Construction and material solution for the building
Based on the geological exploration of nearby buildings, the bottom structure is not located on a landslide or undermined area, on quicksand or plastic clay. The character of the subsoil and other factors influencing the stability and uneven settling of foundations do not change in the ground plan. There is soil with carrying capacity of more than 100 kPa under a fill from crushed stones. The bottom structure consists of a floating monolith 200 mm reinforced concrete slab. It is laid on the 800 mm compacted sub-base of crushed stones. A 200 mm XPS polystyrene thermal insulation compacted to E2,def = 40 MPa is placed directly under the slab. The stone layer is drained and the drainage runs into the local horizontal sewerage. The hydro-insulation, designed with respect to ground dampness, is located on the top side of the reinforced concrete slab. An investigation showed only a very low radon presence.
Designed products, materials and main construction features:
Concrete construction C25/30 – XC1 – S2
Reinforcement B 500 A (10 505 (R)) and KARI nets
200 ml underlay extruded polystyrene: Styrodur C, type 3035 CS
Permitted permanent compressive tension under foundation slab σ = 130 kPa
Flexibility modulus E= 20 Mpa
The fill under the foundations: G2 – G3 crushed stones, coarse-grained gravel, fraction 16 – 32, compacted in layers to E2,def = 40 Mpa (verified through checks in the location) in the whole layer of the fill. The relative compactness of the active zone up to 0,8 m under the polystyrene (of the fill) was min. Id = 0,85. The compacting process of the fills was performed in individual layers of 200 mm.
A modern timber-construction technology was used for the top construction of the building, which means that wall, partition and ceiling panels based on timber were used for the assembly. The composition of the peripheral structures is performed through a diffusion with a vapour barrier. The external facade consists of a combination of the most common insulation systems. It contains a contact insulation system, a ventilated facade with wooden panelling and ventilated facade with facade panels. The surface weight of load-bearing panels does not exceed 100 kg/m2.
When designing the disposition, a modular coordination and unification of construction parts are used. A 600 mm wide construction models is used as the basic dimension. Consequently, the ground-plan and height proportions of the house are derived from these regulations. Clamps, screws and nails are used to connect the parts. The used construction and insulation material is made from natural products with respect to ecology and environment.
The load-bearing construction of the peripheral walls consists of a frame structure from l-beams (60×300 mm, 90×300 mm), its external surface is covered with a 15 mm gypsum fibre-board and the internal surface with a 15 mm vapour barrier board. This panelling transfers the horizontal and diagonal load from the ceiling structure onto the bearing slab. Cavities of the frame structure are filled with wood-fibre insulation. From the inside, the wall consists of a pre-wall (60×60 mm timber frame profile panelling with a 15 mm gypsum fibre-board) and filled with wood-fibre thermal insulation. The external layer consists of wood-fibre panels with a thin layer of plaster. The total width of the peripheral wall is 552 mm.
Internal load-bearing walls are made from a 120 mm thick timber frame construction and double-sided panelling from 15 mm thick gypsum fibre-boards. The frame is filled with mineral-felt insulation. The total width of the wall is either 90 mm or 150 mm. Internal partition walls (not load-bearing) are made from a timber frame construction (60 mm and 120 mm thick), doublesided panelling from 15 mm thick gypsum fibre-boards. The frame is filled with mineral-felt insulation.
Ceilings above the ground-floor
The load-bearing parts of the ceilings between the ground-floor and the attic consist of 60×240 mm wooden ceiling beams, on which 22 mm hardboard decking is laid. A 120 mm acoustic mineral–felt insulation is placed between the beams. The ceiling made from 2×12,5 mm drywall panels is attached to timber battens (30×60 mm). The floor construction consists of sound insulation, anhydrite coat and floor cover. The total width of the ceiling is 467 mm.
The staircase is three-flight, wooden, without substeps with two stair stringers on the sides into which the steps are housed.
