2nd August 2013, Volume 126 Number 1379

Julie Gillespie-Bennett, Michael Keall, Philippa Howden-Chapman, Michael G Baker

Imagine a country where all the houses are warm, dry, energy efficient, safe, sustainable, and meet the needs of the occupants who live in them. Also imagine that advertisements for houses to rent or buy don’t just have icons for the number of bathrooms, bedrooms and garages but also communicate vital information about the health, safety, energy efficiency, and earthquake resilience of housing and its suitability for different groups of people including families with children, the elderly and people with disabilities.

We argue that New Zealand desperately needs a system for rating the quality of its houses. Such a system should at the very least define a minimum standard (a warrant of fitness) and provide well validated quality rating on a number of important scales to encourage improved housing performance above this minimum level. While there are costs of implementing such a system, the costs of inaction are considerably greater, and are already being borne on a day-to-day basis by many individuals and whānau (extended family).

Housing quality in New Zealand

Housing is one of the key material determinants of health and shelter is a fundamental human need.1 New Zealand has substandard housing, which has resulted from poor regulation of minimum housing standards and lack of maintenance. This situation has been compounded by an increasing reliance on market solutions for affordable housing and an emphasis on housing as an investment supported by imported capital and tax-breaks for landlords.2

The result has been an inequitable distribution of housing assets as well as a rise in housing costs, regardless of housing quality. In addition, there are growing health inequalities between different groups in society, with negative health impacts particularly on Māori, Pacifica and low-income households.3,4

Two-thirds of New Zealand houses have timber frames, iron roofs and are on concrete or wooden piles, and the majority of homes have single-glazed windows.5 One-third of homes are un-insulated and many households are inadequately heated and are colder than recommended by the World Health Organization.6

In comparison to other developed countries, New Zealand households use less energy for home heating, although the percentage of the household budget spent on energy is similar.7

The public health and economic consequences of poor quality housing

People in the developed world spend around 90% of their lives indoors and as most of this is spent in the home,8 the quality of housing affects the health and safety of the population. There are many consequences of poor housing.9,10 However, the most important in developed temperate countries such as New Zealand are probably negative effects on respiratory health and injury. Housing quality also affects how much energy is required to heat the house.

Poor quality housing and respiratory health—The link between cold, damp, mouldy housing and poor health has been highlighted in several international and New Zealand studies.11–13 Houses that are cold are also likely to be damp, which leads to the growth of moulds that can increase respiratory symptoms.14–16

Cold, damp substandard housing changes the way in which the occupants live within a house. New Zealanders tend to crowd together in one room to stay warm, which promotes the transmission of viral infections. It has been suggested that respiratory viral infections may influence asthma frequency, with deficient immune responses to viral infections not limited to children with atopic asthma, but also present in atopic children without asthma.17 Furthermore, data from longitudinal studies suggest that wheezing episodes associated with viral infections early in life are a major risk factor for the development of asthma later in life.18–20

Indoor air pollutants, such as nitrogen dioxide, produced by unflued gas heaters have also been shown to increase respiratory symptoms.21 Almost one-third of New Zealand households (386,000 houses) use portable unflued gas heaters to heat their homes. The use of indoor, unflued gas heating occurs disproportionately in lower socioeconomic groups, with single parent and Māori families over-represented.22 One of the most common chronic respiratory diseases of childhood and adolescence is asthma, which carries with it a significant impact on daily activities, including school attendance.23,24

In New Zealand, asthma rates are among the highest in the world, with more than one-quarter of children25 and one-in-six adults suffering from asthma.26 As well as the stress associated with having a chronic illness, asthma leads to higher health service utilisation and pharmaceutical costs. The economic burden of asthma in New Zealand has been conservatively estimated at over $800 million per year.26

Apart from asthma, new cases of other respiratory disorders, such as bronchiectasis, are rapidly increasing and compared to New Zealand’s neighbouring Pacific countries we have higher rates of admission for diseases such as pneumonia.27 New Zealand has a high incidence of preventable respiratory disease in comparison to other OECD countries.27

There is good evidence to link poor quality housing and increased respiratory symptoms. A study by Keall and colleagues reported that in a sample of about 1,000 houses, people who were classified as living in the poorest quality houses, would have a 33% reduction in respiratory symptoms (relative risk 0.67 with 95% CI 0.53 to 0.85) if these people lived in the best performing houses.28 One way to reduce New Zealand’s burden of respiratory symptoms is to improve the quality of housing.

