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New study: Even brand-new apartments in cities can have poor indoor air quality

"What works in a single family home in the countryside is not necessarily adequate for a small apartment in the city,” says researcher.

New and beautiful does not always equal good. Researchers find that small, urban apartments often need better ventilation solutions.
Ida Rambæk Communications Adviser
Presented by: Presented by: Presented by: SINTEF
Published

More and more people live in small apartments in densely populated areas. Many of these apartments have an open kitchen layout. Noise and air pollution mean that it's not always a good idea to open the window.

That is the background for the Urban Ventilation project.

“We wanted to investigate whether the current ventilation requirements are adapted to these apartments. Because what works in a single family home in the countryside is not necessarily adequate for a small apartment in the city,” says Kari Thunshelle, a researcher at SINTEF.

The researchers therefore mapped the floor plans, ventilation systems, and use of new apartments. 

They also conducted extensive lab testing of various ventilation solutions. How effective were they when residents showered or cooked?

Minimum requirements do not always suffice

The researchers brought together developers and manufacturers, including the Røroshetta company, which builds ventilation solutions for kitchens.

“Our motivation for participating in the project was to document what air volumes are actually needed to achieve a good indoor climate in different types of homes,” says Håvard Augensen, CEO of Røroshetta.

His experience is that the minimum requirement is not always sufficient. Nevertheless, some developers choose the simplest solution.

The result? Unsatisfied customers and poor indoor air quality.

Røroshetta has therefore worked to adjust the air volumes so that they ensure a healthy indoor climate.

“We hope that more developers and technical contractors will be responsive to our recommendations, now that we have documented knowledge about capturing cooking fumes and air volumes,” says Augensen.

Confirmed by lab tests

Researchers at SINTEF conducted the lab tests, which largely confirm Augensen's experiences.

The minimum extraction requirement in kitchens when cooking is 108 cubic metres of air per hour.

The products that were tested did not capture enough of the fumes from cooking.

Various ventilation solutions being tested in the lab. The researchers prepared 72 salmon dinners and monitored the indoor climate. Photo shows Wojciech Wojnowski at the University of Oslo in action.

But both extractor hoods and ventilators that pull the cooking fumes down into the hob are adequate when the air volume is sufficient. 

The tests showed a big improvement when the air volume was increased to 180 cubic metres per hour. 

Would not recommend recirculating air

“The correct amount of air depends on the individual product and how it and the hob are situated,” says Thunshelle.

Solutions where the air is recirculated, such as carbon filters, require less space for ducts. These are popular in small apartments. But their filtration is currently not good enough.

The recirculating solutions that were tested captured some food odours and particles. But they were far less effective at handling the gases and ultrafine particles that formed during cooking.

“For now, we would therefore not recommend recirculation as a complete solution on par with systems where the cooking fumes are ventilated into the open air,” says Thunshelle.

Håvard Augensen at Røroshetta was also aware that carbon filters are not as effective as other solutions.

“The research and development collaboration has given us useful information about particle dispersion and organic odours. That knowledge will help us develop solutions where charcoal filters can still be chosen in some cases,” he says.

Bathrooms require less ventilation

The tests for bathrooms showed that the standard performance for so-called forced exhaust air provided more air than needed to remove moisture from normal use.

“With a correctly placed exhaust valve, a lot of moisture is removed from showering even with basic exhaust air according to the current requirements. But it should be possible to increase the exhaust air to 75 cubic metres per hour if necessary, for example when you want to get rid of offensive odours,” says Thunshelle.

The Norwegian Building Technical Regulation (TEK) sets requirements for extraction from kitchens and bathrooms, and for air suply in bedrooms.

What about living areas?

For other living spaces, TEK only specifies requirements for minimum air volume per square metre. 

This does not necessarily ensure healthy indoor air quality in small homes.

Where noise or air pollution makes it difficult to open windows for ventilation, it is particularly important to ensure enough air with mechanical ventilation. 

Measurements and simulations carried out in the research project showed that regulating the air volumes is desirable in order to avoid dry air and unnecessary energy consumption.

“The project has given us a lot of important answers. However, we have to acknowledge that we’re not yet at the point where we can provide solutions that ensure a healthy indoor climate for everyone, with low environmental impact, and a reasonable cost picture. But it’s good to see that several of the partners are already working on improving the solutions,” says Thunshelle.

Reference:

Thunshelle et al. Urban ventilasjon: Ventilasjon for godt inneklima i urbane boliger (Urban ventilation: Ventilation for a good indoor climate in urban homes), SINTEF, 2025.

Here are the researchers' main findings

Cooking and exposure:

  • Ventilating into the open air removed pollutants significantly more effectively than the recirculating solutions and are currently the preferred solution.
  • The filters examined in the project removed the smallest particles only to a small extent, and tests show that exposure to small particles can increase when using a recirculating ventilator.
  • A minimum of 180 cubic metres per hour is needed to provide satisfactory fume collection capacity for a hob with a height of 60 centimetres placed against a wall.
  • The downdraft solution gave good results on par with a standard kitchen hood.

Moisture:

  • Forced extraction of 75 cubic metres per hour is considered sufficient for removing moisture from showering and clothes drying.
  • Total air volume that is less than 78 cubic metres per hour in apartments for two people, and 110 cubic metres per hour in apartments for four people, will result in too high a moisture load.
  • Recirculating kitchen hoods do not remove moisture. When using a recirculating solution, greater basic ventilation is needed than is available today to avoid the risk of condensation on windows, particularly in small kitchens.

CO2/Person load:

  • Today's regulations require some use of window ventilation, which is not always desirable in urban areas.
  • To handle CO2 from residents, an air volume of 150 cubic metres per hour is necessary in apartments for four people, and 75 cubic metres per hour in apartments for two people.

Layout and ventilation:

  • The design of the ventilation solution must be adapted to the design of the home and the expected load to ensure a good indoor air quality. The current approved solution in the TEK17 guidelines does not ensure this in all cases.

Current test standards:

The current test standards should be changed. Tests should be comparable for standard kitchen hoods, downdraft solutions and other relevant ventilation solutions. The test standards should address both fume collection capacity and exposure.

  • Performance (fume collection capacity, noise, and energy) should be documented at several comparable air volumes, for example 108 – 180 – 250 cubic metres per hour, in addition to the maximum air volume in standard testing with exhaust to the outside. This will make it easier to compare and select products. For recirculating systems, tests should be developed that document the filters' ability to reduce grease, specified VOCs and small particles, both for new filters and after a realistic pre-exposure.

About the project

The Healthy Energy-efficient Urban Home Ventilation project was a competence project for the business sector with funding from EnergiX in the Research Council of Norway and corporate partners. The goal was to establish knowledge and provide recommendations for robust ventilation solutions for new homes in an urban environment.

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Read the Norwegian version of this article on forskning.no

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