JP4595568B2 - Double roof structure - Google Patents

Description

    The present invention relates to a roof structure of a building, and relates to a double roof structure that improves the heat insulation characteristics of a roof heat insulation ventilation method.

    Since it is effective for forming a comfortable indoor environment and saving energy to make the exterior of a building a heat insulating structure, various techniques have been proposed for the heat insulating structure. Among them, heat input control from the roof is one of the most important issues in the summer.

    Broadly speaking, there are a roof insulation ventilation method and a heat insulation double folded plate roof structure to prevent the solar heat incident on the roof surface from flowing into the room.

Non-Patent Document 1 relates to a roof heat insulation ventilation method, which describes a method of laying a heat insulating material on a field board and providing a ventilation layer on the top to spread the roof material. The ventilation layer has a function of exhausting the heat of the roof material, which becomes high due to solar radiation, through a ventilation hole provided in the upper part of the building, and effectively blocks the solar radiation indoors. The following two points can be given as the action of the ventilation layer.
(1) When the air in the ventilation layer is heated by heat transfer from the upper covering material, a ventilation driving force due to buoyancy acts and the air is exhausted from the upper part of the building to the outside, so that the amount of heat flowing through indoors is reduced.
(2) Since the upper material to be heated by solar radiation and the lower structure are separated by the ventilation layer, it is possible to suppress direct solar heat from flowing through the lower structure by heat conduction.

    Patent Document 1 relates to a heat-insulated double folded plate roof, a metal that normally becomes a heat bridge in a structure in which metal roofing material is double-spreaded and the gap is filled with heat insulating material to prevent the solar heat from flowing into the room indoors. The heat insulation of the connection member of the upper folded board and lower folded board of a roof material is improved, and the heat flow from an upper folded board to a lower folded board is suppressed.

    It is pointed out that the insulation double-folded roof has a heat insulation effect that depends on the thickness of the heat insulation material. Yes.

  FIG. 6 shows a schematic structure of an example of a heat insulating double folded plate roof, in which a heat insulating material 300 is sandwiched between an upper roof material 100 and a lower roof material 200.

In addition, as a technique for improving the heat insulating property of the roof, which does not belong to these methods, a technique for applying a coating containing glass beads or the like to the surface of the roof and exhibiting a heat shielding effect has been developed.
Explanation article "Next-generation energy-saving standards and guidelines for houses" P237-256 Japan Housing and Architecture Energy Conservation Organization JP-A-7-207844

    The effect of the ventilation layer in the roof insulation ventilation method is 30 mm when calculated by assuming that the ventilation layer reduces the solar absorptivity and long-wavelength radiation (definition: radiation emitted at normal temperature) of the exterior material. The result is that the heat flow through is reduced by about 10% with a ventilation layer with a width of.

    However, no proposal has been made to effectively demonstrate the effect of this construction method, and the heat shielding effect of the ventilation layer has not been sufficiently obtained.

    An object of this invention is to provide the metal double roof which improves the efficiency of a roof heat insulation ventilation method, and has the outstanding heat insulation effect.

The present inventors examined in detail about the influence which the presence of the ventilation layer in the roof insulation ventilation method has on the heat flow of solar heat from the roof to the lower structure. Generally, in the heat insulation design of the roof, 20 kcal / m ² h ° C. is used as the total heat transmissivity on the outside air side.

    The total heat transfer coefficient is composed of a convective heat transfer coefficient and a radiant heat transfer coefficient, and the convective heat transfer coefficient is premised on a normal wind speed of 3 m / s. In this case, the contribution of the radiant heat transfer coefficient is about 25%. However, recent studies reveal that the actual wind speed in the ventilation layer is about 0.1 m / s, and the convective heat transfer coefficient in this case is reduced to about １ ／.

    As a result, the ratio of the transmission rate by radiant heat becomes relatively high, and the amount of heat transfer by radiation between the upper and lower facing materials sandwiching the ventilation layer is an important factor for improving the heat insulation effect. I found out.

In this study, the calculation of the convective heat transfer coefficient was based on the Jurges forced convection heat transfer coefficient calculation formula (α _c = 5.0 + 3.4 v, v: wind speed m / s).

