Updated: 26 Jun 2009

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Introduction

During winter the indoor air is more polluted than the outside. The good news is that problems with our homes can be fixed.

We like to think we are clean and green. The state of our houses tells a different story.  There is ample evidence that the environment inside our homes is bad enough to have a major effect on our health and wellbeing.

We look at simple, cost-effective ways to improve your indoor air quality at home.
 

Importance of quality air

For us to keep healthy the air we breathe has to be as free as possible of pollutants and agents that can harm us. Those pollutants and agents can come from many sources that are directly related to the way our houses are built and the way we live in them. The biggest issues are winter cold and damp.

It's not the cold and damp that harms us. Rather, they provide the conditions for mould to grow and dust mites to breed. These are the two that cause havoc, and in combination can lead to serious health problems. Over 40 percent of our homes have mould problems.

In 1948 the World Health Organisation (WHO) published guidelines for minimum indoor temperatures for healthy living. These guidelines have not changed. They are:

• 18°C for living areas
• 16°C for bedrooms
• Temperatures lower than 12°C can have a significantly detrimental impact on health.

More than 60 years after those recommendations were published, far too many kiwi homes still fall short. Our housing stock needs upgrading.

 

The Waitakere NOW Home

Beacon Pathway is a research consortium working towards making homes more resource efficient to build, cheaper to run and healthier to live in.
 
The Waitakere NOW Home, built in 2005, was the first project for Beacon Pathway. It was designed to show that a sustainable house which is comfortable to live in can be built affordably using readily available materials and products.

The single-storey house with attached garage was built for $218,000 (excl. GST) and has three bedrooms, two bathrooms and a floor area of 146 square metres. It is an attractive yet modest home combining simple, proven designs and technologies. It also incorporates simple features which address indoor air quality:

•  Weathertight construction.
• North-facing orientation with lots of windows on the northern side.
• Wide eaves that let in winter sun but keep out summer sun.
• A concrete floor to store heat from the sun and release it when the air is cold.
• A high level of ceiling, wall and floor insulation – much higher than required by the Building Code.
• Double-glazed windows to keep the heat in and most of the noise out.
• A rangehood in the kitchen and an extractor fan in the bathroom to remove moisture from these very wet areas.
• Passive ventilation to keep down moisture levels and to avoid overheating.
• Good natural light in all rooms.
• An airlock or small foyer at the front door to provide privacy for the main living space and to reduce heat loss.

The company recognised that our traditional houses have problems.

Up to 1977, most houses were built without insulation, on piles over the earth. These houses are typically timber framed, with weatherboard cladding and wooden window frames. They leak heat, moisture and air, and as a result are cold, damp and draughty in winter.

These houses have many separate rooms, with the main heating appliance (often a fireplace) in the lounge. Thus during winter the lounge area of the house is heated (sometimes overheated) while the bedrooms and the back of the house are not. Ventilation typically comes from opening windows. During winter these are often kept closed to ‘keep out the cold’. The unventilated, unheated bedroom and bathroom areas have the potential to become musty and mildewy.

Newer houses are often better. Concrete slab construction keeps ground moisture at bay, insulation helps keep the house warm and open-plan design lets heat spread. Better-sealing windows minimise draughts. But these newer houses are still not good enough. The problem with many insulated, well-sealed houses is moisture build-up from cooking, washing and bathing, as well as everyday human activity
 

Health improvements

The Waitakere NOW home was extensively monitored during the two years a family of four lived in the house.

Soon after moving into the home the family noticed they experienced fewer illnesses. A child who had previously suffered from asthma showed improvement too.

The family noticed the evenness of the indoor temperature. An electric heater and electric blankets were needed only on the coldest of winter days. The concrete floor which was warmed by the winter sun was not cold to walk on. But the family found that the house was too warm in the summer, so it was planned to supplement the window in-frame ventilators with window security stays to allow the windows to be left open without compromising security.
 
Less expected, perhaps, was that the family’s social life blossomed after moving into the NOW Home. Friends and relatives wanted to visit. The family attributed this to living in an easy-to-clean, quality, comfortable house that was aesthetically pleasing and spacious, with indoor-outdoor flow.

The experience of the NOW Home tenants indicates that warm, dry homes are not only vital for physical health. They are just as important for mental health.
 

Tips for improving air quality

Research has shown that making improvements to our living environment is cost effective in many ways. In addition to reduced heating bills, there’s a reduction in healthcare spending and associated productivity gains from less time off work and school due to sickness.

Here’s what to do…

Reduce dampness: 

• Use extractor fans in the bathroom and rangehoods that are vented to the outside in the kitchen.
• Put a sealed moisture-control sheet on the ground under the house.
• Dry clothes outside and vent dryers outside.
• Use a dehumidifier.

Insulate

• In ceilings.
• Under the floor.
• In exterior walls, if possible – starting with the south facing walls and bedrooms.
• Take advantage of the recently announced home insulation subsidies.
   

Heat

• Heat lounges to at least 18°C, bedrooms to 16°C.
• Use energy-efficient heating like heat pumps, flued gas heaters, clean-burning wood burners, or pellet burners if possible.
• If using a woodburner, install a heat distribution system to heat the whole house.
• If you are using electric heaters make sure they are fitted with a thermostat.
• Do not use unflued LPG heaters.
   

Ventilate

• Use extractor fans in the bathroom and rangehoods that are vented to the outside in the kitchen.
• All houses need to be aired. Open the windows regularly during the winter to remove stale air. Consider window vents or security stays so the house can be ventilated when you are not at home.

 

More information

• Consumer Build: www.consumerbuild.org.nz
• Smarter Homes: www.smarterhomes.org.nz
• Beacon Pathway: www.beaconpathway.co.nz
• Home insulation subsidies (EECA): www.eeca.govt.nz