Natura Matéria restores mill with hemp concrete in Guimarães

An old medieval mill, probably dating back to the XNUMXth century, has just been rebuilt with industrial hemp by Natura Matéria for the Local Accommodation market, in Guimarães. The use of light industrial hempcrete, selected for its excellent thermal and acoustic comfort, has a strong presence in the house, remaining visible in some walls and in the ceiling cladding. The old mill has been transformed into a local accommodation with exuberant architecture and vintage style, adapted to the present day and respecting the principles of sustainability.

The mill, whose housing on the top floor was rebuilt in 1928, was renovated over the past year by Natura Matéria, a spinoff from the University of Minho, which is dedicated to stimulating a culture of innovation in modern architecture, using natural or recycled materials, with low environmental impact. To Cannareporter, César Cardoso, responsible for the company, said that the concept of the project was “to maintain a compromise between the old and the contemporary, both in construction techniques and in architectural details”.

The option to use natural materials and construction technologies based on traditional techniques influenced the building's architecture itself, having been considered from the beginning. “In this way, it was possible to build with walls of reduced thickness, while maintaining good performance. The wooden structure and partition are still present, but in a more contemporary way. The use of light industrial hemp concrete, selected for the excellent thermal and acoustic comfort it provides, has a strong presence in the house, remaining visible in some walls and in the ceiling cladding”, says César Cardoso.

“House Natura – Moinho d'água” available at Airbnb 

The house / mill has become a luxurious space, where guests can rest and enjoy the sound of the surrounding water, being, according to César Cardoso, an excellent opportunity for a “Digital Detox”. “Here it is possible to disconnect from the screens and enjoy this space in the company of those you love most, in a direct interaction. An incredible opportunity for guests to get to know each other even better.”

On purpose, the mill also does not have a TV, “but they can enjoy the suggested recreational activities. There is Internet access, but the idea is to use it only for really important situations, like work. The mill is also a great space for creative activities and has acoustics worthy of a music studio”, points out the engineer. The house also includes a veranda over the river, garden with water channels and access to a small river beach. The mill is located next to the Medieval Bridge of the River Selho, in Guimarães, just 2,2 km from the historic city centre, which is a World Heritage Site.

Very soon, the area will have access to a 22 kilometer pedestrian and cycle path along the entire length of the Selho river, which crosses the municipality of Guimarães and also connects to the Ecovia do Ave.

Housing characteristics and performance

According to engineer César Cardoso, the space has no need for cooling in the summer and little need for heating in the winter, even with walls of reduced thickness, having only a small stove of 5,5 kW for the approximately 35 m2 of useful area. 

“The exterior walls in hemp concrete guarantee a thermal transmission coefficient value of less than 0,4 W/m2ºC, meeting the thermal regulatory requirements for the region, a thermal delay of 8,5 h, a thermal accumulation capacity of the space 10.7 Wh/m internal²ºC, the latter being the amount of energy it can accumulate per m² for a temperature rise of 1°C. This means that hemp concrete has good thermal inertia, contrary to what one might think”.

As for soundproofing, Cardoso claims that hemp has unique properties. “The acoustics are really worthy of a music studio! The reverberation time T (s) measured in the unfurnished room with exposed hemp concrete surface on ceilings and walls over 40% of the total area, between the 400 Hz and 1250 Hz bands is 0.28 s, measured with a sound level decay of 20 dB (T20). This parameter, although not a requirement in living spaces, reveals the excellent behavior of hemp when left uncoated. For a better comparison, a parking lot can be 3 s, a corridor 2 s, a meeting room 0.5-1 s, recording studio 0.3 s.”, he says.

In terms of acoustic insulation, the façade achieved an excellent performance, considering a total thickness of around 19 cm, having recorded 37 dB in the insulation index for air conduction sounds standardized on site, with 18% of glazed area (33 dB is the regulatory minimum required).

The mill is now available for short term rental na Airbnb platform, for anyone who wants to discover this reconstruction with hemp and enjoy different, more ecological days.