The Development of Energy-Efficient and Sustainable Buildings: A Case Study in Vietnam

Abstract

This paper reports on collaborative activities to promote energy- and resource-efficient construction practices in Vietnam. First, the governance framework was introduced, including government decrees and technical standards. Then, a laboratory with building physics measurement technology was designed and partly set up at the local partner, the Vietnam Institute for Building Materials (VIBM). This can be used to determine the essential characteristic values required for the implementation of energy standards. The requirements of the national technical regulation on energy-efficient buildings of Vietnam—QCVN09:2017/BXD—form the basis for the prioritization of characteristic values. Furthermore, the description of basic characteristic values from international standards can also be used for calculations to optimize the energy consumption of buildings. To carry out transient hygrothermal computer simulations, special characteristic values are also included. These are particularly useful for the research and development of new building materials and the evaluation of entire buildings in terms of thermal and moisture protection. In this way, the practical means for implementing governance instruments are provided, and the associated technical applications are supported. Based on the example of Vietnam, this paper indicates how a developing country can develop a road map for improving its systems for testing, rating, and labeling building materials for energy performance towards sustainable development.

1. Introduction

The building sector accounts for 35% of global energy consumption [1]. According to the International Energy Agency (IEA), the building sector is one of the most cost-effective sectors for reducing global energy consumption and CO₂ emissions [2]. Many countries have issued building energy policies to reduce energy consumption and CO₂ emissions in the building sector [2,3,4]. Building codes and regulations have been developed and implemented for both new and existing buildings. In addition, considerable attention has focused on the development of energy-efficient buildings, green buildings, net-zero-energy buildings, energy performance certifications, labeling programs, etc. [5,6].

Building materials account for a large proportion of energy consumption in building construction. Therefore, the amount of energy consumed by materials is essential for developing and evaluating energy-efficient buildings, green buildings, green urban areas, and green construction technologies [7,8,9]. Clearly, building materials play an important role in determining the energy footprint of a building. To save energy, it is very important to choose suitable building materials right from the design stage. Many developed countries are focusing on building testing, rating, and labeling programs for building materials. Korea, for example, has now adopted a national testing system [10]. In the United States, different building materials may go through different testing, certification, and labeling processes by independent associations; for example, the U.S. Environmental Protection Agency will issue an Energy Star label for windows with National Fenestration Rating council (NFRC) labels [11]. In Europe, many labeling and certification programs for energy-saving building materials have been issued [12]. This has been significantly effective in reducing energy consumption in buildings, leading to the large increase in the number of energy-efficient buildings. In contrast, most developing countries have their own building energy policies, although the testing, rating, and labeling systems to assess the energy performance of building materials are still limited.

According to the Ministry of Construction, the growth rate of the construction industry in Vietnam increased by approximately 3.65% in the first six months of 2022 compared with the same period in 2021 [13]. The national urbanization rate was approximately 41%, and the average housing area reached approximately 25.2 m² of floorspace per person [13].

It has therefore become necessary to find solutions, apply new materials, recycle materials, and utilize sustainable and eco-friendly building materials to minimize the negative impacts of the construction industry on the environment and on people’s lives.

As a result of Vietnam’s rapid economic development, residents’ lifestyles and needs are changing, and new building types are being introduced, using materials, structures, and supply systems not previously common in Vietnam. The materials are being exposed to new indoor conditions, while the outdoor climate is extremely warm and humid.

Efforts to save energy and conserve resources are urgently needed as national and global policymakers identify resource shortages, secure energy, pollution, and climate change as pressing issues. The construction sector, with its material flows (e.g., cement demand in Vietnam increased by 66% between 2015 and 2020 [14]) and rising energy demands (e.g., a tripling of electricity demand by 2030 compared with 2015 levels [15]), significantly contributes to these problems in Vietnam, and indeed, in most countries around the world.

In this regard, the use of materials such as unburned bricks for walls is currently being introduced in the Vietnamese construction industry in order to reduce energy and pollution through the production and consumption of arable land for the production of clay. Masonry blocks made of alternative materials, such as aerated concrete blocks and concrete blocks, are being advertised as substitutes. However, such new materials require adapted technologies and processing and integration into the building system in order to become a permanent and sustainable substitute for the technologies already established in the marketplace. In particular, moisture protection is of great importance in this context [16].

