To achieve this ambition, about 50,000 existing homes per year must be made more sustainable, and after 2021 as many as 200,000 homes per year. "What is astonishing is that in numerous national discussions about making buildings more sustainable, people mainly talk about solar panels, heat pumps and heat networks. The instrument 'a well-insulated envelope' is of secondary importance, while with this a substantial gain can be achieved simply and cost-effectively," believes Claus den Dunnen, Sales Manager at Celdex. "With a good airtight building envelope, we can reduce energy loss by as much as 30%. What we don't consume, we don't have to save!"

"In order to meet the large renovation and new construction task in the future and to guarantee the quality of the future Building Quality Assurance Act (Wkb), prefabrication is increasingly being used," Den Dunnen said. "Not surprisingly, because with prefabrication a constant, high construction quality can be guaranteed. Production takes place in the factory, under the best (climatic) conditions. Moreover, production can already be started while the foundation is still being poured on site. This leads to significantly shorter construction times, thus lower costs. In addition, fewer skilled hands are needed." Industrial construction makes construction more attractive to young people, he knows. Failure costs are also significantly reduced and factory construction is safer. "In combination with good air sealing, the new BENG requirements can also be met, as well as the increasing demand for a well-insulated shell to enable energy-neutral construction. Just under 9,000 of the nearly 71,000 new homes built last year were manufactured industrially. This means that one in eight homes now "comes from the factory. This is quite apart from the large amount of prefabricated building components that are used on site."
In order for sealing techniques to properly reflect this development, a different approach is needed. "This is because the sealing of building elements is also moving from the construction site to the factory," says Den Dunnen. "For this purpose, a new generation of 'dry' sealing products has been developed, with foam tapes that are prefabricated and offer the possibility to seal all building elements directly airtight during assembly. The products have durable repair capability and provide the solution for demountable and circular construction. This means a change for the contractor, who no longer has to apply traditional 'wet' sealing products such as PU foam, sealant and coating afterwards for many details." Thanks to savings on several fronts, the new sealing products are being embraced by contractors fairly quickly. "However, the approach does require a new approach to the construction column. From architect, manufacturer, contractor to installer: everyone must do their part to achieve the required performance."

Since 1983, Celdex has been a manufacturer of plastic foam sealing products that are thermally, acoustically, water, driving rain and airtight. Examples include Airseal filler blocks and strips, Stelkozijnband, Pre-Seal foam tapes, roof penetration and meter box sleeves. "To tie in with the aforementioned developments, Celdex has developed the Dichtgarant concept. This provides stakeholders in the construction industry with all the essential building blocks to demonstrate the performance delivered in the field of airtight construction," said Den Dunnen. "The solutions are carefully created and products are extensively tested externally. In addition, Celdex supervises the processing of the products throughout the construction process and records the results. Airtight construction with Celdex Dichtgarant thus fits seamlessly into the quality assurance system."
That a lot is possible within this approach is demonstrated by Celdex at Education and Cultural Complex Amare in The Hague, which had a high sustainability ambition (BREEAM-NL 'Excellent'). "Through careful preparation, the critical connection details were mapped out by the parties involved. As many airtightness products as possible were applied to the 8-meter-high HSB façade elements in advance at the factory. For the remaining details, smart products were used, which could be processed quickly and weather-independent. Amare is thus an excellent example of a complex construction project in which the building consortium consciously decided to make optimum use of the prefabricated construction method with regard to the airtightening of the building envelope. Construction speed, cost and performance were the deciding factors. It is an illustrative example of how Celdex can come up with responsible solutions together with its construction partners."