Practices

Casa Cesti: energy retrofit of farmhouse

A Subliniat Caz September 2017
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Casa Cesti is a complete renovation of an existing traditional farmhouse in a farming complex which was built in 1942. The buildings are divided into residential use, office space and livestock facilities and are typical of the rural area of ​​the Oleggio municipality (Province of Novara) in the Italian region of Piedmont. The original house was made of brick masonry and stone courses and is oriented along an east-west axis with the main façade facing south. The two storey house opens onto the courtyard. The gabled roof has different pitches, the southern slope is steeper or more accentuated and the northern slope is slightly less inclined.

 

The renovation of the structure was done in order to create a "modern farm" - an energetically efficient building, designed according to the criteria of the Passivhaus Institute by respecting the impact on the outdoor environment through the rational use of clean and renewable energy throughout the life cycle and excluding the use, for any purpose, of fossil fuels, without losing comfort and style for the occupants.

The choice of environmentally friendly construction materials to be used for the refurbishment included:  insulation made from wood fibre recycled from machining waste, rectangular bricks for low conductivity, interior counterparts made of natural material, interior plastics free from cement and heavy metals, plaster interior finishes which would naturally improve the hygroscopic characteristics of the internal moisture regulation; original structure made from local stone.

 

 

Location

 

Via Galli, 6, 28047 Oleggio (Novaro, Italy)

 

 
 

Project team

 

Architectural design, contractor and project management

 

-Marco Cesti

 


Construction

 

-construction thermal works/insulation, envelope: A.F. Impresa Edile di Allia Francesco 


-IT and monitoring system: Forghieri Massimiliano (home automation)


-hydro-thermal sanitary systems:  Motti Cesare (heating, cooling and mechanical ventilation)

 

-ventilation equipment, scaffolds and material equipment Stiebel Eltron: Enercomb S.r.l.

 

 
 

 

Time schedule

 

Built: 1942

Renovation works: 2012 – 2013

 

 

 

Building use and area

 

The farming complex  is located on the edge of the town of Oleggio in an area characterized by a low building density, and is comprised of a two-storey detached house and multi-storey buildings surrounded by green agricultural areas.

 

Plot area: 778 m2

Built-up area: 39.5 %

Green area: 400 m2

Total Usable Floor Area: 250.45 m2

 

The goal of the project was to create a single large living unit. Living areas are placed on the ground floor: kitchen, bathroom, double-height living room space with loft and architect office. The upper floor consists of bedrooms, a laundry room, walk-in wardrobe and another bathroom.

 

 

 

Renovation costs

 

Global cost: 360,000.00 €

Renewable energy system cost: 21,000.00 €

 

 

 

Envelope performance
 

Different solutions for the thermal intervention of the façades were applied to the existing building which is composed of a mostly brick structure with stone courses in some areas and plaster on top and a total thickness of approximately 42 cm on the ground floor and 30 cm on the first floor.

 

The internal intervention was carried out by implementing a new row of load-bearing bricks on which the new floor slab was supported. Between the two walls there was a 16 cm gap filled with high density rock wool panels. The exterior walls were protected with EPS outer coating with different thickness (5 – 10 cm) due to restrictions imposed by neighbours on the north side and the small size of the road section of Via Galli.

 

The resulting walls have a total thickness between 65.9 cm to 82.8 cm and a global envelope U-value of 0.15 W/m2K.

 

Negative spaces (holes) were solved with triple glazed Windows with PVC frames having a global U-value of 0.636 W/m2K. The ground floor has 1.5 rectified ceramic flooring, 3 cm XPS panel as a radiant heating system holder element, 8 cm EPS panel with increased thermal insulation of aerated lava and 7 to 27.5 cm lightweight cellular screed with high insulating power. The floor has a total thickness of 25 cm in the kitchen, living and bathroom area with a transmissibility value of U = 0.198W / m2K, while in the bedrooms equipment room and the bathroom , the floor thickness Is 45.0 cm with a transmissibility value of U = 0.123 W / m2K.

 

The wooden roof was dismantled and reclaimed and the original Portuguese tiles were recycled leaving the existing structure in which a moisture damper and an air space were laid. The thermal insulation consists of 18 cm thick wood fibre and a breathable sub-tile membrane to ensure the outflow of any moisture and protecting it from water penetration. On the interior of the old wooden roof structure, additional 14 cm thick wool panels were added to fill the space between the supporting beams which were then nailed from the bottom  of the finishing spruce boards.

