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Documentation Index

Fetch the complete documentation index at: https://help.ratemyflat.co.nz/llms.txt

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Proper ventilation is essential for removing moisture from a home. Without it, everyday activities like cooking and showering lead to mould growth and dampness, which can cause respiratory issues.

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The 5% rule for windows

All “habitable rooms” (living rooms, dining rooms, kitchens, and bedrooms) must have at least one window, door, or skylight that opens to the outside. The total openable area must be at least 5% of the floor area of that room. These windows must be able to be fixed in the open position to allow for consistent airflow.

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Extractor fan requirements

Mechanical ventilation (extractor fans) must be installed in any room with a cooktop or a shower/bath.
  • Kitchens: Fans installed after 1 July 2019 must have a diameter of at least 150mm or an exhaust capacity of at least 50 L/s.
  • Bathrooms: Fans installed after 1 July 2019 must have a diameter of at least 120mm or an exhaust capacity of at least 25 L/s.
  • External venting: Fans must vent directly outside. Venting into a roof cavity or “into the eaves” isn’t permitted — it just moves the moisture to another part of the building.

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How to check your home

  • Visual check: Open your windows. Do they stay open? Are they large enough to equal 1/20th of the floor size?
  • Fan check: Turn on your kitchen rangehood and bathroom fan. Hold a single square of toilet paper against the fan grille. If the suction is strong enough to hold the paper in place, the fan is likely working, though it may still need a professional check to ensure it meets the L/s requirement.
  • External vents: Go outside and look for the exhaust cowls on the wall or roof. If you can’t find them, your fans might be venting into the ceiling space illegally.

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Tenant tips for a drier home

Landlords provide the fans, but you need to use them:
  • Run the fans: Always use the extractor fan while cooking or showering, and leave it running for 10 minutes after you finish.
  • Cross-ventilation: Open windows on opposite sides of the home for 15 minutes a day to “flush” the air.
  • Wipe condensation: If you see water on your windows in the morning, wipe it off. This prevents mould from growing on the sills and curtains.

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Sources