdoor relative humidity. This is mainly due to activities within the home ( showers, cooking, washing, dryer, etc)
|The optimum RH zone for the wellbeing of the building as well as the health of its occupants is between 30 and 55 % relative humidity. |
Outside of this range the growth of bacteria, fungi, viruses as well as increased chemical off-gassing and ozone production is promoted.
Allowing outside air to enter the house through fixed vents (uncontrolled ventilation) or the use of windows and doors will only improve humidity levels in the home occasionally. However, the relative humidity level of the outside air is often too high or too low to create a healthy indoor environment. (see RH Levels Chart below for Sydney and Melbourne.)
To add to these problems, on still days insufficient airflow occurs and so pollution levels can increase in the home. Windy days could provide sufficient air changes to remove indoor pollutants, however comfort and energy costs can also be compromised by outdoor drafts reducing the effectiveness of heating or cooling.
A phenomenon known as ‘Short-circuiting’ can also reduce the effectiveness of ‘natural’ ventilation through fixed vents. This occurs when fresh air flowing in through fixed vents is not able to flow throughout the entire home. Long hallways, closed doors and other barriers limit the flow and mixing of air. Also much of the fresh air entering the home can often leave through another vent before thoroughly mixing with the indoor air. The result is ‘dead spots’ where air is stagnant or exchanged less often.
Another disadvantage of the fixed vents system is the uncontrolled entering of pollen, and traffic pollution into the indoor environment together with the fresh air.
The above problems can only be solved by creating a well sealed building envelope and introducing a balanced mechanical ventilation system. This will give the occupant full control over indoor air quality, relative humidity and comfort levels in the home.
These levels are monthly averages. Readings are taken at 9 am and 3 pm. Statistics on February 3, 1997, For long-term data for any location in Australia see the Bureau of Meteorology
Note – most months register in both cities at a level that is above the optimum (healthy) zone of 30% to 55% RH.
If you suspect unhealthy conditions in your home due to excessive humidity, then there is a tool known as a Thermo-Hygrometer to find out what is going on. This handy and healthy tool registers (digitally) indoor and outdoor temperature and indoor relative humidity levels. It memorises the minimum and maximum temperature and relative humidity readings as well as providing a read out of present conditions. Using a Thermo-Hygrometer is the best way to learn about and understand your indoor environment.
* Canadian Home Builders Association, Building Manual, section 2: Aspects of Building Science.
* Residential Indoor Air Quality & Energy Efficiency. Peter du Pont & John Morrill,
American Council for Energy Efficient Economy
* Australian Bureau of Meteorology
What are the main sources of humidity in our homes?
|The volume of humidity in the air produced by various household tasks|
|Activity (for a family of 4)||Litres/Week|
|Cooking (3 meals a day for one week)||6.3|
|Dishwashing (3 times a day for one week)||3.2|
| Bathing (0.2 litres per shower) |
(0.05 litre per bath)
|Washing (per week)||1.8|
| Drying clothes indoors or use of a dryer without |
an external vent (per week)
|Floor cleaning 30.5 m2||1.3|
|Occupants normal breathing and perspiration||38.0|
|The total volume of humidity per week||63.0 Litres|
What are the key steps to improving Indoor Air Quality?
There are 3 key elements to solving indoor pollution problems and creating a healthy indoor environment in the long-term. They are:
The first step to a healthier home is to eliminate offending chemicals from the indoor environment. This can be as simple as removing old paint pots, cleaning chemicals, etc from under the sink. When dust mites are a problem, eliminating products such as carpets and curtains can be of great benefit. Using paints that do not contain any VOC’s (such as the Dulux Breath Easy paint) is definitely a major step in the right direction.
