Foreword

QCVN 09:2013/BXD on “Energy Efficient Buildings” was compiled by the Vietnam Association of Building Environment, reviewed by the Department of Science, Technology and Environment, and promulgated by the Ministry of Construction under Circular No. 15/2013/TT-BXD dated September 26, 2013. The National Technical Regulation QCVN 09:2013/BXD replaces the Vietnam Building Code QCXDVN 09:2005 “Energy Efficient Buildings” issued under Decision No. 40/2005/QD-BXD dated November 17, 2005 by the Minister of Construction.

The National Technical Regulation QCVN 09:2013/BXD was developed with the participation and input from international experts sponsored by international organizations, including: International Finance Corporation (IFC), United States Agency for International Development (USAID), Danish Energy Agency (Kingdom of Denmark).

I. GENERAL PROVISIONS

1.1. Scope of regulation

1.1.1. The National Technical Regulation “Energy Efficient Buildings” stipulates mandatory technical requirements that must be complied with when designing, constructing new or renovating civil works (offices, hotels, hospitals, schools, commercial, services, apartments) with a total floor area of 2500 m² or more.

1.1.2. The provisions in this regulation are applied to:

1) The building envelope, except for the envelope of storage spaces or warehouses that do not use air conditioning;

2) Building equipment including:

a) Interior lighting systems;

b) Ventilation and air conditioning systems;

c) Water heating equipment;

d) Energy management equipment;

e) Elevators and escalators.

1.2. Subjects of application

This regulation stipulates mandatory technical requirements that must be complied with by all organizations and individuals involved in activities related to energy efficient buildings.

1.3. Referenced documents

1) ARI 340/360 – Performance rating of commercial and industrial unitary air-conditioning and heat pump equipment.

2) ARI 365 – Performance rating of commercial and industrial unitary air-conditioning condensing units.

3) ARI 550/590-2003 – Performance rating of water-chilling packages using the vapor compression cycle.

4) ASHRAE 90.1-2001 – Standard 90.1-2001 (I-P Edition) — Energy Standard for Buildings Except Low-Rise Residential Buildings (IESNA cosponsored; ANSI approved; Continuous Maintenance Standard).

5) ASHRAE 90.1-2004 – Energy Standard for Buildings Except Low-Rise Residential Buildings.

6) DIN 4702-1 – Boilers for central heating; terms, requirements, testing, marking.

7) ISO 6946:2007 – Building components and building element – Thermal resistance and thermal transmittance – Calculation method.

8) TCVN 298:2003 – Building components and elements – Thermal resistance and thermal transmittance – Calculation method.

9) TCVN 6307:1997 – Refrigeration systems – Test methods.

10) TCVN 7830-1:2012 – Air conditioners – Part 1: Energy efficiency.

1.4. Definitions

1.4.1. Terminology

1) Economizer: A device including dampers and automatic controls that allow fans to supply cooler outdoor air into the building to minimize the energy consumed for cooling or to eliminate the need for mechanical cooling.

2) Building energy cost: The total annual costs paid for energy consumption of the building.

3) Cooling COP (Coefficient of Performance): The ratio of obtained cooling capacity to the input electrical power consumption in the same unit of measurement, tested according to national standards or design operating conditions. The COP value is determined to evaluate the energy efficiency of electric air conditioners with air-cooled condensers, including compressors, evaporators, and condensers. The COP value is also determined to evaluate the energy efficiency of packaged chillers (excluding chilled water pumps, condenser water pumps, and cooling tower fans).

4) Heat Pump COP: The ratio of obtained heating capacity to the input electrical power consumption in the same unit of measurement, calculated for the entire heat pump system under design operating conditions.

5) OTTV (Overall Thermal Transfer Value): The total amount of heat transferred into the building through the entire surface area of the building envelope, including both opaque walls and windows, normalized per 1m² of the building’s exterior surface, in W/m².

6) Floor area of a building space: The area of the horizontal surface of a defined building space, measured from the inside of the surrounding walls or partitions, at the working plane level (0.8m).

7) Shading coefficient: The ratio of solar radiation energy passing through a window into a room in the case of an external shading device, compared to the case of a window without a shading device.

8) Overall heat transfer coefficient U_o: The steady-state heat flow rate through a unit surface area of the building envelope when the air temperature difference between the environments on both sides of the structure is 1 K. Unit: W/m².K.

