- Overall Concept and Design
- Building Construction
- Heating, Ventilation & Air-Conditioning (HVAC) System
- Water
- German Passivhaus Standard
Overall Concept and Design
The EcoHouse concept was to have a family home in a holistic environment, marrying sustainability, energy and water conservation with comfort and a strong connection to the land around it. The primary energy conservation concept is that of the German Passivhaus (see below for details). Connection to the surrounding land is reinforced via growing plants either direct rooted in the earth or in pots on paved terraces.
The house was designed by the Austrian architect, Elisabeth Kahlen, based in Graz, who is a specialist in low energy buildings. The Passivhaus energy consumption calculations on her design were made using the approved Passivhaus calculation tool – PPHP – and confirmed that the building conformed to the Passivhaus energy requirements.
The original design was for a three-storey building, with the lowest floor usable as a meeting area for presentations on Passivhaus and energy conservation in general. That floor was also designed to house the HVAC equipment and normal household utilities (storage and laundry facilities). The outline drawings were passed to the Montenegrin builder, who was also a registered structural engineer, to provide the final drawings for building permission. He changed the location of the bottom floor to a separate strong reinforced concrete structure to the west of the rest of the house. He deemed this change to be essential to support the main house and so satisfy the earthquake requirements for the building permission.
Building permission was granted in December 2012, with construction starting at the end of January 2013. The owners moved into the house in the spring of 2014.
Building Construction
Outside walls have 20cm thermal brick between the reinforced concrete frame (legally required for this active earthquake zone), all clad with a 12cm EPS layer of insulation. Use of a more environmentally friendly insulation material was considered, but costs, easy availability of alternatives, and the local tradesmen’s inability to install anything other than EPS made this material the only option. Thermal bridging to the first floor terrace and its supporting columns is minimised by extending the insulation to cover all these surfaces.
Windows are all triple-glazed (4-16-4-16-4) and argon gas filled to a Rehau profile manufactured and installed under licence by VH Montenegro (https://www.vhmsolutions.me/), with external roller shutters to help heat loss/ gain. The windows have U values between 0.88 and 1.1W/m2°K. The windows were installed with additional air-tightness tape around the frames to further reduce air leakage. While the heat transfer rate is higher than the Passivhaus requirement of 0.8W/m2K, this was the best available in the country at the time of construction.
The south side of the house has wide overhangs over each of the two floors, designed to reduce direct sunlight hitting the windows in summer, and maximise sunlight entry in winter. This reduces solar gain in summer, while allowing it in winter, both being passive methods of energy conservation.
Although installation of photovoltaic solar panels was uneconomic at the time of construction, ducting was installed from the roof to the solar panel control room at the garage. This allows easy installation of photovoltaic solar panels in future. There is space in the room for energy storage equipment (eg batteries) and the associated control equipment.
It was not possible to carry out an air-tightness test on the building at the appropriate time, as there were no qualified personnel and equipment available within economic reach. This means that it has not been possible to prove official conformity to the Passivhaus standard.
Heating, Ventilation & Air-Conditioning (HVAC) System
There is an integrated heating and cooling system with a Daikin 10kW air-to-water heat pump as the energy provider. The original heat pump was rated at 7.1kW for heating, 7.8kW for cooling, with a Coefficient of Performance (COP) of 2.4. The pipework as installed had too many bends from the heat pump, which reduced its effectiveness, and it was up-rated. Heating is through Rehau under-floor distribution controllers and water pipes, while cooling is via fan coils in the ducted ventilation system., A Systemair ventilation recuperative unit constantly recycles the internal air, drawing in about 25% external fresh air through a heat exchanger. Extraction points are in both toilets, as well as on the upper floor.
Domestic hot water is heated by a single Viessmann 2.5m2roof-mounted solar panel, set at 35º to the horizontal, feeding a Viessmann 160l tank, with auxiliary electrical heating. The whole HVAC and hot water installation was designed and installed by Ening d.o.o. of Nikšić (http://www.ening.co.me/).
The end result is a very comfortable interior environment (see a summary of electricity consumption below). The internal temperature in winter and summer is between 23°C to 25°C compared to mid to high 30°sC, sometimes over 40C°, outside during June to early September. The outside winter temperature is usually in the low teens, down to 5°C at times during December to February. Frosts are (fortunately) rare, but cause havoc with the garden if they last longer than a few hours. The original PHPP calculations were made using 20ºC as the internal temperature, with temperatures over 25ºC rated as occurring for 10% of the year, using Roma Practica di Mare data as the basis for climate.
