Discussion on thermal insulation materials in data center buildings

    With the rapid development of the Internet, big data, artificial intelligence and the advent of the concept of the metaverse, modern society has officially entered the era of digital economy and informatization. Coupled with the digital transformation and upgrading of traditional industries, the market demand for data centers has risen rapidly, and the scale of data center construction of electronic information systems has increased day by day. As the most basic support for electronic informatization, the construction scale of data center buildings in my country has increased year by year. As a high-energy consumption industry, data centers use a large amount of insulation materials in buildings and are located in many places. Therefore, the fire resistance of insulation materials in data center buildings is of paramount importance.

    Overview of thermal insulation materials in data center buildings

As a large energy consumer, data centers consume a large proportion of energy, in addition to the energy consumption of rack equipment itself, the cooling and cooling of high heat dissipation during equipment operation also accounts for a considerable proportion of energy consumption.

In addition to newly built dedicated data room buildings, renovated data centers that share other building functions are becoming more and more common. Data center rooms operate uninterruptedly all year round, and the refrigeration equipment in the room also maintains the cooling and cooling of the room. Whether from the perspective of energy saving of refrigeration and constant temperature of the room, or to prevent condensation due to temperature differences in different adjacent functional rooms in the building, the insulation of the maintenance structure of the data room is essential.

The insulation materials used in buildings are mainly the following three categories: inorganic insulation materials, organic composite insulation materials, and inorganic insulation materials. These insulation materials have different components, material properties, and combustion performance levels. It is necessary to select appropriate insulation materials according to the different building properties of the data center and the type and functional requirements of the room, especially the fire resistance of the insulation materials, to ensure the safety of the building and the data room.

    Scope of use and selection of thermal insulation materials for data centers

The insulation of the enclosure structure of the data center computer room is mainly reflected in the walls (inner walls of the computer room), room ceilings, room floors, doors and windows, holes in the wall for equipment pipelines, and floor holes.

(1)     Walls (inner walls):

In addition to the insulation of the exterior walls of the original civil buildings, the inner walls of the computer room need to take wall insulation measures according to the specific conditions of the equipment power. The inner wall insulation materials of the computer room generally include rockwool, rockwool sandwich panels, metal-faced sandwich color steel panels (special color steel composite panels for computer rooms), etc.

The method of choosing rock wool insulation requires laying a keel frame on the original wall in combination with light steel keels, filling rock wool between the keels, and then sealing the surface with fireproof gypsum panel;

The rock wool composite panel and metal-faced sandwich color steel panel are composite products of panels and fireproof insulation sandwich materials. After laying the light steel keel frame on the inner wall of the computer room, the finished panel can be directly installed and fixed on the keel to meet the insulation requirements. In particular, metal-faced sandwich color steel panels have good thermal insulation and fire resistance. The metal panels are high in strength, the panel surface is smooth and delicate, dust-free, and maintenance is simple, which greatly guarantees the cleanliness requirements of the data room. The panel paint is rich in color, which can meet the functional requirements of the data room and take into account the aesthetics of the data room.

(2)     Ceiling top surface:

The insulation methods for the ceiling of the data room mainly include suspended ceiling closure, direct attachment to the bottom of the panel, and insulation mortar plastering.

Among them, the insulation method of suspended ceiling closure adopts a light steel keel hanger system, and the rock wool felt building adhesive is pasted in the light steel keel, and then an aluminum panel mesh surface layer or fireproof gypsum panel is fixed on the keel frame for sealing. The advantage of this method is that the concrete beam at the bottom of the panel can be hidden if the floor height allows, the appearance of the computer room is good, and the space volume of the cold pool in the computer room can be reduced, which has a certain degree of effect on the energy saving of the computer room. However, due to the large number of equipment bridges and pipelines in the data room, the floor height of the general computer room is not sufficient.

