Kitchens are one of the highest moisture-generating rooms in any home, and in the Illawarra’s already-humid coastal climate, a kitchen without adequate ventilation is a reliable mould generator. Boiling, frying, dishwashing, and the simple act of rinsing vegetables under a tap all add moisture to the kitchen air. Combine this with the ambient humidity of a summer Wollongong day and inadequate extraction, and you have conditions that are, without intervention, going to grow mould on the ceiling, under the sink, inside upper cabinets, and around the window frame above the sink. This guide gives practical, specific advice for Illawarra kitchens. For existing mould in kitchen cabinets, see our dedicated kitchen cabinet mould guide.
Quick Answer (BLUF)
Adequate extraction (a rangehood that exhausts to outside, not a recirculating unit), sufficient ventilation during cooking (window or exhaust fan running), and diligent under-sink and bench hygiene prevent most kitchen mould in Illawarra homes. The single biggest impact change most kitchens can make is replacing a recirculating rangehood with one that genuinely exhausts moisture out of the building.
The Kitchen Moisture Problem in Numbers
A typical cooking session, 30 minutes of boiling pasta, a pot of sauce, can add 300-500ml of water vapour to the kitchen air. Dishwashing adds another 100-200ml. In a small kitchen (15-20 m²) with one air change per hour (no ventilation), ambient humidity can spike from 60% to 85%+ within minutes of cooking and remain elevated for hours.
In the Illawarra, where outdoor relative humidity is already 65-80% on a typical summer day in coastal suburbs like Thirroul, Austinmer, and Wollongong CBD, there is very little headroom, kitchen humidity can reach 90%+ without effective extraction, providing ideal conditions for every surface in the room to support mould growth.
Rangehood Selection and Installation
The Recirculating Rangehood Problem
The most common kitchen ventilation mistake in the Illawarra is the recirculating rangehood, a unit that draws air through a carbon filter and expels it back into the kitchen. These units remove grease and some odour from cooking fumes but return all the moisture to the room. They do absolutely nothing for humidity reduction.
A significant proportion of kitchens in Wollongong and the Illawarra, particularly in apartments, townhouses, and older homes, are fitted with recirculating units, either because ducting to outside was never installed or because the unit was replaced without rerouting the ductwork.
The solution: Replace the recirculating unit (or convert it) to a ducted rangehood that exhausts directly outside. If no external ductwork exists, this is a construction job, a hole through the external wall or ceiling void with a duct run to a wall or roof cap. The cost is typically $300 to $600 for the ductwork and installation, and the benefit to kitchen humidity is immediate and significant.
Sizing and Selection
A rangehood’s airflow capacity is rated in m³/h (cubic metres per hour). AS/NZS 5601.1 recommends a minimum of 10 air changes per hour for kitchen ventilation. For a typical 15-20 m² kitchen with 2.4m ceiling height:
- Kitchen volume: 15m² × 2.4m = 36 m³
- Required airflow: 36m³ × 10 ACH = 360 m³/h minimum
- For coastal Illawarra conditions, choose a rangehood rated 400-600 m³/h
A rangehood that exceeds these numbers and can be turned down is preferable to an undersized unit at full capacity.
Duct Diameter
Undersized ductwork is a common cause of poor rangehood performance in retrofitted installations. The duct diameter should match the rangehood outlet (typically 150mm or 200mm for residential units). Reducing the duct diameter to fit through an existing penetration reduces airflow dramatically and should be avoided.
Kitchen Exhaust Fans as a Supplement
In kitchens without a wall position suitable for a rangehood directly above the cooktop (some Illawarra homes have island benches, or cooktops against interior walls with no exterior wall access), a ceiling-mounted exhaust fan is a supplement. It will not capture steam at the source the way a rangehood does, but it will extract moisture-laden air from the kitchen generally.
Run it during cooking and for at least 15 minutes afterward. A timer-run fan is ideal.
Window and Natural Ventilation
Opening the kitchen window during cooking is the zero-cost option and still effective. In the Illawarra, sea breezes from the north-east (dominant in summer afternoons) can provide substantial natural ventilation in coastal kitchens with north or east-facing windows. In winter or on still days, mechanical ventilation is necessary, natural ventilation alone is not adequate.
Under-Sink Cabinet Hygiene
The space under the kitchen sink is one of the most mould-prone locations in any home:
- Slow leaks from supply hoses, isolation valves, or drain connections are common and easily go unnoticed
- Cleaning product residue on timber or particle board shelving provides a food source for mould
- The base of the cabinet sits above a cold concrete slab or timber floor that creates a condensation surface
Prevention:
- Inspect under-sink plumbing quarterly, look for evidence of drips, staining, or soft shelving
- Install a waterproof shelf liner on the cabinet base (cut to fit, available in rolls)
- Leave under-sink cabinet doors ajar occasionally to promote air circulation
- Do not store wet sponges, damp cleaning cloths, or moist bin bags in the undersink cabinet
Bench and Surface Hygiene
Kitchen benches made from porous materials (raw timber, rough-cut stone, some grout-heavy tile surfaces) can support mould growth if they are left wet. In the Illawarra:
- Dry bench surfaces after every food preparation session, a microfibre cloth takes 30 seconds
- Clean around tap bases and the joint between the splashback and bench, these are the spots where moisture accumulates and mould starts
- Seal natural stone benchtops annually, unsealed stone is significantly more porous and mould-prone
- Replace worn silicone or grout between the splashback tiles and the bench surface, this is the most common mould location in a kitchen
FAQs
My kitchen has no outside wall for a rangehood. What can I do?
For island or interior cooktop positions, an island rangehood that ducts upward through the ceiling void and exits through the roof (via a roof cap) is the correct solution. This is more expensive to install ($800 to $1,500 with ductwork) but is the only way to genuinely extract steam from a cooktop with no adjacent external wall.
How do I get rid of the mould smell in my kitchen?
A musty smell in a kitchen usually comes from one of: active mould in an enclosed cabinet (under the sink, inside upper cabinets), the dishwasher drain or filter, or a blocked or slow kitchen drain. Check each systematically, clean or treat what you find, and improve ventilation. See our musty smell guide for a full diagnostic approach.
Can I put a dehumidifier in the kitchen to reduce mould?
A dehumidifier helps but should be a supplement to extraction ventilation, not a substitute. During active cooking, a dehumidifier’s capacity is overwhelmed by the rate of moisture production. Extraction ventilation removes moisture from the building; a dehumidifier simply moves it into the condensate tank. Extraction is the priority.