What changes about doing laundry in a passive house?

Laundry is one of those household tasks that most people don't think about until something makes it inconvenient. In a passive house, a few things about how you do laundry change, some for the better, one or two requiring a small adjustment in habit. None of it is complicated, but understanding what's different and why helps you get the most out of the home from day one.

Drying your clothes

The biggest practical change for most passive house owners is how and where laundry is dried. In a conventional home, you can hang wet laundry inside – particularly in winter or on rainy days. The building's natural leakiness allows the resulting moisture to escape through the fabric without much consequence.

In a passive house design, drying laundry indoors on racks or airers introduces a significant moisture load into a tightly sealed building. That moisture has nowhere to go except into the air, and while the mechanical ventilation with heat recovery (MVHR) system continuously manages humidity throughout the home, a large load of wet laundry drying in a living room or bedroom can push indoor humidity levels higher than the system is designed to handle as a matter of routine.

This doesn’t mean you can never dry laundry inside a passive house. It just means you need to think about where and how. A dedicated drying room or laundry space with its own extract ventilation is the most effective solution, and it’s worth discussing with your passive house designers in Australia at the design stage if indoor drying is part of your household’s normal routine. Some passive house designs in Australia include a purpose-designed drying room, recognising that it’s one of the most practical indoor moisture management challenges for Australian households.

If you want to include a mechanical drying option, a heat pump clothes dryer is the most compatible solution for a passive house. Unlike a conventional vented dryer – which exhausts warm, moist air to the outside through a duct that needs to be carefully detailed for airtightness – a heat pump dryer is a closed-loop system that condenses moisture from the clothes into a reservoir rather than venting it to the outside. It uses less energy than a conventional dryer, produces no moisture load on the indoor air and requires no penetration through the building envelope.

Washing machines and water temperature

Washing machines in a passive house work exactly as they do in any other home. There's no specific adjustment needed for the machine itself. The main consideration is water temperature. Most modern washing machines heat their own water internally, which means the heat generated during a wash cycle contributes to the home's internal heat gains – a small but considerable addition to the thermal balance that passive house energy modelling accounts for alongside other appliances.

Laundry placement and ventilation

Where the laundry is located within the floor plan of a passive house design is more important than it would be in a conventional home. A laundry generates humidity from both the washing machine and any drying that takes place there, and that humidity needs to be extracted effectively before it migrates into the rest of the home.

In a passive house, the laundry is typically included in the MVHR extract zoning. Stale, moist air is drawn out of the laundry continuously, just as it is from bathrooms and the kitchen. This is effective for managing background humidity from the washing machine, but a laundry that's also used for indoor drying may need a higher extract rate or a dedicated boost function to handle the additional moisture load.

Positioning the laundry adjacent to a bathroom or wet area, where the MVHR extract infrastructure is already concentrated, is a practical design choice that simplifies the ventilation layout and ensures the laundry's moisture load is managed effectively without requiring a separate duct run across the building.

Outdoor drying

For passive house designs in Australia, where sunshine is reliable for most of the year in most areas, outdoor drying on a clothesline or retractable rack is both practical and consistent with the home's low-energy ethos. The main design consideration is ensuring that the outdoor drying area is accessible from the laundry without requiring occupants to carry wet laundry through the main living areas.