 

The thermal bridges were analysed with specific computing software, (despite the complexity of the intervention on an existing building) and were mostly negative (including the insulation against the perimeter masonry), while the internal masonry and the floor planes have a positive linear coefficient equal to 0.4681 W / (mK)

 

 

 

Energy consumption
 

Primary energy need before renovation: 300 kWh/m2.year

Primary energy nee: 12.00 kWh/m2.year

Primary energy need for standard building: 63.64 kWh/m2.year

 

Calculation method: UNI TS 11300

 

 

 

Energy systems

 

The heat production management for heating, cooling, mechanical ventilation (VMC) and domestic hot water (DHW) is done with a centralized heat recovery ventilation unit. The unit is able to use all the renewable energy sources through electronic management set with priority usage that, starting from solar thermal energy for all DHW production and heating needs, can be integrated with the electric heat pump in case of the need for additional energy. The electric booster guarantees the thermal needs even with temperatures of  -20 ° C.

 

In addition, by utilizing both the residual thermal energy present in the exhaust air expelled from the VMC and the energy dispersions of the DHW cylinder, it has an air-to-water heat pump with a degree of real efficiency (with operation of the VMC system) far above average of individual products, even at temperatures below 0 ° C. 

 

Heating system:  Low temperature floor heating through heat pump and solar thermal panels

Hot water system:  Heat pump and solar thermal panels

Cooling system:  Low temperature floor cooling through reversible heat pump

Ventilation syatem:  Double flow heat exchanger and geothermal groundwater system well

Renewable energy systems:  Solar thermal and photovoltaic

 

A 5.87 kW grid-connected photovoltaic system was installed on the roof, consisting of 25 modules with an area of ​​40.48 m² and two flat vacuum solar collectors with a surface area of ​​the absorber of 4.76 m².

Both systems are exposed to the south, with an inclination on the horizon of 15.45 °. Solar collectors provide 2,135.83 kWh for hot water production and 362.33 kWh for winter heating, typically in late October and early March. The photovoltaic system makes for self-sufficient housing in terms of electricity generation, with a share of self-consumption of about 26.2%, compared to an average annual production of 7.088 kWh /year.

 

 

 

Daylighting and building controls 

 

Implementation of direct solar energy with large windows on the south facade and use of solar shading elements such as the porch and gutter are used to maximize summer cooling without reducing winter solar gains.

In order to guarantee the comfort and well being of residents, in particular regarding indoor daylight - light intensity or darkness based on day time the use of domotics (ISAAC DEVICEs) have been choosen for the adaptability to the outdoor environment.  Different scenarios are available for the management of the 11 sliding window shades of windows and doors. It is also possible to plan in a simple and intuitive way the conditions for which the winter season (when solar inputs are needed most) allowing the automatic system to adjust accordingly. At mid-morning, the shades open completely when the sun rays begin to make an effective contribution to the heating of the room.  The shades change to a horizontal position at dusk.

In the summer season, however, ISAAC keeps slats tilted so that direct sunlight does not pass through the window frames. The system was designed by the customer, so each room responds to specific needs. In the bedrooms, consequently, the programming takes into account occupancy needs before solar ones. In addition, the programming of the device in spring and autumn limits the solar inputs to a reasonable overheating, then automatically places the slats at a 45 ° angle to block the solar inputs in order to avoid discomfort for occupants due to excessive internal temperatures (26 ° / 27 ° in the house at the end of September).

 

 

 

Indoor Air quality

 

Mechanical ventilation with high efficiency cross-flow heat exchanger operating at 200 mc / hour ensures the correct and constant replacement of indoor air. Filters installed upstream of the air-ground exchanger and the heat exchanger inside the machine ensure a high level of dust and pollutant emissions compared to the air exchange for natural ventilation. The geothermal heat exchanger also ensures a reduction in indoor humidity during the summer period by naturally reducing the relative humidity of the air in the mechanical ventilation system (with the soil temperature at about 14 ° C).

 


 

Water management

 

A lifting station was installed in the existing well and the use of non-drinking water for all non-food uses was also taken into account (irrigation, courtyard cleaning/car/solar plant, wc drainage).
 
Consumption from water network:    25,00 m3
Consumption of grey water: 0 m3
Consumption of harvested rainwater: 0 m3
Water Self Sufficiency Index: 0,44 %
Water Consumption/m2: 3,08 m3/m2
Water Consumption/Bedroom: 180,00 m3/Bedroom

 

 

 

Awards and recognition

 

Green Solutions Awards finalist in Low Carbon category 2017

 

 

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