Contribution to Active Thermal Protection Research—Part 2 Verification by Experimental Measurement

Abstract

This article is closely related to the oldest article titled Contribution to Active Thermal Protection Research—Part 1 Analysis of Energy Functions by Parametric Study. It is a continuation of research that focuses on verifying the energy potential and functions of so-called active thermal protection (ATP). As mentioned in the first part, the amount of thermal energy consumed for heating buildings is one of the main parameters that determine their future design, especially the technical equipment. The issue of reducing the consumption of this energy is implemented in various ways, such as passive thermal protection, i.e., by increasing the thermal insulation parameters of the individual materials of the building envelope or by optimizing the operation of the technical equipment of the buildings. On the other hand, there are also methods of active thermal protection that aim to reduce heat leakage through nontransparent parts of the building envelope. This methodology is based on the validation of the results of a parametric study of the dynamic thermal resistance (DTR) and the heat fluxes to the interior and exterior from the ATP for the investigated envelope of the experimental house EB2020 made of aerated concrete blocks, presented in the article “Contribution to the research on active thermal protection—Part 1, Analysis of energy functions by the parametric study”, by long-term experimental measurements. The novelty of the research lies in the involvement of variant-peak heat/cooling sources in combination with RES and in creating a new, original way of operating energy systems with the possibility of changing and combining the operating modes of the ATP. We have verified the operation of the experimental house in the energy functions of thermal barrier, heating/cooling with RES, and without RES and ATP. The energy saving when using RES and ATP is approximately 37%. Based on the synthesis and induction of analogous forms of the results of previous research into recommendations for the development of building envelopes with energy-active elements, we present further possible outcomes in the field of ATP, as well as already realized and upcoming prototypes of thermal insulation panels.

1. Introduction

We live in an era marked by the unnecessary waste of primary energy sources. Since the essence of the application, operation, and expected cost-effectiveness of an active thermal protection system lies in the use of secondary (renewable) energy sources; active thermal protection might, at first sight, appear to be a suitable tool to reduce the energy consumption of buildings and at the same time significantly help to meet the stringent thermal protection criteria for buildings set by the standard.

This method is characterized by using renewable energy sources through wall energy systems (active thermal protection of envelope structures). The verification of the results of the parametric study of the energy potential and energy functions of active thermal protection (ATP) of building envelopes with low thermal conductivity layers towards the interior from ATP by long-term experimental measurements on the family house EB2020 immediately follows the article “Contribution to Active Thermal Protection Research—Part 1, Analysis of Energy Functions by Parametric Study”.

We are conducting research based on the reuse of already generally known technologies characterized by their advanced solutions. In this paper, we verify the energy functions and energy potential of the envelope of the experimental EB2020 house made of aerated concrete blocks using long-term experimental measurements. The novelty of our research lies in the incorporation of variant-peak heat sources with RES-based heat/cooling sources (such as solar-energy roof (ESR), ground heat/cooling storage (GHS)) and in the creation of an entirely new, original way of operation of heat/cooling sources and energy systems with the possibility of changing and combining the operating modes of active thermal protection (ATP) (thermal barrier (T.B.), heating, cooling, etc.). Our contribution to ESR and GHS research has already been presented in several papers but most extensively in the papers listed in the literature, such as [1,2].

To clarify our contribution to the research on active thermal protection using long-term measurements on the EB2020 experimental house, it is essential due to the close link to ESR and GHS; it is necessary to reiterate some information regarding the building design, the energy systems design, the methodology in terms of measurement points, instruments, equipment, time, data recording method, and the implementation of the experimental measurements. However, they have already been published in the publications mentioned above. Furthermore, partial information on the application and experimental measurements of ATP has also been published previously in the context of ESR operation and the impact on GHS discharge. Therefore, in this paper, we describe the results of experimental measurements of ATP in the energy functions of T.B. and heating/cooling and analyze and validate the results of a parametric study with measured values.

Our scientific research aims to determine the efficiency and energy efficiency of the combined building–energy systems through detailed calculations and long-term experimental measurements. In this paper, we rigorously analyze the energy potential and functions of active thermal protection for residential buildings using an experimental measurement. A more detailed description of the subobjectives and research methodology, i.e., a description of the planning, organization, and implementation of the research, is presented in Section 2. The most important output of our research is the presentation of the realized experimental family house, type EB2020, which we designed, managed its construction, and carried out experimental measurements. An integral part of the obtained results is a detailed description of the actual experimental measurements of ATP and the subsequent evaluation of the measured parameters of the monitored physical variables in Section 3. In the discussion, specifically in Section 4, based on a detailed analysis of the measured results of the experimental measurements, we evaluate and validate under which specific conditions it is worthwhile to effectively use active thermal protection that performs the function of a thermal barrier, wall heating/cooling. Finally, in Section 5, the conclusion, we summarize the most important results of our research in this area. We also reflect on and define the goals of our further research planned soon. Furthermore, we provide information on the development of thermal insulation panels with integrated energy-active elements and prototypes that have already been implemented, and we also describe new panel prototypes that are in preparation and will be experimentally verified in a test cell.