Ducting input air to the heat pump via an underground pipe, as recommended in standard Passivhaus literature, was not possible due to the layout and soil of the site. A minimum of 30m is required at a depth of at least a metre. There was not enough space. Additionally, a layer of insulation underneath the reinforced concrete foundation was not within the capabilities of the building team, quite apart from the additional cost.
Water
Water conservation was an important part of the overall concept for the EcoHouse. The public water supply suffers shortages, especially in summer at the height of the tourist season.
A severe storm can give 30 to 40cm of water over a 24-hour period, and 10cm to 20cm is normal for an average storm. Risan’s annual precipitation from 1961 to 1984 was 3.1metres, most of which seems to fall at once!
While normal domestic consumption is not large, with only two people living in the house, the garden needs a substantial amount of watering in summer. The garden areas are not contiguous, being around the perimeter of the house, and there is an 8m difference in height from the north side (back) to the south side (front).
An underground 15m3tank was built on the east side of the house to collect rainwater from the roof. This water is pumped to the garden areas on the north side of the house, including the section along the roadside, feeding a comprehensive piped drip irrigation system, allowing more precise and controlled water flow to plants. The main piped system covers all the sections of the garden and uses the main water supply, with battery-operated timers allowing different times and durations for the 10 zones.
Heat recovery from domestic hot water was considered, but the equipment and installation required was deemed uneconomic for the small amount of heat recovered.
While the main water is drinkable, drinking water is collected from a spring 200m above sea-level about 2km from the house. This spring (Smokovac) is used by many of Risan’s residents.
German Passivhaus Standard
Passive House requirements
For a building to be considered a Passive House, it must meet the following criteria ( for detailed criteria, please see the building certification section):
1. The Space Heating Energy Demand is not to exceed 15 kWh per square meter of net living space (treated floor area) per year or 10 W per square meter peak demand. In climates where active cooling is needed, the Space Cooling Energy Demand requirement roughly matches the heat demand requirements above, with an additional allowance for dehumidification.
2. The Renewable Renewable Primary Energy Demand (PER, according to PHI method), the total energy to be used for all domestic applications (heating, hot water and domestic electricity) must not exceed 60 kWh per square meter of treated floor area per year for Passive House Classic.
3. In terms of Airtightness, a maximum of 0.6 air changes per hour at 50 Pascals pressure (ACH50), as verified with an onsite pressure test (in both pressurized and depressurized states).
4. Thermal comfort must be met for all living areas during winter as well as in summer, with not more than 10% of the hours in a given year over 25°C. For a complete overview of general quality requirements (soft criteria) see Passipedia.
All of the above criteria are achieved through intelligent design and implementation of the 5 Passive House principles: thermal bridge free design, superior windows, ventilation with heat recovery, quality insulation and airtight construction.
The following five basic principles apply for the construction of Passive Houses:
Thermal insulation
All opaque building components of the exterior envelope of the house must be very well-insulated. For most cool-temperate climates, this means a heat transfer coefficient (U-value) of 0.15 W/(m²K) at the most, i.e. a maximum of 0.15 watts per degree of temperature difference and per square metre of exterior surface are lost.
Passive House windows
The window frames must be well insulated and fitted with low-e glazings filled with argon or krypton to prevent heat transfer. For most cool-temperate climates, this means a U-value of 0.80W/(m²K) or less, with g-values around 50% (g-value= total solar transmittance, proportion of the solar energy available for the room).
Ventilation heat recovery
EcoHouse Montenegro Technical Details.docx page 3of 4
Efficient heat recovery ventilation is key, allowing for a good indoor air quality and saving energy. In Passive House, at least 75% of the heat from the exhaust air is transferred to the fresh air again by means of a heat exchanger.
Airtightness of the building
Uncontrolled leakage through gaps must be smaller than 0.6 of the total house volume per hour during a pressure test at 50 Pascal (both pressurised and depressurised).
Absence of thermal bridges
All edges, corners, connections and penetrations must be planned and executed with great care, so that thermal bridges can be avoided. Thermal bridges which cannot be avoided must be minimised as far as possible.
Electricity Consumption
The internal liveable area of the house is 59.33m2 + 54.26m2, total 113.59m2. This results in an expected consumption of 37.34kW per day. The actual electricity consumed over the period January 2015 to December 2024 averages 9.9% more than the standard Passivhaus requirement of 120kW per m2 per year. The actual internal temperature, though, is between 23ºC to 25ºC compared to the standard as used in the PHPP calculation of 20ºC, ie 20% higher.
It is therefore reasonable to state that the house performs close to the Passivhaus requirement.
Ecohouse Montenegro 