From the above examination, the problem of the present invention is solved by the following means.
1 A roof structure in which a ventilation layer is provided between an upper facing material and a lower facing material, wherein the long wavelength emissivity of the lower surface of the upper facing material facing the ventilation layer is the lower facing surface facing the ventilation layer. A roof structure characterized by being larger than the long wavelength emissivity of the upper surface of the material, wherein the long wavelength emissivity of the upper surface of the lower covering material is less than or equal to the long wavelength emissivity of the lower surface of the lower covering material.
(2) A roof structure in which a ventilation layer is provided between an upper facing material and a lower facing material, wherein an upper surface of the lower covering material is covered with a heat insulating material, and a long wavelength of a lower surface of the upper facing material facing the ventilation layer The emissivity is larger than the long wavelength emissivity of the upper surface of the heat insulating material facing the ventilation layer, and the long wavelength emissivity of the upper surface of the heat insulating material is equal to or lower than the long wavelength emissivity of the lower surface of the lower covering material. A roof structure characterized by that.
[3] The roof structure according to [1] or [2], wherein a long wavelength emissivity of a lower surface of the upper covering material is larger than a solar radiation absorption rate and / or a long wavelength emissivity of an upper surface of the upper covering material.
[4] The roof according to any one of [1] to [3], wherein the surface facing the ventilation layer is painted, coated or plated with a material containing at least one of zinc, lead, magnesium, aluminum, and titanium. Construction.

    ADVANTAGE OF THE INVENTION According to this invention, in the roof structure which employ | adopts a roof heat insulation ventilation method, the heat insulation efficiency of a ventilation layer improves, the outstanding heat insulation characteristic is acquired reliably, and construction of a favorable thermal environment is attained.

    The present invention is directed to a roof structure that employs a roof insulation ventilation method, in order to suppress the flow of solar heat into the indoor space, to reduce the amount of heat transferred from the upper roofing material to the lower flooring material that is disposed with the ventilation layer interposed therebetween. It is characterized by improving the heat insulating properties of the structure, suppressing radiant heat transfer in the ventilation layer, and promoting the heat shielding effect against solar radiation and heat dissipation in indoors that have become hot.

    The most desirable mode is to reduce the solar absorptivity on the outdoor surface of the upper covering material to suppress the solar absorptivity and increase the long wavelength emissivity to enhance the radiation cooling effect. And it is good to make small the long-wavelength emissivity of each surface which faces the ventilation layer of an upper covering material and a lower covering material.

When the wall surface or room temperature becomes high due to the western sun in the summer, the long-wavelength emissivity of the surface facing the indoor side of the underlaying material is set to be greater than or equal to the inside of the ventilation layer, so that the radiation from the indoor side is absorbed and the ventilation layer It is configured to exhaust heat.

FIG. 1 is a schematic cross-sectional view showing an example of a roof structure by a roof insulation method to which the present invention is applied. In the figure, 1 is a roof structure, 2 is an upper covering material, 3 is a lower covering material, and a ventilation layer is provided between the upper covering material 2 and the lower covering material 3. Arrows in the ventilation layer indicate the direction of air movement due to natural ventilation.

    FIG. 2 is a partial sectional view of the roof structure shown in FIG. In the present invention, the long-wavelength emissivity of the lower surface 21 facing the ventilation layer of the upper covering material 2 is made larger than the long-wavelength emissivity of the upper surface 31 facing the ventilation layer of the lower covering material 3. The long-wavelength emissivity of the upper surface 31 facing is set to be equal to or lower than the long-wavelength emissivity of the lower surface 32 of the lower covering material 3. In the present invention, the lower surface 32 of the lower material 3 is a surface facing the indoor side, and the upper surface 22 of the upper material 2 is a surface facing the outdoor side.

  The amount of radiant heat radiated from the upper material 2 to the lower material 3 depends on the difference between the form factor of the lower surface 21 and the upper surface 31 facing each other with the ventilation layer interposed therebetween, the long wavelength emissivity, and the fourth power of each absolute temperature. Proportional.