If products can not be eliminated from the house for whatever reason, it will be necessary to separate them from the inside environment and our airways. This way, the chemicals, and their off-gassing cannot reach our lungs and therefore pose little risk to our health. An example of separation is the complete laminating of the kitchen cupboards, doors and benchtops. By laminating all sides, the formaldehyde, present in the medium density fibreboard (MDF), will be trapped and will not be released into the environment.
is the use of fibreglass insulation batts. The ADA technique (Airtight Drywall Approach) ensures that any fibres stay where they belong: behind the plasterboard. This technique is well practised in North America and Europe.
Although natural ventilation ( opening windows, external doors or wall registers) has it’s benefits, the biggest drawback is the lack of control for the homeowner. Air will flow in and out of the house at will, depending on the whim of Mother Nature. When there is no wind, there is no ventilation. Another drawback is the loss of energy. To guarantee a supply of fresh air throughout the house, a balanced, ducted mechanical ventilation system is required. The Energy Recovery Ventilator is one such system . It introduces fresh, filtered air from the outside and at the same time, removes polluted, moist air from the house. During this air exchange, it also recovers over 70 % of the energy (heat or cool) that would normally be lost in the outgoing stale air and controls the humidity level in the house. The benefits of controlled humidity are: limiting dustmite growth, elimination of moulds and mildews and prevention of chemical off-gassing.
Why build a “Healthy House”?
Australians spend at least 90% of their time indoors. As our energy-conscious homes and office buildings are being built more tightly and with better insulation, indoor air quality and proper ventilation have become important health issues. In some instances, the air we breathe, indoors,may be more polluted than the outdoor air ! A ‘Healthy Building’ is designed not only to improve the indoor air quality, but improve the building’s energy efficiency.
What does it take to make a house ‘Healthy’ ?
A Healthy House is all about choices. People with asthma and allergies might be particularly interested in pursuing many of the technologies that make up a ‘Healthy House’. Others may want to take just a few steps, such as eliminating carpets, choosing household products more carefully, or controlling humidity to prevent dustmites.
Are there any design restrictions?
Building a ‘Healthy House’ is not restricted by house design. Some issues to be conisdered in building a ‘healthy house’ are:
- Avoid the use of any building products that could cause health problems to the occupants,
- Examine ways to eliminate certain pollutants by separating them from the indoor environment,
- Recommend the use of certain building products and building technologies that will improve the indoor air quality of the home,
- Introduction of a proper mechanical balanced ventilation system – Critical areas in the house such as the kitchen, bathrooms and laundry can create substantial pollution and high humidity levels, which need to be eliminated by means of ventilation, and
- Insulating and sealing a house off properly is all part of the ‘Healthy House’ concept and will not only result in a more comfortable living space, but also reduced running costs.
What are the design principles for a “Healthy House”?
A ‘Healthy Building’ is one which is highly energy efficient, environmentally sound and addresses the health of the building’s occupants. This is accomplished through the introduction of a range of techniques and technologies which combine to protect the quality of the indoor air stream. There are four basic principles which need to be taken into consideration in order to make your home ‘Healthy’.
These Four Principles are:
- Sustainable and Energy Efficient Building Design:The choice of building products is done in accordance with sustainable ideals. Timber and other building products are chosen which are either from a sustainable source and/or are low in embodied energy in their manufacture. A highly energy efficient design is needed in order to achieve an acceptable level of control over the indoor environment. This benefits our natural environment and our health through reduced energy consumption and increased indoor temperature control.
- Elimination: eliminate (choose a ‘friendlier alternative) or significantly reduce the introduction of products which may prove to be toxic to the environment and unhealthy for you and your family; eg. medium density fibreboard (MDF) which contains high levels of formaldehyde.
- Separation: If potentially unhealthy building products must be used within the building, separation techniques can be applied to separate it from the environment; eg. Formaldehyde containing particle board (MDF) can be sealed with laminate or paint.
- Ventilation: Proper ventilation is crucial in order to reduce the build-up of pollutants and moisture within a building and to provide ‘fresh’ air for the occupants. Asthma and allergy groups around the world state that ventilation of a home is needed to control the level of dustmite and moulds; two key asthma and allergy triggers. The American Lung Association advocates mechanical ventilation of homes to control these two asthma triggers and provide a healthy level of indoor air for the occupants.