The failure of such new applications, for example, cracks in plaster or moisture ingress, will discredit such sustainable construction practice and is therefore detrimental to sustainable development. However, at present, there is insufficient knowledge of the physical building properties or capabilities of the Vietnamese construction industry. In fact, there is an urgent need for major studies into the development of infrastructure for the study of new materials, their physical behavior, and their technical application in order to prevent new, more resource-efficient technologies from being discredited in the market through any malfunctioning, thereby resulting in premature failure. Although new building energy codes have been introduced, the calculation tools, checklists, and other means of support for architects and engineers are still missing. Around 1200 materials can be used in energy-efficient buildings, according to the building material consumption survey conducted in 2020 by the Vietnam Institute for Building Materials. However, the values of essential properties for energy saving and other physical building assessments are still missing and are not available in Vietnam.

In this study, the need for the strategic development of technical infrastructure to promote sustainable construction practice was identified as a key objective. The key elements include reviewing the building energy efficiency policies in Vietnam and developing a comprehensive laboratory concept for the installation of instruments, procedures, and test standards for the characterization and research of energy-efficient building materials and construction products. One focus of the empirical research was to investigate the legal regulatory framework for energy-efficient, resource-efficient, and sustainable construction. The essential material tests necessary for the effective implementation of basic energy standards were identified and prioritized. Based on this, it became clear which test equipment was needed to implement energy standards. Through a strategic implementation plan for research and testing facilities, the relevant material properties (e.g., thermal conductivity and moisture absorption) for use in the Vietnamese construction industry have been determined.

2. Methodology

The methodology is described in this section. Figure 1 presents the study procedure.

(i)

An overview

A literature review was performed in this part.

(ii)

Location of the study

The study was conducted) in Hanoi, Vietnam. In the exiting VIBM rooms, the measuring and testing equipment was set up to determine the basic materials’ properties required for the application of Vietnamese energy efficiency regulations and to determine which are relevant for performance-oriented design (e.g., simulation studies).

(iii)

Selection of criteria and material specifications

The criteria and material specifications in planning practice were determined through analysis of planning data and a survey among the relevant stakeholders. The selected criteria were those required in energy regulations in Vietnam with regard to thermal and moisture protection and durability, taking into account the desired room climate. These material parameters were then adopted as the basis for the laboratory concept to be developed.

(iv)

Selection of measuring equipment and applied standards

All the necessary test equipment and test methods were precisely identified using measurement ranges, measurement accuracies, and test boundary conditions.

(v)

Build an energy-saving laboratory

The findings from the construction of two building physics laboratories in Vietnam were scaled up to simulate the possible physical infrastructure for further testing and research, and the approach for implementing such a facility was developed.

(vi)

Training to improve testing capacity for staff

The Vietnamese researchers and laboratory staffs were trained in Germany and laboratory personnel from Germany visited the locations in Vietnam to exchange experience and further education. A comparative investigation between the German and the Vietnamese laboratories was performed to validate the new measuring equipment.

3. Current Development and Policy

3.1. Current Policies Related to Energy-Saving Building Materials in Vietnam

All countries around the world, including Vietnam, are responsible for implementing energy-saving measures and greenhouse gas emission reductions in response to climate change. To reduce energy consumption in the building sector, the Vietnamese government has introduced various policies related to economical and energy requirements:

• The Law on the Economic and Efficient Use of Energy No.50/2010/QH12 requires methodologies for the economical and efficient use of energy in construction activities [17].
• Decision No.1266/QD-TTg was issued in August 2020 concerning the Strategy for the Development of Building Materials in Vietnam for 2021–2030, with objectives to work towards by 2050. It emphasized the importance of the efficient use of natural resources, saving energy and raw materials, and minimizing the environmental impact of the mining process for the production of building materials and products [18]. This aligns with the global response to climate change in terms of targeting building materials to reduce greenhouse gas emissions and conserve natural resources.
• In the national technical regulation on energy efficiency in buildings in Vietnam-QCVN09:2017/BXD, the requirements are for (a) the thermal resistance, R₀, of the opaque part, i.e., exterior walls above ground level (opaque parts of the walls) of the air-conditioned spaces should maintain a minimum overall thermal resistance value, R₀, not smaller than 0.56 m²K/W, and flat roofs and roofs with a gradient of less than 15 degrees placed directly above the air-conditioned spaces should maintain a minimum overall thermal resistance value, R_0min, not smaller than 1.00 m²K/W; (b) for construction and installation products applied in wall structures and building roofs, the thermal conductivity coefficient, λ, of materials should be announced; and (c) in the requirements for the transparent parts (glazing), maximum SHGC values should comply with the values specified in

  Table 1. WWR-related SHGC for glazing in Vietnam from the national technical regulations on energy efficiency in buildings (QCVN09:2017/BXD).

