Prefabricated Modular Elements for nZEB Energy Renovation of Buildings Stock


Idea authors: Targo Kalamees & Peep Pihelo _____________________________________________________________________ This is the first example of an old apartment building being renovated to meet the requirements of a new nZEB (nearly zero energy building) using prefabricated multifunctional modular elements. The developed multifunctional renovation elements are suitable for the whole building envelope (facade and roof) and for the installation of building service systems. These elements can be combined, selected, and configured by the end-user, based on his specific needs. In the Europe, more than 70% of the residential buildings are over 30 years old and about 35% are more than 50 years old. New recast of the Energy Performance of Buildings Directive (EPBD) requires that Member States shall establish a long-term strategy facilitating the cost-effective transformation of existing buildings into nZEB. An average annual renovation rate of 3 % would be needed to accomplish the energy efficiency ambitions. Today, the renovation rate is around 1% only. Therefore, complete technical improvement of buildings condition has been receiving increasing attention with a search of ways of efficient industrialized production and installation. An efficient and innovative method of mass-renovation of the existing building stock is the application of prefabricated renovation elements, which has the potential to reduce costs and renovation time, lower disturbance for inhabitants, and enhance quality and performance in terms of energy efficiency and indoor climate. In the current solution, hygrothermal and energy performance are considered to offer solutions for nZEB renovation of apartment buildings with prefabricated wall and roof insulation elements, where LVL as loadbearing frames is foreseen. In addition to energy performance, special attention to the moisture safety measures in the design is taken into account. High thermal resistance and vapour permeability of the external layers are key components of a well-functioning building envelope. The structure of the prefabricated insulation element is based on LVL framing (c/c up to 600 mm) with different thicknesses (preferably 120...300 mm), where air and vapour tightness from the inner side has to be guaranteed with an air and vapour control/barrier layer and the external side covered with a diffusion-opened wind barrier layer. The main insulation layer of the element consists of mineral wool or cellulose wool. To minimize convection in between the structures and to compensate the roughness of the original wall, up to 50 mm light mineral wool as the buffer layer will be added onto the back side of the prefabricated element. The buffering layer is fixed in zigzag with strings, which are released after the element is installed. The buffering layer and all other layers of insulation, also windows, flashings, sills etc. are installed in the factory and are protected with plastic foil against weather damage during transport and on the building site. The elements will be hanged onto the external walls with help of preinstalled anchors and onto the roof to the prebuilt LVL framing (if needed). The number of installed elements is in average 150-400 m2 per day, directly from truck, helped by crane. Installation is done by 3-4 skilled workers from forklift baskets. Elements can be produced either for horizontal mounting (with dimensions (HxW) about 2,9m x 10m) or vertical mounting (dim. (HxW) up to 10m x 2.5m). We developed smart anchoring solutions for modular panels that allow to adjust supporting point in all three directions. We integrated ventilation ducts inside the insulation elements to spare the space for new indoor climate systems in the apartments. Old windows/external doors will be removed after the prefabricated modular elements are mounted. Therefore, the installation does not pose disturbance to proprietors and can be carried out in cold weather conditions as well.

Key benefit

Multifunctional modular elements for nZEB renovation with timber-based framing, produced off-site, guarantee high quality and fast installation with insignificant disturbance to houseowners

Material list

- Precut Kerto LVL beams, columns, battens, boards
- Insulation materials (mineral wool and/or cellulose wool)
- Fixing anchors (adjustable in 3 directions)
- Air and vapour barrier/control layer
- Wind barrier layer
- Facade boarding/rainscreen
- Roof membrane

Ecological values

The existing building stock can be renovated to meet the same energy-efficiency levels as a new buildings. This allows to avoid demolition of an existing building and construction of a new one that raises the global cost at least four-fold as compared to renovation. Analyses of embodied energy via CO2 emissions from the materials and the energy production used in a building during 20 years demonstrate that a new building has higher environmental impact than deep energy renovation. With economically feasible additional insulation solutions with prefabricated timber-based elements, about 70-80% reduction of primary energy use is possible to achieve. With that, reduction of CO2 emissions in a whole process (production-building use and maintenance-demolition-reuse/recycling) is remarkable. Mounted onto the external envelope elements (walls and roof) are dismountable and reusable/recyclable.



  • Economical span (mm) 10000
  • Thickness (mm) 380
  • Airbourne sound reduction factor (dB) 48
  • Impact sound transmission (dB)
  • Resistance to fire class 60 R
  • Thermal properties 10 R 0.1 U



  • This Hybrid City Competition entry is a renovation idea for any type of existing structure. It creates a new, thermally high performance envelope to a building. The detailing allows for variations in the thickness of the envelope to match the requirements for each project and location. Using pre manufactured panels is an effective and fast way to insulate the existing housing stock in any location.
  • It's really a good project and idea, perfectly fitting the huge challenge of insulation improvement of existing buildings. Obviously realistic since realized, and facing up the challenge to use less fossile resources.
  • Very effective looking structures for energy renovations. Connections allow the use of prefabricated panels making the onsite operation fast and reducing the affect to the people living in the building.


Operation In Progress, Please Wait!!!