BIM for Enhancing the Energy Efficiency and Sustainability of Existing Buildings

Abstract

Most of the buildings of the post-earthquake period in Skopje are built in “beton-brut” architectural style and nowadays, they are treated as an important cultural heritage of the city. Unfortunately, the envelope of those buildings is built without thermal insulation materials and consequently, they are large energy consumers responsible for tons of CO₂ emission per year. They don’t meet today’s criteria for energy efficiency and the circular economy (CE) practices can hardly be implemented. But, if circularity is understood from the aspect of prolonging their use and improving comfort instead of destroying them, as well as reducing the negative effects caused by their use, then it can be said that the principles of CE have been achieved. In order to improve the energy performance and the building sustainability, as well as to prolong the lifespan with minimal impact on the authentic façade appearance, a renovation with a new façade nanomaterial with high thermal properties is proposed. The simulations of the existing building and the renovated scenario using Building Information Modeling (BIM) is conducted and comparative analyses between the actual condition and the improved scenario of the building are carried out. According to the simulation results, by adding the new material on the façade a significant improvement in the building's energy performance is achieved. It can be concluded that BIM has a great potential in assessing the improvement of energy efficiency of buildings and the possible implementation of CE for existing buildings.

1 Introduction

The post-earthquake architecture, also known as architecture of Modernism, is built after the catastrophic earthquake in 1963 and represents an important cultural heritage of Skopje. According to the construction standards of that time, those buildings are built with lack of thermal insulation materials, which results in a poor thermal comfort, high heating, cooling and maintenance costs, degradation and deterioration. These buildings need to be properly renovated according to current energy efficiency standards. On the other hand, the authentic appearance of the architecture that is considered as a cultural heritage should not be compromised in the renovation process. Since the aim of the circular economy (CE) is to eliminate waste and pollution, circulate products and materials and regenerate the nature, the building sector has one of the biggest potentials for CE implementation. Improved design and new construction techniques based on CE will produce highly efficient new buildings, but most of the existing construction sector does not meet CE criteria [1]. Most of these buildings are historical buildings with cultural values and no change in appearance is allowed. The real challenge is to implement the CE strategies in existing buildings, by improving their sustainability, energy efficiency and durability, which will lead to cutting the CO₂ emissions, reduction in energy consumption and financial costs. The adoption of CE principles in the renovation of buildings can reduce the amount of materials used for renovation and thus minimize the emissions embedded in building materials [1]. Building information modeling (BIM) is one of the most promising developments in construction process, which encourages collaborative working between all the disciplines involved in design, construction, maintenance and use of buildings.

This paper deals with the potential renovation activities that could improve the sustainability and energy efficiency of an existing building and reduce the embedded emissions, by using BIM. A simulation of a renovated scenario of a post—earthquake building is made by using EnergyPlus. In order to enhance the energy efficiency and in the same time to keep the authenticity of the building, a sustainable insulation façade material is used in the scenario. The results showed positive impact of the new material in terms of energy savings, emissions, sustainability and durability of the building, which indicates that BIM has great potential to facilitate CE adoption.

2 Case Study Building

2.1 Building Description

The Hydrometeorological Service building in Skopje is built in the post- earthquake period in a specific architectural style, known as “brutalist” architecture, which means that the whole building is constructed in raw exposed natural concrete, known as “beton—brut”, (see Fig. 34.1). The selected case study building has and architectural and cultural value, not only for its brutalist appearance, but also for its unique plan and design. Since the building facade is made only of natural concrete and doesn’t have any exterior finishing layers or insulation, the energy efficiency and thermal comfort are quite poor, which results with large energy consumption for its maintenance and also carbonization and decay of the unprotected concrete. The proper functioning of the building is compromised and her authentic appearance and lifespan is endangered. In order to extend the building lifespan by improving it’s durability, sustainability and energy efficiency, and to ensure it’s better functioning, the building needs to be properly renovated, by implementing the CE principles such as adaptive reuse of the building and by using sustainable materials on the façade which won’t make a significant imapct on the original appearance of the building.

Fig. 34.1

Different views of Hydrometeorological Service building

2.2 In Situ Measurements

In order to determine the real U values of the concrete facade walls of the building, ‘'in situ'’ measurements of the heat flux and the surface temperatures of the facade walls were performed. The measurements were conducted in the period from 6 to 13th of March, 2020. The measurements were performed by TRSYS01 [2] which is a high-accuracy building thermal resistance measuring system with two measurement locations (see Fig. 34.2).

