Damp properties cause mould build-up and can lead to illness. But it’s not just humans who suffer, dampness can also ruin the structure of a home, cause problems with walls, carpets, ceilings, furnishings and even foundations.

No-one wants a damp home: you’ll spend heaps of money on repairs, your home may lessen in value and it breaks the Healthy Homes tenancy rules.

The Healthy Homes ventilation standard was put in place to address the dampness issue in New Zealand housing. If you haven’t put the appropriate ventilation systems in your home yet, due to a long-term tenant, you have until July 1, 2025, to do it. If the tenant leaves before this, you’ll have 90 days from when you renew the tenancy agreement. Everyone else needs to ensure they adhere to the ventilation standards now to avoid penalties.

Dampness and mould can build up in bathrooms, window frames, around cooking and washing facilities in the kitchen. Walls can attract condensation in the winter if the home is not properly ventilated. Read below about everything you need to know to get your home up to standard.

The Healthy Homes standards stipulate that all rental homes must have windows that open in the living rooms, dining rooms, kitchen and bedrooms, as well as extractor fans in the kitchen and bathrooms or acceptable continuous mechanical ventilation systems.

Kitchens require new fans or rangehoods installed after July 1, 2019, to have a minimum diameter (including ducting) of 150mm, or an exhaust capacity of at least 50 litres per second. Bathrooms require new fans installed after July 1, 2019, to have a minimum diameter (including ducting) of 120mm, or an exhaust capacity of at least 25 litres per second.

Rangehood Options

Rangehood costs vary depending on the external structure of the house and will be upwards of about $300 to purchase, plus installation costs, which start at about $350.

Extractors for bathrooms generally cost a minimum of about $150, including installation kit. Installation costs will depend on several factors such as the exterior material of the house, roof access and how many levels the house has. Cement, brick or window installation will generally cost more as they are more expensive to cut through.

The other option is to use a company that sells and installs these for one overall fee. The approximate cost for installing either a kitchen or bathroom extractor to meet Healthy Homes standards is around $1200-$1300, plus $200 if there is glass cutting.

Mechanical ventilation systems aren’t mandatory to meet Healthy Homes standards but can be useful for keeping homes clean and dry. The benefits of a mechanical ventilation system include eliminating condensation, dampness and mould, and they can also eliminate the risk of damage to the building’s structure. There are four types of mechanical ventilation system, each with their own advantages and suitability for your specific property.

• MVHR - Mechanical Ventilation Heat Recovery System: Can recover up to 90 per cent of heat which would normally be lost and save money on energy bills.
• C-MEV - Centralised mechanical extraction system, most commonly known as Mechanical Extraction Ventilation (MEV): It’s more efficient and has separate fans in each room. More beneficial than fans as they do not create air leakage, heat loss or drafts.
• D-MEV - Decentralised mechanical extraction system: Low energy systems which work continuously to draw moisture out of bathrooms.
• PIV - Positive input ventilation system: Redistributes trapped heat from the roof void. Helps to eliminate condensation build-up and improves air quality by distributing filtered air through the property.

Tenant Factor

Tenants need to be made aware and schooled up on the best way to use these systems so they can keep condensation from building up and reduce dampness or mould.

Several companies offer quotes, advice and full installation of extractor units and home ventilation systems. However, you would be looking at upwards of $2,000 to have one installed.

As with heating, the choice of ventilation options within your rental property will come down to climate, what type of property it is and your personal budget for complying with the standards and keeping your property well maintained.