There are some reasonably simple steps you can take to improve your tenants living standards and better protect your rental property. A video from the Palmerston North eco design adviser, Nelson Lebo, is excellent. View this video here.
Consider installing extractor fans in the kitchen and bathroom. This is where a lot of moisture in a home comes from.
Check your underfloor areas and if there is rising damp, get a ground vapour barrier installed. They are relatively inexpensive and can reduce large levels of moisture from getting into the property.
Consider adding to your tenancy agreement that unflued gas heaters cannot be used in the property as they produce a considerable amount of moisture.
Tell new tenants that drying close inside on racks significantly increases moisture and makes the property harder and more expensive to heat. You can help them to comply by installing clothes lines in garages, carports or other covered areas.
Unfortunately one of the biggest sources of moisture in a property is the tenants themselves through perspiration and breathing. You may not be able to use the tenancy agreement to prevent them from breathing, but you can let them know that opening doors or windows and creating a through draft for 20 to 30 minutes a day will make their home dryer and easier to heat.