The Commission is in the process of updating some of the content on this website in light of the withdrawal of the United Kingdom from the European Union. If the site contains content that does not yet reflect the withdrawal of the United Kingdom, it is unintentional and will be addressed.

REZ L2: semi-detached wood frame NZEB in Rovello Porro Italy

Highlighted Case April 2017
Share this Post:

The building REZ L2 is located in an area of residential expansion outside of the urban centre of the city of Rovello Porro (CO), Lombardia Italy. This two storey, semi-detached residential dwelling is made with a wood frame construction.  


The client decided on the use of this constructive system for the following reasons:


Speed of construction work (with a consequent decrease in amount of  problems generated by a traditional construction site).
High energy performance achieved through dedicated design of the building.
High cost control (given the increased emphasis on the design phase which is a typical practice of prefabrication).



This building also follows the approach of sustainability required by a nearly zero-energy building (NZEB):


Locally resourced wood for frame and panels and used as insulation material with thickness according to Passivhaus standard.
Low invasiveness of the site with a roof and façade designed to generate maximum shading in the summer and maximum solar gains in the winter.
Exterior window coverings have a folding shutter system which allows for maximum natural light gains but also serves for cooling in summer months as solar shading devices.

High energy efficiency system through Aerotherm technology installed as a whole HVAC system.





20 Via Bernardino Luini, 22070.  Rovello Porro, Provincia di Como, Lombardia region, Italy



Project team


Project management and architect design: Gritti Architetti (Gianpaolo Gritti)

Structural engineering:  Fabio Telini

Wood structure: ILLE Prefabbricati SRL

HVAC system:  Andrea Epinati

Electrical system:  Pietro Campanale

Contractor: Impresa Ferrario Mario & C.Snc / ILLE Prefabbricati SRL

Risk labor and safety:  Silvia Lazzari



Time schedule

Design: 2013

Construction: 2014-2015



Building use and area


The building is comprised of two storeys which correspond, respectively, to two dwellings of equal size. There is an external staircase to access the second level (as well as the basement). This external staircase is covered by an extended roof which was designed to take into account the southern solar exposure. The two stories are built on top of a basement which is used as a garage and for storage. The basement is made of a concrete structure.



Total Usable Floor Area: 350 m2 (around 120 m2 each dwelling)



Construction costs


Global project cost: 495,000 €

Renewable energy systems cost: 23,000 €

Cost of studies: 42,000 €



Envelope performance


Average U-value: 0.11 W/m2.K

Walls, horizontal and roofing slabs are made of wood frame construction.  

Insulation has an average of between 35 and 40 cm, according to Passivhaus certified products.

The panels used for the walls are made up of a solid wood frame structure and are closed on both sides by wood-based panels for better insulation properties. According to Passivhaus standard, the outer surface elements represent an insulation average level of between 35 and 40 cm. The high airtightness level assures a minimum of energy consumption for heating.



Energy consumption


Primary energy consumption: 11.52 kWh PE/m2.year

Primary energy consumption for standard building: 87.00 kWh PE /m2.year



Energy systems


The HVAC system is based on an Aerotherm system (technical details not provided).

Renewable systems: data not available



Awards and recognition


Finalist in the Green Building Solutions Awards 2016 in the Low carbon category, see Villa bifamiliare ad energia quasi zero in legno (


Additional information


Project video:

REZ L2 on Gritti Architetti website:

Photos during the construction stage:

Award labels

Additional documents

Available link languages