Between 2017 and 2018 the Spanish Passive House association, Plataforma de Edificación Passivhaus (PEP), undertook a monitoring campaign in 36 schools across the country, measuring indoor air temperature, relative humidity, and CO2 concentrations. On average, across all the sites, measured over a 1-year period, climate conditions and air quality were found to be inadequate 84% of the time—translating to 5 out of every 6 hours that children spend in school. Indoor CO2 concentrations were less than 1000 PPM during only 32% of class hours.

In classrooms in the Mediterranean coastal climates and warm climate zones, conditions were slightly better, but still were not good. Indoor air temperature and relative humidity were only within the optimum comfort zone during 56% of class hours, while indoor CO2 concentrations were less than 1000 PPM only 40% of the time. Clearly, there is much work to be done.

Learnlife Eco Hub

LearnLife is an organization based in Barcelona whose goal is to build an open ecosystem for a new lifelong learning paradigm alongside existing education systems. Seeking to construct a pop-up learning space, the organization found a suitable site in Castelldefels, just a stone’s throw from the sea and 25 km (15 miles) from the city of Barcelona.  LearnLife’s goals for this space, dubbed the Eco Hub, included that it would be a scalable model for the rapid assembly of healthy learning spaces with good air quality and thermal comfort, fit for warm climates.

The building was designed by architect Solange Espoille, and we at Praxis Resilient Buildings were brought in as the Passive House and mechanical systems consultant, with ZEPHIR as the certifier. This pop-up learning space and sustainability and innovation center targeted and attained the Passive House Classic certification. Passive House certification proved to be a key quality control tool to ensure that the design and execution were up to scratch and that the building would perform as expected.

Off-site construction, timber, and Passive House: the perfect partners

In addition to meeting its Passive House goal, LearnLife set out to strongly focus on using healthy, low emission materials from renewable sources, to ensure the project would have a low embodied energy. Toward that goal, the Eco Hub was constructed using a series of prefabricated lightweight timber modules that were built off-site and assembled on the site, creating a 14m x 8m (46 x 26 feet) learning space. The structure, thermal insulation, airtight layer, and most of the windows, which have timber frames, arrived pre-installed. All timber was PEFC certified; 18-mm (0.7 inches) OSB board was used for the airtight layer, rather than plastic membranes; and wood-fiber insulation was used throughout.

Internal finishes included water-based low-emission paint on fiberboard made from recycled gypsum and cellulose fibers from post-consumer wastepaper, as opposed to conventional gypsum plasterboard. External shading devices were essential for reducing solar gain, with a pergola on the southern openings and motorised external screens on the eastern and western windows, which were intentionally kept small to minimize the possibility of overheating.

The joints between the modules were sealed on site, to complete the airtight layer. The final blower door test achieved an ACH50 of 0.48.

No concrete was used, either for the foundation or structure. Instead, the modules were installed on screw pile foundations, ensuring the Eco Hub can be disassembled in the future, moved, and re-assembled elsewhere.

Constant fresh air is provided by a PHI-certified Zehnder mechanical ventilation system with heat recovery, while heating and cooling are supplied using a mini-split unit. As the demand for hot water will be small, given that the only warm water in the space is used for handwashing in the one bathroom, an electric on-demand water heater was installed. As the unit takes up little space, it was able to be located close to the sink, minimizing the length of the plumbing pipes and the associated heat losses. A 2.73-kWp PV array generates around 90% of the building's energy consumption.

Off-site prefabrication helped achieve a higher build quality, reduced on-site waste, and cut construction times and costs. Although the Eco Hub is a small pilot, it successfully demonstrates that LearnLife’s goal of creating a scalable and replicable educational center is a practical one.

All photos courtesy of Jordi Villa i Marta