The amount of heat radiated from the indoor to the lower covering material 3 is also proportional to the indoor long wavelength emissivity and the long wavelength emissivity of the lower surface 32 of the lower covering material 3. The long wavelength emissivity is larger than the long wavelength emissivity of the upper surface 31 of the lower covering material 3 on the ventilation layer side, and the long wavelength emissivity of the upper surface 31 of the lower covering material 3 on the ventilation layer side is the indoor side of the lower covering material 3. If it is set to be equal to or lower than the long wavelength emissivity of the lower surface 32, the amount of heat transfer between the lower surface 21 and the upper surface 31 facing each other with the ventilation layer interposed therebetween is suppressed. The following more preferable forms are further conceivable for the above definition.
One form is that the long-wavelength emissivity of the lower surface 21 of the upper facing material 2 on the ventilation layer side and the upper surface 31 of the lower facing material 3 on the ventilation layer side is within the range of about 0.1 to 0.4. This is a case where the long wavelength emissivity is set to be larger than the long wavelength emissivity of the upper surface 31, and the radiant heat from the upper material to the lower material is reduced, and the heat insulation performance can be improved, which is more preferable.

  Furthermore, by setting the long wavelength emissivity of the lower side 32 of the lower facing material 3 to be equal to or higher than the upper surface 31 on the ventilation layer side, radiation heat input from the upper facing material 2 to the lower facing material 3 is suppressed. In addition, since the cold radiation from the cooled floor surface is absorbed, the temperature decrease rate of the indoor surface of the roof can be increased.

In another embodiment, the long wavelength emissivity of the lower surface 21 of the upper facing material 2 on the ventilation layer side is made larger than the long wavelength emissivity of the upper surface 31 of the lower facing material 3 on the ventilation layer side, and the lower surface 21 of the upper facing material 3 The long wavelength emissivity is made larger than the solar radiation absorption rate and / or the long wavelength emissivity of the upper surface 22 of the upper covering material.
Originally, if the solar radiation absorption rate on the upper surface of the upper material is made very small, and the long wavelength emissivity of the upper surface 22 on the outdoor side of the upper material 2 is made larger than that of the lower surface 21 on the ventilation layer side, Since the temperature rise is suppressed and atmospheric radiation is promoted, and the upper roofing material 2 is prevented from reaching a high temperature, the amount of heat passing through from the roof to the room is greatly reduced, which is a very preferable mode.
However, in general, a material having a large long wavelength emissivity often has a large solar absorptivity except glass. If the solar radiation absorption rate of the upper surface 22 on the outdoor side of the upper roofing material 2 is increased, the effect of increasing the surface temperature due to solar radiation becomes greater than the cooling effect due to atmospheric radiation by increasing the long wavelength emissivity, as described above. It is difficult to expect improved heat shielding performance.
Therefore, in order to suppress the absorption of solar radiation by reducing the solar radiation absorption rate of the upper surface 22 of the upper facing material 2 on the outdoor side, and to promote cooling by radiation, the long wavelength radiation of the lower surface 21 on the ventilation layer side By making the rate very large, the amount of heat stored in the upper material 2 is radiated into the ventilation layer to promote heat dissipation.
In this case, the long wavelength emissivity of the lower surface 21 of the upper facing material 2 on the ventilation layer side is about 0.8 to 1, and the long wavelength emissivity of the upper surface 31 of the lower facing material 3 on the ventilation layer side is 0.1 to 0. It is particularly desirable that the solar radiation absorption rate of the upper surface material 22 of the upper facing material 2 is about 0.1 to about 0.4.
Since the heat radiation amount is proportional to the long wavelength emissivity and the fourth power of the absolute temperature as described above, in this embodiment, the amount of heat radiated from the upper material 2 into the ventilation layer increases, and the temperature of the upper material 2 decreases. Can be promoted. On the other hand, the long wavelength emissivity of the upper surface 31 of the lower facing material 3 on the ventilation layer side is very small, and by reflecting most of the radiant heat from the upper facing material 2, the amount of radiant heat transfer to the lower facing material 3 is It becomes even smaller. Although the temperature of the air in the ventilation layer rises, since it is discharged from the natural exhaust port provided in the ridge, the heat absorption of the lower covering material 3 can be reduced.

    Further, since the amount of heat radiated indoors from the lower covering material 3 is larger than the radiant heat absorbed by the lower covering material 2 from the upper covering material 2, the amount of heat retained as the roof structure is quickly reduced, and the heat shielding performance is improved.