  WWR (%)	SHGC
  	North	South	Other Orientations
  20	0.90	0.90	0.80
  30	0.64	0.70	0.58
  40	0.50	0.56	0.46
  50	0.40	0.45	0.38
  60	0.33	0.49	0.32
  70	0.27	0.33	0.27
  80	0.23	0.28	0.23
  90	0.20	0.25	0.20
  100	0.17	0.22	0.17

  NOTES: WWR calculated for each of the facades, then averaged for the entire building; If WWR did not match with the values in the table, SHGC values were determined through linear interpolation using the nearest higher and lower WWR values.

  [19].
• Decision No.280/QĐ-TTg was issued in March 2019 by the Prime Minister, approving the National Program on Economic and efficient use of energy in the period of 2019–2030 that clearly defines the targets up to 2025, such as (a) achieving energy-savings levels from 5.0% to 7.0% of the total national energy consumption from 2019 to 2025; (b) achieving 80 construction projects (150 construction projects up to 2030) that are certified as green constructions, using economic and efficient energy; (c) building one data warehouse information center for energy and at least two national training centers for using economical and efficient energy, one energy-efficient urban model, five demonstration models on investment loans for projects relevant to economical and efficient energy use, and two energy-efficiency-testing laboratories. Up to 2030, energy labels will be implemented for at least 50% of all types of building material products with insulation requirements [20].
• Circular 01/2018/TT-BXD relevant to the required criteria for the development of urban green construction was issued in January 2018 [21].
• National standard TCVN 9258:2012 on heat protection for houses—design guidelines and Standard TCVN 4605–1998 for cladding structures—design standards for the thermal insulation of cover structures for buildings and constructions with microclimate conditions were issued [22,23].

3.2. Current Situation of the Utilization of Energy-Saving Materials in Vietnam

In 2019, Vietnam had over 1600 production facilities of unburned building materials, with a total design capacity of about 10.2 billion standard pellets/year (nearly 30% of the total design capacity of the building materials production line) [24]. Popular unburned building materials include concrete bricks, autoclaved aerated concrete bricks, autoclaved aerated concrete slabs, and precast hollow concrete wall panels. Actual production/consumption output reached 4.83 billion standard unburned bricks [24].

Many construction products and materials with resource-efficient, environmentally friendly, and energy-saving features are currently available on the Vietnamese market. The state encourages and supports numerous projects for the production of energy-saving building materials, such as low-E glass and unburned bricks. Generally, the research, production, testing, and widespread use of products and materials with energy-saving and environmentally friendly features are largely the result of companies’ efforts to produce and distribute such products and building materials. However, there is a lack of comprehensive activities by the state and credit institutions to support businesses in this field. In particular, there has been no focus on the testing, rating, and labeling of these materials because of the insufficient capacity to test the hygrothermal properties of building materials (e.g., thermal conductivity, moisture absorption, etc.). Some enterprises need to send products to foreign testing laboratories, which costs a lot of time and money. Therefore, there is an urgent need to build a material testing laboratory with sufficient capacity to test, evaluate and label energy-saving building materials and construction products. This falls in line with global development trends.

4. Challenges and Opportunities

In 2005, the governmental decree 102/2003/ND-CP on the economic and efficient use of energy was issued. Nearly 20 years later, we have seen some positive results. However, a lot of limitations and challenges remain, concerning the implementation of the contents of economical and efficient use of energy in the fields of construction, production, and in particular, in the use of building materials with energy-saving features [25]:

• It is not easy to access specific financial incentives for projects that produce energy-saving and environmentally friendly building materials and products.
• There is a lack of mandatory or recommended regulations for the assessment, certification, and energy labeling of construction products and building materials.
• There is still inadequate awareness and interest by stakeholders such as investors, construction contractors, operation management units, and users in economical and efficient energy use.
• There are no mandatory regulations for new construction or renovation works to meet green building standards.

The above limitations and challenges, combined with pressures of the rising prices of raw material and energy, limited supply, as well as firm government commitments on environmental protection, energy saving, and reducing greenhouse gas emissions, create significant opportunities to vigorously develop energy-saving and environmentally friendly products, goods, and building materials to be used in energy-efficient buildings and constructions, green buildings, and low-emission buildings.