What is “Sick Building Syndrome”?
The term “sick building syndrome” is used to describe situations in which building occupants experience acute health and comfort effects that appear to be linked to time spent in a building, but no specific illness or cause can be identified…. Solutions to sick building syndrome usually include combinations of the following:
- Pollutant source removal or modification,
- Increasing ventilation rates,
- Air cleaning, and
- Education and communication.
Does filtration improve indoor air quality?
The use of ventilation to improve indoor air quality is the main approach taken for reducing the harmful effects of airborne pollutants that enter the home or are generated internally within the home.
Ventilation helps to remove and dilute airborne pollutants within the home but may actually increase such pollutants depending on external local environmental conditions.
Filtration can be used in conjunction with ventilation systems to further reduce airborne pollutants and thereby improve indoor air quality. Effective filtration relies on:
- a filter that removes airborne pollutants such as particles and gaseous pollutants,
- an appropriate rate of air flow through the filter, and
- a ventilation system to ensure adequate air exchange throughout the home.
Filters are rated to ASHRAE Standard 52-76 American Society of Heating, Refrigerating, and Air Conditioning Engineers. However, the efficiency of such filters is influenced by the rate of air that flows through them. Testing in-duct systems for “medium efficiency” has been undertaken by the U.S. Environmental Protection Agency and the results are shown below.
|Filter Applications for In-duct Systems Based on ASHRAE Atmospheric Dust Spot Test|
|Air Cleaner Efficiency Ratings|
|Used in window air conditioners and heating systems |
Useful on lint.
Somewhat useful on ragweed pollen.
Not very useful on smoke and staining particles.
|Used in air conditioners, domestic heating, and central air systems. |
Fairly useful on ragweed pollen.
Not very useful on smoke and staining particles.
|Used in heating and air conditioning systems, and as pre-filters to high efficiency cleaners. |
Useful on finer airborne dust and pollen.
Reduce smudge and stain materially.
Slightly useful on non-tobacco smoke particles.
Not very useful on tobacco smoke particles.
|Use same as 40%, but better protection. |
Useful on all pollens, the majority of particles causing smudge and stain, and coal and oil smoke particles.
Partially useful on tobacco smoke particles.
|Generally used in hospitals and controlled areas. |
Very useful on particles causing smudge and stain, and coal and oil smoke particles.
Quite useful on tobacco smoke particles.
|Use same as 80%, but better protection. |
Excellent protection against all smoke particles.
|1. Efficiency rating by ASHRAE Standard 52-76 atmospheric dust spot test. |
Source: U.S. Environmental Protection Agency
Are Energy Efficient Houses Healthy?
The answer is yes they can be, provided the design of the house includes adequate ventilation with filtration. The main method currently used to significantly reduce energy loss from a building is to ensure that the building envelope (ie the building shell) is as air tight as possible. As a result, natural ventilation into the building is reduced and the issue of indoor air quality becomes a significant one.
In February 2005 the California Air Resources Board produced a draft Report on Indoor Air Pollution in California * which recommended to “Amend the building codes to address indoor air quality, with a focus on assuring adequate ventilation under all circumstances.”
The report also states that: ” California adults spend an average of 87 percent of their time indoors, and children under 12 years of age spend about 86 percent of their time indoors. …. the trapping effect of buildings, and people’s proximity to indoor sources of emissions, there is a much higher likelihood that people will be exposed to indoor pollutants than outdoor pollutants. Investigators have calculated that pollutants emitted indoors have a 1000-fold greater chance of being inhaled than do those emitted outdoors”
“Build Tight Ventilate Right”
In April 2006 the United Kingdom amended their building regulations to ensure that adequate ventilation is achieved in all new buildings. The UK building codes now state that:
“Ventilation is required for one or more of the following purposes:
- provision of outside air for breathing;
- dilution and removal of airborne pollutants, including odours;
- control of excess humidity (arising from water vapour in the indoor air); and
- provision of air for fuel-burning appliances.” **
The four approved methods of achieving such ventilation are as follows:
- Background ventilators and intermittent extract fans;
- Passive stack ventilation;
- Continuous mechanical extract; and
- Continuous mechanical supply and extract with heat recovery.
