Netherlands: Energy Demand Reduced to 25 kWh/m²a in Just One Day

Roosendaal1In recent years, Roosendaal’s De Kroeven, the Dutch city’s district of terraced houses built in the 1960s (left photo), has radically changed not only its stone face but also its energy performance (right). Netherland’s largest passive-house retrofit project equipped 246 houses with new insulation and solar thermal energy systems. 50 of these houses were part of European project E2ReBuild, which is short for Industrialised Energy Efficient Retrofitting of Residential Buildings in Cold Climates.
Photos: Demonstrator Roosendaal report / E2ReBuild
 
Roosendaal is one of seven E2ReBuild demonstration projects. The others are located in the German cities of München and Augsburg, as well as in Halmstad, Sweden, Oulu, Finland, Voiron, France, and London, UK. The final draft of the E2ReBuild monitoring report for Roosendaal was completed at the end of June. It describes the retrofit in many photos and contains interesting observations on the contribution of solar thermal energy to the project’s overall energy performance. This news piece is based on that report (which has not yet been publicly available). 
 
Roof and facade elements replaced in one day 
The authors of the E2ReBuild report are Chiel Boonstra, Advisory Board Member of the International Solar Cities Initiative, and Ad van Reekum, Representative of AlleeWonen, the social housing corporation which owns the now retrofitted buildings. Boonstra is also the owner of energy engineering company Trecodome, which directed the energy efficiency project in Roosendaal (see attached document). According to the report, one special characteristic of the project was its systematic and quick execution, which allowed the tenants to stay in their homes. “Once the renovation was up to speed, four houses were renovated in one week. On one day, the existing roof and windows were replaced by the new prefabricated roof and facade elements. Each day, one truck load for one house arrived on site and was mounted on the same day,” the authors explain. 
 
Roosendaal2Three prefabricated elements for each housing unit: facade (left), roof with collector (middle), as well as heating and air unit, including small solar tank (right)
Photos: Demonstrator Roosendaal report / E2ReBuild
 
Both the facade elements and the solar collectors were mounted onto the roof elements in the factory before being transported to and installed onto the Roosendaal E2ReBuild houses in just one day (see the photo above). A crane was used to lift the integrated passive house system through the open roof. The system consists of a small gas heater for space heating and hot water, mechanical ventilation with heat recovery and a solar storage system connected to the solar collectors (right photo above). This system fulfilled the expectations of high energy efficiency, Boonstra and van Reekum report. Gas consumption “for space heating, hot water and cooking was reduced by 65 %. Given that cooking is constant and hot water reduced by 50 % because of the solar thermal system, the space heat reduction is between 75 and 80 %.” 
 
The E2ReBuild retrofit of the demonstration buildings has resulted in 67 % lower gas bills for the tenants. A comparison between the passive house standard of 25 kWh/m² for space heating and current standards implemented in nearby buildings of identical dimensions shows the latter having a much weaker competitive edge, only reducing heat demand by 18 %. 
 
Energy-saving guarantee convinces tenants
In addition to the quick retrofit process and the innovative passive house heating unit supported by solar thermal, Boonstra and van Reekum believe the project’s financing to have been a pioneering act: The amount of energy saved has been guaranteed by the housing company, AlleeWonen, so that the rent increase of EUR 65 per month will not exceed the amount saved over the first five years. It was the crucial point in convincing the tenants to agree to the retrofit. As with other renovation measures, 70 % of the tenants concerned must agree to such a project before the renovation of all housing units can start, the authors explain in the paper.
 
Assuming that retrofit costs for such projects will decrease, there should be a market for the demonstrated solution, Boonstra and van Reekum are convinced. Both believe that the pilot project’s innovative approach could open up intriguing opportunities not only on the Dutch market with its two million homes but across all of Europe’s other markets as well. 
 
More information:
Aramis AlleeWonen: www.alleewonen.nl
 
Frank Stier is a Sofia-based freelance journalist working for print and online media, as well as news agencies: www.socb.de
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