As people’s living standards and incomes improve, it is becoming more vital to ensure healthy and comfortable conditions within a building. Technical requirements in line with indoor air quality regulations and standards have been developed to guarantee comfort and limit the impact of microorganisms and mold. Their application encourages research, development, production, and the use of construction materials with energy saving, economical, resource efficiency, and environmentally friendly features to reduce emissions and ensure the health of users. The process of integration and globalization, and the participation in linkage chains, supply chains, and global value chains, place pressure on enterprises producing and distributing products, building materials, as well as investors. The investment and operation management units of construction works must comply with and apply criteria and standards and perform the assessment, certification, energy labeling, and eco-labeling of construction materials used in the building.

5. Study on the Facilities and Equipment for Testing Energy-Saving Materials in Vietnam

Determining the heat transfer, moisture transfer, and durability properties of materials plays a significant role in energy-efficient and economical buildings worldwide, including Vietnam [26,27,28]. Therefore, it is vital to determine the type of material suitable for intended use in the project. Furthermore, following the trend of using innovative materials and energy-saving materials, along with the mandatory implementation of QCVN 09:2017/BXD in the near future, there will be a greater need to research and test heat and moisture transfer features, as well as the durability of building materials utilized for suitable selection to the actual climatic conditions. Therefore, it is essential to research and improve testing capacities in this field, new to Vietnam, to bring about long-term improvements.

A laboratory for testing building physics properties has been established to determine the basic materials’ properties required for the application of Vietnamese energy efficiency regulations and to determine which are relevant for performance-oriented design, necessary for a simulation study. All the necessary test equipment and test methods have been precisely identified using measurement ranges, measurement accuracies, and test boundary conditions.

5.1. Necessary Material Parameters for the Energy Code

• Thermal transmittance (U₀-value)/total thermal resistance (R₀-value)

R₀-value/heat conductivity, λ

The total thermal resistance describes the resistance of a building to heat flow when a temperature difference is present at the component boundaries. The R₀-value is the reciprocal of the U₀-value and is calculated from the thermal conductivities of individual component layers and the transition resistances at the surfaces. To determine the R₀-value, it is necessary to know the installation situation to determine the surface resistance. Independent of the installation situation, the thermal conductivity of building materials used in the component must be determined. The thermal conductivity is a material parameter that indicates the heat flow at a 1 K temperature difference of a 1 m thick sample. Determination of the thermal conductivity by means of a plate device is described in national and international standards, which will be indicated later in this research. For the measurement of the characteristic value, measuring equipment for determining the material thickness must be available. Likewise, both a heating cabinet and a climatic cabinet are necessary for preconditioning. Depending on the plate equipment used, material specimens with dimensions of 0.3 m × 0.3 m to 1.0 m × 1.0 m must be prepared. Depending on the material, a bandsaw may be useful for cutting the material specimens. To prevent the influence of strong temperature and air humidity fluctuations in the laboratory room, the room in which the measurement with the plate instrument takes place should be air-conditioned. The thermal conductivity of a material depends on the temperature and the moisture content, and can also be determined as a function depending on these influences during measurements. The thermal conductivity was determined in laboratory A1 (Figure 1), as well as in the extended laboratory, A2 (Figure 2), with guarded hot plate devices No.2 and No.3, respectively.

U₀-value

The thermal transmittance (U₀-value) is a measure of the heat transfer through a building component and is used to determine the transmission heat loss/gain of a building component. The value can either be calculated from the thermal resistance of the individual materials and the surface resistance or determined directly via a hotbox method.

$${\mathrm{U}}_0=\frac{1}{{\mathrm{R}}_0} ({\mathrm{m}}^2·\mathrm{K}/\mathrm{W})$$

The hotbox method is usually employed to determine the U-value of inhomogeneous structures, such as windows and doors. The test setup requires two separate air-conditioned rooms with an opening in the partition wall for the installation of a test specimen. Thermal transmittance is determined in two steps. In the first step, the test stand-related surface resistances are determined using a calibration plate with known thermal properties. In the second step, the thermal transmittance of the test specimen is determined. The size of the test rig depends on the size of the test specimen to be measured. Test stands for windows and doors should have a base area of approximately 5.0 m × 5.0 m. Figure 2 shows a test rig with a floor space of 25 m². The U₀-value using the hotbox method could only be determined in the extended laboratory A2 No.10 (Figure 2).