Window panes and doors
The windows with timber frames have a glued profile with glazing designated for low-energy houses.
The coefficient of heat transfer is Uw = 0,71 W/m2.K
The entrance door is made of wood.
The coefficient of heat transfer is Uw = 1,0 W/m2.K
- PROPOSED MATERIALS WITH R ESPECT TO ENVIRONMENT, HEALTH AND SAFETY
- • Reinforced concrete slab – less concrete is necessary to make the slab compared to foundation strips
- Supporting elements – engineering spruce timber
- Panelling – gypsum fibre-board panels and dry-wall panels
- Insulation – wood-fibre panels, for technical reasons polystyrene was used only under the bottom structure
- Panes – made of wood
- Facade – wood-fibre panels, wooden panelling from the north, cement-fibre facade panels from the west
If regular maintenance is sustained, the life-span of the top structure is set at over 100 years.
Energy concept and parameters of the building
Energy concept of the building
With respect to the basic requirements, the shape and construction concept is solved in line with the principles and regulations defined for passive houses in ČSN 75 0540-2 (2002). The below listed text describes parameters which were taken into account during the process of designing the building and its constructi.
- The overall concept of the building:
- the shape of the building (compactness and segmentation of the building) – the surface area to volume ratio has low values
- maximum restrictions of thermal bridge causes and distinct thermal connections between constructions
- the layout of internal premises and thermal zones with respect to the orientation towards the four cardinal directions
- chosen locations of glassed areas in the facade and their appropriate size for passive solar gains and limited overheating of the interior
- a suitable concept of connections between the technical equipment systems of the building
- effective regulation to reduce the energy consumption necessary for heating and cooling
- recuperation of extracted warm and cold air where cooling with night-time air or ground register with a maximum reduction of mechanical cooling is used
- for buildings with higher glassed surfaces the internal premises are secured against overheating
- use of shading (vertical sidebars and sun screens)
Heating and cooling:
- The roof construction U≤0,10W/m2.K
- The peripheral wall U≤0,10W/m2.K
- The floor adjacent to the soil U≤0,12W/m2.K
- Windows Uw Uw≤0,8W/m2.K
- The entrance door Uw Uw≤1,2W/m2.K
- The solar radiation permeability through window panes and doors: Windows g≥0,5
- Average coefficient of thermal transmittance Uem≤0,21W/m2.K
Thermal characteristics of peripheral constructions:The coefficient of heat penetration of all peripheral constructions on the border of heated premises:
- The external wall adjoining another external structure, e.g. foundations, ceiling above unheated space, another external roof, roof, loggia, balcony, bay window, etc. ψk≤0,2W/m.K
- The external wall adjoining a window or a door ψk≤0,03W/m.K
- The roof adjoining a window or a door ψk≤0,10W/m.K
Linear factors of heat penetration:
Quality of external environment and heat loss through air recuperation:
- Heat recovery
- Recovery efficiency of heat from extracted air η≥85%
- • Non-permeability of the building envelope in the stage prior to internal completio n50≤0,6 h-1
- • Non-permeability of the building envelope after the completion n50≤0,6 h-1
Joint air permeability
- The highest air temperature in the summer Φi≤27oC
Range of temperature contentment in the interim period and in the summer period
- Specific consumption for heating EA≤15kWh/m2.a
Heat requirement for heating
- • Requirement of primary energy from non-renewable sources for heating, heating service water and the technical system of the building PEA≤60kWh/m2.
Potřeba primární energie
BASIC TECHNICAL AND ENERGY PARAMETERS OF THE BUILDING
The building complies with energy parameters for passive houses under ČSN 730540-2(2002). After including solar gains and temperature released by occupants present in the building, we can predict only a small difference between the energy used and needed for heating. It is possible to achieve parameters of a zero-energy building by adding photovoltaic panels in future, for which the centre is prepared.
