Building energy maintenance on rental properties.

'We are constantly challenged to come up with new solutions'

Over the past few years, Willems Vastgoedonderhoud has carried out architectural energy maintenance on several residential blocks for the De Zes Kernen housing foundation in Geervliet. The last residential block was recently completed. 

Thomas Moeken, plan developer at Willems Vastgoedonderhoud: "Between 2015 and 2022, we made just under eighty homes in Geervliet more sustainable. This last block took a while, because there was still an owner-occupied house in between. So the plan was roughly already there, but we fine-tuned this each time."

The homes were fitted with new, prefabricated front and rear facades, complete with new window frames and exterior wall insulation. In addition, as needed, roofs were renovated, solar panels installed and a new ventilation system and heat pump installed. The end walls were provided with cavity wall insulation. Moeken: "The client comes to us with a sustainability ambition and a budget for a particular complex. Then we see what we can do with it. We calculate everything, including the energy label. We have in-house architects who do the design. For a number of these projects, that was myself in recent years, from my background as an architect."

Two homes at once

So in this project, the choice was made to completely replace the front and rear facades. This is done with two houses at the same time: in the morning demolish debris fillings and from 10:00 am lift the elements and place the new facade. At 4 p.m. it will be delivered wind and watertight. The same process followed the next day, but for the rear facade. Finally, only the inside had to be finished.

Working with prefabricated elements does, of course, require preparation. "The facades are made by BSK. Together with this partner for facade construction, we engineer the elements. Here we specify the conditions, which the new facade must meet, such as the desired insulation value. In this case, we used HSB elements filled with 120 mm mineral wool and provided with a layer of EPS (100 mm). On the first floor, the exterior was finished with stone strips and on the upper floor with tongue-and-groove panels made of steel fiberboard. The elements are about thirty centimeters thick in total. The tongue-and-groove elements and plastic window frames have the appearance of wood. Only the entrance frames and garden doors are still real wood. This is because we did not want to make the daylight size of the doors narrower." 

Circularity on a small scale

In terms of roof insulation, some homes already had attic insulation. Therefore, it was chosen to maintain the roof and also insulate the other roofs on the inside. This was possible because the attic in these homes is not a living space. Moeken: "We did have to move some skylights to make room for post-insulation and the solar panels. The chimneys were also removed. They caused a thermal bridge, cast shadow on the solar panels and are prone to leakage anyway. We raised the roofs in those areas and installed reused roof tiles. That provides a piece of circularity on a small scale and we didn't have to deal with the long delivery times." The current scarcity of building materials provides additional motivation to think carefully about reusing roof tiles, for example, he says. "Nine times out of ten, new roof tiles are installed, even though the sheets underneath are watertight by themselves. The function of the roof tile becomes
so less critical."

Because the facades have an average RC value of 5.5 after the work, ventilation comes under pressure. Therefore, ventilation points were installed in the wet areas. A ventilation heat pump directs air past a heat exchanger, which transfers heat to the central heating boiler. 

Willems Vastgoedonderhoud performs many projects for Woonstichting De Zes Kernen. "They are always interesting projects, often pilots for us. The corporation challenges us to keep coming up with new solutions. We are currently already in the planning phase of the next project."