Net Zero Energy in one day
In Nieuw Buinen, housing association Lefier and constructor VolkerWessels completed three Net Zero Energy pilot houses as part of the Stroomversnelling (‘currency accelerator’) deal. After learning from the first and particularly the second house, an improved version was completed within two months. A conversion that only took one day! The pilot houses serve as test cases for another 119 1970s terraced houses in Nieuw Buinen.
The test houses
Most renovations in the past standardly received energy label B. A Net Zero Energy property is a big step ahead, and the pilot project in Nieuw Buinen is the ultimate way to test the technical conditions. For the first pilot house, a property was chosen that would be demolished. This way, the renovation could start immediately.
Measures in the first test house
The measures applied in the first pilot house:
- The Smart Portal; all installation components including heat recovery and heat storage (boiler) are located in the outer wall elements or roof elements. This enables maintenance without inconvenience for the residents and allows occupants to be absent in case of repairs. The portal is circular and easy to install. In addition to this, it is possible to easily replace the complete installation cabinet in case of, for example, a revision. In the future, the coating on the outside of the Smart Portal can be adjusted to the style of the house and the taste of the occupants.
- In the further development of the Smart Portal, the focus will be on a smaller size cabinet which fits into the wall.
- Heating and hot water is generated by a heat pump linked to evaporator panels. This is a fairly unique concept in the Netherlands.
- Ventilation by means of balanced heat recovery system
- Solar panels
Challenges after the first house
One element that needed to be thoroughly tackled is the foundation. It takes too much time to put the outer walls on the foundation. Basically, the house was technically restored in two days, but due to this problem, the restoration took four days. After completing the first house, various possibilities have been explored for attaching the new wall construction on the existing faÃ§ade.
Net Zero Energy in one day
The second test house was realized just before Christmas in 2014. The purpose of this house was to test whether the technique regarding the installations was functioning properly. Using the knowledge gained from this second test home, the third test house was completed in the second quarter of 2015. This took no longer than one single day. This is only possible if everything is perfectly attuned and logistics runs smoothly. The logistics on the day itself begins at the assembly point of VolkerWessels in Rijssen. At this location, everything that is required for the execution of the renovation is supplied. All materials have been made to measure in advance, as a result of which only the ‘definishing’ touch has to be done at the construction site. The dimensions fit perfectly because the house was fully digitally measured in advance. With the help of 3D-BIM, the elements can be produced exactly fitting per property.
Lessons learned from the second house
A lot was learned from the test house, and learning went quickly. Within two months, adjustments have been developed and put into practice. These are the lessons:
- Improvement of logistics by having a car crane unload and place simultaneously.
- Keeping the construction site clean and tidy saves cleaning time.
- Even more prefabrication, there was still too much “tinkering” during the building, and that takes time.
- Just-in-time planning, and having suppliers guarantee delivery times.
The technical differences with the first test house
- Completely new construction of the shell
- Sandwich faÃ§ade panels instead of wooden skeleton
- A steel sandwich roof instead of wood with insulation.
- Convenient connection details that makes sealing redundant
The sandwich faÃ§ade panels consist of layers: OSB-EPS-OSB. These materials make additional reinforcement of the foundation unnecessary, removing the foundation problem of the first residence. Moreover, the prefabricated outer walls consist of one piece, so there are no welding seams across the width of the house, which is pretty unique. The faÃ§ade is still stacked per floor. The new faÃ§ade is easier and much faster to install. In general, the structural components in this second and third test house are much lighter in weight and, therefore, quicker to install.
The most progressive element in this version is a completely new type of heating installation. Instead of air heat pumps, this system uses evaporator panels that are connected to a special heat pump. The advantage is that there are few moving parts, making the system quiet and giving a higher output.
Another special improvement is the type of solar panels used. The panels that VolkerWessels uses for ground-bound dwellings have a lower yield, but always function, even in diffused light. As a result, the total annual yield is bigger. Applying this type of panels will lead to output improvement.
Residents from surrounding neighborhoods have raised the question when renovations will start for them. Perhaps this is partly because the test house has been on television at the RTL4 program Ons Huis Verdient Het (‘our house deserves it’), which can be watched back in episode 6 of season one.
Residents in Nieuw Buinen are generally enthusiastic. For them, the renovation is neutral with regard to housing costs. They pay their current energy bills as energy advance to the housing association and are given a more comfortable home in return.
The collaboration between housing association Lefier and constructor VolkerWessels was nothing new. However, entering the Stroomversnelling together did mean a change in the request. The request of Lefier was compact and only concerned energy performance. Because of this, VolkerWessels had to give a warranty regarding energy performance.
Current status Q2 2015
The first test house has been demolished, the second and third test house have been completed. The next four houses are currently being renovated. This will be followed by another 24 properties as part of the testing phase. With all the knowledge and experience gained from this test phase, the rest of the total of 119 homes will be tackled.