2. Objectives of the Research and Methodology

The main objective of the research described in the present paper is to analyze the energy potential and energy functions of active thermal protection of buildings employing an experimental measurement.

2.1. Objectives of the Research

The objectives of our research can be summarized in the following points:

• illustrate the wiring diagram of the energy systems and heat/cooling sources of the EB2020 experimental house;
• describe the implementation of the experimental house EB2020;
• present the experimental measurements carried out;
• validate the results of the experimental measurements;
• define the optimal way of operating the ATP in different energy functions;
• synthesize the knowledge obtained by scientifically solving the set objectives;
• transform the necessary data for ATP design;
• induce analogous forms of design solutions and define recommendations for ATP application;
• transform the knowledge obtained by research to develop science and technology in building structures with integrated energy-active elements.

2.2. Methodology of Experimental Measurement

Long-term experimental measurements were carried out on the experimental house EB2020, which we designed, projected, and managed its construction, Figure 1. The original idea we were inspired by was the ISOMAX system [3]. However, the novelty of our research lies in the incorporation of variant-peak heat sources with RES-based heat/cooling sources (e.g., solar-energy roof (ESR) and ground-source heat/cooling (GSHP)) and in the creation of an entirely new, original way of operating heat/cooling sources and energy systems with the possibility of changing and combining the operating modes of active thermal protection (ATP) (thermal barrier (T.B.), heating, cooling, etc.), which was not possible with the ISOMAX system.

In December 2011, the energy system was operated using active thermal protection and underfloor heating, with a low-temperature gas boiler and a hot-water fireplace insert temporarily used as heat sources. Different inlet temperatures to the ATO and underfloor heating were set to find the optimum use of the energy system and evaluate the parameters of the individual operations. The energy system with active thermal protection was measured in the function of large-wall cooling and thermal barrier and underfloor heating for two heating periods. The active thermal protection in the function of large-area wall cooling was measured for one summer period (July to October 2012). The energy roof was commissioned in July 2012. The measurement of the energy roof and the charging of the ground heat storage in the charging cycle was carried out for one summer period [4,5].

2.2.1. Description of the Operation of Heat Sources and Energy Systems on the Experimental Family House EB2020

Figure 2 shows a schematic diagram of the energy systems and heat/cooling sources in the EB2020 experimental house. The different energy functions of the combined building–energy system have been marked in colors. For example, heat sources are marked in red, heat accumulation in orange, underfloor heating in purple, thermal barrier in green, ground cooling circuits in blue, and forced ventilation with heat recovery in purple and grey.

The heat source in the experimental family house is an energy roof, hot-water fireplace inserts, and a low-temperature gas boiler. The hot-water fireplace insert has an output of 16 kW, and the low-temperature gas boiler Buderus Logamax UO52-24 has an output of 24 kW. The energy (solar) roof is made of PE-RT plastic pipes placed under the roof covering circuits: 3 × 100 m, ø 16 mm. The plastic pipe is located on the southwest side of the roof (area 109 m², slope 35°, above the dormers 15°) and on the northeast side (area 55 m², slope 30°). The plastic pipes are fixed with plastic joints to the roof battens on which the red roofing material is laid. As a result, the plastic pipe absorbs, and the roof becomes a solar collector.

Legend:

1	BUDERUS low-temperature gas boiler—U052-24—8.9–24 kW, the boiler includes a three-way switching valve and a pump;
2	Fireplace insert EDILKAMIN—ACQUATONDO 22–25.6 kW—with cooling loop;
3	Combined storage tank—REHAU -SOLECT 750/180—575 L of storage water, 180 L of hot water;
4	Pressure expansion vessel REFLEX-N 250/6 with a volume of 250 L, initial system pressure 1 bar, final system pressure 2.25 bar;
5	Pressure expansion vessel REFLEX-EN R 35/3 with a volume of 35 L, initial system pressure 0.8 bar, final system pressure 1.35 bar;
6	Combined distributor and collector—D.N. 32;
7	Air separator, absorption, threaded—FLAMCO—FLAMCOVENT—D.N. 25;
8	Dehumidifier threaded—FLAMCO—CLEAN—D.N. 25;
9	Filling and draining fitting;
10	Plate heat exchanger—26 kW—ALFALAVAL CB77-70H;
11	Device for automatic refilling of water into a closed system—HONEYWELL NK295S(including ball valves, filter, check valve, pressure reducing valve, and pressure gauge;
12	Pressure expansion vessel REFLEX-S 12/10 with a volume of 12 L, initial system pressure 0.4 bar, final system pressure 1.5 bar;
13	Electric resistance coil.

