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House inside a greenhouse adds solar gain in winter

Posted by Alex Barrett on 19 December 2016 at 11:15 am

Many of us use greenhouses to keep our plants warm through the winter. It turns out we could use the same technology to keep warm ourselves. Marie Granmar and Charles Sacilotto live near Stockholm in Sweden. They have built a massive greenhouse that entirely surrounds their home. This keeps the house much warmer in winter, and means that the building itself is not exposed to the weather.

Greenhouses have been around for hundreds of years. The original idea of growing plants out of season by capturing the warmth of sunlight originated with the Romans. In medieval times “fruit walls” were used to trap sunlight, creating a warmer microclimate around the plants. It wasn’t until the invention of plate glass that greenhouses became the entirely glass buildings we are familiar with today.

A greenhouse works by capturing the heat from sunlight. Light in the visible part of the spectrum can pass through the glass, and warm up the materials within. These reemit radiation in the infrared region of the spectrum. This infrared radiation is not able to pass through the glass, and so the heat is retained within the greenhouse. The glass of the greenhouse also keeps the warm air from escaping. It is not able to mix freely with the cold air outside and so heat loss by convection is greatly reduced.

Insulating dwellings is very important for reducing energy use, but is usually done by improving the glazing of windows or fitting extra layers of insulation within the walls and roof. Building a house inside a giant greenhouse is quite a novel approach. The concept was pioneered by Bengt Warne, a Swedish architect. He designed the first “Naturhus” in the 1970s, but very few have ever been built. Mostly in cold regions such as Scandinavia.

In this video from they explain how their radical insulation approach works and provide a guided tour of the environmentally friendly systems they use.

The Granmar-Sacilotto family do still need to heat their house during the cold Swedish winter, but the period during which this is required is dramatically reduced. The greenhouse means that they still have use of their outside areas during times when other people are trapped inside. They grow a range of crops in and around their house, making use of water recycling and other environmentally friendly systems.


  1. Fair Companies
  2. The Granmar-Sacilotto house, the Naturhus concept
  3. Bengt Warne

Image credit: Fair Companies

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