Application of thermal insulation coatings in green buildings!

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《（2020）》，201845%，10，21.

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2007JC/T 1040-2007《》，JG/T235-2008《》、GB/T 2561-2010《》，

In order to promote the application of reflective thermal insulation coatings, the state and some provinces and cities have successively issued relevant building design specifications, especially in the green building design specifications, which clarified the scope and requirements of reflective thermal insulation coatings in buildings

National standard GB50176 "Code for Thermal Design of Civil Buildings"

4.

National industry standard JGJ/T229 "Code for Green Design of Civil Buildings"

6.

6.

Beijing Local Standard DB11-938 "Beijing Green Building Design Standard"

The clause 7.

Zhejiang local standard DB33/1092 "Green Building Design Standard", design requirements for green buildings above two-star level:

5.
3.
2 Building roof design.
.
.
Light-colored finishing materials should be used, and white or light-colored reflective thermal insulation coatings should be used.
"

5.
4.
14 Exterior wall design.
.
.
Use light-colored finishing materials, preferably white or light-colored reflective heat-insulating paint
.

Guangdong Provincial Local Standard DBJ/T 15-201 "Guangdong Province Green Building Design Code"

Insulation design of envelope structure 5.
3.
10 Description: Applying thermal insulation coating on the roof is another very effective method to solve the problem of roof insulation.
Thermal insulation coating can reflect a large amount of solar radiation, thereby reducing the temperature of the roof surface
.
Of course, the roof covered with thermal insulation paint will also reflect part of the solar radiation in winter, so the more south, the more suitable this technology is
.

Most of these standards mention the disadvantages of reflective insulation coatings in winter
.
Can it avoid the disadvantages of reflective insulation coatings in winter? If it is equipped with both thermal insulation and thermal insulation, it can be used in green buildings and passive houses to reduce the thickness of the insulation layer, which not only increases the internal space of the building, but also reduces potential safety hazards
.

Use of functional materials in green buildings

National industry standard JGJ/T 229-2010 "Code for Green Design of Civil Buildings"

7.
3.
5 Functional building materials are building materials that have functions that are beneficial to environmental protection or human health during use, and have a relatively small load on the earth's environment
.
Its main characteristics are: ①It has the functions of purifying, treating and repairing the environment during use; ②No secondary pollution is formed during its use; ③It is easy to recycle or regenerate
.
Such products have multiple functions, such as anti-corrosion, anti-moth, anti-mildew, deodorization, heat insulation, humidity control, anti-bacterial, anti-radiation, anti-static, etc.
, and even have the function of regulating human body functions
.
For example: antibacterial materials, air purification materials, health functional material, an electromagnetic wave shielding material and the like
.

Zhejiang Green Building Design Standard

6.
2.
8 Formaldehyde, benzene, toluene, organic volatiles, and man-made mineral fibers in indoor air are the main pollutants that endanger human health
.
In order to actively provide an environment conducive to human health, this article encourages the selection of building materials that have the function of improving the ecological environment of the house and health care
.
At present, many domestically developed materials that are beneficial to improving the indoor environment and human health, such as: multi-functional materials with antibacterial, anti-mildew, deodorizing, heat insulation, humidity control, fire prevention, anti-radiation, anti-static and other functions
.
The research and development of these new materials provide a basic material guarantee for the construction of good indoor air quality
.

Green Building Design Code of Hunan Province

8.
3.
2 Functional building materials are building materials that have functions that are beneficial to environmental protection or human health during use, and have a relatively small load on the earth's environment
.
Its main characteristics are: ①It has the functions of purifying, treating and repairing the environment during use; ②No secondary pollution is formed during its use; ③It is easy to recycle or regenerate
.
Such products have multiple functions, such as anti-corrosion, mothproof, mildew proof, deodorant, heat insulation, humidity control, antibacterial, anti-radiation, antistatic, etc.
, and even have the function of regulating human body functions
.
For example: antibacterial materials, air purification materials, health functional material, an electromagnetic wave shielding material and the like
.

8.
3.
3 When selecting exterior wall decoration materials (especially high-rise buildings), materials with better durability should be selected to extend the time interval for exterior facade maintenance and repair
.
Because of the low cost of construction in our country, more paints and facing bricks are used for exterior wall decoration materials
.
The paint needs to be repainted every 5 years or so, and the maintenance cost is relatively high, especially in high-rise buildings
.
Facing bricks often fall off due to the quality of construction, and it is easy to cause safety hazards when applied to high-rise buildings.
.
.

These standards all require or recommend the selection of building materials with some functions, such as heat insulation, heat preservation, deodorization, humidity control, fire prevention, antistatic, air purification, and health care functional materials
.
Is there such a material that can combine many functions and one body?

The answer is yes, it is thermal insulation coating
.

