“When you have wind and sun you don’t need oil” – an energy saving housing project in the Netherlands

August 30th, 2010 by Richard Lord

The Iguana Project, which is a development of nine energy efficient homes, lies on the outskirts of the pretty harbour town of Stavoren, which sits on the eastern bank of the Ijsselmeer in the Dutch province of Friesland.

Hendrik Gommer and Elsa Visser who devised the project in 1997 called it the Iguana Project because like the iguana, Iguana homes obtain their warmth from the sun.

Vesta wind turbines capture the energy from the wind racing off the Ijsselmeer (click image to expand - ©RLLord)

One’s approach to Stavoren passes many large wind turbines.  They dot the flat farm land that rises above the Ijsselmeer.  Flocks of birds rest at the foot of the wind turbines, and solitary herons stand by roadside drainage ditches.

When the Iguana Project was built it was exposed to the full force of the wind coming off the Ijsselmeer but since the project’s completion, trees have grown up to shelter the development and soften its appearance.  This is a tranquil place where the noise one hears is from the rustling reeds growing out of the canals.

The Iguana Project company house and presentation building with a south facing conservatory. Photovoltaic panels cover the south side of the building. More photovoltaic panels on the roof are angled towards the sun. (click image to expand - ©RLLord)

The energy efficient dwellings are immediately recognisable as their roofs are covered with photovoltaic panels.

Mr. Gommer believed that traditional building materials and building techniques were not environmentally benign.  They generated too much waste and the buildings wasted and consumed too much energy during their use.

Hendrik Gommer envisioned a development that used renewable or recyclable materials, and took advantage of the sun’s radiation.  The energy efficiency achieved by the development is based on high levels of insulation to reduce thermal load, a ground source heat pump for home heating and hot water, and a large array of photovoltaic panels to provide electricity.

The project uses wood frame construction, EPDM roofing, and larch coping, which was less expensive than traditional building materials.  However costs were increased by the use of cellulose insulation, lime render on the interior walls, and the construction of a south facing conservatory to capture the sun’s heat.

The south facing conservatory can heat the home in winter and cool the home in summer. The conservatory roof is covered to prevent overheating when the sun is high in the sky. It also provides a perfect angle for photovoltaic panels to capture the sun's rays (click image to expand - ©RLLord)

The nine homes that make up the development are located between two canals.  The north side of each home has only one small bathroom window to reduce heat loss.  Sedum roofs also occur on the north side of each property to off-set the loss of habitat from the footprint of the buildings.

The north side of each home has only a tiny bathroom window to reduce heat loss. (click image to expand)

The development was used to experiment and test ideas.  Photovoltaic panels from 14 different manufacturers were installed to assess how panels from each manufacturer performed.  Some homes were designed with the bedrooms downstairs while in others the bedrooms were upstairs.

One of the nine Iguana Project properties with photovoltaic panels on the roof (click image to expand - ©RLLord)

One of the nine Iguana Project properties with different photovoltaic panels on the roof (click image to expand - ©RLLord)

Iguana Project home owners are required to keep their trees trimmed to a maximum height of six metres to prevent trees shading the photovoltaic roof panels.

One of the Iguana properties with 12 square metres of photovoltaic panels (click image to expand - ©RLLord)

A couple invited my wife and I to see their energy efficient property.  The timber-framed walls of their home are 35 cm thick.  Cellulose fibre from the paper industry fills the inside of the framing.  The interior walls are rendered in lime.

Their property has a ground source heat pump that extracts heat from an 80 metre borehole.  The heat pump located under the stairs feeds hot water pipes that run inside the interior walls of the house.

Warm water pipes from the heat pump run inside the walls of the property (click image to expand - ©RLLord)

A lime rendered bedroom wall with an embedded hot water pipe that warms the room in winter (click image to expand - ©RLLord )

The  300 litre Techno energiesystemen cylinder is heated by electricity.  According to the Iguana Project it has sufficient capacity for supplying hot water to the shower for 50 minutes.  If it is drained of hot water it takes 11 hours to heat up again.

The power cable from the photovoltaic panels on the roof and on the conservatory feed into the Mastervolt inverter (click image to expand - ©RLLord)

The Mastervolt inverter in the stairwell of the property converts Direct Current from the photovoltaic panels into Alternating Current for use in the home (click image to expand - ©RLLord)

In the ten months from October 2009 the photovoltaic panels on the couple’s home produced 1527 kWh of electricity.  During this time their home consumed a total of 2086 kWh.

Electricity meter showing electricity produced by photovoltaic panels from October 2009 to early August 2010 (click image to expand - ©RLLord)

Electricity used by the property from October 2010 to early August 2010 (click image to expand - ©RLLord)

The kitchen has a dishwasher, and a washing machine, but to reduce energy consumption the couple wash dishes in the sink.  The couple choose to live simply to minimise energy consumption.

During the coldest day of the year when the outside air temperature fell to -18° C the home interior remained comfortable.

The home owners find the timber frame house more comfortable to live in than a brick house.  The fabric of the home is made of natural materials.  The floors are covered in cork linoleum or Marmoleum. The lime rendered walls are breathable.  Even though the property is surrounded by canals, dampness in the home is not a problem.

The conservatory on the south elevation provides an important function for moving air around the house.  The vents at the top of the conservatory that can be opened to allow warm air into the main body of the house.  The six metre-wide conservatory, and the windows are all double glazed.  The glazing would probably be improved if such a development was constructed in the Netherlands today.

One of the Iguana Project homes nestled in amongst the trees and with a reed-bordered canal in the front garden (click image to expand - ©RLLord)

The couple who kindly showed us around their energy efficient home are extremely pleased with it.  They enthusiastically told us how pleasant it was to live in such a home.  This development is now over ten years old but it is still very energy efficient by today’s housing standards.  The wife, a school teacher, said “when you have wind and sun you don’t need oil.”   Their home is a testament to that.

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