Heat Recovery Systems can provide fresh filtered air to buildings as well as recovering up to 80% of the heat from the exhaust air, thus maintaining energy efficiency as well as providing acceptable levels of indoor air quality.
- Read the draft Report on Indoor Air Pollution in California * pub. February 2005.
- Download document Part F “Ventilation” – United Kingdom** pub. 15 March 2006.
What is HRV technology?
HRV stands for Heat Recovery Ventilator. It is a technology that has been used for the last 40 years worldwide to provide high quality indoor air into buildings for the benefits of the occupants. HRV technology is used for commercial and industrial buildings as well as residential buildings.
A genuine HRV system will provide the following:
- fresh air into a building,
- extract stale air from the building,
- filter the fresh air entering the building to remove pollutants,
- recover heating and cooling from the stale air using a heat exchange core,
- and transfer the recovered heating or cooling to the incoming fresh air.
In housing, HRV systems are fully ducted systems delivering fresh filtered air from outside the building (external to the building and associated roof space) to the living and bedrooms and extracting stale air from high moisture areas such as bathrooms, kitchens and laundries. Typically, an HRV is able to recover 70 to 80 percent of the heat from the exhaust air and transfer it, via a heat exchanger, to the incoming air.
This type of ventilation is referred to as balanced mechanical ventilation.
Whole building ventilation
What is it?
- It is a ventilation machine that is specifically made for new buildings or ‘renovated’* old buildings.
- It filters the outside air as it comes in and removes old (or polluted) air from inside the building.
- The INCOMING and the OUTGOING air come in and out at the same rate (so its called a balanced system).
- It provides the whole building with a continuous (and controlled) fresh airflow, no matter what is happening in the building or outside.
- When we say ‘controlled’ it means we have a say in how much outside air is brought in and how filtered that air is.
What else does it do and why is it now so important?
- Depending on the season we may have a ‘heater’ or a ‘cooler’ on inside the building (lets call this ‘heat’ or ‘cool’ energy). It costs money to heat or cool our homes.
- The ventilation machine brings new air in and removes the stale old air, it does not heat or cool the air.
- The air in your home has been either been heated or cooled by a heater or air conditioner. As the air leaves the building the ventilator (AIR2ENERGY systems) catches the energy (hot or cool) and passes it to the new air stream coming in. This is an energy (heat or cool) transfer.
- The air streams never mix but pass so close to each other that the energy (heat or cool) flows to the new air.
So, that means that we don’t lose that energy to the outside. We have paid to heat or cool our inside air and by recovering that and reusing it, we become very energy efficient and also save money.
Two types with different names for different jobs.
One is called a ‘Heat Recovery Ventilator’ (HRV) because it was invented for cold climates to ‘catch’ the heat in the old or polluted air that is being removed.
- So not to waste that ‘heat’ the ventilator passes that ‘heat’ (or energy) to the new air being brought in.
- This saves an enormous amount of energy (heat) being lost outside as well as new energy being used to reheat the new air coming in. HRVs can also remove excess moisture from your home.
A variation of an HRV is an ERV (or Energy Recovery Ventilator).
- Like the HRV, the ERV allows you to ‘recover’ heat or cool but also to monitor and control moisture in the air to suit the climate. They are usually used in hot humid or hot dry climates. The moisture comes from what we do in the house. We breathe, our bodies give off moisture, we cook and shower etc. This moisture affects your health and the health of the building.
