Home ventilation in Sweden: FTX, natural draught and OVK explained

Poor ventilation is rarely obvious at first. It shows up as condensation on windows, stale air in the hallway, morning headaches and, at worst, mould behind a wardrobe on an external wall.

Here are the three system types found in Swedish homes, what each needs, and what service costs.

Three systems, three maintenance needs

Natural draught exists in houses built before the 1970s and relies on temperature differences. It only works if fresh air vents are kept open and clean.

Extract systems, common from the seventies onwards, pull air out with a fan while fresh air enters through vents. FTX systems recover heat from the extracted air and are found in newer homes: the most efficient, and the most maintenance-hungry.

Filter changes and cleaning

Filters in an FTX unit should be changed twice a year, normally spring and autumn. A clogged filter reduces airflow, raises electricity use and cuts heat recovery.

Kitchen hood grease filters go in the dishwasher monthly, and extract valves in bathrooms and bedrooms should be cleaned at least yearly. Mark the valves before unscrewing them, they are balanced and must go back in the same position.

OVK, what it means

The mandatory ventilation inspection is required by Swedish law and carried out by a certified inspector. Apartment buildings with FTX are checked every three years, extract systems every six. Single-family houses only need it at new installation.

A failed OVK means the property owner must fix the faults within a set time. In a co-op the association is responsible, but residents must give access.

Service costs

Service and filter change on a house FTX unit typically costs 1,800 to 3,500 SEK including filters. Cleaning and rebalancing the whole duct system runs 6,000 to 15,000 SEK depending on house size.

Work in a home you own qualifies for the ROT deduction. Book in September, before everyone notices condensation on their windows at the same time.