Table 3

Housing improvement studies reporting an economic evaluation (ordered by intervention type, study quality and date)

Author, date, location	Description of housing intervention	Study design	Summary of effect directions on health outcomes by domain**				Summary of economic data and analysis reported
Author, date, location	Description of housing intervention	Study design	General health	Respiratory	Mental health	Illness/symptom	Summary of economic data and analysis reported
Intervention: Warmth and energy efficiency improvements (post-1980)
Barton et al, 2007, UK31 45 69	Upgrading heating provision and energy efficiency according to need. For some houses, roofs were fitted with breathable roofing felt, plus 50 mm insulation, Cavity insulation with rockwool fibres, and double glazing. Over ceiling insulation topped up to 200 mm (glass fibre quilting), Front and back doors and French windows were replaced with uPVC doors.	RCT	<>	◄►	<>	▾	Paper states cost effectiveness analysis was carried out using SF-36 data, and report no significant differences between groups or over time in SF-36 subscales, but no data reported. Bootstrapped cost-effectiveness estimate (presented graphically) suggests that intervention dominated (more costly, less effective). Costs of intervention for each year. 49 houses improved in 1999, cost per house of £7760, 63 houses improved in 2000, average cost per house of £4819
							Compares costs (£GBP) between intervention and control groups for 3 years
							Costs per person (Year 1999)	Intervention	Control
							Annual equivalent intervention costs net of annual energy saving	£0	£0
							All NHS costs*	£204.86	£220.49
							Benefits
							SF36 (adults)	0.73	0.75
							Value of lost education	£240.7	£288.44
							Costs per person (Year 2000)	Intervention	Control
							Annual equivalent intervention costs net of annual energy saving	£-18.82	£0
							All NHS costs*	£224.97	£171.54
							Benefits
							SF36 (adults)	0.77	0.8
							Value of lost education	£352.28	£247.59
							Costs per person (Year 2001)	Intervention	Control
							Annual equivalent intervention costs net of annual energy saving	£0	£-16.56
							All NHS costs*	£135.72	£165.56
							Benefits
							SF36 (adults)	0.72	0.8
							Value of lost education	£80.92	£169.92
Chapman et al, 2007, New Zealand42 50 70 71	Ceiling insulation, draught-proofing of windows and doors, sisalated paper (insulated foil) strapped under floor joists, and polyethylene covering over the ground.	RCT	▴	▴	▴		Cost of intervention per household was $(NZ)1800. Assumed lifetime of benefits is 30 years
							Economic value of benefits ($(NZ)).
							Change in GP visits	165*
							Reduced hospital admissions	2231
							Reduced days of school	242
							Reduced days of work	179
							Energy savings	786
							CO₂ savings	100
							Total savings	3374
							* negative saving
							Calculated per household: savings $NZ 3374; intervention cost $NZ1800. Net benefit of $1574 per household. Benefit-cost ratio of 1.87:1 Estimated value of savings was around $NZ 25 a year.
Mackenzie et al, 2000, UK44 46	Grant up to £2500 to improve heating and reduce damp and mould growth in house, intervention agreed according to need. (Gas central heating, n=28 (47%), electric storage heater, n=22 (37%), solid fuel central heating, n=7 (12%), oil-fired central heating, n=2 (4%)).	UBA		▴			Average cost of intervention £3061 per house Data on health service contacts and prescribing data (before and after intervention) available for 47 children (48% 47/97 invited to take part) Costs estimated for NHS contacts and prescriptions and school absences.
							Annual equivalent cost of improvements	£329.49
							Less
							Estimated annual saving on fuel bills	214.81
							Est. annual saving on NHS treatment costs	£499.54
							Est. annual increase in prescribing costs	−£11.41
							Est. annual value of increased school att.	£108.36
							Total estimated benefits from home improve	£810.23
							Net benefit per annum	£413.33
Laing and Baker, 2006, New Zealand43 72–74	Insulation (26.5%) & ventilation (43.5%) improvements, improved heating system (4.4%), extensions (8.7%), plus housing and health advice, improved links with health and other support agencies	RC	No health impacts only service use				In house cost benefit analysis Direct benefit to cost ratio −0.87 net present value to household, $(AUS)2222; when some indirect benefits included benefit to cost ratio 1.15 and net present value to household of $(AUS)2471 No detail of methods or outcomes measures for analysis are provided. CBA planned

*Study design: RCT, randomised controlled trial; CBA, controlled before & after; UBA, uncontrolled before & after; RC, retrospective controlled study.
**Effect direction: upward arrow, positive health impact; downward arrow, negative health impact; sideways arrow, no change/mixed effects/conflicting findings.
Sample size: final sample size (individuals) in intervention group: large arrow, >300; medium arrow, 50–300; small arrow, <50.
Statistical significance: black arrow, p<0.05; grey arrow, p>0.05; empty arrow, no statistics/data reported.