• Total energy transmittance g-value

The total energy transmittance, g, is the sum of the direct radiation transmittance, τ, and the secondary heat loss rate, qi, of the glazing to the inside. The latter is caused by heat transfer due to convection and long-wave IR radiation of the proportion of incident radiation absorbed by the glazing [DIN EN 410:201104] [29]. A spectrometer can be used to determine the g-value for simple glass samples. Here, radiation properties such as the direct radiation transmittance, direct radiation reflectance, and direct radiation absorptance are determined. From these characteristics, both the primary and secondary energy inputs for single and multiple glazing can be determined. For special components, such as glazing with integrated solar shading or curved components, the g-value can be determined using the calorimetric method. For this method, the test specimen is exposed to artificial solar radiation in the range 300 to 900 W/m², and an energy balance is carried out for measuring the space behind the specimen for defined ambient conditions.

A No.1 UV/VIS/NIR spectrometer device (Shimadzu, Kyoto, Japan) was used to determine the total energy transmission g-value of smaller samples (600 mm × 600 mm) in the simple laboratory, A1. Solar simulator No.12 (Figure 3) was utilized to determine larger samples in the extended laboratory, A2.

5.2. Characteristic Values for Energy Optimization

• Air permeability of building components

An airtight building envelope can prevent energy input/loss through convective heat flows in leakage areas. The connection of joints should be designed to ensure the lowest possible air permeability, particularly in the case of openings such as windows and doors, but also in the case of structural connections of different building components. The air permeability of building components is defined by the air volume flow rate that passes through the leakages of a building component over time at an existing pressure difference. Depending on the standard, this value can refer to the length of a connection joint or the area of a component. To determine the air permeability, an airtight test stand is required in which an opening is provided for the test specimen. A fan is used to generate positive or negative pressure on the test specimen. Air permeability as a function of the applied pressure difference is determined from the measured values of a flow meter and a pressure gauge. Independent of the laboratory measurement, mobile devices can also be used to determine the air permeability of entire buildings. This is advantageous after completion of the airtight building envelope in the shell state, because it allows the performance of the connections to be checked and possibly improved. For air permeability, an air exchange rate of 1/h of the building volume at a pressure difference of 50 Pascal is often determined. An air permeability test of components can be performed in extended laboratory A2 in leak test stand No.11 (Figure 2).

• Radiation characteristics

In addition to the total energy transmittance, radiation-related characteristic values can be determined for transparent as well as opaque components, which are helpful for energy optimization.

• Light transmission factor

From the spectral data, which are also determined by means of a spectrometer when determining the g-value, the light transmittance for standard light, D65, can be calculated. This value can be used in living and working spaces to optimize the use of daylight and thus reduce energy consumption when using artificial light. Light transmittance can also be determined with UV/VIS/NIR spectrometer No.1 in laboratory A1 and extended laboratory A2 (Figure 2).

• Thermal emissivity

Emissivity is a wavelength-dependent quantity and a measure of the radiation exchange of a material with its environment. In building physics, the thermal long-wave radiation range is of particular importance. This characteristic value can be used, for example, to calculate the long-wave radiation of facade and roof surfaces. In the interior, thermal emissivity is a necessary parameter for assessing the operative temperature, and thus is a factor for evaluating comfort. The thermal emissivity can be determined with emissometer No.2 in both A1 and A2 laboratories (Figure 2 and Figure 3).

5.3. Additional Hygrothermal Parameters for the Research and Development of Damage-Free Buildings

• Temperature- and moisture-dependent thermal conductivity

As already described, thermal conductivity is a parameter that describes the heat transport through a material. This parameter is strongly dependent on the water content as well as the prevailing temperature. When evaluating a component, simulation programs make it possible to consider the thermal conductivities dependent on the ambient conditions. The specific thermal conductivities can also be determined with the aid of plate instruments. Similarly to simple thermal conductivity, temperature- and humidity-dependent thermal conductivity can also be determined in the A1 and A2 laboratories (Figure 2 and Figure 3). Plate instruments No.2 and No.3 are required for this purpose.

• Heat capacity

Heat capacity is a quantity that reflects the heat storage capacity of a material. In the laboratory, this value is determined by dynamic differential calorimetry. In simulation programs, heat capacity is included in calculations of heat transfer and is a factor responsible for the phase shift of heat transfer under transient boundary conditions. When calculating the energy consumption of a building, this parameter can be used to determine the effective heat storage capacity, which is a building-specific variable that describes the amount of heat that can be absorbed by the interior building components. The heat capacity could be determined in both laboratories A1 and A2 with the necessary measuring device (Figure 2 and Figure 3). Space for such a measuring device is provided under No.8.

