Underground garage moisture condensation management
DATE:2024-08-14 10:21:26
Read:
SHARE:
Due to the lack of specific norms constraints, moisture and condensation in the design process is easy to be ignored. When the project is completed into the completion acceptance and delivery period, if the problem occurs, it is generally difficult to solve, which will bring certain safety management risks and economic losses to the construction unit and operation management.
Through the analysis of the condensation phenomenon of a new underground garage in the main city of Lingang New Area of Shanghai Pilot Free Trade Zone, it is concluded that, from the overall plan position, the condensation phenomenon is lighter in the close area compared with the area far away from the garage entrances and garage patio openings, and the area close to the basement exterior wall is heavier than the other areas.
Underground garage wet condensation is the root cause of the basement water content is too large, the source of this part of the water there are 2 kinds of: (1) by the basement floor and wall waterproofing defects caused by soil moisture infiltration into the basement; basement waterproofing mainly rely on waterproofing roll-roofing materials, coatings, and the waterproofing performance of the concrete itself, when waterproofing materials or coatings are not in place and the concrete structure is not sufficiently compact or construction cracks, the groundwater (or water generated by the ground part of the building) will infiltrate into the basement or increase the air humidity by vapor infiltration. Groundwater (or water generated by the above-ground portion of the building) can infiltrate into the basement or increase air humidity by vapor infiltration. The increase in air humidity leads to a corresponding increase in the risk and severity of condensation. (2) Basement air contains a high level of moisture. When the dew point temperature of the air is higher than the temperature of its contact surfaces, moisture in the air will precipitate out and form condensation on the contact surfaces.
The temperature of the basement enclosure tq is slightly higher than the soil temperature tr, which is lower than the air dew point temperature td, i.e., tq < td, so condensation is likely to occur.
Closer to the garage entrances and exits or more frequent exchange of air with the outside world, due to air convection heat transfer, the surface temperature of the structure in this part of the region and the dry bulb temperature of the outdoor air is close to the dry bulb temperature of the outdoor air, higher than the dew point temperature, and therefore the problem of condensation is lighter. On the contrary, in the depth of the garage, dead ends or corner areas, due to less heat exchange with the outside air, the surface temperature of the structure is lower, prone to condensation phenomenon.
Under the condition of natural or mechanical ventilation in the garage, in the fall and winter seasons, as the temperature of the underground garage is higher than the outdoor air temperature, the ventilation can discharge the excess moisture from the basement, which is helpful to alleviate the condensation. However, for the high temperature and high humidity summer, the underground garage temperature is lower than the outdoor air temperature, and frequent ventilation will bring the air with higher humidity into the garage, exacerbating the problem of condensation in the area of lower temperature of the enclosure structure.
By comparing the condensation situation of underground garages in the main Lingang district of Shanghai Pilot Free Trade Zone, it is found that the condensation phenomenon of newly built underground garages is often more serious than that of underground garages that have been put into use for a period of time. This is because the underground garage has been put into use due to the heat emitted by the relevant equipment room, the heat emitted by the automobile exhaust and the heat emitted by the personnel in and out of the basement temperature is generally high, and the humidity content of the air remains unchanged, so its relative humidity is low, resulting in a lower dew-point temperature, the dew-point problem is also lighter.
Back
Through the analysis of the condensation phenomenon of a new underground garage in the main city of Lingang New Area of Shanghai Pilot Free Trade Zone, it is concluded that, from the overall plan position, the condensation phenomenon is lighter in the close area compared with the area far away from the garage entrances and garage patio openings, and the area close to the basement exterior wall is heavier than the other areas.
Underground garage wet condensation is the root cause of the basement water content is too large, the source of this part of the water there are 2 kinds of: (1) by the basement floor and wall waterproofing defects caused by soil moisture infiltration into the basement; basement waterproofing mainly rely on waterproofing roll-roofing materials, coatings, and the waterproofing performance of the concrete itself, when waterproofing materials or coatings are not in place and the concrete structure is not sufficiently compact or construction cracks, the groundwater (or water generated by the ground part of the building) will infiltrate into the basement or increase the air humidity by vapor infiltration. Groundwater (or water generated by the above-ground portion of the building) can infiltrate into the basement or increase air humidity by vapor infiltration. The increase in air humidity leads to a corresponding increase in the risk and severity of condensation. (2) Basement air contains a high level of moisture. When the dew point temperature of the air is higher than the temperature of its contact surfaces, moisture in the air will precipitate out and form condensation on the contact surfaces.
The temperature of the basement enclosure tq is slightly higher than the soil temperature tr, which is lower than the air dew point temperature td, i.e., tq < td, so condensation is likely to occur.
Closer to the garage entrances and exits or more frequent exchange of air with the outside world, due to air convection heat transfer, the surface temperature of the structure in this part of the region and the dry bulb temperature of the outdoor air is close to the dry bulb temperature of the outdoor air, higher than the dew point temperature, and therefore the problem of condensation is lighter. On the contrary, in the depth of the garage, dead ends or corner areas, due to less heat exchange with the outside air, the surface temperature of the structure is lower, prone to condensation phenomenon.
Under the condition of natural or mechanical ventilation in the garage, in the fall and winter seasons, as the temperature of the underground garage is higher than the outdoor air temperature, the ventilation can discharge the excess moisture from the basement, which is helpful to alleviate the condensation. However, for the high temperature and high humidity summer, the underground garage temperature is lower than the outdoor air temperature, and frequent ventilation will bring the air with higher humidity into the garage, exacerbating the problem of condensation in the area of lower temperature of the enclosure structure.
By comparing the condensation situation of underground garages in the main Lingang district of Shanghai Pilot Free Trade Zone, it is found that the condensation phenomenon of newly built underground garages is often more serious than that of underground garages that have been put into use for a period of time. This is because the underground garage has been put into use due to the heat emitted by the relevant equipment room, the heat emitted by the automobile exhaust and the heat emitted by the personnel in and out of the basement temperature is generally high, and the humidity content of the air remains unchanged, so its relative humidity is low, resulting in a lower dew-point temperature, the dew-point problem is also lighter.