Poor quality housing and injury—Poor quality housing increases injury rates.29,30 Globally around one-third of injuries occur in the home.31 In New Zealand during the 2007/2008 year long period there were 715,218 claims to the Accident Compensation Corporation (ACC) as a result of unintentional injuries in the home.

Approximately 36,000 people who suffer from an injury in the home are hospitalised each year, which makes home the most common location for injuries resulting in hospitalisation.32 Excluding self-harm, assaults and transport accidents New Zealand has approximately 250 injury deaths a year at home.33

In 2010 more than 261,000 New Zealanders were injured as a result of everyday slips, trips and falls in their homes. Collectively, the social cost of these injuries and deaths have been estimated to be around $13 billion annually (at 2008 costs), 3½ times more than are associated with road injuries,33 making the average social costs per home injury approximately $26,000.33

One way to improve the burden of these injuries and their associated costs is to reduce injury hazards in the home. The findings of an economic analysis conducted on about 1000 houses in Taranaki indicated that, for an average of around $500, most householders can fix certain injury hazards in their homes and reduce their injury risk. For each additional home injury hazard enumerated, there was a significant associated increase in the odds ratio of a home injury of 22%.34

Poor quality housing and energy efficiency—Poor quality housing can increase energy consumption. Excessive use of energy contributes to CO2 emissions and climate change.

In 2003, the United States residential sector produced more than 20% of total United States energy-related CO2 emissions.35 In New Zealand, houses account for approximately 13% of the country’s total energy use, with 34% of energy used on space heating and 29% used on water heating. Annually on average each New Zealand house spends around $2000 on energy and produces 2 tonnes of CO2.36

In Britain, a study of private rental housing found that retrofitting insulation was effective in terms of modelled reductions in fuel use.37 An Irish study modelled the returns on domestic energy conservation opportunities and concluded that a home retrofitting programme would result in a 3:1 benefit cost ratio including energy savings, health benefits and reduction in avoidable mortality.38

In New Zealand the Housing, Insulation and Health Study showed that insulating 1350 houses, built before insulation was required, improved the occupants' health and well-being as well as household energy efficiency.39 A cost-benefit analysis of this study concluded that valuing the health gains, energy and savings on CO2 emissions suggests that the total benefits are 1½ to 2 times the magnitude of the cost of retrofitting insulation.40

An evaluation of the roll-out of the Warm Up New Zealand: Heat Smart programme found the benefits exceeded the costs by 5-to-1; the most significant contribution came from reduced mortality in older people.41

Improving energy efficiency is one of the most constructive and cost–effective ways to address the challenges of high energy prices, lack of energy security, air pollution, and global climate change. Most importantly, improving the energy efficiency of older housing means houses are warm and comfortable to live in and the health of the occupants is improved.42

Poor quality housing and inequalities—Māori and Pacific children are over-represented in low-income families and more than half of the children living in poverty are Māori or Pacific.43 These children live disproportionately in substandard housing, which means they suffer a greater health burden as they are exposed to additional housing hazards.

Hand-in-hand with living in substandard housing, people who have lower incomes are struggling to heat their houses given it is very expensive to heat an un-insulated, damp house to a comfortable, healthy temperature. It is estimated that between 10 and 14% of New Zealand houses or some 400,000 people live in fuel poverty nationwide.42

How the Healthy Housing Index works

In New Zealand the residential housing stock is largely built, so improving the quality of the existing built environment would benefit from a diagnostic tool that identifies deficiencies in the home environment that can be addressed by retrofitted improvements.44

The Healthy Housing Index (HHI) was developed by the Housing and Health Research Programme/He Kainga Oranga and the Building Research Association of New Zealand (BRANZ) and is the only outcome-validated housing quality assessment tool available internationally. The HHI is an independent, science-based, practical tool, which translates knowledge gained from health and building science research and practical experience during a 10-year period into an ongoing system for informing housing improvement.