• Bulk density

Bulk density is the ratio of the mass of a specimen to its total volume. It is a basic characteristic value that is necessary for a number of calculations. Many other characteristic values refer to the bulk density of a material. In simulation calculations, for example, bulk density is used to convert the mass-specific heat capacity into the volume-specific heat capacity or to display water contents in mass percentages. Bulk density is determined after drying with the aid of vacuum water absorption and weighing an impregnated specimen. To determine bulk density, space is provided in both laboratories A1 and A2 for the necessary measuring equipment, such as balances, under No. 5 (Figure 2 and Figure 3).

• Porosity

Porosity is the ratio of the volume of a specimen to the volume of the pores in [m³/m³]. In a porous material, pores can be in contact with ambient air, but they can also be cavities closed off on all sides. Accordingly, they are usually described by “open” or “closed” porosity. Open porosity is determined by vacuum water absorption in the same procedure as the bulk density. By crushing and weighing a sample, it is possible to infer the pure density, and thus, also the total porosity. Open porosity can be used to infer the maximum water content of a material. However, because most simulation calculations are not very sensitive to the maximum water content, the value is of little importance. For the determination of porosity, areas No.5 and No.8 are provided in laboratories A1 and A2, respectively (Figure 2 and Figure 3).

• Water vapor diffusion resistance number (µ-value)

The µ-value indicates the factor by which the diffusion resistance in the material is higher than in still air. This characteristic value is necessary to determine moisture penetration via diffusion processes when a partial pressure difference is present and is, therefore, an essential characteristic value for assessing the freedom from the damage of a building structure. In the laboratory, this value is determined by means of the dry/wet cup method. The specimen is exposed to a water vapor partial pressure difference by placing it in an airtight container with a desiccant or an aqueous saturated solution and storing it at a constant climate. The amount of diffused water vapor can be determined by weighing the test setup at regular intervals. Water vapor diffusion resistance can be determined in both laboratories A1 and A2 with the use of climatic chamber No.4 (Figure 2 and Figure 3).

• Moisture storage function

A porous hygroscopic substance binds water molecules on the inner surfaces of its polymer system until it reaches an equilibrium water content corresponding to the humidity state of the surrounding air. This relationship between the relative humidity and the water content can be represented in a so-called sorption isotherm (moisture storage function), which can be divided into two areas: (i) sorption range, hygroscopic range, where some of the water molecules in the pore air are bound to the pore walls by absorption and accumulate there with increasing air humidity, first as single molecules, then as molecular groups, then as monomolecular layers, and finally as multimolecular layers consisting of several molecular layers, so that the equilibrium water content increases approximately in proportion to the air humidity; (ii) capillary water area, over-hygroscopic area, in which from a relative humidity of approximately 0.6 to 0.8, additional condensation phenomena occur due to the reduction in the saturation vapor pressure in fine capillaries, resulting in a significant increase in the equilibrium humidity. The pores then contain not only absorptive bound water, but also unbound liquid water.

In simulations, the moisture storage function helps to make statements about the water content, and thus, also about the thermal conductivity of a material. In the sorption range (up to ≈ 0.9 RH), the function is determined by storing material samples in a climatic chamber at constant temperature and relative humidity and determining the water content gravimetrically. In the capillary water range (above 0.95 RH), a suction stress measurement is carried out with suction stress apparatus. Characteristic values of the moisture storage function can also be determined using climate chambers No.4 and No.9 (Figure 2 and Figure 3).

• Water absorption coefficient

The water absorption coefficient of a material is defined by the water absorption per area and time. Depending on where a building material is used, the water absorption can be determined according to different standards:

-

Determination of the water absorption coefficient during partial immersion (capillary water absorption);

-

Water absorption during long-term immersion;

-

Water absorption by diffusion.

The determination of water absorption can be helpful in various areas. Among other things, the water absorption coefficient can be used to evaluate the rain protection effect of a facade or to classify building materials for use in components in contact with the ground. The water absorption can be determined in both laboratories A1 and A2 with the help of trolley No.5 and the dip tanks under No.6 (Figure 2 and Figure 3).

