Definition
A passive house is a building that “passively” from the sun, from internal heat sources and from recovered heat comfortably warm is kept, thus it does not require a conventional heating system with additional radiators in each room.
In comparison to a modern low energy house requires a house built with passive house standard approx. 75% less energy for heating and compared to an average New Zealand home over 90%. Converted in oil for heating a passive house requires less than 1.5 liters/m2. This sensational savings achieved by the passive house concept solely through his two basic principles: avoid heat loss and optimize heat gain!
We have provided a brief introduction (guideline) on the topic of passive house standard on our website. All important aspects are covered by the insulation of thermal bridge, air tightness and window quality to the heat recovery.
Construction Principles
Good thermal insulation and compactness
All components of the outer shell (thermal envelope) must be completely insulated very well. Edges, corners, connections and penetrations must be very carefully planned in order to avoid thermal bridges. All not translucent components of the outer shell of the house’s insulation (i.e. external wall) shall be so good constructed that it possess a heat transfer coefficient of U < 0.15 W/(m² K) (R-value = 1/U), means that per degree celcsius of temperature difference and square meters of external wall not more than 0.15 watts will be lost. The more compact a building envelope is built, the easier and cheaper it possibility to realize the passive house standard.
North orientation and shading freedom
Appropriate orientation, shading freedom and a reduced share of window frames are additionally essential so that the “passive” solar gain can be optimized and will be the critical heat supply. Especially with detached houses an increased insulation can be avoided. In apartment buildings (multi storey building complex) and other forms of compact building passive house standard is achieved even without South orientation.
Super Glazing and Super Frames
The windows (glazing including window frames) should not exceed a U-value of 0.80 W/(m² K). Please note the special window frames with thermal insulation are required. The glazing has a g-value by 50% (g-value = total energy transmittance, percentage of available space for the solar energy). The windows of thermal bridges must be built into the insulation level of the wall construction.
Passive preheating of fresh air
The fresh air could be led through soil tubes or ground heat exchanger (in the earth layed special ventilation ducts) into the house. Even on cold winter days the air will be preheated to a temperature of about 5 ° C. This is a sensible option, but not necessarily required for a passive house.
Highly efficient recovery from the exhausted air with a countercurrent heat exchanger
A comfort ventilation with heat recovery, possess in the first place a very good indoor air quality, in the second place it is great energy savings. In the passive house standard at least 75% of the heat from the exhaust air will be fed back to the fresh air through a heat exchanger. For this purpose, fresh air and exhaust air past each other in separate channels. Thus, the heat can be transferred without the mixing of the air. For the ventilation, however, may only be permitted a minimal power consumption.
Heating of domestic water with partially renewable energies
To reduce the consumption of fossil energy sources further can be the preparation of the domestic hot water completely or in part with solar panels, wood boilers or heat pumps happen.
Energy saving devices / Green Star rated appliances for the household
The reduction of electricity not only protects the environment and the household budgets, it also avoids unnecessary heating of the rooms in summer. Refrigerator, stove, freezer, lights and washing machine as high-efficiency power management devices are an indispensable component for a passive house. To dry the clothes are great, the clothes line (solar dryers), or an oven, in contrast to air or condensing dryers has a very low power consumption.
Optimize overall concept = Reducing of construction cost
To achieve the passive house standard, all components must be optimized, coordinated and well planned ahead according to specifications, requirements and circumsatnces of site (location). This will be taken into account in the passive house configuration calculation. This calculation is a energy balance assessment for heat and primary energy inclusive the calculation of many additional aids i.e. optimization and determination of window, external wall and roof U-values (R-values), influence of orientation and shading, building heat load and frequency of overheating in the summer. This method enables the optimization of all critical components of the passive house standard and cost effective solutions can be achieved appropriately.
Explanations
Internal heat sources
Unlike conventional buildings in the passive house itself makes the heat dissipation of household appliances and residents quite noticeable (every person “heats” with approx. 80 watts). For the calculation of residential buildings a total of 2.1 watts/m² of internal heat sources will be taken in account. Accurate measurements in a built passive show house have shown a permanent power of 1.0 watts/m². The German DIN 4108/Teil 6 from 2002 has set for the internal heat source a value of 5 W/m² which is unrealistically high. Especially for the indoor climate in summer it is very important to keep the internal heat sources low, means use of high-efficiency and energy saving household appliances is inviteable.
Recovered heat
A passive house concept can only work with a highly efficient heat recovery, which has an efficiency of at least 75%. With a pure exhaust system, as used in low energy houses, the heat loss through the ventilation at the same air exchange rate 24 kWh/m² per year. This is not acceptable for a house built in passive house standard, because at a maximum heating demand of 15 kWh/m² may no longer be possible to compensate high heat losses through additional heat gain. Moreover, because of the colder outside air which would flow directly into the living rooms additonal radiators will be required.