- Calculation parameters:
- Specific energy consumption of the building EPa: 35 kWh/m2.a
- Specific heat consumption for heating the building Ea: 10 kWh/m2.a
- Average coefficient of heat penetration of the building envelope Uem: 0,13 W/m2.K
- Heat loss Φi: do 2kW
- Coefficient of heat penetration through roof structure: U≤0,09W/m2.K
- Coefficient of heat penetration through peripheral wall: U≤0,10W/m2.K
- Coefficient of heat penetration through the floor adjacent to the soil: U≤0,12W/m2.K
- Coefficient of heat penetration through the window: Uw≤0,71W/m2.K
- Coefficient of heat penetration through the entrance door: Uw≤1,0W/m2.K
- Permeability of solar radiation through window panes and doors: g≤0,5
- Recovery efficiency of heat from extracted air: η≥85%
- Non- permeability of the building envelope after the completion: n50=0,52 h-1
- The highest air temperature in the summer θi≤27oC
Other actual parameters:
Technical equipment of the building
The heating system includes a superior regulation of the designed heat sources with the possibility to utilise them for research and educational purposes. The system enables to measure all necessary quantities, flows, powers and thermal energy. BMS outputs are connected to a PC with a graphic display of the given scheme, the selected source and the heating system. It is necessary to ensure the cooling of the heating water to provide the removal of the thermal energy during lessons and during necessary measurements, since this is an energy-efficient house. This is especially the case when the building is heated by a source with a higher power, which is not typically used in energy-efficient houses (gas boiler, pellet stove). An electric boiler was selected as a primary heating source for the building. Mechanical ventilation can be used in two ways – the air heating and the controlled ventilation. Both with the waste heat recovery (bathroom, sanitary facilities) and with the possibility to monitor the importance of the underground supply register. Distribution pipes for the heating and the ventilation are visible in the engine room. Further, it is possible to connect one‘s own source through the chimney in the premises of the engine room. It is possible to illustrate and demonstrate the internal equipment of the heating sources for study purposes. The effectiveness and the impact of the sources on the environment inside the heated building can be compared.
DESCRIPTION OF THE SYSTEMS
The overall description of the system and the following detailed solution are connected to the design scheme of the overall proposed technology. The basis of the unit is a thermal energy accumulator with the capacity of 800 litres with an integrated cooler of heating water during the times of an excessive heat output. The thermal energy is supplied from installed heat sources with the temperature specified by the used device. The output of the accumulator is taken at the lowest point at temperature of about 35˚C. Return water temperature can be adjusted with a mixer between 35 and 65˚C.
The removal of loss heat is provided with a tubular heat exchanger fitted in the bottom third of the accumulator. Antifreeze liquid (e.g. 30% ethylene glycol) allows an all year-round operation of an outdoor cooler with capacity of about 12 kW with a frequency-controlled fan so that the temperature of the mixture does not fall below 0˚C during its operation. The heat sources (electric boiler, gas condensing boiler, biomass boiler and heat pump) are connected to a shared manifold. It is expected that only one heat source will be run during lessons and in the operation mode. For this reason, controlling system of the incoming water temperature and the heat measurement is shared by all heat sources. The solar system uses (to simplify the diagram) a connection to the antifreeze mixtures system. The cooling fan is off during measurements. In case of excessive production of solar panels (which occurs in the summer and outside of the opening hours of the centre), an all year-round surplus heat removal is provided by a fan; therefore neither the solar system nor the accumulation tank will overheat.
A heat pump is used a cooling source for the air conditioning system. Heat is removed from the primary system of the heat pump. The antifreeze of a required temperature is brought into the cooler of the air conditioning unit. If we reduce the air flow to 3/6˚C, it is possible to reduced the air temperature to 12˚C in the summer and subsequently it is possible to warm it up again. In this way, it is possible to illustrate dehumidification of the air to the relative humidity level of about 60% under any outdoor conditions as well.
