House Moroder

Orazio street 7


Bolzano, Italy


Arch. Michael Tribus
Griesplatz 6/1 - Piazza Gries, 39011 Lana (Bz)
zusammen mit dem im Haus wohnenden Arch. Augusto Visintini


Helmuth Moroder
Horazstraße 7 - Via Orazio, 39100 Bozen

Contact Details

Alexandra Troi
Hochschule Coburg
The historic residential building is located in the city center of Bolzano. It was built in 1926, near the old town, and it has hardly been changed on the outside, thanks to well thought-out renovation measures from the inside which ensure a new level of comfort and a minimization of the energy demand of the building.
Energy performance
21 kWh/m2.y

Climate Zone feucht-gemäßigtes Klima

Altitude 252 m a.s.l.

HDD 3993

CDD 24

Protection level Not listed

Conservation Area:

Level of Protection:

Building age 1900-1944

Year of last renovation:

Building use Residential (urban)

Building occupancy:
Permanently occupied

Building area Net floor area [m²]: 268,0

Building typology:
Detached house

Number of floors:

Basement yes/no:

Number of heated floors:

Thermal envelope area [m²]:

Volume [m³]:

NFA calculation method:
Useful area (it)

Construction type
Brick masonry wall

External finish:

Internal finish:
Plastered (on hard)

Roof type:
Pitched Roof





The "Haus Moroder" shows the typical style of the urban villas of Bolzano from the 1920s and 1930s: the solid brick building situated in the middle of a large garden, the façade designed with textured plaster with a few decorative elements, and the filigree box-type windows. The internal staircase gives access to the three flats, one for each floor, as well as to the cellar and the previously unused attic.
Urban context
The building is located in a residential area which was developed in the beginning of the 20th century. This area was expanded and the buildings reconstructed over the years, so that today the place is characterised by a colourful mix of buildings from different periods. The neighborhood is close to the old town with good access to the shops and the restaurants. The Petrarca Park on the Talfer river is reachable with a 10-minute walk.

State of repair

Conditions of the envelope
The building was bought in 2015, and at that time it still showed its original condition from 1926. No renovation works have been made during the years and, despite that, the building was showing a perfect overall condition. The external walls and the façades did not require any conservative intervention, since the external plaster had been very well preserved. The indoor spaces too were characterized by no visible defects, but anyway, they needed a modernization to respond to the new comfort requirements and to ensure a pleasant indoor climate.
Description of pre-intervention building services
Old pipes and technical equipments were installed in the entire building. There was no central heating. The apartment on the second floor was equipped with a gas heating system, while the rest of the building was heated only by wood and a number of electric heaters. All the sanitary facilities were in their original condition.


The original aspect of the façade had to be preserved. In order to maintain the original plaster as well as the historic appearance of the windows and the floor frames, the building was insulated exclusively from the inside. The design of the new windows was modelled on the original one, so that no clear difference is visible from the outside. The interior staircase and the entrance door have not been changed.
Heritage Value Assesment
The building is not a listed building. However, the owners considered essential to preserve the architectural character of the house, since it is one of the few houses left unchanged in Bolzano from this specific historic period. In addition to the building envelope, the preservation of the original staircase and the entrance door was another owners´ requirement. For this purpose, alternatives to the standard solutions were sought and found during the energy renovation process.