Figure 3 shows a photograph of the roof at the time of roofing installation. The solar roof is connected through a plate heat exchanger. A mixture of water and glycol-based antifreeze circulates in the primary circuit.

In addition to the combined storage tank Rehau Solect 750/180 (V = 575 L for heating and V = 181 L for hot water), the heat is accumulated in a ground storage tank formed by a P.E. plastic pipe laid in the base plate in five circuits, each with a length of 100 m and a pipe diameter of Ø20 mm. The circuits are connected via a combined distributor collector. Figure 4 shows a photograph at the time of construction of the foundation slab. The 200 mm thick foundation slab and the soil beneath the foundation slab thus become the heat reservoir. The additional heat source in the combined storage vessel is an electric heating insert (6 kW).

The active thermal protection in the building consists of PE-RT plastic piping between the aerated concrete masonry (375 mm) and the facade polystyrene (100 mm) in the mortar bed and in the roof construction in the following circuits: 20 × 100 m, Ø16 mm. The plastic piping is installed using plastic moldings. With the ATP, it is possible to reduce heat loss through opaque structures and heat or cool the building in summer. The ATP is shown in Figure 5. The source of cooling is the cooling circuits, which are located at a non-freezing depth in the soil around the building’s foundation strips. They consist of 3 × 200 m plastic pipe circuits, Ø32 mm.

Heat transfer in the building is also possible through underfloor heating on both floors. Installed circuits: 6 × 100 m, 3 × 200 m, Ø16 mm. An air handling unit with heat recovery is also installed.

From the schematic of the energy system shown in Figure 2, it is clear that the heat obtained from the solar energy (energy roof) is stored in a ground storage tank, while under suitable conditions, it can also be stored in a combined storage tank. A heat exchanger is installed between the primary side (in which the glycol-based antifreeze is circulated) and the secondary side. Heat can also be supplied to the ground heat storage by the fireplace insert, the heat source for the combined storage tank. Another heat source for the storage vessel is a low-temperature gas boiler. An electric-heating insert (6 kW) is also installed in the storage tank. The low-temperature radiant floor heating is supplied from the storage tank. The ATP can be fed from a combined storage tank or ground heat storage.

2.2.2. Breakdown of the Measurement Methodology

The experimental measurements aimed to determine the input values for evaluating the energy roof, ground-source heat storage, and active thermal protection. The methodology of the experimental measurements is divided by criteria [3,4]:

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methodology in terms of measured quantities and measurement points;

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methodology in terms of the measuring instruments used;

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methodology in terms of measurement time.

We have described the description and evaluation of the experimental measurements of the energy roof in paper [1] and of the ground storage tank in paper [2].

2.2.2.1. Measurement Methodology in Terms of Measured Quantities and Measurement Points

Mostly direct-measurement methods were used based on the definition of the measured physical quantities. The location of the fixed metering points is shown in the power-system diagram in Figure 2. The following values were measured [4,5]:

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the temperature of supply and return heat-transfer medium (°C)—in circuits of individual heat sources, heat reservoirs in ATP circuits, and in low-temperature underfloor heating circuits return pipe temperature (°C);

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the flow rate of heat carrier (m³/h)—in circuits of individual heat sources, heat reservoirs in ATP circuits, and low-temperature underfloor heating circuits;

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heat consumption (G.J.)—at the outlet of the individual heat sources (solar roof, low-temperature gas boiler, and hot-water fireplace insert), at the outlet of the ground storage tank, the combined heat storage tank, and at the inlet of the individual consumer circuits (ATP, low-temperature underfloor heating, and heat recovery unit) (Note: ATP is marked as “wall barrier” in the diagram);

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cooling consumption (G.J.)—at the outlet of the cold ground store and at the inlet of the ATP circuits in the large-wall barrier cooling function in summer;

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power (kW)—ATP circuits and underfloor heating;

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outside air temperature (°C)—on the north side of the building;

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indoor air temperature (°C)—on the first and second floors;

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overflow volume (m³);

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the temperature at the exit of the energy roof in front of the plate heat exchanger (°C);

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surface temperatures of building structures (°C).

Measurements shall be recorded at one-hour intervals.

Figure 6 shows the combined splitter/collector for ATP1, ATP2, underfloor heating, circulators, and actuators for the Belimo LR24A-SR three-way control valves. For the ATP1 and ATP2 circuits, two Grundfos Alpha2 15-60 130 circulators with variable speed control are installed, with an electrical input of 5 to 45 W. For the underfloor heating, a Wilo Star RS 25/6 circulator installed with three-stage speed switching and an electrical input of 43 to 84 W. Engelmann Sensostar2 compact heat meters are installed on the individual branches. The same compact heat meter and actuator for the control valve are fitted on all branches of the energy system.