  The finish of the upper surface 22 on the outdoor side of the upper facing material 2 is preferably used in a metallic glossy color, clear coating, or glossy white coating because the solar absorptance and long wavelength emissivity can be reduced. Although it is preferable to use a plated steel plate, a stainless steel plate, an aluminum plate, etc. with a metallic luster color, it is not limited to these. When maintaining the solar radiation absorption rate on the surface for a long period of time, a photocatalyst material such as titanium oxide, a hydrophilic material such as a silicon compound, or a water repellent material such as a fluororesin is appropriately selected and further coated. In this case, the solar radiation absorption rate of 0.1 to 0.4 is maintained.

When reducing the long-wavelength emissivity of the surface on the ventilation layer side with the upper and lower materials, it is necessary to use a bright metal surface, a bright metal color, a bright plating surface, or a bright white coating. preferable. In particular, it is preferable to paint, coat or plate with a material containing at least one of zinc, lead, magnesium, aluminum and titanium. The material here is
a) any metal of zinc, lead, magnesium, aluminum, titanium b) an alloy containing at least one of the above a) c) a compound containing at least one of the above a) d) from the above a) Any one of paint or coating material containing at least one of c) is shown. More specifically, a plated steel plate (for example, a galvalume steel plate), a stainless steel plate, or an aluminum plate using the above a) or b) as a roofing material is used in a metallic luster color, or titanium oxide or aluminum is used for an appropriate roofing material. It is preferable to use a glossy white pigment with a component of. In addition, the surface finishing materials of these upper and lower facing materials are not limited to these as long as the same effect is obtained.

  In the present invention, it is also possible to cover the upper surface of the lower covering material with a heat insulating material to further improve the heat insulating performance. In this case, the heat shielding effect of solar heat can be enhanced. FIG. 3 shows a partial cross-sectional view of the roof structure in which the upper surface of the lower covering material 3 is covered with the heat insulating material 4.

  When covering with the heat insulating material 4, the long wavelength emissivity of the upper surface 41 of the heat insulating material 4 facing the ventilation layer is set similarly to the long wavelength emissivity of the lower surface 31 on the ventilation layer side of the lower covering material 3 in FIG. To do. That is, the long wavelength emissivity of the upper surface 41 of the heat insulating material 4 on the ventilation layer side is set to be equal to or lower than the long wavelength emissivity of the lower surface 32 of the lower covering material 3 on the indoor side.

  The setting of the long wavelength emissivity of the upper surface 41 of the heat insulating material 4 facing the ventilation layer can be realized by using a surface finishing material. For example, it is preferable to cover with a glossy metal sheet such as an aluminum vapor-deposited sheet or a glossy white sheet, or to apply a glossy white coating, but it is not limited to these as long as the same effect is exhibited. An example at the time of using a surface finishing material in FIG. 4 is shown typically.

  As the heat insulating material 4, inorganic fiber heat insulating materials such as rock wool and glass wool, and organic board heat insulating materials such as polystyrene foam, polyethylene foam, phenol foam, and urethane foam can be used, but the present invention is not particularly limited.

  Hereinafter, the present invention will be described in detail with reference to examples.

  The roof structure shown in FIG. 2 was used, and the space between the upper covering material 2 (lower surface 21) and the lower covering material 3 (upper surface 31) was set to 30 mm to form a ventilation layer.

  In the embodiment of the present invention, the upper covering material 2 is a steel roofing material, the outdoor surface 22 is a dark brown colored steel plate (sunlight absorption rate 0.9, long wavelength emissivity 0.8), and the surface on the ventilation layer side. No. 21 was coated with a bright white pigment (long wavelength emissivity of 0.1 or more and 0.4 or less) based on titanium oxide or aluminum. A bright white pigment (long wavelength emissivity) made of titanium oxide or aluminum as a base material and made smaller than the surface 21 on the ventilation layer side of the upper material is formed on the upper surface 31 on the ventilation layer side of the lower material 3. 0.1 to 0.4). The indoor side surface 32 was painted beige (long wavelength emissivity 0.8).

