Dynamic hygrothermal simulation and full-scale validation of a structural insulated panel made from bio-based materials.

Given the environmental impact of the construction sector- responsible for 40% of the total primary energy consumption of the European Union- reducing both the embodied energy of materials at manufacturing stage and minimising operational energy consumption in buildings are urgent tasks. Timber, agricultural residues, and bio-based materials are local renewable resources that can be transformed into buildings products and components, fomenting the creation of circular economies, and reducing the environmental impact of the sector. The objective of the European ISOBIO project, that ran from 2015 to 2019, financed under the Horizon2020 program, was to address these problems through the development of new insulating materials and renders from plant fibres, agricultural residues, and bio-based binders. The article presents the results of dynamic hygrothermal simulations and full-scale validation of a structural insulated panel made from bio-based materials, for use in the construction of nearly-zero energy buildings.

Monitoring Results and Validation

Figure 4 shows a cross section of the modelled panel, with sensor locations. Figure 5 shows the WUFI model of the panel and corresponding sensor locations.

Figure 6 shows measured and modelled temperature and RH at position 2 (between the CAVAC rigid insulation and Biofib Trio insulation). Temperature dynamics are well reflected in the model. RH dynamics are less well reflected.

Figure 7 shows the measured and modelled temperature at position 3 (between the Biofib Trio insulation and OSB board). Temperature dynamics are well reflected in the model, with RH less so. The model nonetheless shows very close alignment with measured results.

Figure 8 shows the measured and modelled temperature and RH at position 4 (between the Intello membrane and the Biofib Trio insulation). Temperature and RH dynamics are well reflected in the model.

Figure 9 shows the measured average heat flow rate, compared with the WUFI modelled heat flow rate, showing very good agreement.

Conclusion

The results of the measured and modelled temperature and RH show good correlation, with dynamic temperature variations accurately reflected in the model. The short-term variations in relative humidity are not reflected with the same precision in the WUFI modelling results, possibly due to the assumption that the equilibrium water content in the materials is instantaneous, where in reality, there is hysteresis [3]. The hourly measured and modelled thermal transmittance data show very good correlation, with a difference of only 4% over the monitoring period.

The results indicate that bio-based materials combined in a composite SIP panel of this type can offer predictable hygrothermal performance for use in nearly-zero energy buildings.

References

• ISO 9869-1:2014 Thermal Insulation – Building elements – in-situ measurement of thermal resistance and thermal transmittance. (Aislamiento térmica – elementos constructivos – medición in-situ de la resistencia térmica y transmitancia térmica)
• UNE-EN 15026:2007, Comportamiento higrotérmico de componentes de edificios y elementos constructivos. Evaluación de la transferencia de humedad mediante simulación numérica.(Ratificada por AENOR en junio de 2010.)
• N. Reuge, F. Collet, S. Pretot, S. Moisette, M. Bart, O. Style, A. Shea, C. Lanos 2019, Hygrothermal transfers through a bio-based multilayered ISOBIO wall – Part I: Validation of a local kinetics model of sorption and simulations of the HIVE demonstrator. Laboratoire de Génie Civil et Génie Mécanique, Axe Ecomatériaux pour la construction, Université de Rennes, 3 rue du Clos Courtel, BP 90422, 35704 Rennes, France.

Casa A, Somió, Gijón: single family home certified as PHI Low Energy Building by Praxis

This single-family home is located in Somió, Gijón, Asturias, Spain, and was designed by
Architect Juan Ignacio Corominas, and certified as a PHI Low Energy Building by Oliver Style
from Praxis. Patricia Borràs was the Passivhaus Designer on the project. Outer walls have 12cm
of external insulation fixed to 24cm honeycomb brick, U = 0.208 W/m2·K. The roof has 28cm of
XPS thermal insulation, U = 0.117 W/m2·K. The walls to ground of the heated basement have
8cm of insulation, U = 0.437 W/m2·K. The suspended floor slab has 15cm of insulation, U =
0.137 W/m2·K.

Window frames are Passivhaus certified Cortizo COR-80, Uf = 0.94 W/m2·K, with low-e argon
filled with triple glazing, Ug = 0.50 W/m2· K and g= 49%. Exterior roller blinds on all windows
control summer solar heat gains. A 9.2 kW Baxi PBM 10 air-source heat pump provides
underfloor space heating, as well as generating domestic hot water. A Passivhaus certified
ventilation unit, Aldes InspirAIR Side 240, provides controlled mechanical ventilation. The
Blower Door test result was N50 = 0.89 ren/h.