The assessment is based on an inspection conducted by a trained building professional. The inspection takes about an hour and involves both observation and measurement of the house. Results are recorded on a tablet computer with data from the inspection downloaded once there is an internet connection.

The assessment has two outputs. The first is a pass/fail Warrant of Fitness type of assessment as to whether the home meets basic health and safety standards. The second output rates each major assessment area (health, safety and energy efficiency) potentially on a five-point scale (the exact form of this scale is still being refined).

In addition, a report is provided to the home-owner, which lists identified problems along with prioritised solutions and remediation options to improve the health, safety and energy efficiency of the house. Figure 1 is an example of how the HHI summary assessment could look.

Figure 1. An example of how the HHI housing assessment certificate could look


There are some operational aspects of the HHI that are still being developed. For example the exact standards required to ‘pass’ the warrant of fitness are being refined in consultation with councils and the New Zealand Green Building Council and the role of the additional scales is currently being discussed with key agencies.

An expanded workforce of inspectors needs to be trained and quality control measures put in place. There are also important details about how the information generated would be held and communicated, for example, whether it will be made available on-line to owners, renters and potential purchasers of properties.

It is envisaged that the HHI will be implemented in a phased manner, starting with rental housing, and initially focusing on health, safety, and energy efficiency. There are opportunities provided by new housing construction in Christchurch to provide a common metric as represented by the HHI assessment to guide design and construction quality standards.

It is expected that inspections would be carried out a maximum of once every 5 years or when a house is rented or sold. Table 1 gives examples of components assessed during a HHI inspection and indicates what components could be required to pass an inspection. It also gives examples of additional components that may be required to gain extra points on the proposed five-point scales.

It is important to note that the HHI and WOF cannot, and should not, cover every important aspect of housing relevant to its condition and impact on the health and safety of the occupants.

Firstly, even a high-quality house can be used in unhealthy and unsafe ways. A key example is household crowding, which is a function of the composition of the household in relation to the size of the house. Household crowding is a serious problem in New Zealand and is almost certainly contributing to our high rates of serious infectious diseases.3,45 However, its solution depends on increasing the supply of affordable housing so there is less pressure on low-income people to live in crowded conditions.

Secondly, the HHI and WOF cannot fully cover house conditions and maintenance, except for selective aspects that are relevant to health, safety, and energy efficiency. By analogy with motor vehicles, there is a WOF relating to the safety of the car, but in addition there is a driver’s license relating to the skills and behavior of the driver, and various vehicle inspection services covering vehicle maintenance and condition.

As noted in Table 1, some of these aspects of housing may be included in a ‘suitability statement’ associated with the house WOF, but this element requires further consideration.

Table 1. Examples of components assessed by the Healthy Housing Index
Name of scale
Examples of components required to pass the WOF based on the HHI
Examples of additional components to gain extra points on a proposed 5-point scale
Core modules
Respiratory diseases
Cardiovascular diseases
Infectious diseases linked to enteric transmission
Ceiling and under-floor insulation where possible, installed to EECA standards
Excess heat and cold control
Sanitary areas to include a toilet and personal washing facilities
Control of all indoor pollutants
Storm-water and waste-water drainage to Council Standards
Sound proofing for noise
Adequate food preparation and storage areas, including an operational stove and oven
Mechanical ventilation in kitchens and bathrooms
Potable water supply (hot and cold)

Adequate control of mould and dampness; including dry underfloor/vapour barrier and reduced moisture sources

Safe and energy efficient heating

Working windows for ventilation; to include safety latches/stays

Reasonable state of repair and weather tightness (E.g. doors, windows, walls, roofs)

