A major problem

Almost a quarter of Amsterdam’s residents have mould in their living room or bedroom, as revealed by the GGD’s health monitor. Since the launch of the joint initiative by Amsterdam’s housing associations, over 15,000 reports of damp and mould issues have been received up to March 2025 — accounting for 6.7 per cent of the housing association stock. And those are only the reported cases. The actual scale is likely to be much greater.

The usual response: ventilate, clean, repeat

The standard response to mould complaints is predictable: residents are advised to ventilate better, air out more often, and shower less. Sometimes this is followed by a one-off treatment of the affected surface. But simply wiping away the mould without tackling the underlying cause solves nothing. The problems are often due to decades of neglected maintenance, poor insulation and inadequate ventilation. A pot of paint won’t fix that.

The real cause lies in the indoor climate

Mould does not develop because residents are doing something wrong. It develops because the indoor climate is structurally out of balance: excessive humidity, insufficient air exchange, and insufficient heat combined with thermal bridges in the building structure. The !WOON Foundation has observed a rise in reports, partly due to higher energy prices — residents are heating their homes less, which exacerbates damp and mould problems. The indoor climate is constantly changing. Without continuous monitoring, no one knows exactly what is going on.

Measurement provides insight; insight enables action

We believe that you can only truly solve a problem once you understand it. By continuously measuring humidity, temperature and CO₂ levels in a home, you gain a reliable picture of where and when the indoor climate is at risk. This is fundamentally different from a one-off inspection or dealing with a complaint after mould has already become visible. With the right sensor data, you can identify patterns: which rooms are vulnerable, at what times does humidity peak, and how is the ventilation system actually performing?

Housing associations can take targeted action

Councillor Zita Pels argues that the problem is so vast and complex that local authorities and housing associations cannot solve it alone. That is true — but it certainly starts with data at the building level. Housing associations that have access to continuous climate data per home or per complex can prioritise: which homes require immediate intervention, where is an adjustment to the ventilation system sufficient, and where is structural intervention truly necessary? That is the difference between a generic approach and a targeted approach that actually works.

Healthy homes start with insight

The City of Amsterdam has set itself the goal of making all homes mould-free by 2030. That’s a laudable aim — but it will only succeed if housing associations and homeowners know where to start. We’re happy to help with that. Using accessible sensor technology and a clear data platform, we provide insight into the indoor climate of homes. Not just to generate reports, but to bring about real change. Curious about what continuous climate monitoring could mean for your housing portfolio? Let’s have a chat.