This article is drawn from wider notes and analysis compiled for the Spinoff article Welcome to Mouldy-wood, Aotearoa, written by Pete McKenzie.
Housing remains a hot issue across New Zealand. But there’s not as much focus on the quality of the housing we endlessly debate. In part, this lack of focus is because we haven’t had great insights to work with – and what gets measured gets managed. But Infometrics analysis of Census 2018 data shows some disturbing results, with a concerning number of mouldy, damp or cold houses.
Houses are the literal foundations that people base their lives from. Poor housing outcomes have a considerable effect on New Zealander’s wellbeing and can cause a range of related cascading issues. Here, we examine how many houses have quality issues, and where they are concentrated.
Over 20% of Kiwi houses are damp
In 2018 there were 318,891 houses across New Zealand that were sometimes or always damp. This figure of 318,891 represents 21.5% of all 1.48m reporting dwellings.  Of these 318,891 dwellings, just over 44,500 were always damp, with the balance (274,371) being sometimes damp.
As Map 1 highlights, the location of these damp houses is unevenly distributed. Areas in the South Island have lower proportions of their housing stock being considered damp, ranging from 8.6% of Central Otago dwellings to 25.1% of Westland homes.
In the North Island, Kāpiti Coast has the lowest proportion of damp housing, with 12.4% of the local housing stock. Wairoa District has the highest rate, with 35.6%.
Cities across New Zealand have higher shares of damp housing, with 22.6% of city housing being damp. District areas have a lower average rate, of 19.7%. Hamilton (25.1%), Auckland (24.8%) and the cities in the Wellington region (all 20%+) contribute to this higher urban dampness rate.
One in six New Zealand homes are mouldy
Mouldy homes follow a similar geographical distribution to damp homes, although fewer houses overall are mouldy. Census 2018 shows 252,855 mouldy dwellings, representing 16.9% of the 1.49m reporting dwellings. 
Map 2 shows a similar geographical distribution of mouldy housing compared to damp housing. Central Otago and Westland again bookend the South Island, with 4.4% and 16.5% respectively. Wairoa retains its top spot (27.4%), but South Wairarapa sneaks in below Kāpiti Coast (third lowest) and Carterton (second lowest) with the smallest proportion of mouldy housing (9.9%) in the North Island.
Compared to damp housing, a greater proportion of mouldy dwellings are reported to be always mouldy. Just over 64,500 dwellings were always mouldy – a quarter of total mouldy housing.
Four percent shiver without heating
For the first time, Census 2018 also gathered information about the main heating type for each dwelling.  Just under 60,900 dwellings are recorded with “no heating used” – 4.0% of reporting dwellings. There may be a few explanations for this figure. An obvious explanation is that some dwellings might be warm enough to not need heating, although this seems doubtful year-round.
However, it’s just as likely that many of these dwellings don’t have access to, or can’t afford to use, heating.
As Map 3 shows, only a few parts of the country are “cold-spots” when it comes to the lack of heating. The South Island has very low rates of no heating used, ranging from 0.2% in Waimakariri District to 1.2% in Nelson City.
But northern New Zealand shows higher rates of no heating used, with Auckland having the highest rate at 8.6%. Northland areas are close behind with all three Districts above 5%. Three other areas have no-heating-used rates above the 4.0% national average: Wellington City (4.8%), Ōpōtiki District (4.5%), and Hamilton City (4.1%).
Christchurch is heat pump central
Interestingly, the spread of heat pumps shows up as very scattered across New Zealand. Christchurch is red-hot, with 77% of dwellings using a heat pump. Part of this high usage rate is likely to be due replacement of fireplaces with heat pumps due to earthquake damage and to meet clean air requirements. Nationwide usage is a bit lower, with just under half of all Kiwi households using a heat pump as a main heating source.
Building more, and building better
It’s easy to rattle off various proportions and draw maps. But the numbers that sit behind these maps are stark. Anywhere between one in every five to six homes across New Zealand is damp or mouldy, or both. Nearly one in every 20 has no heating. Worse housing outcomes are directly linked to poorer health outcomes for occupants, and the issues with some of New Zealand’s housing leads to both economic and social issues. People living in poorer-quality housing are more likely to be sick and are less productive. Children brought up in cold, damp, or mouldy housing may also develop lifelong health issues that limit their potential.
New Zealand continues to face a shortage of housing. But just as importantly, the country suffers from having some disturbing levels of low-quality housing. We need to build more, sure. But we also need to build better, renovate what we can, and overhaul what we can’t. People’s health, and potential in life, depend on it.
 Census 2018 data shows that the 1.48m dwellings for which data was captured about dampness represent 89% of all dwellings in New Zealand.
 Census 2018 data shows that the 1.49m dwellings for which data was captured about dampness represent 90% of all dwellings in New Zealand.
 The question around the main types of heating is a new question that goes further than prior Census questions that gathered information on all the heating fuel types used in the dwelling.
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