Thermal problems in the application of reflective insulation coatings

What is excellent reflection and heat insulation performance

Excellent reflection and heat insulation performance must not only have a high solar reflectance, but also a high radiation power
.
The reflection of sunlight is not equal to the reflection of solar radiation.
The reflection of solar radiation includes the radiation power of the reflection of sunlight and heat radiation on the surface of the object, which is a comprehensive value
.

Equivalent thermal resistance

Ordinary white reflective thermal insulation paint reduces the indoor temperature by reducing the heat entering the room from the exterior wall and roof in summer, which is equivalent to adding an equivalent thermal resistance to the enclosure structure; while in winter, it is the opposite, which is equivalent to adding an equivalent thermal resistance to the enclosure structure.
An equivalent thermal resistance is reduced, the indoor heat is transferred to the outside faster, and the indoor heating energy consumption is increased
.

Thermal insulation coating

Thermal insulation coatings, when the external temperature is high in summer, can effectively inhibit the external heat from entering the room to achieve a cooling effect; when the external temperature is low in winter, it can inhibit the internal heat transfer to the outside to achieve a thermal insulation effect, which solves the common reflection Disadvantages of thermal insulation coatings in winter
.
The following is an applied research on the thermal characteristics of thermal insulation
.
The main component of this coating is micron-level special hollow ceramic microspheres
.

Heat transfer characteristics

Immerse the container with higher temperature water in lower temperature water

Heat is transferred from a place with a higher temperature to a place with a lower temperature

When heat is transferred from a container containing higher temperature water, the temperature of the surrounding water will rise
.
When the temperature of the two reaches the same, the heat transfer will stop

Heat transfer characteristics of buildings

The temperature field of the walls, roofs, etc.
of houses caused by the periodic changes of solar radiation over time, and the periodic changes of the temperature of the earth's surface layer caused by the change of seasons, etc.
, belong to the periodic unsteady heat conduction process
.

Solar radiation reflectivity

Tested by the Japan Paint Inspection Association, thermal insulation coatings have strong solar radiation reflectivity.
When the film brightness L*=0.
94, the reflectivity of the solar radiation full wavelength range (300-2100nm) is 87.
9%; the visible light range ( The reflectivity of 300-780nm) is 86.
5%; the reflectivity of the near infrared range (780-2100nm) is 89.
5%
.

Thermal storage coefficient

The heat storage coefficient of the material
.
In layman's terms, it is the ability of the material to store heat
.
The smaller the value, the smaller the heat absorbed per 1K increase in the temperature of the material, which means that the surface temperature of the material can easily adapt to the outside temperature
.
The heat storage coefficient is related to the thermal conductivity, specific heat and density of the material
.

Calculation formula of heat storage coefficient:

Thermal storage coefficient = (thermal conductivity × specific heat × density) 0.
5

Calculated:

The heat storage coefficient of thermal insulation coating is 37.
6% of that of ordinary coatings, indicating that it can adapt to ambient temperature better than other coatings
.
It shows that as long as it absorbs or releases other coatings to absorb or release 37.
6% of the heat, it can be consistent with the surface temperature of other coatings
.

The relationship between heat storage coefficient and ambient temperature

For substances with "high" heat storage coefficient, the surface temperature is not easy to adapt to the ambient temperature, and the heat storage is large
.
Absorb or release the same amount of heat, and the temperature difference between the surface and the air is large
.

Substances with a "low" heat storage coefficient have a surface temperature that easily adapts to the ambient temperature, and the heat storage is small
.
Absorb or release the same amount of heat, and the temperature difference between the surface and the air is small
.

The effect of the temperature difference between the coating film and the environment on heat transfer

The heat storage coefficient is large, the temperature difference is large, and the heat transfer is large
.

The heat storage coefficient is small, the temperature difference is small, and the heat transfer is small
.

Since the coating film of the thermal insulation coating can quickly adapt to the ambient temperature, the temperature difference between the coating film and the environment is reduced, thereby inhibiting the transfer of heat
.

Heat radiation ability of coating film

According to Stefan-Boltzmann law

E = ε σT4

 Among them: E is the radiation force; ε is the emissivity; σ=5.
67×10-8 W·m-2·K-4, which is the Stefan constant; T is the temperature
.

According to experiments, the far-infrared emissivity of GAINA coating film reaches ε = 0.
946 at 41.
2°C, that is, the emissivity is 94.
6%
.

Under the same temperature, the higher the emissivity, the stronger the radiation power
.

Generally, the emissivity has the characteristic of increasing with the increase of temperature, but the thermal insulation coating has the characteristic that it can play its role even in the normal thermal environment
.

