Shirasu-kabe’s Eco-Friendly Properties

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Shirasu-kabe and the Environment: The Green Features of Shirasu-kabe

1. Low Carbon Emission Manufacture

Shirasu consists of loose particles. Unlike silica soil etc., which is cut from lumps, it can be extracted easily without crushing. And the obtained shirasu is sun-dried to remove excess moisture, making calcination unnecessary.
Takachiho Shirasu-kabe is manufactured based on a total commitment to low tech methods, using human hands without depending on machinery wherever possible. It is an eco-conscious building material which consumes little energy and leaves only a small global environmental footprint.

2. Energy-Saving Properties

Shirasu-kabe’s outstanding humidity-conditioning properties help purify indoor air and keep indoor humidity at a comfortable level, reducing the power consumption needed for air-conditioners and air purifiers.

Cool Summers with Less Power Consumption

Lower humidity reduces the effective temperature (the temperature you feel). Since Shirasu-kabe helps regulate indoor humidity, it helps lower the effective temperature in summer. Air-conditioners can therefore be set a few degrees higher, reducing daily energy consumption and utility bills. And since Shirasu-kabe is also a highly effective thermal insulator, it can greatly help lower the energy consumption needed for heating and cooling throughout the year.

Measured Data Confirms Effectiveness

(Values were measured inside a second-floor room of a ‘shirasu + α’ home in Kashiwa, Chiba on August 27, 2007.)
Missenard’s formula: Effective temperature (ºC) = 1/2.3 × (Actual air temperature – 10) × (0.8 – Relative humidity/100)

2 am

6 am

10 am

2 am

6 am

10 am

Humidity (%)

59

59

59

59

58

59

Temperature (ºC)

32.2

31.3

32.5

33.6

34.1

33.4

Effective temperature (ºC)

30.2

29.4

30.4

31.4

31.8

31.3

Temperature difference (ºC)

-2.0

-1.9

-2.1

-2.2

-2.3

-2.1

Note that the difference between the effective temperature and actual air temperature is always about 2ºC. Shirasu-kabe’s humidity-conditioning property makes the room feel cooler. (It is said that setting air-conditioners higher by 1ºC reduces power consumption by about 10%.)

3. Long Life

Since shirasu is a natural inorganic ceramic material, it never fades or deteriorates, and its ability to regulate indoor humidity helps slow the aging of buildings and furniture that humidity accelerates.

4. Eco-Friendly Properties

Shirasu-kabe helps prevent global warming by reducing CO2 emissions in two ways.

(1)
Lower CO2 emissions during manufacture
The manufacturing process used to make Shirasu-kabe consumes little energy and produces low levels of CO2. Manufacturing conventional or diatomaceous earth plaster materials requires grinding or kiln-firing of the raw materials, but the raw material used to make Shirasu-kabe is originally a fine powder, so it doesn’t need grinding. Since Shirasu is a natural ceramic material created from magma sintered deep beneath the earth’s surface, it requires no kiln-firing. Only sun-drying is needed to turn it into a wall plaster material.
(2)
Lower CO2 emissions during use
Shirasu-kabe’s outstanding properties enable users to save power used for air-conditioners, helping reduce CO2 emissions.

Shirasu-kabe’s annual CO2 emission reduction per air-conditioner
(compared to conventional plaster; Takachiho estimates)

CO2 reduction from synergistic combination of
(1) Thermal insulation + (2) humidity conditioning

Power savings (percent)

Power savings (kW)

CO2 reduction

Heating

8% (max.)

41.6kW

16.6kg

Cooling

20% (max.)

43.2kW

17.2kg

Total

-

84.8kW

33.8kg

The assumptions below were used to calculate the table values and CO2 reduction per household.

Assumptions

  • Total floor space per household: 100 m2; number of air-conditioners in use per household: 3
  • Power consumption/CO2 reduction was calculated based on the power consumption of a typical household air-conditioner designed for a 10 m2 room (104 kWh/month for heating, 48 kWh/month for cooling), when used for heating for 5 months, and for cooling for 4.5 months.
  • When the cooling setting was increased by 1ºC and heating setting decreased by 1ºC, the annual CO2 reduction per air-conditioner was assumed to be 30 kg. (The figure given on the Tokyo Electric Power Company’s website is 32 kg.)

Annual CO2 reduction per household enabled by Shirasu-kabe = 90 kg approx.

(Theoretical value for use as a guideline only.)

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