Figure 7 shows the Wilo Star RS 25/6 circulation pump connecting a hot water fireplace insert and the actuator for the three-way control valve. An Engelmann Sensostar2 compact heat meter with a three-way control valve is mounted above the actuator. Figure 8 shows the combined distributor/collector of the ground heat storage with the actuator for the three-way control valve and the compact heat meter. The heat delivered to the storage tank from the solar roof and the fireplace insert, and the heat from the ground storage tank removed to the ATO and the combined water storage tank are measured. Figure 9 shows the circulation pump for the solar roof on the secondary side (behind the plate heat exchanger), the actuator for the three-way control valve, and the compact heat meter. The heat from the roof can be delivered to a ground-source heat-storage tank or a combined water storage tank.

Figure 10 shows a combined water storage vessel for heating and hot water. A Wilo Star-Z Nova (ROW) circulator for circulating hot water with an electrical input of 4.5 W is visible. Figure 11 shows a Rehau EHK electric heating insert (6 kW) in a combined water storage vessel. Figure 12 shows the Buderus Logamax UO52-24 low-temperature hanging gas boiler. Figure 13 shows the gas meter for measuring gas consumption by the boiler—Elster BK-G2,5M.

The power system’s control, regulation, and monitoring are implemented via an internet connection, Figure 14. This allows the operation of the power system to be controlled and input parameters to be changed at any time. For example, using the internet connection, it is possible to switch on or off the operation of ATP1, ATP2, or floor heating, to set the desired input temperature or to start the system’s operation with equithermal control by setting the desired internal temperature. The measured data is also stored on the server and can be checked anytime. The program can display the heat in G.J. delivered to ATP1, ATP2, and underfloor heating, Figure 15, in any period (the last 24 h, week, month, year, or a specific time period can be entered). The power and flow rate of ATP1, ATP2, and underfloor heating can also be displayed.

The program lets you view the data sensed at individual measuring points—gas boiler, solar roof, ground storage tank (inlet and outlet), fireplace insert, hot-water consumer circuits, ATP1, ATP2, underfloor heating, and cooling circuit. The delivered heat or cold, the total amount of working substance overflow, and the flow rate and temperature of the working substance in the supply and return pipes are displayed in Figure 16.

The solar roof circulators are commissioned under favorable conditions (suitable temperature difference in the solar roof and the heat storage tanks). If the temperature in the combined heat storage tank is lower than the inlet temperature at the outlet of the solar roof, heat is stored in this vessel. Once the integrated heat storage tank is charged, the heat is then transferred to the ground heat storage. This also applies if the inlet temperature at the outlet of the solar roof is lower than the temperature in the combined storage tank. When the fireplace is used, the fireplace insert’s circulation pump is started, and heat is stored in the combined storage tank; once the desired temperature has been reached, the heat flow is redirected to the ground heat storage. The peak heat source is a low-temperature gas boiler. The ATP and hot-water floor-heating circuits are supplied with heat from the ground heat storage and, in the event of insufficient heating water-supply temperature, from the combined heat store. In summer, the ATP can be used in large-wall cooling, setting the desired supply temperature. The cold is supplied to the circuits from a ground cold storage tank. Hot water preparation is two stage. In the first stage, the cold water is preheated in the ground heat-storage tank and then reheated to the desired temperature in the combined heat-storage tank with the integrated hot-water storage tank.

2.2.2.2. Measurement Methodology in Terms of Measured Quantities and Measurement Points

Different measuring instruments were used in the experimental measurements. The Engelmann Sensostar2 compact heat meters are fixed in the experimental family house at the energy roof (measured behind the plate heat exchanger), fireplace insert, gas boiler, ground-source heat storage, active thermal protection, and underfloor heating. In addition, two compact heat meters are fitted at the ground storage tank to measure the values during the charging and discharging cycles (heat supply to the energy system from the heat storage tank). The temperature in the supply and return pipes (°C), power (kW), flow (m³/h), flowed volume (m³), and heat (G.J.) can be measured using the measuring device. The compact meter is shown in Figure 17. Figure 18 shows the metering and recording control panel for data acquisition with automatic data transfer to software accessible via the internet. Basic characteristics of the compact meter:

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ambient temperature: 5 to 55 °C;

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temperature range: 1 to 150 °C;

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temperature resolution: 0.01 °C;

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minimum temperature difference: 0.2 K;

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measurement frequency: min. 1 s, [3,4].

The Testo 845 infrared thermometer was used for noncontact measurement of building structures’ surface temperatures (°C). It is shown in Figure 19. Basic characteristics of the infrared thermometer:

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measuring range: −30 to 950 °C;

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measurement accuracy: ±0.75 °C, (at 20 to 99.99 °C);

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temperature resolution: 0.1 °C;

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emission factor adjustable from 0.1 to 1.

