Thermal bridges: the temperature factor fRsi

We continue our series of articles on the topic of thermal bridges: this time, we illustrate the fRsi value, which describes the thermal ”strenght” of a node under the point of view of internal surface temperatures.

As we have explained in a previous article, the PSI value describes a higher or lower heat flow caused by a discontinuity in the thermal envelope – a thermal bridge – the fRsi factor is of primary importance for health and comfort considerations.

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Passive House Days in Cavriago: a great success

On Saturday 14th and Sunday 15th, our construction site in Cavriago was open to the public for the International Passive House Days. On Friday 13th, the local Scuola Edile visited us for a class on energy efficiency.

The event was a great success: the unexpected number of visitors (more than 100!) shows the great interest for Passive Houses in Italy.

In Cavriago, we’re currently building two certified Passive Houses, with a load bearing concrete frame and baked clay blocks as infill, and a wooden roof.  For the first time in the world for a “warm” country, the whole construction system is being certified: we’re going to present it at the 2016 International Passive House Conference in Darmstadt, Germany.

A - scuola edile

A moment during the visit of the local Scuola Edile.

The event attracted over one hundred people, with a mixture of professionals and non professionals. We’d like to thank the visitors who came from Garfagnana and Faenza (over 100 km away!), as well as people from Reggio Emilia, Modena, Parma and Cremona.

We also would like to thank the local Architect’s Association, who attributed continued education credits to our event. Our site was visited by over twenty architects.

F - cucina

The construction site open to the public, on Saturday and Sunday.

The event was a success: one of its main goal was to locally share information about Passive Houses. For this reason, we are considering replicating the event later on, probably around February 2016.

We include here the photos of the information panels we prepared for the event.

01 - Edificio preesistente

Pre-existing building

02 - Salute e comfort

Heath and comfort

03 - La Casa Passiva

The Passive House

04 - Progettare una Casa Passiva

The design of a Passive House

05 - Dettagli costruttivi

Construction details

06 - Calcolo dei ponti termici

Thermal bridges

07 - Ventilazione meccanica e tenuta aria

Mechanical ventilation and airtightness

08 - Foto di cantiere

Construction photos

09 - I costi di una Casa Passiva

Costs of a Passive House

10 - Il pannello solare più efficiente - La finestra

The most efficient solar panel: the window

11 - Verifiche in cantiere

On site verification

12 - Certificazione


Thermal bridges: the PSI value

For new builds as well as energy retrofits, worldwide the construction industry is shifting more and more towards zero energy buildings and Passive Houses.

With the thermal envelope becoming more and more advanced, the correct evaluation of thermal bridges becomes critical: with this article, we explain the PSI value.

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International Passive House Days in Cavriago, Italy

The International Passive House Days are an event organized by the Passivhaus Institut, to publicize what a passive house is, and to let people “touch” the state of the art of construction in terms of comfort and energy efficiency.

This year, we take part to the event with our Cavriago project, where we are currently building two single-family passive houses: our construction site is going to be open to the public on Saturday 14th and Sunday 15th.

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What’s the “time constant” of a building?

Among the many parameters than play a role in the thermal behavior of a building, whether or not it is built to be a Passive House, the time constant is one of the least known ones.

Nontheless, this parameter influences the way a building responses to changes in internal and external conditions, and therefore it is has a very important role in the correct operation of the building and its heating/cooling system.

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The volume created with the standard SketchUp modelling tools is transformed into a thermal block with DesignPH: the remaining step to take is to model the surrounding building and terrain.

DesignPH: the SketchUp plug-in to design Passive Houses in 3D

We finally had the chance to test DesignPH, the SketchUp plug-in that allows you to carry out the preliminary design of passive buildings in 3D. Once the model is created, you can export the data to PHPP (the energy balance software for passive house design), to further the energy design in depth.

Even though this plug-in has been available on the market for a couple of years, since version 8.5 of PHPP, our recent meetings with passive house professionals tell us that this tool is not yet very widespread. It is the case of Italy, as well as the impression we got from our recent trip to the USA.

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Discovering Colorado, the cradle of passive houses

A few weeks ago, for professional reasons we visited Denver, Boulder, Aspen and surrounding areas, in Colorado.

At the foot of the Rocky Mountains, in the hearth of the United States, this region saw some of the very first passive buildings being built in the world, thank to the Rocky Mountain Institute, founded in 1982 by Amory Lovins in Snowmass. We had a chance to visit this extrahordinaire building, which we described in its own article.

View of the Rocky Mountain Institute

South façade of the Rocky Mountain Institute

Thanks to the kindness of so many local colleagues and contractors we met, we also had the chance to visit several construction sites of low-energy buildings and passive houses. The overall experience was very interesting, allowing us to compare our European experience with a reality that is very different from it in terms of mobility, use and life span of buildings, use of energy and resources, and so on. In the eyes of a European, the USA remain a land of contrasts, with interesting lessons to be learnt.

One of the first “passive” construction sites we visited was located in Berthoud, thanks to Harrington Construction.

The interior of the Berthoud passive house

The interior of the passive house, before the packing of the cellulose insulation in the perimeter walls.

Construction techniques used in the US are evidently different from the ones we’ve used to far, for example in the two passive houses we are currently building in Cavriago. Nontheless, the construction quality remains high, to guarantee the level of comfort and energy efficiency of a passive house thermal envelope.

A second example of a passive building, in Boulder, was shown us by Mark Attard of AE Building Systems, a company specializing in products and components for low-energy buildings.

A passive house in Boulder

View from the inside of the passive house of Boulder, looking down onto the valley.

We also had the chance to visit some buildings with energy retrofit, as in the case of a house in Louisville, where the existing structure was insulated with rockwool (for the perimeter walls) and expanded perlite (for the slab on ground). Overall speaking, the peculiar climate of Colorado, which is very dry year round, allows to easily solve some retrofit problems that are particularly risky in our Italian climate, which is on the contrary very humid.

The thermally refurbished crawl space

The crawl space, with perlite insulation under the black sheet.

At the Alliance for Sustainable Colorado (which brings together several associations around the topic of environmental sustainability), we assisted to the presentation by Ashley Perl of the City of Aspen, about the effects of climate change on the city and its economy. The overall raise in temperatures is leading to a steady decrease in snow fall, and to the shortening of the skiing season. For climatic reasons, therefore, the city of Aspen is forced to re-think its entire economy.

The city of Aspen, with its 6.000 permanent residents, currently employs four people in several activities to diminish the environmental impact of the city. The “Canary Initiative” specifically includes a variety of initiatives to reduce consumption of energy and water, as well as to promote waste recycling. Given the small size of the city, its initiatives are generally used as pilot projects for the entire state of Colorado.

Among other meetings, we also had the chance to visit Alpen Widnows, the company producing some of the most performing windows currently available on the American market.

Alpen Windows

A window by Alpen Windows. The balloons are used to compensate the pressure difference between the glazing and the surrounding environment, caused by the high altitude.

Last but not least, we assisted to the presentation by Andrew Michler about his book “Hyperlocalization of Architecture”, which summarizes the state of the art of architecture in several countries around the world. The book also includes interviews with several eminent people such as Wolfgang Feist, founder of the Passivhaus Institut.

Andrew Michler

Andrew Michler during the presentation of his book.

Overall, our trip to Colorado was very enjoyable, besides our professional meetings. We also managed to meet with old friends, have breakfast with donuts and dinners with elk burgers and craft beer. You can’t live on passive house alone.