Fig. 34.2

Method of connecting the measuring equipment with the structural element: (1) measurement and control unit; (2) power adapter; (3) computer data reading; (4) two pairs of temperature sensors; (5) two heat flow plates (fluxometers)

The sensors were placed on the both sides of the façade wall (a—inside sensor position; b—outside sensor position), shown in Fig. 34.3. Two of the internal sensors measure the heat flux trough the wall, and the other two sensors measure the surface indoor surface temperature of the wall. The other pair of external sensor measure the outdoor surface temperature of the wall. After the eight days measurement the data were processed by LoggerNet software and U values calculations were made.

Fig. 34.3

TRSYS01—a building thermal resistance measuring system

Figure 34.4 shows the graph of the measured U values of the façade wall and the average value is 1.5 W/m²K. The maximum prescribed U value for external façade walls is is 0.35 W/m²K, which indicates that the building has very poor thermal properties. Figure 34.5 shows the graph of the surface temperatures of the wall, where the big difference between the indoor and outdoor surface temperature can be seen, which leads to the conclusion that a lot of energy is needed for heating the indoor spaces.

Fig. 34.4

Average U values during the measurement period

Fig. 34.5

Average values of surface wall temperatures during the measurement period

2.3 Nano Materials Selection and Properties

Recently, the use of nanomaterials as thermal insulation building materials has been increased. A façade nanomaterial such as silica aerogel based plaster with good thermal insulation properties, which has a minimal impact on the original architectural appearance of the building is used for the analysis. The aerogel plaster has a low thermal conductivity λ, ranging from 0.028–0.014 W/mK, thanks to its porous nano structure [3]. Silica aerogel material has many applications and it can be modified to meet a number of specific purposes required by CE, since they have low embodied energy, lower than traditional insulation products [4]. Aerogel can be mixed to develop a green building material with unique characteristics and have a great potential for an application in green and sustainable buildings [5]. According to the criteria for protection of historical buildings, aerogel plasters have a mild impact on their authenticity, but it is important that they are compatible with the chemical composition of the original materials, and can be easily removed without damaging them and there is no need for additional fastening that would damage the original material [6]. They have great flexibility in applying on uneven surfaces and complex architectural details [7]. The application of the new material will not only improve the energy efficiency and sustainability of the building but also it will protect it from climate conditions and expand its lifespan. Due to the composition and method of application, aerogel plasters perfectly mimic the texture of natural concrete and it’s difficult to distinguish it from the original (see Fig. 34.6), while the original material remains preserved. The thermal properties of the material are shown in Table 34.1.

Fig. 34.6

Façade material—concrete texture

Table 34.1 Facade nanomaterial thermal properties

Two dynamic energy simulations have been conducted: a simulation of the existing condition and of an improved scenario by adding aerogel plaster to the facade walls. Conventional thermal insulation materials such as rock wool and EPS are added to the rest of the envelope (floor slab and roof). The existing windows have been replaced by aluminum framed double glazed low emission glass with U value of 1.06 W/m²K.

3 Energy Modeling and Simulation

3.1 Modeling, Zoning, Geometry and Materials

The detailed building modeling is obtained by using BIM software and the dynamic energy simulation is carried out by using EnergyPlus together with Design Builder software tool. The modeled capacity of the building is 150 employees, organized into several types of offices and departments. Figure 34.7 shows the ground floor position of thermal zones. All four facades of the building are exposed to wind, its entrance part is north oriented, surrounded by vegetation.

Fig. 34.7

Thermal zones—ground floor

The building is divided into a total of 140 thermal zones. Each of the zones is defined with its own design temperature, orientation, number of people, lighting, electrical equipment and appliances, type of heating, cooling, ventilation, glazing area, etc. Figures 34.7 and 34.8 show the ground floor thermal zones divided in the following groups: occupied zones (zones with people, conditioned during working hours); corridors (no people, but conditioned during working hours); unconditioned zones (stairs and toilets); 24 h occupied zones (conditioned zones with permanent stay of people).

Fig. 34.8

Thermal zones—first floor

Table 34.2 shows some of the most important parameters of the building geometry, summarized for all zones (conditioned and unconditioned). The building envelope is mainly composed of reinforced concrete solid walls without external finishing layer, except in certain parts, where a brick masonry wall appears. The facade walls, the roof and floor slabs are not insulated. The façade fenestration is made of aluminum framed single glazed windows with U value 5.7 W/m²K. All of the parameters indicate poor energy performance of the building and bad thermal comfort.