9) Total thermal resistance R₀: The reciprocal of the overall heat transfer coefficient U_o: R0 = 1/U_o, unit is m².K/W.

10) Lamp efficacy: The ratio of the luminous flux of a lamp to its electrical power, in lumens/W.

11) HVAC system efficiency: The ratio of output energy (useful energy at the time of use) to input energy with the same unit of measurement for a defined period, expressed as a percentage.

12) Heat recovery efficiency: The ability of HVAC equipment, boilers, etc. to recover cooling/heating, resulting in energy saving efficiency.

13) Annual energy use efficiency: The ratio of annual output energy to annual input energy of a building or equipment.

14) Indirectly conditioned space: An enclosed space in a building that is indirectly cooled (not directly cooled) and has heat transfer from this space to adjacent conditioned cooled spaces.

15) Lighting Power Density (LPD): The ratio of electrical lighting power to the illuminated area, in W/m².

16) Daylight sensor: An automatic device that turns on or off the electrical energy input for lighting near windows to maintain appropriate illuminance for work, when natural light directly or indirectly does not ensure or ensures the required illuminance.

17) Thermostat: An automatic device that responds to temperature.

18) Building envelope: The building envelope, also known as the building enclosure, includes opaque or transparent walls, windows, doors, roofs, skylights, etc. that form enclosed spaces inside the building.

1.4.2. Symbols, units of measurement, and abbreviations

1) SHGC (Solar Heat Gain Coefficient) – The solar heat absorption coefficient of glass, published by the manufacturer or determined according to current standards, non-dimensional. In case the manufacturer uses the shading coefficient SC, then SHGC = SC x 0.87;

2) SC – Shading Coefficient.

3) T – Absolute temperature K.

4) R₀ – Total thermal resistance (the reciprocal of the overall heat transfer coefficient U₀) of the building envelope – m² K/W;

5) U₀ – Overall heat transfer coefficient (including heat transfer through the two air boundary layers on both sides of the structure), W/m².K;

6) U_o,M – Overall heat transfer coefficient of the roof structure, W/m² K;

7) U_o,T – Overall heat transfer coefficient of the wall, W/m² K;

8) AHU – Air Handling Unit;

9) ARI – Air-Conditioning and Refrigeration Institute;

10) ASHRAE – American Society of Heating, Refrigerating and Air-Conditioning Engineers;

11) BEF – Ballast Efficacy Factor for Fluorescent lamps, %/W;

12) BF – Ballast Factor, %;

13) COP_cooling – Cooling Coefficient of Performance – The ratio of obtained cooling capacity to input electrical power consumption kW/kW;

14) COP_heating – Heat pump Coefficient of Performance – The ratio of obtained heating capacity to input electrical power consumption kW/kW;

15) EER – Energy Efficiency Ratio of air conditioners – The ratio of obtained cooling capacity to effective electrical power, kW/kW;

16) FCU – Fan Coil Unit – a heat exchanger consisting of multiple rows of plain or finned tubes, with chilled water or hot water circulating inside the tubes to supply cooling/heating for air blown by a fan for the purpose of cooling/heating a room. FCU is a terminal device of a central chilled water HVAC system with chiller;

17) IEER – Integrated Energy Efficiency Ratio, kW/kW;

18) IPLV – Integrated Part Load Value – fully understood as Integrated Part Load Energy Efficiency Index; kW/kW;

19) OTTV_W – Overall Thermal Transfer Value through Wall – Average heat flow intensity transmitted through 1 m² of exterior wall into the building, W/m²;

20) OTTV_R – Overall Thermal Transfer Value through Roof – Average heat flow intensity transmitted through 1 m² of roof structure into the building, W/m²;

21) PIC – Power Input per Capacity – The ratio of electrical power consumption measured in kW to cooling capacity calculated in RT (refrigeration tons), kW/RT;

22) VLT – Visible Light Transmission – The visible light transmission coefficient of glass – represents the percentage of light energy transmitted through the glass compared to the light energy incident on the glass surface, %;

23) VRV/VRF – Variable Refrigerant Volume/Flow air conditioning system;

24) VSD – Variable Speed Driver – A device that adjusts the rotational speed by changing the frequency of the power supply – commonly called a variable frequency drive;

25) WWR – Window to Wall Ratio, non-dimensional.