Working fire alarms
High standards of driveway & boundary fencing
Injuries and poisonings
All power outlets/ light switches safe, functional and in a good state of repair
High security from intruders
Safety from falls (E.g. handrails for stairs/outside steps and safe floor coverings)
Fire resistant materials & design
Structural soundness of house
High standards of fall protection
Safe access to house
High standards of external lighting
Adequate lighting
High standards of noise insulation
Water heating set to safe temperature
Fire extinguishers
Ranch-sliders and low level windows to have safety visibility strips

Secure storage for potential poisons

Pool fencing
Basic security from intruders (locking doors/windows)

Energy efficiency
Financial and
environmental costs
Ceiling and under-floor insulation where possible, installed to EECA standards
Energy efficient lighting
Safe and energy efficient heating
Sustainable heating
Solar orientation

Thermal mass

Optimal house layout

Heating and cooling systems

Solar water heating

Window efficiency/double glazing

Possible additional modules for future consideration

Yet to be developed

Injuries from natural hazards
Yet to be developed
Financial costs
Environmental costs
Infectious diseases linked to household crowding
#The suitability module is proposed to provide useful information for occupants on aspects such as the number of rooms (and therefore number of occupants the house can accommodate before it becomes crowded), disability issues (such as wheelchair access), and suitability for children, but it will not form part of the rating system.

Benefits of the Healthy Housing Index

Assessing house quality has two broad functions: first to assist house owners, renters, property managers and compliance agencies in making informed judgements about the management of individual properties; and second to provide a robust basis for policy development, compliance monitoring and research regarding the quality of housing stock.44

Adequate housing quality data in New Zealand are almost entirely absent to support decision making by local authorities and national policy agencies with responsibility for health, safety and housing quality. Quotable Value records contain basic information and some data are available from the BRANZ House Condition Survey. But there is a lack of more comprehensive quality data on individual residential properties.

The HHI focuses on building condition rather than the occupants or the way they might live within a house. The HHI provides a measure of how likely it is that occupants will suffer ill health or injuries due to a housing factor(s). Each measure included in the inspection was selected on the basis of previous local and international research, together with expert opinion. In addition each individual element has been validated against respiratory health outcomes28 and injury claims to ACC.34

Alternative quality rating schemes for housing

There are other home rating tools available in New Zealand, but their scope is more limited, focusing mainly on the energy efficiency of the building. Several organisations that provide home rating tools and information on building maintenance, energy efficiency, and renovations are listed in Appendix 1 at the end of this paper.

The Energy Efficiency Conservation Authority (EECA) states that there is a lack of public information on energy efficiency and this is a major barrier to the uptake of insulation and efficient heating systems.46 It is also worth noting that the involvement of the building industry in supporting a housing quality measure does present issues with conflicts of interest and minimises the focus on the effect of the indoor environment on health and wellbeing, as noted by the WHO in its recent report on Health in the Green Economy.47

A range of countries have developed labels and standards for green building or energy efficiency for buildings.47 As is mirrored in New Zealand, many international housing rating systems and assessment tools that consider energy efficiencies fail to measure housing aspects related to health impacts—beyond basic safety. Assessment of housing quality that includes health, safety and sustainability can provide a more robust basis for policy development, compliance monitoring and research on the quality of housing stock.47

In 2001 the United Kingdom established a ‘Decent Homes’ standard, which states that houses should be warm, weatherproof and have reasonably modern facilities.48 Such homes are a key element in developing thriving, sustainable communities where crime is reduced and where employment and educational opportunities are improved.

Alongside the Housing Act, 2004 the Housing Health and Safety Rating System (HHSRS) measures housing conditions.49 Rather than assessing against a fixed standard, the HHSRS employs a risk assessment approach to enable risks from hazards to health and safety in dwellings to be minimised. The system applies to all dwellings, regardless of ownership.

Once it is accepted that unsatisfactory housing conditions can have a negative effect on health, it is logical to assume that there will be a cost to society. In the United Kingdom the Audit Commission has recently stated that every £1 spent on providing housing support for vulnerable people can save nearly £2 in reduced costs of health services, tenancy failure, crime and residential care.50

Furthermore, a report that combines housing quality data from the HHSRS and health service costs highlights potential savings of more than £600 million a year from dealing with the most pressing housing problems, such as slips, trips, falls, mould and other treatable aspects of unhealthy housing. This saving to the health sector is thought to be around 40% of the total cost saving to society.51

What needs to be done to introduce a housing quality rating tool in New Zealand

Based on more than a decade’s experience with systematically assessing the quality of approximately 3000 New Zealand houses, we see no significant scientific or technical difficulty with introducing a valid, practical and useful housing quality rating scheme for New Zealand.

