People pay more and more attention to the excessive consumption of energy, and energy conservation has become an indispensable part of national development, while building energy conservation.
Energy saving is also the most important. Through the analysis and comparison of the most easily overlooked roof structure in the building envelope, the following conclusions can be drawn.
The advantages and disadvantages of different roof forms in energy saving and structure have the function of adapting to local conditions and learning from each other's strengths in future architectural design.
Key words: building roof energy saving; Roof form; Scope of application; Energy saving effect
Among many factors affecting building energy saving, the thermal insulation of building envelope is undoubtedly one of the most important factors.
The enclosed space consists of structural materials and surface decoration materials that separate indoor and outdoor, including walls, doors, windows and roofs. The shell structure must be balanced.
Ventilation and lighting requirements, and provide heat and moisture protection suitable for the climate conditions of the construction site. [1] Improving the thermal performance of building envelope is the guarantee.
One of the key problems of indoor thermal comfort conditions is energy consumption in building operation, and roof energy-saving technology is one of them.
An important part of; Roof energy-saving technology is closely related to the structural form of building roof, which can be roughly divided into structural insulation partition walls.
Hot roof, building thermal insulation roof, ecological covering thermal insulation roof, etc.
1 structural thermal insulation roof
Structural thermal insulation roof, which is often referred to as plate thermal insulation roof, is mostly added to the roof structure.
Add a layer of heat insulation material, and block the entry of external heat and the loss of internal energy through materials with low heat transfer coefficient and high thermal inertia. This type of house
The surface is roughly divided into traditional thermal insulation roof and inverted roof, the main difference is that the position of thermal insulation material layer in the roof structure is different.
1. 1 traditional thermal insulation roof
The traditional roof construction method, that is, vertical roof, generally adds insulation layer under the waterproof layer, because the traditional roof is insulated.
Generally, perlite, cement polystyrene board, aerated concrete, ceramsite concrete, polystyrene board (EPS) and other materials are used in the temperature layer.
The problem of high water absorption is widespread. If water is absorbed, the thermal insulation performance will be greatly reduced, which can not meet the requirements of thermal insulation, so waterproof layer must be made.
On the top, the purpose of heat preservation can be achieved by preventing the infiltration of water and ensuring the dryness of the insulation layer. In order to improve the thermal insulation of the material layer, it is best to choose the guide bar.
Materials with small thermal properties and large heat storage capacity should be considered, and materials with large capacity should be considered to prevent roof overload. Roof insulation is not
Materials with high water absorption should be selected to prevent the insulation layer from absorbing a large amount of water when the roof is wet, and to reduce the water that is not easy to be excluded in the hot material layer.
Designers can determine the thickness according to the thermal design calculation of the building. This type of roof is suitable for new buildings in cold areas and hot summer and cold winter areas.
Roof insulation of newly-built and rebuilt houses shall ensure that the difference between the inner surface temperature of the roof and the outdoor heating environment temperature in winter is less than 4℃.
1.2 Inverted roof
Figure 1 Inverted roof
The so-called inverted roof is the inverted form of external thermal insulation roof.
Type (as shown in figure 1), the insulation layer is designed on the waterproof layer, which is greatly weakened.
The waterproof layer is affected by the atmosphere, temperature difference and ultraviolet radiation of the sun, so it can be prevented.
The water layer is not easy to age, so it can maintain its softness and ductility for a long time.
Can effectively prolong the service life. [2] According to foreign data, it can be extended.
The service life of long waterproof layer is 2~4 times. The inverted roof saved the traditional house.
The air barrier on the surface and the leveling layer on the insulation layer simplify the construction and are more economical.
Even if there is leakage in some places, it can be handled by uncovering a few heat insulation boards, which is easy to maintain. At the same time, the structure of the inverted roof should be
The insulation layer should be made of materials with low water absorption, such as polystyrene foam board, foam glass and extruded polystyrene foam board. , and in heat insulation.
Concrete, cement mortar or dry-laid pebbles should be used as the protective layer on the insulation layer to avoid damaging the insulation material. When protective layer concrete is used,
Materials such as plates or floor tiles can be paved with cement mortar and cobblestones for protection, and a layer of puncture-resistant and durable should be paved between cobblestones and thermal insulation materials.
Fiber fabric with good corrosion resistance. [2] This kind of roof is suitable for building and rebuilding houses in cold areas and hot summer and cold winter areas.
Roof insulation, and can ensure that the temperature difference between the inner surface temperature of the roof and the outdoor heating environment in winter is less than 4℃; The service life of the waterproof layer can be prolonged.
2~4 times.
2 building form thermal insulation roof
Ventilation roof is a typical architectural form of thermal insulation roof. Ventilation roof changes the roof from a solid structure to a closed or ventilated roof.
