Our passive house is the first Polish timber frame passive house with a certificate of the Passive House Institute in Darmstadt. The house has a perfect thermal insulation and passed a leakage test. It was thoroughly verified by specialists dealing with designing passive houses.
House has the following parameters:
- House with a surface of 120m2 and cubic capacity of 320m3 constructed near Tarnowskie Góry
- Unfavorable geographical orientation – south-east, significant shading by nearby buildings, substantial deviation from the south
- House with five permanent residents
Applications in the house:
- NEURA EUROPA heat pump with a power of 5kW with a flat exchanger,
- Floor heating on the entire surface,
- Mechanical ventilation with PAUL 300 NOVUS heat recovery,
- Wooden windows, Sokółka GOLDLINE triple glazing,
- Interior average temperature during winter +23*C,
- External walls U=0,09 W/m2k,
- Roof U=0,10 W/m2k.
The diagram below shows CWU heating costs and house heat-up costs in the coldest periods (December, January, February). It is worth mentioning that house heat-up worked only for 3 months. Domestic hot water heating costs were higher than house heating costs..
Annual CO and CWU heating costs in 2011 equaled PLN 1125 gross. These are total costs, whereas CWU heating costs were692PLN, and heat-up costs 433PLN. A recuperator’s operation costs for the entire year were only 80PLN/year.
Conclusions: passive house standard significantly lowers the maintenance costs. Heat-up costs are negligible, while thermal comfort – very high. In a passive house, an average temperature exceeds the temperature in other buildings, even energy-efficient ones. A heating season in a passive house is half as long and lasts only 3 months. It is feasible only in the case of houses constructed by a prefabrication method which assures no thermal bridges and very high air-tightness.
Lack of tightness in buildings causes inter alia the following
Noticeable deterioration of heat-insulating properties of materials used to produce wall barriers and in effect increase of heating costs.Damp of internal room surfaces (walls, floors and ceilings) which leads to mould growth that contributes to deterioration of interior esthetics and affecting health and comfort of tenants. Internal damp of wall barriers which leads to mould growth inside structural materials, which in turn results in considerable deterioration of their endurance and life. Abnormal change of air in rooms with gravity ventilation in relation to parameters specified in project documentation.mDeterioration of efficiency and loss of effective control (regulation) of ventilation processes in air conditioning systems and mechanical ventilation devices, and in particular reduction of recuperation process efficiency in systems with heat recovery.
„Blower Door” test is a measurement, not a calculation
performing the leakage test allows of obtaining data about real parameters of a tested building. Identification of leakage at a relevant construction stage enables the builders to eliminate it, and consequently reduce these effects. Checking the degree of building tightness via “Blower Door” test helps assure that conditions providing the highest efficiency of heating and ventilation systems were created, which leads to highest benefits with lowest operation costs. The test results can be used for further calculations necessary when defining the building energy specification and checking parameters of previously designed ventilation system. In the light of the entire financial expenditure when building a house, the leakage test is only a small part of expenses, while benefits resulting from identification of abnormalities in building and possibility of their elimination are incomparably higher.
„Blower Door” test
checks the quality (precision) of workmanship of external wall barriers in terms of their air permeability (infiltration and exfiltration). The procedure and conditions of performing the test are determined by PN-EN 13829:2002.
When performing „Blower Door” test
by means of the ventilation frequently located in the place of external doors (on aluminum frame covered in canvas), negative pressure (or overpressure) is so big that air enters the interior intensively via all, even invisible, points of air leakage. The purpose of the test is to detect places of uncontrolled air flow in the building and indicate n50 ratio specifying its tightness degree. The leakage test is to be performed during the construction – before finishing works and shortly after works are completed in order to confirm the results. The tested facility is subject to negative pressure test and overpressure test. The entire process is fully automated, while test results are presented in the special protocol jointly with the certificate of tightness (optional). A degree of building tightness is defined via n50 ratio which shows the number of change of air within one hour between internal environment and external surrounding as a result of air leakage with difference of pressures equaling 50 Pa. Such a difference occurs in the face of wind pressure with a velocity of roughly 9m/s, which applies to force 5 winds. In the attachment no. 2 to the applicable up to 1 January 2006 amendment to the Directive of the Minister of Infrastructure dated 12 April 2002 on technical conditions buildings and their locations should satisfy (WT2009) in the section of a title: „Thermal insulating power requirements and other requirements related to saving energy” it was specified that “in dwelling buildings, collective dwelling buildings, and public utility buildings, as well as production buildings, non-transparent external wall barriers, barriers joints and window connections with reveals shall be designed and manufactured in order to achieve their complete tightness in terms of air permeability”. Additionally, it is recommended to perform a test that checks the air tightness of the building and indicate required n50 ratio values which equal: for buildings with gravity ventilation: n50≤ 3,0 [h-1] for building with mechanical ventilation: n50≤ 1,5 [h-1].
In passive buildings thanks to reduction of heat loss, acquisition of heat from environment, as well as accumulating it inside the building, energy-related expenses related to provision of convenient conditions are limited. Such a philosophy of house construction caused the annual balance – after considering all gains and losses – to require addition of max. 15 kWh(m2*year) of external energy. It should be reminded that in the case of traditional construction performed and designed in line with applicable standards, a demand for energy frequently exceeds 120 kWh (m2*year). An inconsiderable demand for energy of passive buildings causes the traditional central heating system (omnipresent in traditional construction industry) to become redundant, apart from few cases. However, it is feasible to heat rooms only with application of ventilation system. A stream of heated air supplied to rooms is able to transport a suitable amount of heat. No expenses related to heating system at the stage of constructing a passive building causes the expenses to pay for themselves. There is additional saving due to the absence of operational costs incurred by operating plumbing system in a traditional building.