The MobIR M4 infrared camera has been used to detect heat leaks, temperature distribution on building structures, and to detect ATP pipe lay. It is shown in Figure 20. Basic characteristics of the infrared camera:

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temperature range: −20 to 250 °C;

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measurement accuracy: ±2 °C or ±2% of the measured range;

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temperature resolution: 0.1 °C;

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emission factor adjustable from 0.1 to 1;

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video sensor: CMOS, 640 × 480 pixels, 24-bit color depth;

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spectral range 8–14 μm.

2.2.2.3. Measurement Methodology in Terms of Measured Quantities and Measurement Points

Experimental measurements have been running continuously since December 2011, when the energy system with automatic data collection was put into operation. In two heating seasons, the system was measured when using ATP in the function of wall heating and thermal barrier, and in one summer season, the system was measured when using the energy roof, charging the ground heat storage, and using ATP in the function of wall cooling. In terms of the time interval of data collection, the following values were recorded in hourly averages:

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supply-pipe temperature (°C),

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return-duct temperature (°C),

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power (kW),

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flow rate (m³/h),

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overflow volume (m³),

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heat (G.J.),

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outside-air temperature (°C),

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indoor-air temperature at 1st floor (°C),

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second-floor indoor air temperature (°C),

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the temperature at the exit of the energy roof in front of the plate heat exchanger (°C) was recorded at 5 min intervals.

Surface temperatures of the building structures and infrared-camera temperature distribution measurements were carried out manually under suitable conditions [4,5].

3. Results

Based on the synthesis and analysis of scientific and practical knowledge obtained from published works of researchers and experts in the field, and transforming these data, we designed and managed the construction of the experimental family house EB2020 for the investigation of combined building-energy systems, in particular ESR, GHS, and ATP. We performed long-term experimental measurements, recorded measured quantities, and evaluated different heat/cooling source operations, heat accumulation, heat/cool transfer by different end elements of energy systems, and ATP in different energy functions. In this section, we present the results obtained so far from the long-term experimental measurements of ATP.

3.1. Project and Implementation of the Experimental Family House EB2020

A significant output of our research is the experimental house EB2020, which we designed and projected, managed its construction, and carried out experimental measurements on it. In the design and projection of the experimental family house EB2020, we based on the idea of the method and operation of the combined building–energy system ISOMAX. The novelty and results of our solution consist in the integration of variant-peak heat sources with RES-based heat/cooling sources (solar-energy roof, ground-source heat/cooling storage) and in the creation of a new, original way of operating of heat/cooling sources and energy systems with the possibility of changing and combining the operating modes of active thermal protection, which the ISOMAX system did not allow.

The implementation of the experimental house EB2020 was described in detail in papers [1,2], which focused on the description and evaluation of the experimental measurements of the energy roof and the ground heat storage. This section presents basic photo documentation of the construction and implementation of heat sources and energy systems.

Figure 21 and Figure 22 documents the implementation of ground heat storage. The application of the piping of the cooling circuits is shown in Figure 23. The rough construction is made of aerated concrete blocks, Figure 24. Figure 25 shows an example of the implemented ATP on the perimeter walls of the ordinary experimental house EB2020. The implementation of the energy roof is captured in Figure 26. The peak heat sources are a low-temperature gas boiler, Figure 27, a hot-water fireplace insert, Figure 28, and an electric heating insert in a combined storage tank for heating water and domestic hot water (DHW), Figure 29. Figure 30 is the heat-recovery air-handling unit. The control, regulation, and metering of the heat sources and power systems are described in Section 2.2.2.1.

3.2. Results of Experimental Measurements of Energy Functions ATP

The operation of the house was controlled and monitored via an internet connection. In the experimental family house, the heat delivered from the solar (energy) roof, from the fireplace and gas boiler to the combined storage tank, from the gas boiler to the DHW storage tank, the total heat delivered to the ground heat storage and from the ground heat storage to the ATP was measured. The total heat delivered to the ATP is measured. The heat delivered to the underfloor heating and the cold delivered from the cooling circuits to the ATP were also measured. The system recorded temperatures and flow rates at the inlets and outlets of the heat sources, the combined heat-storage vessel, and at the inlets and outlets of the floor heating and active thermal protection. The temperatures on the first floor, second floor, and outside were recorded. Through an internet connection, changing the inlet temperatures to the individual systems or setting the desired indoor temperature was possible.

Experimental measurements were carried out, and the operation of the energy systems at different input temperatures of the heat transfer medium to the ATP and the floor heating were compared, as well as the variant without ATP operation. With the experimental measurements, we wanted to verify the possibility of using the ATP in the functions of thermal barrier and wall heating and cooling [4,5].