Double-layer roof structure with air interlayer is widely used in hot summer and cold winter areas in China, especially in hot and rainy summer.
The roof structure shows its superiority. The roof has changed from a solid structure to a structure with closed or ventilated air compartments, passing through the air compartments.
The airflow on the first floor took away the solar radiation heat, which greatly improved the thermal insulation ability of the roof. [3] However, in the design and construction of ventilated roofs, it should be based on
The bearing capacity of base should be simplified, the length of ventilated roof and air duct should not be greater than 15 m, and the air interlayer should be about 200 mm; aerial
A distance of 250 mm should be set aside between the insulation board and the gable; At the same time, in the process of overhead thermal insulation construction, waterproof protection should be done well.
The principle of attic floor ventilation is the same as that of roof ventilation. The difference is that the attic has a high space and the ventilation effect is better than that of overhead step bricks.
The roof is good, and the attic has good rain and sun protection function, which can effectively improve the thermal quality of the roof of the house, as shown in Figure 2. This form of roof
It is suitable for roof insulation of new and renovated houses in hot summer and cold winter and hot summer and warm winter areas.
Figure 2 attic roof
Ventilation roof has obvious cooling effect. See table 1 for the thermal insulation effect of solid roof and ventilated roof under natural ventilation.
Table 1 Comparison Table of Thermal Insulation Effect between Ventilation Roof and Solid Roof℃
Difference of ventilation roof of solid masonry roof
The average temperature of the inner surface 29. 9 34.9 5
The highest temperature of the inner surface is 3 1. 1.39.48.3.
The average room temperature is 29 degrees. 7 3 1.3 1.6.
The highest room temperature is 30. 2 32.7 2.5
3 Eco-covered thermal insulation roof
Ecological covering thermal insulation roof is covered with ecological materials.
Building roofs are produced by using the changes of the covering itself to the surrounding environment.
Corresponding countermeasures to make up for the unfavorable energy loss of the building itself, including
Planting roofs and water storage roofs are typical.
3. 1 planting roof
In the past, there were many application examples of "soil storage planting" roof, which was usually called planting roof. At present, this kind of roof is widely used in buildings.
Widely used, the roof is used to grow grass and flowers, even shrubs, rockeries and fountains to form a "playground roof" or roof garden, which is ecological.
Fig. 3 Planting roof structure
Energy-saving roof. Planting a roof is to cover it with plants planted on the roof.
Solar energy is a heat insulation measure to prevent the room from overheating (Figure 3).
Its heat insulation principle has three aspects.
First, the shading effect of vegetation stems and leaves can effectively reduce the roof.
Outdoor comprehensive temperature, reducing the temperature difference of roof heat transfer; The second is plants.
Photosynthesis consumes solar energy for transpiration; The third is the vegetation foundation.
Evaporation of soil or water consumes solar energy. Therefore, planting roofs is one of the most important tasks.
Very effective thermal insulation and energy-saving roof, if the vegetation belongs to shrubs,
It can also help to solidify carbon dioxide, release oxygen and purify the air, and can
Play a good ecological effect. [3]
The construction requirements of planting roof are relatively complicated, and the structural layer adopts integral structure.
Cast or prefabricated reinforced concrete roof slab; The waterproof layer shall be provided with coating waterproof layer and reinforced fine stone concrete rigid waterproof layer.
The method of composite waterproof fortification of road defense line to ensure its waterproof quality; Do leveling layer on the structure layer, leveling layer appropriate uses 1: 3 cement mortar, including
The thickness is 15~30 mm according to the type of roof base (according to the technical specification of roof engineering), and the leveling layer should be solid and flat. Leveling layer should be reserved.
Pavilion seam, seam width is 20 mm, and sealing material is used, and the maximum spacing of separation seam is 6 m; Roof cultivation should choose plants with shallow roots, such as various plants.
Plant flowers, grass, etc. Generally, it is not suitable for planting plants with deep roots; The slope of planting roof should not be greater than 3% to avoid the loss of planting medium. This form of house
It is suitable for thermal insulation of residential roofs in hot summer and cold winter and hot summer and warm winter areas. The energy-saving effect of planting roofs is shown in Table 2.
Table 2 Comparison of thermal effects of planting roofs
The difference between planted roofs and non-planted roofs
Maximum external surface temperature /℃6 32.6
External surface temperature amplitude/℃ 6 24 22.4
Maximum temperature of inner surface /℃2 32.2 2
Inner surface temperature amplitude /℃2 1.3 0. 1
The maximum heat flux on the inner surface/(w/m2) 2.215.313.1.