- Education set of heat sources:
- direct-heating electric boiler with the power of 6 kW
- electrical coil with the power of 2 kW
- gas condensing boiler with an adjustable power in the range of 2 to 10 kW
- automatic pellet boiler with the output of up to 12 kW
- heat pump ground/ water the power of 6 kW
- solar system with vacuum tubes with the area of approx. 4 m2
- panel radiators rated at the thermal gradient of 50/43°C
- floor heating rated at the thermal gradient of 40/35°C
- ventilation heating rated at the thermal gradient of 50/43°C
- ventilation cooling rated at the thermal gradient of 6/12°C
- hot water heating (HW) rated at the thermal gradient of 55/48°C
The heating systems of the building:
The heating systems collect the necessary thermal energy from the upper layers of the heat accumulator. Return water is sent back into the accumulator above the level of the inserted cooling pad. Each circuit is equipped with a circulation pump with an electronically controlled differential pressure and with a mixer so that a desired heating water temperature could be set. Calculation parameters of the heating systems are designed with respect to the heat pump operation as well. So that the premises could be heated outside of the lessons, it is expected that the accumulated heat energy from the educational operation mode of the heat sources or solar energy will be used. We do not presume a continuous operation of the defined heat source (although it is possible) with respect to the proposed passive house.
DETAILED DESCRIPTION OF PARTICULAR HEAT SOURCES
800 litre heat accumulator
800 litters atypical heat accumulator provides a perfect quantitative and pressure separation of the heat sources circuit from the heating circuits. The upper part of the accumulator, with the capacity of approx. 500 l which allows accumulation of approx. 6 kW at the difference of temperatures of 10 °C, is used for such accumulation which is sufficient to accumulate an hourly output of the installed heat sources. The inlet pipe is connected at the upper part. The outlet pipe leading to the heat sources is brought out from the bottom part of the accumulator. An electric immersion heater with the power of 4 kW equipped with its own operating thermostat set at 50°C and a safety thermostat set at 80°C is installed in the accumulator. This immersion heater will be used to maintain moderate heating of the building during a long-term shutdown period in the winter (holidays between semesters).
To achieve the outlet temperature of about 35°C, a tubular heat exchanger (cooler) leading into a dry outdoor cooler is installed into the system of heat sources circuits in the lower third of the accumulator. This circuit is, with respect to the part located outside the building, filled with antifreeze with a freezing point below -25°C. This exchanger also uses heat energy from solar connectors. The heat accumulator has pools for installation of thermometers and controlling temperature sensors. Four pieces of sensors to control water temperature and the amount of accumulated thermal energy are fitted. Another two sensors are fitted at the inlet and outlet piping of resources circuits.
Cooler and antifreeze circuit
This circuit cools down the heating water in the lower part of the accumulator and it is filled with antifreeze mixture of 30% ethylene glycol (concentration at -25°C) with respect to the all year-round operation. If it is necessary to cool the heating water (the signal from the temperature sensors), the antifreeze circulating pump is switched on and a fan with frequency speed control maintains the temperature of the outlet return water at approximately 35° C. A dry cooler with the computational power of about 12 kW during the outside air temperature of 25°C is installed behind the building on
two concrete strips. The required water temperature at the lower part of the accumulator is maintained by the fan with frequency speed control.
- Antifreeze circuit is also used for other technological equipment:
- removal of the heat from the primary circuit of the heat pump
- transfer of the heat from the vacuum solar collectors into the accumulator or into the cooler (during the surplus of thermal energy)
- cooling of air condition from the primary circuit of the heat pump
Connections of heat sources
The heat sources are connected to a shared pipeline provided that only one source is always running. A mixer sets the temperature of the return water entering the heat sources. This control allows to stabilise the temperature on a desired level according to the source which is currently run. This temperature can be altered during the operation. Therefore, it is possible to monitor the coefficient of performance (further as COP) of the heat pump; for the condensing boiler it is possible to monitor the efficiency with the condensation (input of about 40°C) and without the condensation (input of about 55°C). Individual sources are connected to this pipeline through isolating ball valves and backflow valves (this prevents the re-circulation when the system is shut down).
