Why the Netherlands Is Telling People to Hang Bedsheets on the Outside of Their Windows

What’s Happening?

Imagine it’s a scorching hot day, and your house feels like an oven. What if the solution was as simple as hanging a bedsheet outside your window? That’s exactly what officials in Amsterdam, the Netherlands, are now recommending!

Here’s the story:

• A heatwave hit the Netherlands, sending temperatures climbing higher than usual.
• Amsterdam’s public health institute urged people to keep direct sunlight off their windows.
• The government activated its national heatwave plan, paying special attention to older adults and other vulnerable people who are most at risk during extreme heat.

Why Are Dutch Houses So Hot?

According to Eline Coolen, the heat coordinator at Amsterdam’s public health institute, there’s a simple reason Dutch homes get so hot:

"In Dutch houses, but also in many houses in northern Europe, you have very big windows. We have always built for the winter, when you want as much sun and warmth in your house as possible."

Think of it this way: Dutch houses were designed like greenhouses — built to trap warmth during long, cold winters. But now that summers are getting hotter, those same big windows are letting in way too much heat, turning homes into saunas.

This isn’t just about comfort, either. As summers continue to get hotter, these large window designs can actually increase the risk of death from heat-related causes.

Creative Cooling Ideas for Cities

Beyond homes, researchers are getting creative with ways to cool down streets and public spaces while keeping things looking nice:

• Fake trees that provide shade
• Pergolas (outdoor structures with a roof of beams and an open lattice)
• Greenery and plants on building walls
• "Shadow art" — artistic installations designed to shield pedestrians from direct sunlight

Why Does This Matter?

You might be thinking, "It’s just a little heat — why does it matter so much?" Here’s why:

Blocking Sunlight Keeps Homes Cooler

By hanging curtains or sheets on the outside of your windows, you block the sun’s rays before they hit the glass and turn your home into a greenhouse. This simple trick can:

• Make indoor spaces much more comfortable during a heatwave
• Lower electricity bills by reducing the need for fans or air conditioning

The Science Is Simple

Bert Blocken, a mechanical engineering professor at Heriot-Watt University, explained it perfectly:

"A huge body of research showed the best way to keep a building cool was simply to keep out the sun. We need to keep our buildings cool, ideally without active cooling devices."

In other words, the best air conditioner might just be a piece of fabric!

A Lot of People Are Already Struggling

A survey by Vereniging Eigen Huis found that:

• 23% of respondents said their homes became too hot during a heatwave
• Most of them had already tried other ways to cool down — and it still wasn’t enough

Heat Costs Money, Too

Heat doesn’t just make you uncomfortable — it can hurt the economy. Sandra Phlippen, who leads climate strategy at ABN Amro, pointed out:

"One night of sleep loss [costs] close to €200 [£173]."

When people can’t sleep because their homes are too hot, they’re less productive at work the next day. That adds up to a huge economic cost across an entire country.

What’s Being Done?

The fight against urban heat needs to happen on multiple levels — from what you do at home to how entire cities are designed.

Step 1: Simple Awareness Campaigns

Werner Hagens, who coordinates the Dutch heatwave plan, shared that newer research shows something encouraging:

Simple awareness campaigns appear to reduce deaths during heatwaves.

Just telling people what to do — like hanging curtains outside their windows — can actually save lives.

Step 2: Exterior Shading (The Cheapest First Step)

The easiest and most affordable thing you can do is add exterior shading:

• Curtains or bedsheets hung on the outside of windows
• Blinds or awnings
• Outdoor screens

These all work by blocking the sun before it reaches the glass, which is far more effective than closing curtains on the inside.

Step 3: Long-Term Upgrades

For even better protection over time, cities and homeowners can invest in:

• Outdoor screens and permanent shading structures
• Reflective roofs that bounce sunlight away
• Trees and green facades (plants growing on building walls)

Jeroen Kluck, who studies climate-resilient cities at the Amsterdam University of Applied Sciences, put it simply:

"If you make shadow, with a nice place to sit underneath and plants that can survive a bit of drought, it all helps."

The Stakes Are High

Here’s a sobering fact from Eline Coolen:

"But every year in Amsterdam alone, 110 people die because of the heat. That could rise to as many as 600 in the future without serious measures."

Step 4: Rethinking Urban Design

Urban planners are increasingly realizing that shade, vegetation, and heat-conscious design aren’t just nice extras — they’re essential tools for protecting people’s health as summers keep getting hotter.

Important Point: Hanging curtains or sheets on the outside of your windows is far more effective than closing them on the inside. Once sunlight passes through the glass, the heat is already trapped inside your home. Blocking it before it hits the glass makes all the difference!

Summary

• The Netherlands is experiencing heatwaves that are making homes dangerously hot.
• Dutch houses were designed for cold winters, with large windows that trap warmth — but now those same windows are causing overheating in summer.
• The simplest and cheapest fix? Hang curtains, sheets, or blinds on the outside of your windows to block sunlight before it enters.
• This can make homes more comfortable, lower electricity bills, and even save lives.
• On a bigger scale, cities are adding shade structures, trees, greenery, and "shadow art" to cool public spaces.
• Without serious action, heat-related deaths in Amsterdam could rise from 110 per year to as many as 600.
• The key takeaway: keeping the sun out is the best way to keep a building cool — and sometimes the simplest solutions are the most powerful.

Frequently Asked Questions

Q1: Why should I hang curtains on the outside instead of the inside?

Great question! When you close curtains on the inside, the sunlight has already passed through the glass and is trapped in your room — like a greenhouse. Hanging curtains on the outside blocks the sun before it reaches the glass, keeping the heat out entirely. It’s a small change that makes a big difference!

Q2: Do I need to buy special outdoor curtains, or will regular ones work?

You don’t need anything fancy! Regular curtains, blinds, awnings, or even bedsheets can work. The key is that they’re on the outside of the window. Over time, you might want to invest in more permanent outdoor shading, but in a pinch, anything that blocks the sun helps.

Q3: Is this problem only happening in the Netherlands?

No! Any country with homes designed for cold winters — which includes much of northern Europe and other cold-climate regions — faces the same challenge. As global temperatures rise, houses built to retain heat are becoming increasingly uncomfortable and even dangerous during summer heatwaves.

Q4: How much can exterior shading really lower my indoor temperature?

While the exact amount depends on many factors, research consistently shows that blocking sunlight before it hits the glass is the single most effective passive cooling method. It can make a dramatic difference in indoor comfort and significantly reduce the need for fans or air conditioning.

Q5: What can cities do to help beyond telling people to hang curtains?

Cities can plant more trees, install shade structures in public areas, encourage green facades (plants on building walls), use reflective roofing materials, and design new buildings with heat in mind from the start. Urban planners are increasingly treating shade and vegetation as essential infrastructure for public health.