Iceland tightens daylight rules, Reykjavik densification exposed, thousands of legal flats miss new standard

• Rules that took effect on 1 May require both consideration of surrounding shadows and a measurable indoor daylight threshold.
• Experts told RÚV that thousands of apartments built in recent years would not meet the new standard.
• Previous rules mainly required window area equal to one tenth of floor space, even when deep balconies or nearby buildings blocked light.
• The new requirements phase in for detailed zoning plans approved after 1 May 2026 and for all such plans from 1 August 2027.

Iceland changed its building code on 1 May to require adequate daylight in all apartments, after experts said years of urban infill had produced homes that were legal on paper but dark enough to resemble “basement apartments on the third floor.” In a report by RÚV, architects and lighting specialists say thousands of flats built in recent years would fail the new standard.

The shift is aimed at a gap that opened as Iceland pushed denser development, especially in the Reykjavik area. Earlier rules largely focused on the size of the window opening: each habitable room needed glazing equal to one tenth of the floor area. That worked in more open, lower-rise settings. It did not account for what stood outside the window. Taller neighbouring blocks, narrow courtyards and deep balconies could leave an apartment with technically compliant windows and very little daylight.

Anna María Bogadóttir, an architect, and Ásta Logadóttir, an electrical engineer specialising in daylight, told RÚV that buyers sometimes purchased flats in winter darkness without realising they would remain dim even in summer. Residents discovered the problem later, they said, when ordinary potted plants failed to survive on the windowsill. Their account puts a sharper edge on a familiar housing-market bargain: more units fitted onto expensive urban plots, with the loss carried inside the apartment rather than on the sales brochure.

Under the new rules, daylight is no longer treated as a matter of window dimensions alone. External obstructions must be counted. If nearby buildings or balcony structures reduce incoming light, the window must be enlarged accordingly. The code also introduces a measurable performance test: 40% of the floor area in a habitable room must receive 300 lux for half of the annual daylight hours. If that cannot be achieved, the room must be made shallower.

That requirement pulls the issue upstream, into zoning and design. Ólafur Árnason, managing director at the Housing and Construction Authority (HMS), told RÚV that daylight now has to be considered much earlier, alongside planning work, because a project that ignores it at zoning stage may be difficult or impossible to fix later. HMS published new guidance last week to help developers and planners meet the revised rules.

The timeline also shows how long the problem sat with the authorities while construction continued. Ásta Logadóttir first raised the issue with government nine years ago. A review of the daylight chapter began five years ago under a previous social affairs and housing minister. The final changes were approved only this January and took effect in May, after thousands of apartments had already been built under the older rules.

The new provisions apply to detailed zoning plans approved after 1 May 2026, and from 1 August 2027 they will apply to all such plans regardless of age. HMS expects the first neighbourhoods designed entirely around the new daylight rules to rise in three to four years. Thousands of existing apartments will remain legal exactly as they are, with windows large enough for the old code and light levels too low for the new one.

Källor: RÚV