Measurements of produced and consumed energy
A flow-meter for an ultrasonic heat meter is fitted in the circuit of the return pipes of the sources on both lines, followed by paired temperature sensors. A thermal energy meter allows to read all values necessary to establish the efficiency of an operating heat source in a particular moment. The supply of electricity into the heat sources will be fitted with a shared three-phase electricity meter allowing to read the consumed electricity of the operated heat source (a part of wiring and BMS).
An electric boiler with the electricity input of 6kW equipped with all facilities for autonomous operation (circulation pump, expansion vessel, operating and safety elements) is designed. The operation of the electric boiler is controlled by the superior control system and according to the educational/training needs.
A wall mounted condensing gas boiler with the modulated output of the burner of about 2 – 10 kW equipped with all facilities for the autonomous operation (circulation pump, expansion vessel, operating and safety elements) is proposed. Both the flue and the combustion air supply is provided by a three-layer steel chimney through the peripheral wall into the outer space (the flue is performed above the roof). The gas boiler operation is controlled by the superior control system and according to the educational/training needs. The natural gas consumption is subtracted from readings of the gas meter (this is the only natural gas appliance).
Boiler for the combustion of biomass – pellets
A small automatic pellet stove with a burner for wooden pellets combustion with the adjustable heat output of up to 12 kW is placed in the building. It is necessary to weigh the burned quantity to monitor the precise fuel consumption. Therefore, when we monitor the efficiency, we can identify the fuel consumption, the electricity consumption for fans and then we can read the heat production on the heat meter.
A small ground/water type heat pump with the heat output of about 6 kW and with the electrical input power of about 2 kW equipped with all facilities for an autonomous operation (both primary and secondary circulation pumps, operating and safety elements) is connected. The connection of the secondary side (output into the system) is performed in DN20 dimension. The heating water mixer can adjust the temperature of the inlet water between 35 and 50°C. The heat is extracted into the cooling circuit filled with antifreeze (30% ethylene glycol). The thermal energy is drawn from the
accumulator cooling system and from the outdoor air. The water temperature entering on the primary side of the heat pump is adjustable according to the needs across the whole operating range of the heat pump between -5 and +15°C. Based on scanned energies – the consumed electric energy and the produced thermal energy, it is possible to monitor the impact of temperature changes in both the primary and secondary side on the multiplicity COP factor in relatively short intervals. The operation of the heat pump is controlled from the superior control system and according to the educational/ training needs. The heat pump can produce cold air for the mechanical ventilation in the summer as well. The inlet air cooler is connected to the circuit of the primary heat pump with the primary water temperature setting to approx. +3 / +6 °C. This low temperature allows also drying the inlet air to the condensation temperature of about +12°C and subsequent heating to the desired temperature of about 20°C in the summer months. The thermal energy will be extracted into the accumulator where it will be partially used to reheat the air after dehumidification. The excess will be extracted by the cooler into the air outside.
Since it is necessary to illustrate the functioning of solar panels during training and education, the solar panels are installed on the ground next to the building. The slope of the vacuumed tube collectors is about 70°- 80°. This gradient reduces the thermal performance in summers and, on the contrary, it increases the thermal performance in winters. The heat transfer will be provided via antifreeze to allow all year-round operation. To simplify the whole system, the thermal energy is transferred from the solar panels into the radiator circuit, next through an inserted tube heat exchanger and then into the heat accumulator. The installed system measures the produced thermal energy. An adequately dimensioned cooler is used for cooling when there is excessive thermal energy in the summer. Its operation (including the circulation pump) is automatically switched on when the temperature in the accumulator reaches 70°C during the times outside the lessons/ training period.
