The health service faces a bill of more than £30 million a year if poor houses in Northern Ireland are not improved, a report has warned.
A fifth of homes in Northern Ireland have a serious safety hazard, with f all risks, excessive cold, dampness and mould growth among problems identified by a Housing Executive review.
Homes dating back to the First World War and earlier are most likely to have issues, with less insulation and steep, winding staircases.
Home safety improvements could make significant savings. However it may take more than 500 years before the cost of dealing with cold homes is paid back in savings to the health service, according to the analysis.
The document said: "This research demonstrates that simple home safety improvements - for example hand rails on dangerous stairs and steps, hard-wired smoke and carbon monoxide detectors, better home security - are very cost effective.
"It is more difficult to demonstrate the cost effectiveness of remedial works to deal with excess cold and dampness problems across the whole housing stock because such works can be much more expensive, but targeting certain types of property with basic packages of work can be very effective."
The expert report called for more work on the impact on mental health, educational attainment, quality of life and social participation.
A housing survey from 2009 suggested some 144,000 (20%) of Northern Ireland's homes had at least one serious hazard.
Despite this, the region has the most modern housing stock in the UK and proportionately less poor housing.
Older properties are likely to suffer from disrepair, which can cause damp problems. Rural homes are more commonly hazardous than urban ones, on average older or likely to be vacant.
Privately-owned houses are twice as likely to have serious hazards as those in the social sector.
The total cost of addressing the most serious hazards could be £469 million. If the houses are left unimproved the NHS could face a bill of just under £33 million per year, the report said.
Almost half of households in Northern Ireland are in fuel poverty, meaning residents find it harder to properly heat their homes.
A programme of measures to better insulate vulnerable homes and install more efficient heating is under way.
The cost of a heart attack brought on by excessive cold can be £22,295 after one year, according to the research.
Even mild asthma caused by damp can carry a price tag to the health service of £180.
The average number of excess winter deaths caused by cold in Northern Ireland from 2001 to 2009 was around 500 per year, but it rose to just over 1,000 in 2008/2009 because of that particularly cold winter.
John McPeake, chief executive of the Housing Executive, said: "At a time of severe constraints on public expenditure therefore, this report is a very welcome addition to the underlying evidence base for well-targeted public investment in housing, which would not only bring significant improvements in the physical and mental health and well-being of households, but would also increase the value of the housing stock and could facilitate very considerable savings in the health budget in Northern Ireland."