Your home and your health

Condensation happens when moist air meets a cold surface - a window, wall or ceiling - and the water vapour turns back into droplets. Everyday activities create a surprising amount of moisture: showers, cooking, drying washing indoors, and even breathing. When that moisture has nowhere to go, it settles on cold surfaces and feeds mould growth, which makes a home feel colder and harder to heat.

Let moisture escape at the source. Use externally vented extractor fans in the bathroom, kitchen and laundry (a range hood in the kitchen, extraction fans in wet rooms). Open a window in those rooms and keep the door closed so water vapour doesn't spread through the house.

Open up on fine days. Air the house when the weather allows to let damp, stale air out and fresh, drier air in.

Find and fix leaks. Check for water getting in through guttering, roofing and plumbing, and have repairs done. Make sure there's good drainage around the outside of the house.

Block ground moisture. Laying black polythene on the ground in the subfloor space keeps the house drier and easier to heat.

Consider double glazing if you're building or replacing windows, as it reduces condensation on the glass.

Clean mould and mildew off walls, ceilings and surfaces with a fungicide such as well-diluted household bleach (follow the product instructions and ventilate the room while you do it).

If a home is insulated, ventilated and heated but damp and mould keep coming back, the moisture is usually getting in from somewhere - damp ground under the floor, a roof or rainwater leak, or a plumbing leak - so it's worth tracking down and fixing the source rather than just cleaning the surface.

An efficient, clean form of heating with good temperature control. Choose one sized for the room, and if you live somewhere that gets very cold, check it works well below 10°C.

Effective and healthier than unflued gas, because the products of combustion are vented outside rather than into your living space.

Distributes warmth through the house (via ducted air, radiators or underfloor pipes) and often lets you set different temperatures in different rooms.

These release both pollutants and water vapour straight into the room - a double problem for damp and for sensitive airways. Avoid them if you can, and never use them in bedrooms or small, unventilated rooms.

These are inefficient, polluting, expensive and hard to control.

These can produce plenty of heat, and newer models burn relatively cleanly if you use dry, well-seasoned wood (dried for at least a year). They do create some air pollution, so they suit some homes better than others.

Government grants for eligible owner-occupiers in homes built before 2008. Covers roughly 50–90% of ceiling and underfloor insulation, and up to 90% of an approved heat pump for the main living area, with the discount taken straight off the installer's quote. Eligibility depends on holding a Community Services Card or SuperGold Combo Card, or living in a lower-income area.

In many regions, community organisations top the grant up further — sometimes to nothing to pay. Check eligibility in about five minutes at warmerkiwihomes.govt.nz or call EECA on 0800 749 782.

A free online assessment (plus optional full independent certification) that tells you how warm, dry and healthy your home is and what to improve.

Practical tips on keeping your home warm and dry while lowering your power bill.

If you rent, your landlord is legally required to meet the Healthy Homes Standards for insulation, heating, ventilation, moisture and draught-stopping. The Ministry of Business, Innovation and Employment (MBIE) publishes guidance for tenants and landlords - see Tenancy Services for what your rental must provide.