3.2.1. ATP Measurements as a Thermal Barrier

In December 2011, the energy system was operated using ATP and underfloor heating, with a gas boiler and a fireplace insert as temporary heat sources. Different inlet temperatures to the ATP (wall barrier) and underfloor heating were set to find the optimal use of the energy system. Figure 31, Figure 32 and Figure 33 show the values from the measurement period from 20 January to 30 January 2012 (240 h). The inlet temperature to the wall barrier was set at 20 °C (return temperature was around 17 °C). The floor-heating temperature was set at 26 °C (return temperature was around 25 °C). The system operated with this temperature setting for the whole month of January. Figure 31 shows the heat consumption in (G.J.) by the wall barrier on the first and second floors and the hot-water floor heating. The heat consumption for the period from 20 January to 30 January 2012: wall barrier on the 1st floor = 0.733 GJ, wall barrier on the second floor = 0.719 GJ and underfloor heating = 0.909 GJ. The indoor and outdoor temperature histories for the first and second floors are shown in Figure 32 and Figure 33, respectively. All variables are measured at one-hour intervals.

The low inlet temperatures to the ATP (20 °C) and floor heating (26 °C) resulted in a relatively high internal temperature. Therefore, the floor heating was shut down on 25 January 2012. At that time, the temperature on the first floor was 24.1 °C and on the second floor 23.2 °C. The underfloor heating was restarted at the request of the residents on 28 January 2012 at 00:00. At that time, the temperature on the first floor was 21.9 °C, and on the second floor 20.9 °C. The drop in the indoor temperature (2.2 K on the first floor and 2.3 K on the second floor) is not large, given that the outdoor temperature dropped significantly at that time (around 6 °C).

Note: The period when the underfloor heating was out of operation (57 h in total) is delimited by vertical lines in Figure 31, Figure 32 and Figure 33 [4,5].

3.2.2. ATP Measurements in the Wall Heating Function

The underfloor heating was shut down again on 1 February 2012. During this period, the operation of ATP in the function of wall heating was tested. It is important to mention that the house was unoccupied at that time, meaning there were no internal heat sources. The average outside temperature was around—11 °C. The indoor temperature at the beginning of the measurement period (1 February 2012) was around 18 °C. The target was to reach 25 °C. The medium temperature to the ATP was gradually increased to an extreme of 45 °C (13 February 2012), reaching a temperature of 26 °C at NP1 and 25 °C at NP2. Figure 34 shows the program outputs from that measurement period (supply and return temperature to the wall barrier from 27 January 2012 to 27 February 2012), in which the energy system could be monitored and controlled at any time via an online connection.

Figure 35 shows the heat-consumption pattern through the wall barrier on the first and second floors, Figure 36 shows the indoor temperature on the first and second floors, and Figure 37 shows the outdoor temperature. Figure 35, Figure 36 and Figure 37 delineate the period when 25 °C was reached indoors from the original 18 °C. By measuring during this period, it was shown that the ATO could heat the building without simultaneously operating an additional heating system [4,5].

3.2.3. ATP Measurements in the Wall Cooling Function

During the summer period, the ATP was in operation in the cooling wall function. The source of cooling is the external cooling circuits, which are made up of plastic piping placed at an unfrozen depth around the foundations of the building. The cold is extracted from the surrounding soil. Thus, only the electricity supplied to drive the active thermal-protection circulators is needed to operate the cooling system. The inlet temperature to the ATP was set at 20 °C, while the return temperature ranged between 20 °C and 23 °C. The cooling was running continuously, with no set attenuation. The cooling was in operation for 79 days, and throughout the operation, the cooling was removed from the surrounding soil. Two periods were selected for analysis—the last two weeks of July—18 July to 31 July 2012, and the last two weeks of August—18 August to 31 August 2012. Figure 38 and Figure 39 show values from the last two weeks of July. Figure 38 shows the indoor air temperatures on the first and second floors and the outdoor air temperatures. Figure 39 shows the waveform of the working fluid temperatures in the ATP supply and return lines on the primary and secondary axis, the waveform of the ATP power in kW. The average power during this period was 0.424 kW. The average temperature in the supply pipe to the ATP was 19.8 °C, and the return pipe temperature was 20.8 °C.

Figure 40 and Figure 41 show values from the last two weeks of August. The average power output during this period was 0.530 kW, the average temperature in the supply pipe to the ATO was 20.5 °C, and the average temperature in the return pipe was 22.0 °C.

Based on the analysis of the measured indoor and outdoor temperatures, it can be concluded that at outdoor temperatures of more than 35 °C, the indoor temperature did not exceed 28 °C [4,5].

4. Discussion

Based on the analysis of the parametric study results and long-term experimental measurements, we validate under which conditions it is effective to use active thermal protection in the function of thermal barrier and wall heating/cooling.

Through the experimental measurements, it is possible to compare the operation of ATP with a conventional heating system, test the system at different input temperatures for active thermal protection, as well as to test the simultaneous operation of active thermal protection and underfloor heating. Experimental measurements have demonstrated the functionality of ATP in four functions, namely as a thermal barrier, wall heating, wall cooling, and heat storage. An evaluation of the energy performance of the measured building and a comparison with the theoretical values that the building should achieve with the given structures without ATP is shown in the recapitulation

Table 1. Recapitulation of measured and theoretical values of the energy performance of the measured building.