Reference: absolute black body, ε = 1

Black coal, ε= 0.
75 (80℃)

ε= 0.
855 (300℃)

※ New discovery of heat radiation ability

Normal materials radiate far-infrared rays, and the thickness must reach 200μm-400μm
.
The thermal insulation coating can radiate far-infrared rays with a thickness of 1/10 to 1/20 of that of general building materials
.
And the time is shorter, with less energy you can start to emit far infrared rays
.

Heat transfer test

experiment method:

1.
Use high and low temperature test chambers to simulate indoor and outdoor scenes, with dimensions of W 2500 × D 3000 × H 3000 mm respectively
.

2.
The test piece is painted with heat insulation coating on one side, the color is N95
.
Install a non-contact infrared radiometer on the side where the thermal insulation coating is applied to measure the heat flux density
.
The comparison test piece is painted with ordinary paint, and the substrate, color and film thickness are the same as the test piece painted with heat insulation coating
.

3.
In the first step, the indoor simulated room will no longer be maintained when the set temperature is 30°C, and the outdoor simulated room will no longer be maintained when the set temperature is 10°C.
Record the heat flux density and thermal insulation performance of the two specimens respectively; Step, the indoor simulation room will no longer be maintained when the set temperature is 10℃, and the outdoor simulation room will not be maintained when the setting temperature is 30℃.
Record the heat flux density and thermal insulation performance of the two specimens respectively
.
The test time is 2 hours
.

The test was completed by the Japan Institute of Industrial Technology
.

Experimental equipment (cold box and hot box)

The first step is to simulate heat transfer from outdoor to indoor

Heat flux (heat flow) density curve when the external temperature is high

Test conclusion: the coating film can inhibit heat transfer from the front side of the coating film

The second step is to simulate heat transfer from indoor to outdoor

Heat flux (heat flow) density curve when the external temperature is low

Test conclusion: the coating film can inhibit heat transfer from the back of the coating film

Application scenario: painting on the exterior wall

Reflection + radiation + coating film temperature adapt to ambient temperature (less heat exchange) + coating film low thermal conductivity → prevent external heat from intruding → heat insulation
.

Reflection + radiation reduction + coating film temperature adapt to ambient temperature (less heat exchange) + coating film low thermal conductivity → prevent external heat from intruding → heat preservation
.

Application scenario: painting on interior walls

Reduced reflection + reduced radiation + temperature of the coating film adapts to the ambient temperature (less heat exchange) + low thermal conductivity of the coating film → prevents the intrusion of external heat → heat insulation
.

Reflection + radiation + coating film temperature adapt to ambient temperature (less heat exchange) + coating film low thermal conductivity → prevent indoor heat transfer out → heat preservation
.

From the test results, whether it is used internally or externally, it is effective day and night in summer or winter
.
It is effective even without the influence of solar radiation
.

Comfort test

☆Impact on human body's radiant heat exchange and metabolism

experiment method:

1.
Use gypsum board to build two experimental rooms, one is painted with GAINA on the internal walls and ceiling, and the other is painted with other paints of the same color
.

2.
The tester wears a breathing mask, which can measure oxygen consumption
.
Put a thermometer on your body's skin to measure your body temperature
.

3.
The tester first sits quietly in two rooms for 120 minutes to measure oxygen consumption and skin temperature, and then exercise for 30 minutes to measure oxygen consumption and skin temperature
.
The human metabolic rate is measured by breathing oxygen consumption
.

Test Conclusions:

A room painted with thermal insulation paint can increase the body's metabolism, especially when the body is exercising, it can increase the body's metabolic rate by 10%, and has a health care function
.

According to the Japanese Ministry of Health, Labour and Welfare's "Japanese Dietary Intake Standards", if the metabolic rate is increased by 10%, the human body's function is equivalent to that of when it was 10 years younger
.
The reason is to paint the GAINA room to promote heat dissipation of the human body
.

This experiment was completed by the University of Tsukuba
.

Paint heat insulation paint in the room on the left, paint other paints in the room on the right

★ ★ ★

★ ★ ★

Human metabolic rate transition curve Metabolic rate at each age

Skin temperature transition curve Rectal temperature transition curve

☆ Even room temperature

experiment method:

In two identical rooms, one room is painted with GAINA, the other room is painted with other paints, and the temperature difference between 0.
1-1.
1m on the floor of the room is tested
.

Experimental conclusion: The room temperature difference of thermal insulation coating is 1.
79℃, which is lower than the 3℃ standard stipulated by ISO7730
.
The room temperature is more comfortable
.

This experiment was completed by Tokyo Metropolitan University
.

Painted GAINA's room

Room painted with other paint

Painted GAINA's room

Room painted with other paint

According to ISO7730, the requirements for high-comfort indoor temperature difference: The temperature difference between 0.
1-1.
1m from the ground is ≤3℃
.

☆ Effects on body temperature during sleep in winter

experiment method:

1.
Two identical rooms, one room is painted with thermal insulation paint, and the other room is painted with other paints
.