  On the other hand, in the comparative example, the upper roofing material 2 is a roof material of a normal coated steel plate, and the outdoor surface 22 is a dark brown colored steel plate (solar absorption rate 0.9, long wavelength emissivity 0.8). Since no special consideration is given to the lower surface 21 of the ventilation layer 2 of the straw material 2, the upper surface 31 of the ventilation layer side of the lower material 3, and the lower surface 32 of the indoor side, beige-based coating (long wavelength emissivity 0. 8).

The results of effect comparison are shown below. Topping material 2 when solar radiation is 740 (kcal / m ² h ° C), night radiation 26 (kcal / m ² h ° C), outside air temperature 31 (° C), wind speed (3 m / s), room temperature 28 (° C) The surface temperature of this was 63 ° C., and the temperature of the lower surface 32 on the indoor side of the lower covering 3 was 31 (° C.).

Amount of radiation heat to Q ₁ ventilation layer portion of the specification of this embodiment,
Q ₁ = (0.1 to 0.4) ² × 4.876 × 10 ⁻⁸ × ((63 + 273.16) ⁴ − (31 + 273.16) ⁴ ) = 2.05 to 32.9 (kcal / m ² h ° C).

On the other hand, radiation heat transfer amount _{Q 2} of the ventilation layer portion of the comparative ^{_{example, Q 2 = 0.8 2 × 4.876}} × 10 -8 × ((63 + 273.16) 4 - (31 + 273.16) 4)
= 131.4 (kcal / m ² h ° C.), and according to this embodiment, the amount of radiant heat transfer can be about 1.5 to 25%.

If the wind speed in the ventilation layer is 0.1 m / s and the convection heat transfer amount is common to the upper and lower winder material sides, and is 5.34 (kcal / m ² h ° C.), the convective heat transfer amount Qc. = 1 / (1 / 5.34 + 1 / 5.34) × (63-31) = 85.4 (kcal / m ² h ° C.) Therefore, the amount of heat input to the lower covering material 3 is determined by the heat of the ventilation layer. Comparing by the evaluation on the safety side ignoring the resistance, this example shows 86.8 to 118.3 kcal / m ² h ° C., while the comparative example shows 216.8 kcal / m ² h ° C. In this example, It was confirmed that the amount of heat input to the wood material 3 can be suppressed to about 40 to 55% of the normal amount. FIG. 5 schematically shows the result of effect comparison.

The formula used for this trial calculation is shown below.
Amount radiant heat transfer _{Q r = ε 1 ε 2 σ} (T 1 4 -T 2 4)
ε ₁ : Upper wood long wavelength emissivity (lower surface 21)
ε ₂ : Long wavelength emissivity of the lower material (upper surface 31)
σ: Stefan Boltzmann constant (4.876 × 10 ⁻⁸ kcal / m ² h ° C.)
T ₁ : Upper wood temperature (K)
T ₂ : Lower wood temperature (K)

  In the roof structure shown in FIG. 2, the space between the upper covering material 2 (lower surface 21) and the lower covering material 3 (upper surface 31) was set to 50 mm to form a ventilation layer.

  In the embodiment of the present invention, the upper covering material 2 is a steel roofing material, the outdoor surface 22 is a white colored steel plate (sunlight absorption rate 0.3, long wavelength emissivity 0.5), and the surface 21 on the ventilation layer side. Was coated with a black pigment (long wavelength emissivity of 0.9 or more and 1 or less).

  The upper surface 31 on the ventilation layer side of the lower covering material 3 is coated with a glossy white pigment (long wavelength emissivity of 0.1 or more and 0.4 or less) based on titanium oxide or aluminum, The surface 32 was painted beige (long wavelength emissivity 0.8).

  In this configuration, heat is radiated from the upper material 2 into the ventilation layer, but the radiation from the lower material 3 is reflected, and the air in the ventilation layer is warmed and discharged by natural convection. When the temperature condition is the same as in Example 1, the initial radiation amount is larger than that in Example 1. However, since the heat dissipation effect to the ventilation layer is large, the cooling rate of the upper material 2 is higher than that in Example 1. Get faster.

  If the upper surface of the upper facing material 2 is configured as in the present embodiment, the surface temperature rise due to solar radiation absorption is suppressed, so the temperature condition is lower than in the first embodiment and a predetermined effect is obtained. Here, a white colored steel plate is illustrated, but the effect is further enhanced if the metallic gloss color is used.