• Weather data

For the calculation of heating and cooling loads of a building, the boundary conditions of the adjacent temperatures and weather conditions are decisive in addition to the characteristic values of building physics. For the climate inside the building, relevant standards such as DIN 4108, EN 15026, ISO 13788, and ASH-RAE 160 specify characteristic values for the indoor climate as a function of the respective outdoor climate [30,31,32,33]. The outdoor climate is taken from the measured data for the test reference year in simulation programs for calculating building energy consumption. In order to obtain reliable weather data for a region under consideration, several weather stations are necessary. Depending on the configuration of the weather station, the following weather data can be recorded:

-

Direct and diffuse solar radiation in W/m²;

-

Temperature in °C;

-

Relative humidity in %;

-

Wind direction and speed in m/s;

-

Wind direction;

-

Air pressure hPa;

-

Rainfall l/m²h.

For a simple energy consumption calculation, the parameters of temperature and solar radiation are important. The outside temperature, in connection with the thermal conductivity or the U-value of a building component, is decisive for calculation of the transmission heat loss, and is thus directly included in calculation of the heating energy demand. The solar radiation, on the other hand, is used in combination with the g-value to determine the energy input via glass surfaces, and thus, the necessary cooling load of a building. Other weather data are especially necessary for the evaluation of damage-free constructions. For example, simulations using the amount of rain and the wind direction, as well as the water absorption coefficient, can be used to make a statement about the water absorption on a facade surface, and thus, also about the resulting change in thermal conductivity. The relevance of the weather data is to be judged depending on the focus of the observation. Thus, maximum values can also be estimated and determined for the assessment of a worst-case scenario.

5.4. Proposal for a Simple (A1) and Advanced (A2) Laboratory

In this study, two proposals for a smaller (A1) and an advanced laboratory (A2) with the appropriate equipment have been developed to determine the necessary characteristic values required for calculations of the QCVN 09:2017/BXD national technical regulation on energy-efficient buildings in Vietnam. Version A1 shows a smaller laboratory with a floor space of 190 m², with all the necessary measuring equipment to determine the basic building physics parameters. Costs of approximately EUR 500,000 must be calculated for the laboratory’s equipment. All rooms where measurements are carried out must have an air conditioning system to maintain stable climatic conditions. In addition to the laboratory floor plan, office equipment space must be planned. Laboratory proposal A1 is intended for measurements on smaller material samples. Therefore, an average room height of 3–4 m is sufficient for the laboratory rooms. Possible characteristic value determination with a simple laboratory setup is proposed, as shown in

Table 2. Possible characteristic value determination with the simple laboratory setup.

Physical Property	Unit	Measurement Setup	Investment Costs	Test Standard	Ref.
Thermal conductivity Thermal resistance	[W/mK] [m2K/W]	Guarded hot plate apparatus, climate chamber, oven, weighing equipment, and measuring instruments for size determination	EUR 20,000 to EUR 120,000	ISO 8302, ASTM C518, EN 1946-3, EN 12664, EN 12667, EN 12939	[34,35,36,37,38,39]
Heat capacity	[J/kgK]	Differential scanning calorimetry	EUR 160,000	ASTM E1269-11, ASTM E2716-09, EN ISO 11357-1, DIN 51007	[40,41,42,43]
Bulk density	[kg/m3]	Ventilated oven (70 + 5) 9C, vacuum vessel (2.0 + 0.7) kPa, weighing device 0.1%, 0.1 mm, Le Chatelier flask 0 to 24 mL, sieve with a mesh size of 0.1 mm	Climate Chamber 1, EUR 70,000; Climate Chamber 2, EUR 70,000	EN 1097-6, EN 772-4	[44,45]
Porosity	[m3]			EN 772-4, EN 1936	[45,46]
Water vapor diffusion resistance	[-]	Climate chamber ± 5% ± 1.0 K, test vessel (glass metal), sealing compound (microcrystalline kerosene), measuring instruments with which the specimen thickness is determined, analytical balance error limit of 0.001 g, measuring probe, and a data acquisition system for temperature and relative humidity		EN ISO 12572	[47]
Moisture storage function	[kg/m3]	Weighing containers that do not absorb water, balance, with a margin of error of ±0.01% of the mass of the specimen, heating cabinet according to ISO 12570, desiccator, climatic chamber		EN ISO 12571	[48,49]
Water absorption coefficient (partial immersion)	[kg/m2h0.5]	Scale with which the mass of the specimen can be measured to ±0.1%, water tank with a device that keeps the water level constant to ±2 mm, stopwatch		EN ISO 15148,	[50]
Capillary water absorption	[kg/m2min0.5]	Stopwatch, weighing device, oven, climatic chamber, spatula, absorbent filter paper, metal mold		EN 1015-18, DIN EN 772-11:	[51,52]
Water absorption long-term immersion	[kg/m2]	Scale, water tank, stainless steel cage		EN ISO 16535	[53]
Radiation coefficients (τ, ρ, α)	[%]	UV/VIS/NIR spectrometer	EUR 80,000	DIN EN 410	[29]
Light transmittance	[%]			DIN EN 410	[29]
Irradiance	[W/m2]	Pyranometer	EUR 1500

and the floor plan in Figure 2.