Pictures: Juan Ignacio Corominas

Link:

• iPHA de Proyectos Passivhaus Internacional database.
• Plataforma de Edificación Passivhaus PEP database.

Casa AYA: Latin America’s sustainable marvel combining straw bales and Passive House Standard

In the department of Canelones, Uruguay, a modest but groundbreaking architectural gem has emerged – Casa AYA. Designed by Martin Comas of Arquitectura Regenerativa, this eco-friendly dwelling redefines sustainable living in Latin America. Casa AYA stands as a testament to innovation, combining straw bale construction with the rigorous Passivhaus standard, marking a significant milestone in the region’s environmentally conscious architecture.

Redefining conventional construction

Casa AYA challenges conventional construction practices by achieving a remarkable 70% reduction in the use of concrete compared to traditional building methods. The design team achieved this impressive feat by using locally sourced timber on raised foundations and straw bale insulation, a design decision that reflects the essence of the project: reducing the environmental impact of the built environment while providing a super comfortable, healthy home with absurdly small energy bills.

Martin Comas, project architect, explains the path he’s trodden to get here and his recent immersion in the world of Passivhaus

“Before 2019, our constructions were made of concrete, brick and glass, without much real or conceptual technology. That was until I came across Passivhaus. It was a before and after thing…It’s something that opens your mind and gives you tools to take architecture to a much higher level.”

“At first, Passivhaus seemed very German to me…like, very far away. And I wondered…can this be done in Uruguay? Will I be able to find suppliers, labour, know-how and so on…and at reasonable cost? Basically, I was asking myself: is it possible?”

“With this project we not only showed that it was possible, but also, we added some layers of difficulty. For example, we set out to have the smallest possible carbon footprint (using compressed straw wherever possible). And we also set out to build it cheaper than local standard construction, with local labour and in a similar timeframe. In the end we were able to achieve all these goals. It was very challenging, but we are very proud to have managed to raise the bar for construction in Uruguay (which- to be honest- is very low).” 

Km zero and draught-free

To further celebrate its connection to the local environment, the walls of Casa AYA were plastered with clay sourced directly from the site, creating a harmonious union between the building and its surroundings. Furthermore, a mechanical ventilation system with heat recovery was installed, providing excellent indoor air quality with minimal heat loss. The Blower Door airtightness test yielded a result of n50=1.2 ach: not enough to achieve one of the project goals of PHI Low Energy Demand certification, but nonetheless, around 10 times more draught-free than standard construction in the area. When combined with controlled ventilation, reducing draughts and air leaks improves thermal comfort, reduces heat loss and energy bills, and minimizes the risk of moisture damage and unnecessary maintenance costs.

Casa AYA is more than just a home: it’s a symbol of sustainable innovation and a testament to what can be achieved when modern design meets an environmentally conscious mindset. This pioneering project in Carrasco, Uruguay, sets a new standard for environmentally friendly construction in Latin America, proving that we can live in harmony with nature while enjoying the comforts of contemporary living. Casa AYA’s successful integration of modular straw bale construction with the Passivhaus standard serves as an inspiration for architects, builders, and homeowners looking to embrace a more sustainable future.  

After handover, we have asked the architect: what would you recommend to someone when buying or renting a home?

“I would recommend that, if you can, go visit someone who already lives in a Passivhaus, so you can hear a person explain, in a real and non-technical way, what it’s like to live and feel a high-performance house, designed and built for the climate of the next 50 years. That- I think- is fundamental for anyone who is thinking of building a house.  When our clients, who’ve have already been living in these kinds of houses for a while, go to visit their parents or friends, they always comment on how different it is to live in a house with even temperatures in all spaces, damp-free, comfortable and with great air quality”.

Congratulations to Martin Comas and the team at Arquitectura Regenerativa, for designing and building one of the most sustainable homes, not only in the country, but also in the region. Do you want to build or retrofit a nearly-zero energy learning space with excellent air quality, great comfort, and absurdly low energy bills? Contact us and let’s talk through your project.

Photod: Martín Comas