- The created moisture is absorbed into our furnishings and then released. When released the ‘moisture filled’ air is full of pollutants from the glues and chemicals used in the construction process. These pollutants cause health problems- asthma and allergies. Mould and spores love moisture too. Building structures are also badly affected by moisture.
Why do buildings, people and the planet need it NOW?
- It’s all about the air quality in the building. We try to reduce heating and cooling costs by building structures that are well insulated and don’t leak air.
- These ‘tight’ buildings don’t allow ‘moisture filled’ air to escape thereby creating potential health problems.
- CO2 is one of the offending gases warming the planet. If we reduce our energy requirements for heating and cooling then we help reduce C02 levels.
- Reducing air pollution is crucial.
*a ‘renovated’ building will have all existing gaps and cracks sealed to reduce air leakage.
Balanced Ventilation systems – The key to energy efficiency?
When building a new house the issue regarding ventilation is one that must be addressed! With the increasing demand for energy efficient buildings, the end result of the design and building process are often buildings that have significantly reduced air leakage. This is the desired result of energy efficient design and construction, as reduced air leakage means reduced energy loss and therefore reduced energy consumption for heating and cooling. ie fewer gaps and cracks means less energy loss from the building. However we need adequate ventilation for all of the following purposes:
- provision of outside air for breathing;
- dilution and removal of airborne pollutants, including odours;
- control of excess humidity (arising from water vapour in the indoor air); and
- provision of air for fuel burning appliances.
Ventilation systems can place undue negative or positive pressure on a building and cause extra loss of energy through increased air leakage. With new buildings; kitchen range-hoods, gas fired heaters and bathroom, ensuite, toilet exhausts may not function correctly, if at all, due to the “tightness” of the building. As well depending on climate, moisture can be driven into the wall materials and cause mould as well as structural damage.
Build Tight – Ventilate Right
We need buildings that have minimal or no air leakage for maximum energy efficiency but we also need adequate ventilation for the above reasons. A balanced ventilation system solves this problem by ensuring the same amount of air enters the building as is exhausted from the building. When coupled with heat or energy recovery a balanced system contributes to the best solution for achieving the most energy efficient building. The German Passive House (Passivhaus) standard incorporates balanced mechanical ventilation with heat recovery to achieve the most energy efficient buildings in the world.
Existing buildings can be tested for air leakage, retrofitted with a range of energy efficient products and installed with a balanced ventilation system with heat recovery to achieve very high energy efficiency. Again the German Government Energy Agency DENA has demonstrated this with refurbishments of over 375 buildings resulting in a reduction of the energy consumption to a level well below that of a comparable new building.
Read a report Efficient Homes – German Experiences with Deep Retrofit on the project from the The Insitute of International and European Affairs Retrofit Conference 2011
Measuring Building Performance – how do we test for air tightness?
For either new or existing buildings a detailed and accurate measurement of air leakage is important to fully understand the energy performance of that building. Up to 20% of a building’s heating and cooling can be lost by uncontrolled air leakage of the building envelope. New, highly energy efficient residential buildings should have a natural air leakage rate of no greater than 10 air changes per hour at 50 Pa. Internationally, the accepted range for energy efficient housing is between 0.3 and 0.5 ach @50Pa.
By using a blower door device we can identify the overall leakage area of the building. Blower door technology is used in many countries, where energy efficiency is mandated, to measure the airtightness of building envelopes, diagnose and demonstrate air leakage problems, estimate natural infiltration rates, estimate energy efficiency losses from building air leakage, and certify construction integrity. A Blower Door consists of a large fan which is mounted in a frame. The frame is placed in an exterior door and used to either depressurize or pressurize the house. Once the problems have been identified these can be addressed and as a result the energy performance of the building can be maximized.
|Read the report: Low Energy Buildings In Europe: Current State of Play, |
Definitions and Best Practice
|Read the review: Steering through the maze -Nearly zero energy buildings: |
achieving the EU 2020 target.
|Read the paper: User Evaluations of Energy Efficient Buildings||Pub.||Feb. 2011.|