Quality criteria
Passive houses are buildings in which reaches a comfortable temperature in winter without a separate heating system and no air conditioning in the summer with very little energy consumption. The heating requirement is limited to 15 kWh/(m² a) and the primary energy including hot water, auxiliary electricity for heat pump and household electricity to 120 kWh/(m² a). Just by using passive house components, they offer an increased comfort and while securing the structure of the building.
The realization of a house in a passive house standard represents high demands on the components used.
Comfort + convenience
- Only the high internal surface temperatures of all external components (wall and roof), especially windows and doors, as well as small leaks in the building envelope, allowing the waiver of additional heating sourcess in the living rooms.
- A ventilation system with heat recovery provides continuously fresh air without draughts occur (air inlet temperature in the room not under 17°C) and without that the inhabitants have to worry about the active ventilation. The fresh air requirement of 30 m3/h per person in the complete building should not be exceeded in normal operation, otherwise the air is too dry in winter. Such a system shall not to be confused with air conditioning, a moistening of the air within the ventilation system is to be avoided for health reasons.
- The noise impact of ventilation systems should be limited to 25 dBa. These ducts and valves are sufficient dimensioned and silencers shall be used.
- For an adequate cross-ventilation in summer, openable windows in each outer room are required. For the summer operation of the ventilation system a bypass on the heat exchanger shall be available. The optional ground heat exchanger can also provide cool air in the summer.
- To prevent unnecessary heat up of the building adequate sun protection prior to major windows facing east or west must be provided. For north-facing windows is it recommended to achieve an optimal climate.
- The use of energy-efficient lighting and household appliances and a good thermal insulation of domestic hot water storage as well as pipelines also reduces the heat load in the house and facilitate in the summer the “passive cooling” effect.
Quality standard for design and technology
- To avoid moistness of components and mildew a continuous ventilation with a mechanical ventilation system and the high thermal insulation without structural thermal bridges of all external components are required. Especially in the area of insulated windows and doors, thermal frames/profiles, triple glazing and thermally broken spacers in the glass edge seal (not aluminum!) shall be used.
- To ensure the proper functioning of the ventilation and heating and to avoid the damage of the construction due to condensation is an excellent building air tightness required. The air tightness is to be detected by an air pressure test (Blower Door Test). The Blower Door Test at 50 Pascal pressure difference must be limited to 0.6 times the volume of air per hour.
- To ensure a healthy, clean fresh air the use of high-quality filter (at the intake point) and downpipes for condensate of the ground heat exchanger and ventilation equipment are required. The heat recovery from the exhaust air must be ensured without mixing of the fresh air. On a humidification within the ventilation system is omitted for reasons of hygiene (passive houses shall have sanitary ventilation systems, no air conditioning!).
Energy Efficiency
- The heat transfer coefficient (R-values/ U-values) of opaque components shall be below 0.15 W/(m²K), in detached houses often even below 0.10 W/(m² K).
- The Ug-values for the glass shall be below 0.80 W/(m² K) with a high total energy transmittance of 50%, so that even in winter net heat gains are possible. In the edges seal spacers to be used with thermal break, no aluminum!
- The entire window system requires insulated window frame profiles with thermal break systems and multiple lip seal. The resulting heat transfer coefficient of windows (and doors) is limited to: Uw (Ud) < 0.80 W/(m² K), under consideration of glazing (Ug), edge spacers (Ybezel) and Uw (Ud) respectively < 0.85 W/(m² K) with additional consideration to the installed situation of the insulated component (Yinstallation).
- The heat recovery efficiency of the heat recovery ventilation systems must be above 75%. The electricity consumption for fans and control device must be limited to 0.45 Wh/m³ volume of transported air.
- The heat losses of hot water, storage and distribution should be reduced to a minimum by continuous thermal insulation.
- To reduce the overal power consumption high-efficiency building technologies (fans, pumps, control devices) and electrical household appliances and lighting should be applied.
Passive House Criteria
The mere compilation of appropriate passive house components is still not enough to transfer a building into a passive house standard. The interactions between the components of an integrated design make it necessary, with which the passive house standard can be achieved only. This is the case when mathematically proved that the passive house limits are met, such as:
Specific Space Heating Demand: < 15 kWh/(m²a)
Pressurization Test Result n50: < 0,6 h-1
Total Specific Primary Energy Demand: < 44 kWh/(m²a) / < 120 kWh/(m²a) incl. industry factor