In the second version, A2, the small laboratory is extended with a larger hall of 170 m², in which additional characteristic values can be determined. The facilities in laboratory A2 also allow larger material samples and components to be measured and their characteristic values to be determined (see

Table 3. Additional characteristic value determination with the extended laboratory setup.

Physical Property	Unit	Measurement Setup	Investment Costs	Test Standard	Ref.
U-value/R-value	[W/m2K]	Hot box	EUR 300,000–EUR 500,000	DIN EN ISO 12567-1, DIN EN ISO 12567-2, DIN EN 12412-2, DIN EN 12412-4, DIN EN ISO 8990	[54,55,56,57,58]
Air permeability of building components	[m3/h]	Test stand for holding the specimen, fan for generating a pressure difference, air-measuring section for determining the volume flow	4 m × 4 m, EUR 150,000; 1 m × 1 m, EUR 10,000	EN 12114,	[59]
Air permeability of curtain walls	[m3/m2h]			EN 12153	[60]
Air tightness of windows, doors, and gates	[m3/m2h], [m3/mh]			EN 1026, EN 12207, EN 12427	[61,62,63]
Total energy transmittance g-value	[%]	Test rig for determining total energy transmittance by the calorimetric method	EUR 200,000	ISO 19467	[64]

and Figure 3). The additional hall should have a minimum height of 7 m and preferably be equipped with an overhead crane to install heavy components. In addition to the costs of the simple laboratory, a further EUR 850,000 should be calculated for the extended laboratory’s equipment. All cost estimates are only for the technical equipment and not for the buildings.

6. Training and Improving Test Capacity for Staff

The Vietnamese researchers and laboratory staffs were trained in Germany at, and laboratory personnel from Germany visited the locations in Vietnam to exchange experience and further education. Following the implementation and calibration of the laboratory measurement equipment, several relevant materials and material systems were selected for comparative testing. The selected materials were tested in Vietnam and then sent to the -Germany, where the tests were repeated nondestructively on the same samples. Comparing the results allowed potential problems to be identified and resolved through bilateral discussions. This ensures that standard quality standards are adhered to, and the results will be internationally comparable. At the moment, this new laboratory is the only one in Vietnam.

7. Conclusions and Policy Implications

In this study, the governance framework on energy efficiency building materials in Vietnam has been introduced, including government decrees and technical standards. Then, a laboratory concept for characteristic value determination, in accordance with Vietnamese energy standards and building physics materials, components, and building research, was developed and implemented in Hanoi, Vietnam. This research is necessary for the complete assessment of building materials and construction products for the present and future generation of energy-efficient buildings and sustainable buildings. No other comparable studies have been published; therefore, this research has great practical and scientific significance. This academic knowledge will greatly contribute to developing new energy-saving materials, energy-efficient buildings, and sustainable development to help achieve the goal of zero emissions by 2050. Using this research, Vietnam and other developing countries that do not have specific expertise and tradition in this field will also be able to improve their systems for testing, rating, and labeling building materials for energy performance, towards sustainability in countries. Moreover, clear information on the energy performance of building materials by testing, rating, and labeling systems will support the development of energy-efficient and sustainable buildings by helping code officials to easily verify that this material matches the code-compliant design.

Several policy implications can be determined from our results. First, from the results of the overview regulations, policymakers can identify which policies and regulations are missing in order to develop, supplement, and complete the regulation framework for the implementation of saving energy in the building. Secondly, research on the development of laboratory concepts with all necessary equipment is a very good tool for implementing energy efficiency regulations in buildings, such as energy efficiency standards, regulations, and labeling programs. Finally, our results are a very good reference for policymakers from developing countries such as Vietnam to learn how to develop energy-saving mechanisms in buildings, sustainable development, moving towards the goal of zero emissions by 2025.