The second method is to directly attach the insulation material to the bottom of the panel, generally using rock wool panel and microporous calcium silicate insulation panel. These two insulation materials are light in weight and easy to cut. They are bonded to the bottom of the panel with a special adhesive. A small amount of expansion bolts are driven into the floor slab, and then the ends of the expansion bolts are fastened with a two-way steel mesh or a two-way steel wire. After the exposed surface of the insulation panel is sealed with a special adhesive for two times, the anti-cracking putty is scraped flat, and the surface layer is inorganic paint. This method has a good insulation effect and can be implemented at the bottom of the panel in the beam cavity, without any effect on the effective floor height in the computer room.

The third method is to apply the insulation mortar to the bottom of the panel. For data rooms with low energy consumption and low insulation requirements, this type of insulation method can be used. Because it is the insulation mortar at the bottom of the panel, and there are many hanger brackets at the bottom of the panel in the data room, in order to ensure that the mortar is firmly bonded without cracking or falling off, the insulation mortar should not be too thick. Generally, the insulation mortars are selected from vitrified microsphere fireproof insulation mortar, composite aluminum silicate insulation mortar, and perlite insulation mortar.

In addition, in the data center renovation project, if the existing building status is limited, ultra-fine inorganic fiber spray insulation materials can also be used. This type of insulation material is foam-like and is directly sprayed on the bottom of the panel. The construction is simple, but the flatness is poor and it is easy to accumulate dust. If there are requirements for the appearance of the computer room or the return air of the air conditioner, it is necessary to combine the ceiling to seal the top surface.

(3)     Floor:

The insulation of the floor of the data center is mainly the computer room of the air supply system under the air conditioner. The floor of the computer room needs to be paved with anti-static raised floor, and the floor is a closed channel space for the air supply of the air conditioner. In this type of data center, the space under the raised floor is in a low temperature state of cold air supply for a long time. In addition to the insulation and energy-saving requirements of the air conditioning system, especially in the jointly built data center, it is also necessary to avoid condensation on the ceiling of the room below the computer room due to temperature difference; at the same time, because the anti-static raised floor is installed on the ground, the brackets of the raised floor are laid in both directions with a spacing of 600mm, the number of brackets is large, and the brackets need to be directly supported on the solid concrete floor slab, and the space division of the ground insulation material under the floor is trivial. Considering the difficulty of construction process, the large number of floor support brackets lead to the laying of insulation materials under the raised floor to take into account insulation, fire prevention and easy cutting, and even the material itself needs certain deformation characteristics.

After a long period of experience in the construction of a large number of data center projects, the insulation materials selected under the raised floor are mainly the following: aluminum foil rubber-plastic composite insulation materials, microporous calcium silicate insulation panels, and fiber aluminum foil rock wool panel composite insulation materials.

Among them, aluminum foil rubber-plastic composite insulation materials are also called rubber-plastic sponge insulation coils. Compared with the other two insulation materials, the most important characteristics and advantages are that as elastic closed-cell foam materials, they are very flexible, easy to cut, easy to deform, good wrapping for uneven surfaces, and convenient construction. It is particularly suitable for the insulation laying under anti-static raised floors. The bracket of the raised floor has almost no effect on the laying of aluminum foil rubber-plastic composite insulation materials, which can ensure the complete closure of the entire ground insulation layer. However, with the increasing number of data centers in high-rise factories and civil buildings, the defect that aluminum foil rubber-plastic composite insulation materials can only reach the combustion performance level B1 makes this insulation material unable to be used in many cases. The combustion performance grade of microporous calcium silicate insulation panel and fiber aluminum foil rock wool panel composite insulation material are both Class A, which can meet the fire protection requirements and be used in any building.