  The calculation of this configuration is as follows.

  When the equivalent outside air temperature SAT (° C.) is determined as the surface temperature of the upper material 2 from the weather conditions during the experiment shown in Example 1, SAT = 31 + (0.3 × 740−0.5 × 26) / 20 = About 41 ° C. is obtained, which is 22 (° C.) lower than the conditions of Example 1.

  Even if the surface temperature of the lower material 3 is assumed to be 31 (° C.) as disadvantageous as in Example 1, the radiation transfer amount Qr = 6.0 to 26.8 (W / m 2) is obtained, and the same effect is obtained. Has been confirmed to be exhibited.

  In the roof structure shown in FIG. 4, the upper roofing material 2 is a steel roofing material, and the outdoor surface 22 is coated with zinc-aluminum alloy in a clear paint finish (irradiation rate 0.15, long wavelength emissivity 0.2) The surface 21 on the air-permeable layer side was coated with a black pigment (long wavelength emissivity of 0.9 or more and 1 or less).

  A heat insulating material 4 made of glass wool is disposed on the upper surface 31 of the lower covering material 3. An aluminum glass cloth (long wavelength emissivity 0.1 to 0.4) is disposed on the upper surface 41 of the heat insulating material 4 facing the ventilation layer with the glossy surface facing the ventilation layer.

  The space between the upper facing material 2 (lower surface 21) and the upper surface 41 facing the air-permeable layer of the heat insulating material 4 was 50 mm, and an open portion was provided in the outside air on the eaves and the building to form an air-permeable layer. The indoor surface 32 was painted beige (long wavelength emissivity 0.8).

  This configuration is the same as in Example 2 when the upper surface 41 facing the ventilation layer of the heat insulating material 4 is replaced with the upper surface 31 of the lower covering material 3 on the ventilation layer side. Although the amount of radiant heat transferred is the same as that of the second embodiment, the heat transfer amount from the ventilation layer to the room can be further reduced by disposing the heat insulating material 4 below the ventilation layer.

The fragmentary sectional view which shows an example of the roof structure using a roof heat insulation ventilation method. The elements on larger scale which show a part of roof structure using the roof heat insulation ventilation method. The elements on larger scale which show a part of roof structure (when using a heat insulating material) using the roof heat insulation ventilation method. The elements on larger scale which show a part of roof structure (when using a heat insulating material) using the roof heat insulation ventilation method. The figure which shows the relationship between the surface temperature and the time of the lower surface 32 of the lower material in an invention example (Example 1) and a comparative example. Conventional example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Roof structure using roof heat insulation ventilation method 2 Upper covering material 3 Lower covering material 4 Heat insulating material 21, 32 Lower surface 22, 31, 41 Upper surface 100 Upper covering material 200 Lower covering material 300 Heat insulating material

Claims (4)

A roof structure in which a ventilation layer is provided between an upper facing material and a lower facing material, wherein a long wavelength emissivity of a lower surface of the upper facing material facing the ventilation layer is the lower facing material facing the ventilation layer. The long-wavelength emissivity of the upper surface of the lower covering material is larger than the long-wavelength emissivity of the lower covering material, and the lower wavelength emissivity of the lower covering material is lower than the long-wavelength emissivity of the lower covering material. A roof structure in which a ventilation layer is provided between an upper and lower roofing material, wherein the upper surface of the lower heating material is covered with a heat insulating material, and the long wavelength radiation of the lower surface of the upper heating material facing the ventilation layer The rate is greater than the long wavelength emissivity of the upper surface of the heat insulating material facing the ventilation layer, and the long wavelength emissivity of the upper surface of the heat insulating material is less than or equal to the long wavelength emissivity of the lower surface of the lower covering material A roof structure characterized by The roof structure according to claim 1 or 2, wherein a long wavelength emissivity of a lower surface of the upper covering material is larger than a solar radiation absorptivity and / or a long wavelength emissivity of an upper surface of the upper covering material. The surface facing the ventilation layer is painted, coated or plated with a material containing at least one of zinc, lead, magnesium, aluminum, and titanium, according to any one of claims 1 to 3. Roof structure.

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