II. TECHNICAL REGULATIONS

2.1. Building Envelope

2.1.1. General Requirements

The building envelope shall be designed and constructed to ensure:

1. Natural ventilation when external climatic conditions allow;
2. Sufficient thermal insulation and minimization of cold wind;
3. Sufficient natural lighting under normal permissible conditions, while minimizing solar radiation penetration into the building interior;
4. Selection of appropriate materials to enhance the building’s energy efficiency.

2.1.2. Requirements for External Walls and Roofs

1. All external walls of the building above ground level (non-transparent wall sections) must have a maximum total heat transfer value U_o.max not exceeding or a minimum total thermal resistance value R_o.min not less than the values specified in Table 2.1.

Table 2.1. Thermal Technical Requirements for External Enclosure Walls

2. Requirements for flat roofs and roofs with a slope less than 15 degrees:

All types of roofs, including insulated roofs, metal flat roofs, and other roof types, must have a total heat transfer value U_o not exceeding or a total thermal resistance value Ro not less than the values specified in Table 2.2.

Table 2.2. Thermal Technical Requirements for Flat Roofs

3. Window and skylight area

a) The total area of vertical windows for both operable and fixed vertical windows must ensure ventilation and natural lighting.

b) The overall thermal transmittance index of walls and roofs must ensure:

– OTTVW of walls does not exceed 60 W/m²;

– OTTVR of roofs does not exceed 25 W/m².

c) The OTTV values are determined according to technical standards and guidelines.

4. Design windows with glass having an appropriate SHGC value instead of determining the OTTVW index of walls as specified in 2.1.2 – Point 3) – b). The SHGC of the glass must be less than or equal to the maximum allowable value, and the VLT of the glass must not be lower than the VLT_min value given in Table 2.3.

Table 2.3. SHGC of Glass Depending on WWR Ratio

5. In case the building facade has a shading structure, the SHGC value in Table 2.3 is allowed to be adjusted by multiplying it by factor A in Tables 2.4 and 2.5.

Table 2.4. Factor A for Continuous Horizontal Shading Structures (CSS) Placed Directly Above the Window or Placed at a Distance d from the Top Edge of the Window with d/H < 0.1

Table 2.5. Factor A for Continuous Vertical Fins Placed Directly at the Side Edge of the Window or Placed at a Distance e from the Side Edge of the Window with e/B < 0.1

2.2. Ventilation and Air Conditioning

2.2.1. General Requirements

1. Natural ventilation and mechanical ventilation

For each specific space, the ventilation system can be either natural (passive) or forced (active – mechanical ventilation). Natural ventilation systems must meet the requirements in Article 2.2.1 – Point 2).

2. Natural ventilation systems

Spaces are considered naturally ventilated if they satisfy the following requirements:

a) Ventilation openings and operable windows with an area not less than 5% of the floor area. These ventilation openings are easily accessible to users;

b) There must be operable ventilation openings above the ceiling or on the wall opposite the external wind source. These ventilation openings have an operable area ratio of not less than 5% of the floor area. Users can easily access these ventilation openings, and they must directly open to the outside through openings with an equivalent or larger area;

c) The total area of exhaust openings is not less than the total area of intake openings.

3. Mechanical ventilation systems

Spaces not naturally ventilated must be equipped with mechanical ventilation systems to supply air from the outside to each regularly occupied space through ductwork.

2.2.2. Requirements for Ventilation and Air Conditioning Systems and Equipment

1. General requirements:

a) Equipment efficiency: Air conditioning equipment and chilled water production machines must have minimum COP efficiency indices under standard rating conditions and not less than the values given in the following tables:

– Table 2.6: for air conditioners and condensing units using electrical energy;

– Table 2.7: for chilled water production equipment;

– Table 2.8a: for cooling tower equipment;

– Table 2.8b: for condenser equipment.

Notes:

In addition to the COP efficiency index, refrigeration equipment is also evaluated for energy efficiency using the Integrated Part Load Value (IPLV) and Integrated Energy Efficiency Ratio (IEER).

b) Automatic timers: The following equipment must have timers or automatic controls to turn the equipment on and off according to a specified time or set parameters:

– Chilled water production equipment;

– Hot steam supply equipment;

– Cooling tower fans;

– Pumps with a power of 5 horsepower (3.7 kW) or more.

c) Insulation of cooling system ducts:

The refrigerant pipes of air conditioners and chilled water pipes of central air conditioning systems must have an insulation layer greater than or equal to the insulation thickness in Tables 2.9 and 2.10.

