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Renovating a piece at a time

10.11.2014 - (idw) Fraunhofer-Gesellschaft

Coming home from work one day, youre taken aback to find your apartment building encased in scaffolding. And then it hits you that the agency that manages the property did announce that your building is going to be renovated with the promise that a new façade and new windows will mean paying less for utilities. You can now look forward to months of noise pollution and to artificial darkness caused by the scaffolding wrap and there are bound to be interruptions and delays that draw the whole thing out. Strangers will be traipsing through your apartment in dirty boots and youll have to figure out how to tell your boss that youll need to occasionally take off work to let workmen into your private space and hang around until theyre done. If you rent in an apartment building or complex, this may indeed have happened to you. But the truth is that such renovations are by and large both sensible and justified. Older buildings account for over 80 percent of heating requirements in the majority of European industrialized countries, but the current renovation rate aimed at raising energy efficiency is less than one percent per year. One reason may be that property owners tend to have a hard time deciding whether or not to renovate. They want to be sure that, in addition to improving energy efficiency, any renovations they commission can also be carried out as economically as possible, within a reasonable timeframe and ideally with some form of public subsidy to offset some of the cost. Since its common for a number of different contractors to be involved, planning and executing these kind of renovations ends up being rather complicated. And any substandard construction work is likely to anger residents who, in the worst-case scenario, may even seek rebates on rent to compensate for the great inconvenience they have suffered.
Minimally invasive procedures a trend that is gaining ground in the medical world are also making their mark in the construction sector. This is because having a comprehensive and well-planned concept that incorporates minimally invasive renovation processes is a way for both tenants and landlords to avoid the problems described above. Weve found using prefabricated multifunctional building components to be a promising approach for renovating residential buildings and can be used on the majority of existing buildings, explains scientist Horst Stiegel of the Energy Systems department at the Fraunhofer Institute for Building Physics IBP. One of the things Stiegel and his colleagues are working on can aptly be described by the title of one of their projects Developing prefabricated multifunctional systems for the energy-efficient renovation of residential buildings which draws a portion of its funding from the German Federal Ministry for Economic Affairs and Energy (BMWi). Among the aims of this project is the provision of minimally invasive and multifunctional renovation concepts that, thanks to a high degree of prefabrication, are capable of greatly reducing disruption suffered by residents while also streamlining the whole process. In simple terms this involves making, say, window or entire façade modules complete with insulation framing and possibly a ventilation system in the workshop before going to the renovation site and fitting them to the building shell. The next stage is then to integrate or extend existing heating systems into the renovation modules, says Stiegel. But despite being a clear way to save time and with it money there were still some difficult challenges to overcome in terms of how the modules are designed and manufactured.
What Stiegel and his colleagues from the Building Systems and Services working group did was to develop systems and modules tailored specifically to the purposes of renovation.

New concepts
Recent renovation projects to make use of prefabricated elements have tended to use stackable (single-story), horizontal, wood-frame designs featuring built-in windows and doors. The basic design of these wall sections most closely resembles the traditional principles of making prefabricated houses and even uses similar transport logistics and assembly techniques. Integrating segments featuring technical building systems in particular those related to supply lines and channels into these horizontally, stackable, single-story elements proved problematic and the scientists determined that vertical systems designed to cover many or all stories were more suitable for fully integrating these building services segments. Since the channels or lines can then be brought together either in the segment base or under the buildings roof, it is no longer necessary to connect the channels or lines across the vertical segments. However, the sheer size of the segments makes transporting them to the renovation site just as tricky as mounting them onto the existing façade. Each of these large segments would have to be transported on its side by truck and then rotated 90 degrees to stand on end ready for mounting. Attaching such segments means that the building cant have scaffolding around it because the height of them would make feeding one between the building and its wrapper virtually impossible, says Stiegel. This made it clear that we would have to switch to a smaller format. And it soon became obvious what the benefits of going smaller were going to be. The new small segment approach not only simplified the planning process, but also meant not having to abandon the usual logistics. What is more, routing the lines from one small segment, or module, to another was no problem and there were no longer any limitations in terms of what shape modules had to be to execute a particular façade design.

Prefabricated window modules
Windows have always been the most technologically demanding components that go into a buildings envelope. This is true both in terms of what it takes to manufacture windows and to install them in whatever openings a particular building provides. Sadly this is also where you encounter the bulk of faulty planning and workmanship. The more difficult the assembly work, the more likely it is that a mistake will be made, which is why moving operations to the workshop greatly increases the quality of the finished product, explains Stiegel. This is also where in line with the minimally invasive approach to renovation the buildings technical components and supply systems are integrated into the façade modules. Supply systems have to be fed through the exterior wall so they can be connected to the likes of heaters or electrically operated shutters. The Fraunhofer IBP scientists developed a technical systems box that is integrated into the window module directly underneath a removable windowsill. Locating the box here provides an easily accessible space in which to install technical components. In addition to ventilators, heat exchangers and filters, each box accommodates all the building service components required to supply each room. Any attempt to install all these features on the interior walls would prove so unpopular that it would simply be impracticable. What the scientists have done is to produce an insulating collar construction around the window facing a construction that lines the entire existing window jamb, enables the window to be installed at exactly the desired wall depth and removes the need for any significant on-site reworking.

Innovative ventilation solutions
Supplying a building with fresh air can be done using either a centralized or decentralized ventilation system. Equipping an apartment building with a centralized ventilation system capable of heat recovery relies on each apartment having its own ventilation channels in order to ensure the required air flow to and from each room. Adapting the fabric of existing buildings in order to retrofit them with these channels is extremely complicated, expensive and simply for reasons of space often impossible. A promising alternative is to integrate ventilatio
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