Evaluation of the Energy Performance of the Experimental House
Design heat input according to EN 12831 (for −11 °C, interior +20 °C)	5.44	kW
Measured performance at −15 °C, interior +22.5 °C	6.5	kW
Theoretical energy demand for heating according to STN 38 3350 (for Bratislava area and indoor temperature +20 °C)	41.5	GJ/a
Measured actual heating energy consumption per year (average indoor temperature +22.5 °C)	28.86	GJ/a
Theoretical energy demand for hot water preparation STN 38 3350	18.20	GJ/a
Measured actual energy consumption for hot water preparation per year	9.60	GJ/a
Specific thermal energy demand for heating—theoretical—Decree No 35/2020 of the Collection of Laws	61.37 (B)	kWh/(m2·year)
Specific thermal energy demand for heating - actually measured—Decree No 35/2020 of the Collection of Laws	41.50 (A)	kWh/(m2·a)
Specific thermal energy demand for the preparation of hot water—theoretical—Decree No 35/2020 of the Collection of Laws	27.21 (C)	kWh/(m2·a)
Specific thermal energy demand for the preparation of hot water—actually measured—Decree No 35/2020 of the Collection of Laws	14.35 (B)	kWh/(m2·a)
% Savings of actual measured values of energy consumption for heating compared to theoretical values	30.46	%
% Savings of actual measured values of hot water energy consumption compared to theoretical values	47.25	%

.

By applying ATP, the envelope becomes a heat/cool storage reservoir, allowing the low-temperature gradients in the heating/cooling system to be used to ensure thermal comfort. During the period when the ATP inlet temperature of the medium was set at 20 °C and the underfloor heating was shut down, the indoor temperature dropped by 2.2 K during 57 h on the first floor and the second floor by 2.3 K. The drop in indoor temperature over this time period is not as noticeable as the drop in outdoor temperature (approximately 6 K). In the next measurement period, it was shown that the building could be heated with ATP. During the February freezing temperatures (down to −15 °C), an extreme of 25 °C was reached in an unoccupied family house with an ATO inlet temperature of 45 °C with the floor heating shut down, moreover at a time when the building was unoccupied (no indoor heat sources). In the summer period, the ATP was used in the cooling wall function, where comfortable indoor air temperatures of 28 °C were achieved in the building with outdoor extremely high temperatures above 35 °C, using only the energy/cooling supplied from the ground cooling circuit—pipes buried in the unfrozen depth of the ground.

The high potential of energy savings in heating compared to buildings without ATP of up to 30% can be explained by the accumulation of heat/cool in the building structures—by creating a large-capacity heat/cool reservoir from nontransparent envelope structures, which allows the shutdown of the heat source for a particular experimental house for about three days and by taking advantage of the low-temperature gradient of the heating agent up to +30 °C at extreme outdoor temperatures of about −15 °C.

Surface temperatures on the interior and exterior perimeter walls at the same elevation level showed the same values—it was impossible to determine the tubes’ location with the surface-temperature meter. The thermal images also show a homogeneous surface temperature distribution (heat leakage around the infill structures is evident). Figure 42 shows the thermal images taken at a given time from the exterior.

The high potential for energy savings of up to 47% in DHW production can be explained by applying a solar (energy) roof and preheating the cold water (+10 °C) in the ground heat storage up to +22.5 °C.

Currently, in accordance with Act No. 555/2006 Coll. on the Energy Performance of Buildings and Act No. 300/2012 Coll. and the implementing Decree No. 364/2012 Coll. supplemented by Decree No. 35/2020 Coll., the classification of the experimental house in the area of heating to the energy class E.P. = 41.50 kWh/(m²·a) A (≤43), and in the area of hot water preparation to the energy class E.P. = 14.35 kWh/(m²·a) B (13–24), on the borderline of the energy class A. According to the normative assessment, a specific house without ATP and using a solar roof and ground storage would be classified in the heating area in the energy class E.P. = 61.37 kWh/(m²·a) B (44–86), and in the hot water preparation area in the energy class E.P. = 27.21 kWh/(m²·a) C (25–36).

In terms of primary energy for the application without ATP, the use of solar and geothermal energy, the experimental house EB2020 would be classified in energy class A1 and the CO₂ emissions would be 14.20 kg/(m²·a). With the application of ATP and the use of solar and geothermal energy, the experimental house EB2020 would be classified in energy class A0 and the CO₂ emissions would be 14.20 kg/(m²·a), which means a reduction of 37%. A summary of the energy assessment of the two alternatives is given in

Table 2. Energy assessment of both alternatives for operating the experimental family house EB2020.