Aim of retrofit

The aim of the retrofit was to improve the indoor comfort while preserving the architectural character of the building. The main purpose of the process was to maximize the possibility of preserving the building and reaching high energy efficiency levels. To achieve this, the energy retrofit measures were taken exclusively from the inside the building. The concept of the retrofit was to reduce the thermal losses via walls, windows, and thermal bridges, and to use high-performance systems to guarantee high level of indoor comfort with minimum energy consumption. A ventilation system with heat recovery is installed to guarantee fresh air in the building, while space heating and cooling are provided by a heat pump system.
Lessons learned
If the interior insulation is carried out consistently, even across the windows and interior walls, with the appropriate material thickness, the energy efficiency is just as high as with exterior insulation. Comfort in the interior is created by a warm surface temperature of the walls, regardless of whether it is an exterior or interior wall. Therefore, a constant room temperature is the ideal way to create a comfortable ambience. Due to a very strict and well thought-out organization of the craftsmen, the time frame of the renovation work could be kept to the day and a move-in was possible on the planned day.
Stakeholders Involvement
Arch. Michael Tribus
Griesplatz 6/1 - Piazza Gries, 39011 Lana (Bz)
Tel.zusammen mit dem im Haus wohnenden Arch. Augusto Visintini
Tools used
Energy calculation KlimaHaus und PlanFenster


External Walls

Brick masonry with internal insulation

Brick masonry with internal insulation

In order to leave the facade untouched, a 10-cm insulation was placed on the inside of all the external walls. A perlite insulation - TecTem from Knauf - was chosen because of its natural composition, which makes it suitable for indoor use. To install the insulation, the internal plaster was removed from the inner surface of the walls. Moreover, a few centimeters of flooring were removed along the wall joints, in order to place a layer of insulation underneath, to avoid thermal bridges. In this way, there won´t be cold spots that cause heat losses. The same principle is applied to the window connections. For this purpose, the interior insulation was laid up to the new window frame in order to prevent heat from being lost through the window splay. In addition, flank insulation was installed over the entire length of the walls in the stairwell area. Since the stairwell had to be kept in its original condition, the interior insulation prevented heat losses from the apartments to the hallway.

U-value (pre-intervention) [W/m2K]: 2,5 W/m²K U-value (post-intervention) [W/m2K]: 0,38 W/m²K
More Details
Original wall build-up
Render - Zementputz:
15 mm
Brick - Mauerwerk aus Stein:
450 mm
Plaster - Kalkzementputz:
15 mm
Retrofitted wall build-up
Render - Zementputz:
Brick - Mauerwerk aus Stein:
450 mm
Render - Kalkzementputz:
15 mm
Insulation - Innendämmung aus exponiertem Perlit (U Wert=0,4):
100 mm
Plaster - Kalkzementputz:
15 mm


Single window with 3-pane insulating glazing

Single window with 3-pane insulating glazing

With a U-value of about 2.5 W/m²K, the original windows from 1926 would have been a weak element of the building envelope - both in terms of energy loss and of reduced comfort due to the low surface temperature. Since the building is not listed, the client and architect decided to replace the windows and they developed a solution that is fascinating for its simplicity and helped avoid waste material and to reduce costs:

The new wooden window with triple glazing and energetically optimised frame has two sashes again, the division into 3 fields each takes up the look of the original two sashes under the transom and the bottom-hung sash above. It is positioned in the place of the inner plane of the old box window in the existing window frame, so that (i) the window area remains the same size even with the new frame and (ii) the frame perceived on the outside is very filigree, (iii) installation is very simple and (iv) the installation thermal bridge is very easily avoided - by insulating the indentation in the "old" box cavity and on the inside the adjoining reveal. A drawing of the detail, as well as the 2-D calculation of the thermal bridge, for the implemented variant as well as the investigated alternative of keeping the window in the outermost plane can be seen by browsing through the images on the right.

Existing window U-value Glass [W/m2K]: 1,4 New window U-value Glass[W/m2K]: 0,7 Existing window U-value Frame [W/m2K]: 2,7 New window U-value Frame [W/m2K]: 1,1
More Details
Existing window type Box-type window
Existing glazing type Single
Existing shading type Outer shutter
Approximate installation year 1926
New window type Sash window
New glazing type Triple
New shading type Outer shutter
New window solar factor g [-] 0,47

Other interventions



To complete the insulation most effectively, external insulation was placed in the basement and in the attic, i.e. in the non-habitable area. Since the attic was not developed as a habitable space and this project was not in the near future, 20-cm thick polystyrene boards were laid on the floor in a double layer. The final layer is a USB wooden panel to keep the roof truss accessible.

