Complete Guide to 24-Hour Ventilation Systems in Rental Homes — How They Work, Proper Use, and Electricity Cost-Saving Tips
Explaining how 24-hour ventilation systems (mandatory in rental properties since 2003) work and how to use them correctly. We also cover why you shouldn't turn off the switch and tips for filter maintenance.
Buildings that received construction permits after July 2003 are required by Article 28-2 of the Building Standards Law to install "24-hour mechanical ventilation systems (sick house syndrome prevention ventilation)." However, many rental tenants live without knowing of their existence or how to use them correctly, and cases where the switch is kept off are not uncommon. This article provides a thorough explanation of 24-hour ventilation systems: how they work, their types, proper use, and electricity cost-saving strategies.
It is equipment designed to exchange the air throughout a building at least once every 2 hours (0.5 times per hour or more) in order to dilute and expel volatile organic compounds (VOCs such as formaldehyde) and carbon dioxide (CO2) that cause sick house syndrome. It is installed in principle in new properties built after 2003, which explains why ventilation outlets (intake vents) and exhaust fans exist in condominiums and new apartment buildings where you move in.
The law establishes standards for ventilation volume, with a minimum air exchange rate of 0.5 times per hour (replacing half the volume of the room's air each hour).
Types of Ventilation Systems (Type 1, Type 2, and Type 3)
There are three types of ventilation systems.
Type 1 ventilation is a system where both intake and exhaust are controlled mechanically. The "total heat recovery" type with a heat exchanger is widely adopted, and because it adjusts outside air to a temperature close to room temperature before bringing it in, it offers high air conditioning efficiency. It is common in luxury condominiums and energy-efficient properties.
Type 2 ventilation is a system where only the intake is mechanized, while exhaust relies on natural ventilation. It is designed for facilities requiring high cleanliness, such as hospital clean rooms, and is rarely used in residential homes.
Type 3 ventilation is the most common system, where only exhaust is handled mechanically (via exhaust fan) and intake comes naturally through vents (round filter grilles) in each room. Because installation costs are low, it is widely used in apartments and newer condominiums. Since ventilation noise is heard only from the exhaust fan side, tenants often overlook the existence of intake vents.
Common Misuses and Their Risks
Misuse 1: Keeping the switch off constantly
Many tenants turn off the switch because they find the ventilation noise bothersome or feel the electricity cost is wasteful. However, this is not only a violation of the Building Standards Law (a problem on the property owner's side) but also creates a risk of indoor air contamination. VOCs emitted from new building materials and furniture can accumulate, potentially causing headaches, blurred vision, and fatigue (sick house syndrome).
Misuse 2: Closing the intake vent
It is also problematic to seal the round intake vent installed on the wall with tape or leave it in a closed position because you find drafts bothersome or feel cold. When the intake vent is blocked, even though exhaust can occur, fresh air cannot enter, creating negative pressure in the room, which causes doors to become heavy and cold air to easily seep in through gaps.
Misuse 3: Not cleaning the filter
The intake vent is equipped with a filter that captures dust, pollen, and PM2.5. If left unattended, it becomes clogged, reducing ventilation volume, raising electricity costs, decreasing ventilation efficiency, and in some cases becoming a breeding ground for mold.
Proper Use and Maintenance
The correct way to use it is to keep it on 24 hours a day as a general rule. The monthly electricity consumption is only around ¥50–200 (about 5–20W) for small units. Improving indoor air quality provides greater health benefits than energy-saving effects.
The intake vent filter should be cleaned once every 2 to 3 months. Remove the filter and vacuum it; for washable types, rinse, dry, and reinstall. For products requiring filter replacement, confirm with your property management company and clarify who bears the cost (landlord or tenant).
The exhaust fan also requires regular cleaning. Bathroom and toilet exhaust fans easily accumulate dust; when clogged, ventilation volume decreases. Make it a habit to remove the cover and clean every 2 to 3 months.
The cost of filter replacement depends on the property contract. In most cases, it is borne by the tenant as a consumable, but it may be the landlord's responsibility as part of the equipment. Confirm this in your lease or move-in documentation.
Saving Electricity Costs and Optimizing Ventilation Volume
Small Type 3 ventilation fans typically cost around ¥100–200 per month even with 24-hour operation. However, Type 1 ventilation (total heat recovery) consumes more power, sometimes exceeding ¥500–1,000 per month.
An effective cost-saving strategy is using "low mode". Many ventilation systems have high and low settings; switching to high when cooking or having guests and low at other times can reduce power consumption by 20–40%. The key is to adjust while staying within the ventilation volume required by the Building Standards Law (0.5 times per hour).
Coordinating with air conditioning by season is also important. In winter, you can insulate the intake vent to reduce cold air entering directly (while maintaining required ventilation volume). This concern is less of an issue in properties with Type 1 ventilation (total heat recovery).
Things to Confirm with Your Property Management Company
Confirming the following at move-in can prevent later problems:
•Type of ventilation system (Type 1 or Type 3) and installation location
•Who bears the cost of filter cleaning and replacement
•Who is responsible for repairs if it breaks (as part of the equipment, it is typically the landlord's responsibility)
•Location of the ventilation switch and how to operate it (which circuit if multiple)
Summary: 24-Hour Ventilation Is "Health Infrastructure"
The 24-hour ventilation system is an important infrastructure supporting comfortable rental living. Even if you are bothered by noise or electricity costs, continuing to use it correctly—rather than simply turning it off—contributes to your health and building maintenance. Make proper maintenance, such as filter cleaning, a habit and keep your indoor environment comfortable.