The insulation thickness (mm) given in Tables 2.9 and 2.10 is applicable for insulation materials with a thermal conductivity in the range of 0.032 ÷ 0.04 W/m.K at an average temperature of 24oC. The minimum insulation thickness will be increased for materials with a thermal conductivity greater than 0.04 W/m.K or can be reduced for materials with a thermal conductivity less than 0.032 W/m.K.

For insulation materials with a thermal conductivity outside the stated range, the minimum thickness (bmin) is determined by the following formula:

where:

b_min – minimum thickness of the insulation layer, mm;

r – actual outer radius of the pipe, mm;

b₀ – thickness of the insulation layer listed in Tables 2.9, 2.10, and 2.11 for the applicable pipe sizes, mm;

λ – thermal conductivity of the replacement material at the applicable fluid temperature, W/m.K.

d) Insulation of supply and return air ducts: Supply and return air ducts must have an insulation layer greater than or equal to the insulation thickness in Table 2.11. Insulation is not required for exhaust air ducts.

e) Inspection and adjustment: Fans or pumps with a power of 5 horsepower (3.7 kW) or more must adjust the machine’s design flow rate by adjusting the rotational speed using a multi-speed drive, two-speed motor, or variable speed drive (VSD). Avoid adjusting the flow rate of fans and pumps using throttle valves.

f) Cooling tower fan control: Cooling towers with fan motors having a power of 5 horsepower (3.7 kW) or more must use a multi-speed drive, two-speed motor, or variable speed drive (VSD).

g) Chiller water cooling system: Central air conditioning systems using chilled water must be designed with variable flow by using variable speed pumps.

h) Buildings using a central air conditioning system must have a coolness recovery device. The minimum coolness recovery efficiency of the device is 50%.

2. Additional requirements for mechanical ventilation and air conditioning systems

When using mechanical ventilation and air conditioning systems, the following additional requirements must be met:

a) CO₂ sensors: Must be installed to increase the amount of supply air to spaces with a design area standard less than 3 m²/person.

b) Automatic timer controls: Ventilation fans operating intermittently must have timers or automatic controls that can determine their working time and duration.

c) Duct welding: Supply and return air ducts must meet the requirements for air duct joining and insulation according to current regulations.

Table 2.6. Efficiency indices for direct-cooling electric air conditioners

Table 2.7. Efficiency indices for chilled water production machines (Chillers)

Table 2.8a. Technical specifications for cooling towers

Table 2.8b. Technical specifications for condensers

Table 2.9. Insulation layer thickness for copper pipes carrying refrigerant

Table 2.10. Insulation thickness for chilled water pipes

Bảng 2.10. Độ dày cách nhiệt cho ống dẫn nước lạnh

Table 2.11. Insulation thickness for air ducts

2.3 Lighting

2.3.1 General Provisions

1. Scope of Application

This section specifies the maximum allowable lighting power limits for building lighting systems, as well as efficiency limits for common lighting equipment (lamps and ballasts) and lighting control systems. The following cases are not subject to the requirements of this section:

a) Lighting for performance activities, television production, entertainment areas such as dance halls in hotels, nightclubs, areas where lighting is an important technical element for performance functions;

b) Special lighting for medical purposes;

c) Special lighting for research laboratories;

d) Safety lighting that automatically turns on and off during operation;

e) Lighting for special security areas as required by state laws or local government regulations;

f) Safety or security areas for people that require additional lighting.

2. Minimum Illuminance

The minimum illuminance (lux) for functional spaces must comply with the requirements of current technical standards.

3. Maximum Lighting Power Density

a) The average lighting power density (LPD) for the entire building shall not exceed the maximum allowable level specified in Table 2.12. The building’s average lighting power density is calculated by dividing the total building lighting power by the total occupied floor area.