DESCRIPTION OF THE HEATING SYSTEMS
The most commonly used heating systems, i.e. mechanical ventilation and hot air heating, are installed for the purposes of training and education and also for the purpose of heat removal. The thermal energy for these systems is drawn from the training heating operations of those facilities. It is extracted from the top output of the accumulator. The return water is filled to one third of the height so that it would not cool down when the system is shut down. All systems are equipped with their own circulation pumps and a separate temperature control through mixing.
Panel radiators (tube radiators in the bathroom) designed for the thermal gradient of 50/43°C (and with respect to the heat pump parameters) are installed on the second floor. Distribution pipes combine copper and plastic. The radiators will be fitted with thermostatic heads. The operations of the circulating pump and of the circuit mixer are controlled by the central control system.
Floor heating systems
The floor heating is planned for the 2nd floor only. The heating system is designed for the temperature gradient of 40/35°C. The floor construction complies with the selected floor heating system. The heating will be controlled according to the internal temperature. It will be distributed in four areas: sanitary facilities, the utility room, the classroom and the hall.
Hot water heating
The hot water heating is provided in a combined accumulation tank with the volume of 200 l with a hot water insertion rated for the heat gradient of 55/48°C. The heating water for the heating is removed from the heat accumulator which allows heating with thermal energy from all available thermal sources. The hot water distribution with a circulation loop is installed for illustration. As another option, the hot water is heated by a flow in the inserted pipe in the upper third of the accumulator. The thermal energy from all sources can be used but without an option of temperature control (the temperature in the accumulator may reach up to 80°C). For this reason, the outlet pipe is fitted with an automatic mixer with its own thermal drive set at 50°C. Both sources will be connected in parallel. The maintenance staff will decide on the method of heating.
HYDRAULIC CONFIGURATION OF THE HEATING SYSTEMS
The hydraulic system enables to connect the simplified heating sets with various regulatory fittings and to observe their behaviour. A practical example of how to balance heating sets and how to identify characteristics of the controlling and safety fittings on the measuring stool is available. It is possible to demonstrate the connection of the boiler circuit, the cascade of two boilers, the connection in the splitter/combiner, THR or a bypass in the engine room.
The proposed system of thermal sources and the systems for cooling and heating are essential and they are based on such requirements of teaching and training that a practical demonstration of individual heating systems and functioning of thermal sources is necessary. The system can be further expanded and altered depending on teaching and research purposes. The connection uses some aspects that can not be applied in normal heating systems (return water cooling, thwarting the output of the heat pump, extraction of the heat into the accumulator, etc.) However, this connection
allows to use the surplus for heating and hot water heating. Further, this system allows to set the return water temperature for the thermal sources according to the requirements and the temperatures of the primary circuit of the heat pump regardless of external conditions.
Also, the solar system is connected in an unconventional way, but, this is done with respect to the essential requirement to secure the functioning and to demonstrate the system. The solar collectors transmit the thermal energy to the cooling circuit antifreeze. All of the energy is transmitted into the lower part of the accumulator when the cooler shuts down. The whole system assumes a perfect control by the superior panel, or directly through a PC. This can be done either through a suitable cooperation with a university department with an appropriate focus, alternatively, commonly used regulatory sub-panels (Johnson Controls, AMIT, Siemens, etc.) with a communication link to a PC can be used for the system.
Only that part of the device which is currently in operation and is showing all measured and desired values can be displayed in visualization. This visualization can be viewed on a larger display or projector. It will be possible to change the required parameters from a PC. Calculations can be performed automatically for efficiency of the boilers and for the COP of the heat pump. It will be possible to observe changes in the parameters during changes of temperatures of the heating medium, and for the heat pump also to observe temperature changes in the primary circuit – all this in real time. The requirements for the control of the whole system are described in the part Electrical fittings.
- GENERAL INFORMATION
- KNX – INTELLIGENT OPERATION OF A BUILDING
- MEASUREMENTS AND CONTROLLING
- EMERGENCY LIGTING