			Energy Carrier
			Natural Gas	Wood	Electricity
Experimental house EB2020 without application of ATP and use of solar and geothermic energy
Specific energy demand for heating (kWh/(m2·a))	61.37	B	40.81	17.49	3.07
Specific energy demand for DHW (kWh/(m2·a))	27.21	C	18.09	7.75	1.36
Delivered specific energy demand (kWh/(m2·a))	88.58	B	58.91	25.25	4.43
Primary energy (kWh/(m2·a))	77.06	A1	64.80	2.52	9.74
CO2 emissions (kg/(m2·a))	14.20	-	12.96	0.50	0.74
Experimental house EB2020 with application of ATP and use of solar and geothermic energy
Specific energy demand for heating (kWh/(m2·a))	41.50	A	27.60	11.83	2.08
Specific energy demand for DHW (kWh/(m2·a))	14.35	B	9.54	4.09	0.72
Delivered specific energy demand (kWh/(m2·a))	55.85	B	37.14	15.92	2.79
Primary energy (kWh/(m2·a))	48.59	A0	40.85	1.59	6.14
CO2 emissions (kg/(m2·a))	8.96	-	8.17	0.32	0.47

.

The CO₂ emissions, as well as primary energy, were determined based on the calculation methodology established by the legislation of the Slovak Republic, Decree No. 364/2012 Coll., which implements Act No. 555/2005 Coll. on the Energy Performance of Buildings and on Amendments and Additions to Certain Acts, as amended, effective from 10 March 2020. The calculation is based on the total delivered specific energy for the building (kWh/(m²·a)) for a family house; this is the specific energy required for heating and DHW preparation. The total specific energy demand is then multiplied by the CO₂ emission factor (kg/kWh) or the primary energy factor according to the share of energy carriers used for heating and domestic hot water preparation.

5. Conclusions

Research in the combined building–energy systems brings many inspirations, innovations, and also completely new sustainable technical solutions, pointing out the high potential for energy savings, increasing economic efficiency, and environmental friendliness. In this section, we present information on the development of thermal insulation panels with integrated energy-active elements and prototypes that have already been realized, and we also describe new prototypes of panels that are being prepared and will be experimentally verified in a test cell.

Based on personal experience from the implementation of ATP on the experimental family house EB2020 in Tomášov, prototypes of thermal insulation panels with integrated tubes in the heat exchange layer were developed, Figure 43 and Figure 44. The main objective is to eliminate the technologically lengthy and time-consuming method of ATP implementation used so far. According to this technology, the ATP pipes are first fixed to the load-bearing part of the envelope by means of fixing anchors or rails. Subsequently, a covering plaster is applied to the pipes in two or three layers, depending on the pipe dimension. Technological pauses must be observed between the application of the individual layers in order to allow the plaster to mature. Once the cover plaster has matured and reached the prescribed strength, the building is insulated only by bonding the thermal insulation boards.

The proposed thermal-insulation panels with integrated ATP pipes eliminate the shortcomings mentioned above and the implementation is the same as for the classical insulation system. The advantages are mainly in the speed of implementation, the possibility of anchoring the thermal insulation panels also with dowels, and the fact that the end elements of the energy systems (thermal barrier, heating, cooling, or a register for capturing solar energy, ambient energy, and other combinations) are also implemented with the insulation. The procedure for implementing the insulation with thermal insulation panels with integrated ATP pipes can be seen in Figure 45, Figure 46 and Figure 47.

A thermal insulation panel with integrated capillary mats suitable for implementing low-temperature radiant heating and high-temperature radiant cooling has also been developed, Figure 48.

We are currently developing a prototype of a multifunctional thermal-insulation envelope (thermal-insulation panel) with integrated energy-active elements and energy functions: ATP, solar and ambient energy harvesting register, and photovoltaic surface, Figure 49. The research will be conducted using computer simulation and experimental measurements on a test cell, Figure 50.

Research on combined building–energy systems is related to several technical fields in which the results from various scientific and professional publications need to be correlated. Therefore, we list some relevant publications on which we base our research [6,7,8,9,10,11,12,13,14,15,16,17,18,19].

Finally, the pipe, which forms the ATP, is subject to all the prescribed tests during implementation, such as the radiant low-temperature floor, wall and ceiling heating, high-temperature cooling, or TABS systems. It is also assumed that after successful prescribed testing of the system with ATP, there will be no failures during the lifetime of the pipelines. Should the pipe still fail, the repair is less complicated than for pipes embedded in floor layers or plastered walls and ceilings because the pipe is located behind the load-bearing part of the building envelope, in front of the thermal insulation from the exterior. In this case, the identified faulty circuit shall be shut down, and the necessary repair shall be carried out from the exterior of the building. When using thermal-insulation panels with integrated energetic-active elements as a contact or other method of insulating a building, the repair is even easier as only the panel with the defect is repaired/replaced.

6. Patents

Based on our research in the field of combined building-energy systems and experimental measurements, the results have been processed into one European patent [20] and three utility models [21,22,23].