Table 2.12. Requirements for Lighting Power Density (LPD)

b) Other building types subject to the scope of this Regulation that are not listed in Table 2.12 shall have a maximum lighting power density of up to 13 W/m².

c) Mixed-use buildings subject to the scope of this Regulation that have different functional areas shall be calculated according to the function of each area. Each area must satisfy the maximum lighting power density requirements specified in Table 2.12.

d) The average lighting power density of a parking area is calculated by dividing the total lighting power of the parking area by the total parking area.

2.3.2 Efficiency Requirements for Lighting Equipment

1. The minimum luminous efficacy of lamps is specified according to Tables 2.13 and 2.14.

Table 2.13. Minimum luminous efficacy of linear fluorescent lamps

Table 2.14. Minimum luminous efficacy of compact fluorescent lamps

2. The efficiency of ballasts is specified according to Table 2.15.

Table 2.15. Efficiency of electronic ballasts

2.3.3. Lighting Control

1. Lighting control for spaces within the building

Each space enclosed by partitions extending to the ceiling is considered a separate space and must have at least one lighting control device. Each lighting control device is manually or automatically controlled based on human activity in that space. Each control device must:

a) Control a maximum area of 100 m²;

b) The spaces listed in Table 2.16 must have occupancy sensors installed, which are connected to and directly control the lighting system. Occupancy sensors for controlling lights are not connected to emergency lighting and security lighting systems.

Table 2.16. Building types required to install occupancy sensors

c) For parking areas, at least 70% of the lighting system must be controlled by occupancy sensors (the percentage of the system is calculated based on the lighting power supply).

2. Control for daylit areas

For enclosed spaces with daylighting, the following issues should be considered for artificial lighting:

a) The daylit area is the area parallel to windows/exterior glazing within a distance of 1.5 times the height from the floor to the top of the window glass or exterior glazing.

b) All lighting fixtures within the daylit area must have lighting controls as follows:

– Use light sensors to automatically control dimming or on/off switching of lights based on the level of daylight received. Light sensors should be placed at ½ the depth of the daylit area. When the daylight measured by the sensor exceeds the standard level for that occupancy space (e.g., 300 lux for offices), the sensor must signal to turn off the lights.

– Allow separate on/off switching of lights in the daylit area compared to the general lighting system.

c) When a space uses both occupancy sensors and light sensors, occupancy sensors have higher priority over light sensors in controlling the lights.

d) Hospitals, guest rooms in hotels, and apartments are not required to apply regulation 2.3.3 – Point 2).

e) Spaces used for special purposes are exempt from regulation 2.3.3 – Point 2), but specific justifications must be provided.

3. Auxiliary lighting controls

Auxiliary controls for turning on/off permanently installed lights under shelves, cabinets, etc. are used in the following cases:

a) Decorative lighting for hotel guest rooms, lodging rooms, and luxury living rooms;

b) Illustrative lighting for sales or display.

2.4. Escalators and Elevators

2.4.1. Escalators

Escalators must have controls to reduce speed or stop when no passengers are present. Escalators must have one of the following energy-saving features:

1. Speed control: Escalators must switch to low-speed mode after no more than 3 minutes of passenger inactivity. Activating photoelectric sensors must be installed at the beginning and end of the escalator area.
2. On-demand usage: Escalators must automatically turn off after no more than 15 minutes of passenger inactivity. On-demand escalators must be designed with energy-efficient soft-start technology. Escalators must automatically run when needed. Activation is done by photoelectric cells installed at the beginning and end of the escalator area.

2.4.2. Elevators

Elevators must have controls to reduce energy consumption. To meet this requirement, the following features must be integrated into traction elevators:

1. Use multi-winding, variable frequency AC motors on non-hydraulic elevators.
2. Elevator cars use energy-efficient lighting fixtures and display lighting to ensure the average luminous efficacy for all interior fixtures. Average illuminance >55 lumens/W, lights must automatically turn off within 5 minutes of the elevator stopping operation.
3. Elevators operate in idle mode during off-peak hours. For example, power to the elevator control system and other operating equipment such as car lights, displays, ventilation fans automatically turns off within 5 minutes of the elevator stopping operation.

2.5. Electrical Energy Use

2.5.1. Electrical Distribution System

1. Metering

The distribution system to the building must have internal metering to record demand (kVA), energy consumption (kWh), total power factor at check meters. The electrical distribution system within the building can monitor electrical energy consumption at electrical load branches via meters. Check meters are required at electrical load branches with a total installed capacity greater than 100 kVA such as lighting systems, receptacles, air conditioning systems, ventilation, hot water supply systems, electrical consumption centers larger than 100 kVA.