Average heat flow on inner surface/(w/m2)-5.27 9.1.14.4
Maximum outdoor temperature /℃4 36.4 0
Average outdoor temperature /℃ 1 29. 1 0
Maximum solar irradiance /(W /m2) 862 862 0
Average solar irradiance /(W /m2) 2 15. 2 2 15.2 0
3.2 Water storage roof
Water storage roof is to store a thin layer of water on the roof to improve the thermal insulation ability of the roof. Its structure is shown in Figure 4. Water can insulate the roof.
The main reason is that water absorbs a lot of vaporization heat when it evaporates, and most of this heat comes from solar radiation absorbed by the roof.
Therefore, the heat transmitted into the room through the roof is greatly reduced, and the temperature of the inner surface of the roof is also reduced accordingly.
Fig. 4 Water storage roof structure
Water insulation is to use the evaporation of water to consume heat, and the evaporation is different from outdoor air.
The relative humidity of gas is closely related to the wind speed, among which the evaporation of relative humidity is
In the strongest case, the most heat is absorbed from the roof for evaporation. And the roof is at this moment
The outdoor comprehensive temperature is just the highest, which coincides with the strongest heat transfer on the roof.
Generally, spraying water on the roof will also consume heat through evaporation and weaken the heat transfer of the roof.
Use. Therefore, in areas with dry and windy climate in summer, the effect of water isolation is bound to be obvious.
With. [4]
The water storage roof also has some shortcomings. After water storage at night, the external surface temperature of the roof has been constant.
Higher than the waterless roof, it is difficult to use the roof to dissipate heat at this time, and the storage on the roof also increases the static electricity on the roof.
Load, and in order to prevent water seepage, it is necessary to strengthen the waterproof measures of the roof. Adopt waterproof layer
With 40 mm thick, 200# fine stone concrete and 0. 05% triethanolamine or cement.
Dosage: 1% ferric chloride, 1% sodium nitrite (volume concentration: 98%), built-in? 4 mm,
200 mm×200 mm steel mesh has the best anti-leakage performance.
Concrete waterproof layer shall be poured in turn, and no construction joints shall be left. The facade and plane waterproof layer should be completed at one time, and the construction temperature of the waterproof layer should be appropriate.
For 5~35℃, construction under negative temperature or sun exposure should be avoided, and the rigid waterproof layer should be cured in time after completion, and water should not be cut off after storage. [5] This shape
This kind of roof is suitable for thermal protection of residential roofs in hot summer and cold winter and hot summer and warm winter areas. The thermal measurement values of water storage layers with different thicknesses are shown in Table 3.
4 conclusion
To sum up, it is not difficult to see from the comparison of several existing main roof insulation forms that the roof insulation and energy-saving roof is the upper and outer parts of the building.
Thermal insulation of key parts in direct contact with the world is of great significance to building energy conservation. Now all parts of the country have started building energy-saving work to save energy.
Housing is also a brand-new undertaking, which embodies the development direction of building energy saving. In order to save energy, we must follow the world and China.
Create the general trend and trend of energy-saving development, seize opportunities, meet challenges, forge ahead, and try to use a variety of roof construction technologies and ecological modeling.
Do a good job in building energy conservation, improve the indoor thermal environment, promote the development of building technology and construction industry, rationally use resources, protect the ecological environment and improve
Strive to improve people's quality of life.
Table 3 Thermal measurement values of aquifers with different thicknesses
Test project aquifer thickness/mm
5 10 100 150 200
Maximum external surface temperature /℃63 42.90 42.90 4 1.58
External surface temperature amplitude /℃63 7.92 7.60 5.68
Maximum temperature of inner surface/℃
Inner surface temperature amplitude /℃4 1 5.45 3.92 3.89
Minimum temperature of inner surface/℃
Maximum outdoor temperature /℃00 38.00 38.00 38.00 38.00 38.00
Outdoor temperature range /℃40 4.40 4.40 4.40
Maximum heat flux on the inner surface/(w/m2) 21.9217.2314.4614.39.
Minimum value of internal surface heat flow/(w/m2)15.5612.2511.77.76
Average heat flow of inner surface /(W /m2) 0. 5 0.4 0.73 2.49
References:
[1] Shen. Principles and Design of Residential Energy Conservation [M]. Hefei: Anhui Science and Technology Press, 2006: 1.
[2], Wang Jun. The Position of Inverted Roof in Future Housing [J]. Sichuan Architectural Science Research, 200 1( 1): 75-76.
[3] Xu and Li Zhenyu. On Ecological Residential Roof and Building Energy Saving [J]. Shanxi Architecture, 2008,34: 81-82.
Don, Meng Qinglin. Strengthening the research on thermal insulation of water storage roof [J]. Development of building technology, 2000(6): 36.
Liu. Design and construction of water storage roof [J]. Journal of Hunan Urban Construction Institute, 2000(4): 2 1-22.