Microporous calcium silicate insulation panel is a common insulation material on the market. It is inexpensive and has both insulation and fire resistance performance suitable for use in various types of buildings. As mentioned above, microporous calcium silicate insulation panel is a choice of insulation material for the top panel bottom, and is also suitable for use under the anti-static raised floor of the data center computer room. When installing, it needs to be pre-cut into blocks with a module of 600mm according to the distribution of the raised floor bracket, and then fixed to the ground with a special adhesive on the leveled and cleaned ground. The surface of the microporous calcium silicate insulation panel is easy to shed dust, which affects the clean space of the data room. Therefore, a galvanized steel panel with a thickness of about 0.5mm needs to be installed on the microporous calcium silicate insulation panel to seal the insulation material layer.

Fiber aluminum foil rock wool panel composite insulation panel is also a commonly used insulation material with the advantages of easy cutting, slight deformation in some parts, non-flammable, and self-contained aluminum foil coating. The construction process is simple and can be used as an alternative material to aluminum foil rubber-plastic sponge insulation panel. However, the fiber aluminum foil rock wool panel composite insulation panel is easy to shrink, has low strength, and high water absorption. At the same time, it is very easy to form fiber particle dust on the side without aluminum foil. Although the insulation material under the anti-static raised floor does not need to bear weight, it is more susceptible to bumps and damage during construction or later maintenance.

The above three commonly used insulation materials under the anti-static raised floor have their own advantages and disadvantages. It is necessary to select the most suitable insulation material after screening and comparison based on the actual operation needs of the data center computer room and the fire protection code requirements of the interior decoration design of the building.

(4) Doors, windows and building holes

The room evacuation doors of the data center computer room are all fire doors. Whether from the requirements of fire prevention and smoke prevention or room insulation, there are certain requirements for the airtightness of the fire doors. When the fire door is closed, the door leaf fits the door frame, and the gaps on both sides, the upper gap, and the gap between the two doors should not be greater than 3mm. The door frame and door gap are provided with sealing grooves, and the grooves are inlaid with fire-resistant and flame-retardant fire-proof expansion strips.

In the newly built data center building, the planned data room room does not have other external windows except the necessary fire rescue windows. If the computer room is equipped with a gas fire extinguishing system, in order to ensure the pressure resistance requirements of the gas fire enclosure structure in the computer room and the requirements of thermal insulation and energy saving of the computer room space, the inner side of the fire rescue window hole in the computer room needs to be installed with a casement window that can meet the gas fire resistance requirements. The window opens inward and can be opened 180°. The window is in a normally open and unlocked state and can be opened from the outside at any time. The net size of the window hole after the window is opened shall not be less than the standard requirements for the size of the fire rescue window hole. In the rebuilt data center building, in addition to the fire rescue window, the existing building exterior windows must be blocked from the inside. Generally, light steel keel cement fiber calcium silicate panel partitions are used to block windows, and thermal insulation rock wool is filled between light steel keels of lightweight partitions to achieve fireproof and thermal insulation effects.

Due to the particularity of data centers, various professional wiring racks, equipment pipelines, etc. lead to a large number of wall holes between rooms and floor holes on upper and lower floors. After the installation of pipeline wiring racks, etc., such holes need to be fireproofed and blocked, and the thermal insulation of the computer room is also guaranteed.

As an electronic information system room equipped with important machinery and equipment, the data center must be strictly and cautiously designed and implemented in strict accordance with relevant specifications and standards to ensure the safety of people's lives and property. Building decoration materials, especially thermal insulation materials, need to be used in large quantities in data center buildings, and the fireproof performance of thermal insulation materials is crucial to the overall fire protection of buildings. This article focuses on the selection of thermal insulation materials for various parts of data center buildings with an increasing construction scale, combined with the fireproof performance of materials, and after a long period of experience in the construction and design of data center computer rooms and feedback from later operations and maintenance, several choices and practices for thermal insulation materials in various parts of data center buildings are comprehensively drawn. I believe that with the joint efforts of relevant personnel in the industry, the risk of fire in data center buildings will be reduced and the long-term development of the industry will be achieved.