A general principle in the case of passive buildings is to resign from installing a central heating system. However, there are certain exceptions. It is impossible to heat rooms such as a toilet, a bathroom only by means of ventilation air. These rooms are ventilated in the last place. At first, air flows through the living room, the bedroom, and then corridors, halls etc, which results in cooling. For this reason, it cannot serve to heat a bathroom, or toilet, especially when these rooms require a higher temperature when compared to others. Occasionally, one applies heaters which compensate for shortages of heat.
In passive housing gravity ventilation was skipped because it generates too much heat loss. To assure the proper operation of ventilation, there must be a difference of temperatures – then used air from the interior has the tendency to float and is supplied via ventilation stacks outside, and it is not possible to recover heat. As we have mentioned before, in the case of passive buildings we aim to maximize the tightness of external wall barriers in order to eliminate the convection between the facility’s interior and environment. It is another reason why gravity ventilation has been rejected. In traditional construction industry air flowing into the building via leaks in external wall barriers “supports” ventilation. As for passive buildings, any sort of leaks would cause uncontrolled change of air, and hence heat losses. To sum up, one can state that ventilation in passive buildings should do as follows:
- Minimize heat loss by recovering max. amount of heat from dead air, pushed outside the building,
- Assure a suitable level of room ventilation in accordance with technical conditions,
- Provide heat distribution in the entire building in the amount assuring thermal comfort of users.
, a directed flow of air through all zones is necessary. To assure users’ comfort, one has to make sure rooms are ventilated in a proper order, which involves residents’ needs, process and activities taken in particular types of rooms.
In a passive building fresh air from a ventilating unit is supplied via channels to the zone where residential rooms are located (bedrooms, living room, office, possibly other rooms) and to the dining room. Next, the air flows to the indirect zone which includes halls, corridors, kitchen. The last zone which includes ventilation pipes is a set of sanitary rooms (bathrooms, showers, toilet) which are always highly humid. A considerable amount of air flowing through these rooms fosters among others an efficient laundry drying or wet towels drying.
In mechanical ventilation system a ventilating unit or a set of ventilating units play a vital role. They are the main element forcing air circulation in the building. In the case of passive housing, various ventilating units are used, more or less advanced, always equipped with a recuperator (heat exchanger) which recovers heat from the dead air. In order to gain heat in passive houses better, a ventilating unit is usually connected to a ground heat exchanger.
Aside from a recuperator (heat exchanger), it consists of ventilators (fans), filters and an electric heater serving to heat up inlet air. The production of this device is easy, while the price – low. However, what is a drawback is a considerable consumption of electric energy by the heater. Application of a ventilating unit of a small heat pump air/air type is a solution. The pump takes the heat from the air removed from the building and transfers it to the stream of air.
Heat pump increases the device costs. Thanks to the pump, however, it is possible to reduce the energy consumption in relation to the electric heater.
Electric heater and heat pump are not the only sources of heat applied in passive buildings. To heat ventilation air, one also uses heat which comes from biomass, gas, fuel oil burning. Additionally, a ventilation system is frequently integrated with a system generating a domestic hot water.
Ventilating unit should be located in the place which optimizes the distribution of the system in the building. One shall remember that it is advisable to place the unit far away from the bedroom or rooms designed for work due to emitted noise. Also, one should provide a good heat-insulation of ventilating pipes so that pipes’ air is not cooled or heated. A selection of materials used to produce ventilating pipes is of importance.
One applies a number of various materials, starting from plastic, through steel elements, ending up with wood-like products. Selecting a material, one should take into account among others noise inside the pipes, air resistance, microorganism growth, or easy assembly. A recuperator serves to minimize heat loss related to building ventilation. In the winter season in Poland, a difference of temperature between the environment and the interior may be even 40 degrees. Taking air from the environment and not recovering heat, one has to increase the energy expenditure on a regular basis, which is necessary to heat the air by 40 degrees. Application of a recuperator reduces this expenditure by recovering heat from the dead air and transferring it to the fresh air. The device transmits streams of fresh and dead air in opposite directions assuring heat exchange between them and assuring streams are not mingled. Heat exchangers applied in passive housing have a capacity of 75% and higher, which means that such an amount of heat is transferred between streams. For this reason, the energy expenditure required in the winter season to heat fresh air to 20*C is incomparably lower than in the case of traditional heating. In the face of low temperatures, it is necessary to heat up the inlet air. In so doing, one applies various sources of heat. A ground heat exchangers is a very simple machine which serves to heat air that supplies ventilation via recovering heat in the ground. Its operation is based on the use of the fact that in winter the ground temperature at the depth of below 1,5m in our weather conditions always remains the same about 3-6*C and is usually a way higher than the temperature of atmospheric air. Before it enters the ventilator, intake vent air goes through a ground heat exchanger where it is heated to the temperature of above 0*C. It allows of free-of-charge use of energy included in the ground. To assure operation of the device, only a ventilator forcing the air flow is needed. The ground heat exchanger can also be of use in the summer period when the ground temperature is slightly lower than the atmospheric air temperature, which allows of supplying the building with cooled air and it is not necessary to equip it with an auxiliary cooling system. The ground heat exchanger is frequently made of a polyethylene pipe or PCV pipe with a diameter of 160-200mm, located 1,5m under ground, with a slope serving to carry away drips emerging as a result of cooling warm air in the summer.
A device is highly efficient, when a pipe is arranged in a straight line, with no curves which may cause additional air resistance. If a location of the building rules out this solution, pipes can be arranged in a different shape, avoiding curves with an angle of 90°. There are also gravel ground heat exchangers. In this sort of solution intake vent air located outside the building is transmitted via gravel deposit. Gravel ground heat exchanger has however many vices: it requires a good protection against rodents and pollution, as well as needing protection in the event of high level of ground water.