The ecological aspect of this measure is that the material can be dismantled and reused at any time in case of an extension.






Since there was no heating system in the entire house before the renovation, the single gas-heater was replaced by a central heat pump heating system.

To make the installation as easy as possible, the heating system was installed in the ceiling. With a room height of 2.85m, it was possible to install the clay panels with embedded heating pipes in a suspended ceiling. In addition to the insulation made of natural material, a user-friendly design was also chosen for the heating system by using clay. In addition, clay has humidity-regulating properties, which allow the material to absorb the humidity and to gradually release it. The entire system was thus no longer directly visible to the occupant after shoring. After the renovation, all the apartments can be permanently heated.

More Details
New primary heating system
New system type Heat pump
Fuel Electricity
Distribuition system Radiating ceiling
Nominal power 11 kW

In order to guarantee a constant good air quality and to avoid the heat waste related to ventilation, each flat was equipped with a dedicated ventilation system with heat recovery. The ventilation unit themselves were places in the bathroom and the air ducts were led through the suspended ceiling.

No holes had to be drilled in the façade to supply the fresh air and to remove the stale air: the supply and exhaust air is guided via a customized construction in the bathroom window, inconspicuously housed in the area of the former tilting window above the transom.

More Details
Original roof build-up New ventilation system
Type ventilation system Decentralized
Type flow regime Overflow
Heat recovery Yes
Humitidy recovery No
Nominal power 0,27 kW
Electric power 0,27 kW
Control system Continue, 5 control points (30-150 m3/h)

Thanks to the renovation, the cooling of the apartments during summer was also made possible: the heat pump can be switched from heating to cooling mode, and the radiating ceiling can provide space cooling.

This is not a "full air conditioning" (no moisture can be extracted from the air by the cooling surfaces, for example), but rather a supplementary measure to ensure summer comfort. Together with this system, the window shutters - with their flap elements typical of the region - allow to protect the building from overheating while letting a certain amount of light entering the house.

More Details
New cooling system
Type Heat pump
Distribuition system Radiating ceiling
Nominal power 10,61 kW
Electric power 2,72 kW

Energy Efficiency

Energy Performance
Energy performance certificate: Casaclima Class B
Voluntary certificates: No
Energy Use
Primary Energy 45 kWh/m2.y
20151221 Certificato CasaClima.pdf
Consumption_estimation_After: 21 kWh/m2.y

Primary Energy
Consumption_estimation_Calculation_method: Steady state simulation (e.g. EPC, PHPP)
Consumption_estimation_Including_DHW: Yes
Consumption_estimation_Before: 365 kWh/m2.y
Consumption_estimation_After: 45 kWh/m2.y

Internal Climate


Since a heating and cooling system is installed in the entire building, the indoor temperature can be maintained at a constant and comfortable level. This has greatly improved the comfort in the living spaces, as the fluctuations of the outside temperature are no longer perceivable from the inside.

Indoor Air Quality

The new ventilation system ensures fresh and clean air in each apartment. Since a single ventilation unit was installed separately for each apartment, the operation of the system can be managed as needed. An automatic exchange of the entire air volume is assured every 2 hours, but the air flow can be increased or decreased by the users. Thanks to the system, the occupants noticed a clear reduction of dust in the air.


Financial Aspects

The Italian government supplies a financial subsidy to people who take energy-efficiency measures during the building renovation works. In the case of the presented refurbishment, the owners were able to deduct from the taxes the 2/3 of the costs during the years following the work. An additional financial benefit was the reduction of heating need, which led to direct money saving in relation to lower bill payments: the running cost for each apartment was therefore reduced from 5,000-6,000€ to 800€. Since a conventional refurbishment was expected to lead only to a 20% -reduction of the total costs, the additional measures were paid back after only a few years.

Investment Costs
Total investment costs
500.000€ (total)
Running Costs
Total annual energy cost
2.400,00€ im Jahr (total)

Lifecycle cost

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