Table 34.2 Building parameters

3.2 Simulation Results

First, a simulation of the existing condition of the building is conducted, and the results are compared with the actual heating and electricity bills. Comparisons between the U values obtained from the software simulation and the results obtained from the “in situ” measurements are also discussed. The bills’ coincidences with the simulated scenario for both electricity and heating energy consumption are over 90% (see Figs. 34.9 and 34.10).

Fig. 34.9

Electricity consumption (bills and simulation)

Fig. 34.10

Heating consumption (bills and simulation)

The simulated U value of the wall is 1.73 W/m²K, which is slightly higher than the measured one of 1.5 W/m²K. From the comparative analysis between the existing condition (“in situ” measurements and bills) and the simulated scenario, can be concluded that the used BIM technology gives very accurate results.

The second simulation results of the improved scenario, showed significant improvements in terms of total heating energy consumption and total electricity energy consumption (electricity for heating, cooling, lighting and appliances), as well as a drastic reduction in CO₂ emissions. The comparative analysis between the heating energy consumption of the existing condition and the improved scenario showed a big reduction in the improved scenario by 68%. The total heating energy consumption in the existing condition is 332 218.5 kWh annually, i.e. an average of 27 684.8 kWh monthly. The total heating energy consumption in the improved scenario is 105 188.4 kWh annually, i.e. an average of 8 765.7 kWh monthly. The graphs of the heating energy consumption for both, baseline and improved scenario are shown in Fig. 34.11.

Fig. 34.11

Heating energy consumption (existing condition and improved scenario)

The comparative analysis between the electricity energy consumption of the existing condition and the improved scenario showed a reduction in the improved scenario by 40%. The total energy consumption for electricity in the existing condition is 193.888 kWh annually, i.e. an average of 16 157 kWh monthly. The total electricity energy consumption in the improved scenario is 116 833.1 kWh annually, i.e. an average of 9 736.1 kWh monthly. The graphs of the electricity energy consumption for both, existing condition and improved scenario are shown in Fig. 34.12.

Fig. 34.12

Electricity energy consumption (existing condition and improved scenario)

The CO₂ emission for the existing condition of the building is 168.269 kg annually, i.e. an average of 14 022 kg monthly, while the CO₂ emission in case of the improved scenario is 84 215 kg annually, i.e. an average of 7 018 kg monthly. The reduction of CO₂ emission in the improved scenario is 50%.

4 Conclusions

The case study building is a significant cultural heritage built only in natural concrete with no protective façade layers or thermal insulation. That leads to a process of decay, lack of thermal comfort, huge energy consumption, pollution and endangered lifespan of the building. In order to improve the building’s function, sustainability, thermal comfort and energy efficiency, an urgent renovation needs to be done. Since the building has an important architectural and cultural value, its authentic appearance should not be compromised by the renovation process. From the investigated nanomaterials, the aerogel plaster has a minimal impact on the authenticity of building façade, and it is a very promising sustainable material and has a great potential for its implementation in the CE practices according to the new state of the art literature [4, 5, 8]. On the other hand BIM technology allows us to see how the building will behave if it is renovated with the proposed material and what will be the benefits (saving energy, reducing emissions, financial costs and even predicting the life cycle of the building). The purpose of the paper is to connect these two things together, to show the potential that BIM has in CE, and in same time тo show the opportunities and improvements that aerogel plaster brings to the existing buildings with cultural values. Based on the “in situ” measurements and on dynamic energy simulations of existing condition and the improved scenario, comparative analysis between the two scenarios were obtained. The analysis showed a significant reduction of the heating energy consumption in the improved scenario by 68% compared to the existing condition of the building. Also, the electricity energy consumption is reduced by 40% and CO₂ emissions by 50%.

Finally, it can be concluded that the application of the aerogel based thermal plaster on the facade walls, not only improves its energy efficiency, comfort and CO₂ emissivity, but also has a minimal impact on the authentic appearance of the building. BIM technology has proven to be an excellent method for predicting the benefits of the renovated scenario of existing building, giving accurate results and it has a great potential in enabling the design team to simulate renovations and the related cost. BIM provides support to decision-making for component selection; assess the sustainability and even the circularity of the asset during the design process.