In order to get the HHI to function as a housing quality rating tool, stakeholders, such as local Councils, Housing New Zealand, Ministry of Business Innovation and Employment (MBIE), District Health Boards, Ministry of Health, Accident Compensation Corporation (ACC), and Energy Efficiency Conservation Authority (EECA) need to support the implementation of the HHI.

For the HHI to become a nationwide housing assessment tool the essential requirement is national leadership at a political and agency level, and some resources and infrastructure support. The Children’s Commission’s Expert Advisory Group on Solutions to Child Poverty has called for the introduction of a WOF underpinned by a health-based assessment tool such as the HHI and there has been cross-party support for the policy.43

Initially the HHI could be voluntary, but legislative or regulatory measures would be necessary if the rating system was to move from a voluntary to compulsory basis (which would be required if it were to be applied to the most vulnerable populations - those living in poor quality rental housing).


Substandard housing is a major problem in New Zealand that adversely affects the health and safety of a large proportion of our population.

The HHI is a practical risk assessment tool that can measure the physical characteristics of houses to assess the potential risks to the health and safety of the occupants, as well as the energy efficiency of the house. The tool is the only outcome-validated housing quality assessment tool available internationally. A valid housing assessment tool, such as the HHI, can guide improved housing quality and therefore better health, a reduction in home injuries, and an improvement in energy efficiency.

Better housing quality would yield improvements in population health, safety and the economy more generally. There is widespread support for introducing this evidence-based approach. The main elements needed now are high-level policy commitment and resources to coordinate its implementation.


Substandard housing is a major problem in New Zealand, with little recognition of the important aspects of housing quality that affect people’s health and safety. The Healthy Housing Index is a practical risk assessment tool based on strong international evidence and adapted to New Zealand conditions that measures the physical characteristics of houses that affect the health and safety of the occupants.


Substandard housing is a problem in New Zealand. Historically there has been little recognition of the important aspects of housing quality that affect people’s health and safety. In this viewpoint article we outline the importance of assessing these factors as an essential step to improving the health and safety of New Zealanders and household energy efficiency. A practical risk assessment tool adapted to New Zealand conditions, the Healthy Housing Index (HHI), measures the physical characteristics of houses that affect the health and safety of the occupants. This instrument is also the only tool that has been validated against health and safety outcomes and reported in the international peer-reviewed literature. The HHI provides a framework on which a housing warrant of fitness (WOF) can be based. The HHI inspection takes about one hour to conduct and is performed by a trained building inspector. To maximise the effectiveness of this housing quality assessment we envisage the output having two parts. The first would be a pass/fail WOF assessment showing whether or not the house meets basic health, safety and energy efficiency standards. The second component would rate each main assessment area (health, safety and energy efficiency), potentially on a five-point scale. This WOF system would establish a good minimum standard for rental accommodation as well encouraging improved housing performance over time. In this article we argue that the HHI is an important, validated, housing assessment tool that will improve housing quality, leading to better health of the occupants, reduced home injuries, and greater energy efficiency. If required, this tool could be extended to also cover resilience to natural hazards, broader aspects of sustainability, and the suitability of the dwelling for occupants with particular needs.

Author Information

ulie Gillespie Bennett, Post-doctoral Research Fellow, He Kainga Oranga/Housing and Health Research Programme, University of Otago, Wellington


He Kainga Oranga/Housing and Health Research Programme is funded by the Health Research Council of New Zealand.


ulie Gillespie-Bennett, He Kainga Oranga/Housing and Health Research Programme, University of Otago, Wellington, PO Box 7343, Wellington South 6242, New Zealand. Fax: +64 (0)4 3895319

Correspondence Email



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