2.
Maintain a room temperature of 24°C before 0 o'clock in the middle of the night, and stop heating at 0 o'clock
.
The temperature of the body surface of the test subject was photographed with a thermal phase meter every 2 hours
.

Test conclusion: In winter, the human body sleeps more comfortably in a room painted with heat insulation
.

This experiment was completed by Shimane University
.

★ ★ ★

Human body temperature change with thermal insulation coating

Human body temperature changes when other paints are applied

☆ Reduce noise

experiment method:

1.
The walls and ceilings of the rooms on the first floor are painted with thermal insulation paint
.

2.
Make various noises on the second floor, such as falling spoons, shooting basketballs, playing CD music, turning on the vacuum cleaner, draining the toilet and other noises.
Use a decibel meter to measure the noise in the room on the first floor and compare the noise values ​​before and after construction
.

Experimental results:

As shown in the figure below, the noise is reduced by 7dB, 8dB, 8dB, 2dB, 9.
5dB respectively
.

★ ★ ★

Decibel reduction of each noise source

☆ Negative oxygen ion

experiment method:

1.
Paint heat-insulating paint in Room 202 on the second floor of a residential building, and paste wallpaper in Room 102 on the first floor
.

2.
Measure the content of negative ions in the air with an air ion detector in each of the two rooms
.

Experimental results:

The negative ion content in the room where the thermal insulation coating is applied is 4.
3 times that of the room where the wallpaper is applied
.

The high content of negative ions in the air can achieve the functions of deodorization and air purification, and meet its design requirements in the green building design code
.

The higher the content of negative ions in the air, the fresher the air and the more beneficial it is to the human body
.

The average value of negative ions in the GAINA room is 2360/cc

The average value of negative ions in the wallpaper room is 550/cc

Can solve other problems of green buildings

☆ Condensation problems in green buildings

When the room temperature is lower than the indoor air dew point temperature, condensation will occur on the wall surface, commonly known as flooding
.
Too high humidity will reduce the quality and durability of structural materials, hinder indoor hygiene and human health, and affect the beauty of the building
.
There are related requirements in the design code of green buildings
.

The heat storage coefficient of the thermal insulation coating calculated above is very low, and it can quickly adapt to the ambient temperature, so that the wall coating temperature can adapt to the air temperature.
Humidity control function
.

In addition, the thermal insulation coating has developed a special anti-condensation coating for the phenomenon of condensation, which can solve the problem of condensation in various extreme humid conditions
.

☆ Thermal expansion and contraction of green buildings and thermal bridge problems

The thermal insulation coating has a low heat storage coefficient and can quickly adapt to the ambient temperature, so that the wall coating temperature can adapt to the air temperature
.
This can solve the building fatigue cracking caused by the periodic fluctuation of the temperature difference between day and night, and prolong the service life of the building
.

The thermal bridge effect is more common in brick-concrete buildings, and due to the influence of various factors such as temperature, humidity, heat, etc.
, there will be "the same building, some households have serious mildew, and some households are fine.
" Situation
.
Thermal insulation coatings can inhibit the uneven heat transfer, whether used externally or internally, thereby reducing the problem of thermal bridges caused by uneven heat transfer
.

☆ High durability problem

"Coatings need to be repainted every 5 years or so, and the maintenance costs are high, especially for high-rise buildings
.
" (Excerpted from Article 8.
3.
3 of the "Green Building Design Code" of Hunan Province), thermal insulation coatings have undergone a 2000h weather resistance test, and their performance It can also meet the requirements, it is 2-3 times the life of ordinary exterior wall coatings, and the life of thermal insulation coatings can exceed 15 years
.

GB/T9755 "Synthetic Resin Emulsion Exterior Wall Coatings" stipulates that qualified products, first-class products, and superior products can be subjected to 250h, 400h, and 600h aging tests respectively; JG/T206 "Acrylic Coatings for Exterior Wall External Insulation" stipulates I and II The type aging test is 600h and 1500h
.

☆ Light pollution of green buildings

The thermal insulation coating has an ultra-low gloss of 1 degree, nearly 100% of diffuse reflection light, and no glare
.
Under the condition of ensuring the thermal function, the thermal insulation coating has hundreds of colors and appearances to meet the design requirements of individual buildings
.

☆ Anti-static problem

After testing, the surface charge of the thermal insulation coating film is 0
.
It is not easy to absorb particles floating in the air, so that the coating film is not easy to accumulate dust
.

Static electricity is very harmful to people's life and production.
It is easy to cause fire in some fire-prone places; to the human body, it can cause abnormal nerve cell membrane current conduction, affect the human central nervous system, and make people feel fatigue, irritability, insomnia, and headache
.

☆ Construction problems

The construction of thermal insulation coating is convenient and simple
.
The construction is consistent with ordinary interior and exterior wall coatings
.