2. Sub-metering

Sub-meters must be provided for each tenant space and there must be provisions allowing for tenant meter auditing.

Note: When using a shared (central) air conditioning system, the requirement for sub-metering for tenants does not need to be met.

3. Power Factor Correction

All power supplies larger than 100 A, 3-phase must maintain their lagging power factor between 0.90 and 1 right at the connection point.

4. Installed Power Adjustment

The electrical system in the building must ensure the maximum allowable coincidence factor specified in Table 2.17 and the maximum allowable installed power in Table 2.18.

Table 2.17. Maximum coincidence factor ks by load branches

Table 2.18. Maximum allowable installed power

2.5.2. Electric Motors

All permanently wired 3-phase induction motors serving the building have efficiency values marked on the nameplate at full load no less than the values specified in Table 2.19. The manufacturer’s label on the motor lists the minimum efficiency values, rated efficiency, power factor at full load.

Table 2.19. Minimum efficiency requirements for electric motors

2.6. Hot Water Systems

2.6.1. General Requirements

The design load of the hot water system is calculated based on the size of the equipment and must comply with the manufacturer’s specifications.

In cases where other hot water supply solutions (not using electric resistance) with greater economic efficiency can be used, the building is not allowed to use electric resistance water heating solutions.

When the building has a large, centralized hot water supply demand with an installed capacity over 50 kW or energy consumption over 50,000 kWh/year, electric resistance water heating solutions are not allowed to be used.

Order of priority for civil buildings:

1. Scope of domestic hot water supply with temperature ≤ 60°C:

a) Hot water supply by air conditioners with heat recovery;

b) Hot water supply by solar energy combined with heat pump/electric heating;

c) Hot water supply by heat pump;

d) Hot water supply from gas-fired boilers;

e) Hot water supply by electric boilers for projects with a scale < 25 rooms.

2. Scope of hot water and steam supply with temperature ≥115°C (cooking, laundry, sterilization, steam):

In buildings with simultaneous demand for hot water ≤ 60°C (for domestic needs) and hot water/steam ≥115°C (for cooking, laundry, steam, sterilization), prioritize solutions for heating water to 60°C, then continue to heat water and steam to temperatures ≥115°C by using gas or oil-fired steam boilers.

2.6.2 Efficiency of Hot Water Heating Equipment

All equipment for local heating and supply of hot water such as for drinking, heating, swimming pools, water stored in tanks must meet the criteria listed in Table 2.20. For heat pump water heaters, refer to Table 2.21.

Table 2.20. Minimum efficiency of hot water heating equipment

For electric resistance water heaters, the minimum efficiency is determined from the maximum standby loss (SL) when the temperature difference between the heated water and the surrounding environment is 40°C, according to the following formula:

E_min = 5.9 + 5.3V^0.5, W (2.2)

Where:

– V is the volume measured in liters.

Table 2.21. Minimum energy efficiency index (COP) of heat pump water heaters

Electric resistance water heaters are not recommended for use except as a supplement to solar energy systems. It is recommended to use heat pump water heaters powered by electricity as they have higher energy efficiency compared to electric resistance water heaters.

Where permitted, solar hot water systems can be used to supply all or part of the building’s hot water demand. Solar water heaters have a minimum efficiency of 60% and a minimum R-value of insulation of 2.2 m².K/W on the back of the solar energy absorber plate.

2.6.3 Insulation for Hot Water Pipes

The following hot water pipes require insulation:

1. Steam pipelines serving laundry, ironing, cooking needs…
2. Domestic hot water pipelines serving needs such as bathing, heating, cooking…

The insulation thickness for hot water pipes must be greater than or equal to the insulation thicknesses given in Tables 2.22 and 2.23.

Table 2.22. Insulation thickness for steel pipes carrying hot water

Table 2.23. Insulation thickness for PPR, PE pipes carrying hot water

2.6.4 Control of Hot Water Heating System

1. Temperature control systems are installed to limit the hot water temperature at the point of use to not exceed 50°C.
2. Temperature control systems are installed to limit the maximum water temperature supplied to faucets in bathtubs and sinks in public bathrooms to not exceed 43°C.
3. Systems that maintain the use temperature in hot water pipelines must be equipped with automatic ON/OFF valves to maintain the circulating hot water temperature.
4. Circulation pumps used to maintain the temperature in hot water storage tanks are controlled to operate in accordance with the working mode of the hot water supply equipment.

III. MANAGEMENT REGULATIONS

3.1. Design documents for newly constructed, renovated projects with a construction scale within the scope of QCVN 09:2013/BXD must include an explanation of compliance with the provisions of this Regulation.

3.2. The appraisal, evaluation of designs, and acceptance of construction works are carried out according to current regulations, including the content on compliance with the provisions of QCVN 09:2013/BXD for projects within the scope of this Regulation.

IV. IMPLEMENTATION

4.1. The Department of Science, Technology and Environment (Ministry of Construction) is responsible for organizing the dissemination and guidance on the application of QCVN 09:2013/BXD for relevant entities.

4.2. Local state management agencies for construction are responsible for organizing the inspection of compliance with the provisions of QCVN 09:2013/BXD in the design and construction of projects in the locality in accordance with current legal regulations.

4.3. During the implementation of this Regulation, if there are any difficulties, all comments should be sent to the Department of Science, Technology and Environment (Ministry of Construction) for guidance and handling.

APPENDIX (REFERENCE) PHYSICAL PARAMETERS OF MATERIALS, STRUCTURES AND CALCULATION OF THERMAL RESISTANCE OF BUILDING ENVELOPE

1. Formula for determining thermal resistance and overall heat transfer coefficient (U-value) of building envelope

Where:

h_N , h_T – are the surface heat transfer coefficients of the outer and inner surfaces of the building envelope, respectively, W/m².K ;

b_i – thickness of the i-th material layer, m;

λ_i – thermal conductivity of the i-th material layer in the building envelope, W/m.K ;

n – number of material layers in the building envelope;

R_a – Thermal resistance of the air layer inside the building envelope, if any, m².K/W .

Where:

Thermal conductivity λ_i is given in Table 1 of the Appendix.

Coefficients h_N , h_T refer to Table 3 of the Appendix.

Air layer thermal resistance R_a refers to Table 4 of the Appendix.

2. Basic parameters needed for building envelope calculation

Table 1. Physical parameters of building materials

Table 2. Radiant heat absorption coefficient α of material surfaces

Table 3. Surface heat transfer coefficient of building envelope h, W/m².K (according to TCVN 298:2003 and ISO 6946:1996)

Table 4. Thermal resistance of unventilated air layer R_a , m².K/W (according to TCVN 298:2003 and ISO 6946:1996)

3. Some common exterior wall and roof structures and total thermal resistance Ro calculated according to formula (1)

3.1. WALLS

W1. Single wall (conventional thickness: 110 mm) fired clay solid brick

W2. Double wall (conventional thickness: 220 mm) fired clay solid brick

W3. Single wall (conventional thickness: 110 mm) fired clay hollow brick

W4. Calculation of thermal resistance of double wall (conventional thickness: 220 mm) fired clay hollow brick

W5. Foam concrete block brick wall, single wall (conventional thickness: 110 mm)

W6. Foam concrete block brick wall, double wall (conventional thickness: 220 mm)

W7. 3D Panel 180 mm thick

Note:The total thermal resistance of the exterior wall is calculated with the exterior surface heat transfer coefficient h_N = 25 W/m².K and the interior surface heat transfer coefficient h_T = 7.692 W/m².K – see Table 3, Appendix.

3.2. ROOFS

R1. Roof structure with 105 mm thick hollow brick insulation layer

R2. Roof structure with 105 mm thick hollow brick insulation layer and 150 mm thick slag concrete g = 1000 kg/m3

The structure is the same as roof R₁, but above the heat-resistant brick layer, there is an additional layer of lightweight concrete – slag concrete g=1000 kg/m³ – λ=0.41 W/(m.K) 150 mm thick, then the total thermal resistance of roof R₂ will be R_o=1.006 m².K/W – meeting the requirements.

R3. Roof with 30 mm thick polystyrene foam boards

Note: The total thermal resistance of the roof is calculated with the exterior surface heat transfer coefficient h_N= 25 W/m².K and the interior surface heat transfer coefficient h_T= 5.882 W/m².K – see Table 3, Appendix.