Interpretation of vapor barrier film and isolation layer in roof construction

In the construction of building roof Vapor barrier Interpretation of the isolation layer

[Abstract] During the discussion on the optimization of building practices in the east area Vapor barrier There are different views on the choice of the isolation layer. This paper will interpret these two items in combination with relevant atlas and other materials, and discuss with you, hoping to help the future work.

Keywords Vapor barrier , vapor barrier isolation layer

II Vapor barrier

Vapor barrier Is defined as: the structural layer designed to reduce the air permeability of the ground, wall or roof in the building; In roof construction, the vapor barrier is a structural layer designed to prevent indoor water vapor from penetrating into the insulation layer. In severe cold and cold areas, the temperature difference between indoor and outdoor is large in winter, the outdoor temperature is below negative temperature, while the indoor temperature is zero Above ℃, when the actual steam penetration resistance at the inner side of the condensation interface of the roof structure is less than the required value, indoor moisture may enter the insulation layer through the roof structure layer, and water vapor will slowly penetrate into the insulation layer through the concrete roof panel for a long time, forming condensation and moisture in the insulation layer, thus affecting the insulation effect of the insulation layer.

Vapor barrier It shall be set on the structural layer and under the insulation layer, and materials with good air tightness and water tightness shall be selected (such as polyethylene materials, polypropylene and polyethylene composite polymer materials). The vapor barrier film shall be higher than the upper surface of the insulation layer at the junction with the vertical wall surface by no less than 150mm 。 Obviously, the vapor barrier is only available in the upright roof (the waterproof layer is above the insulation layer), but not in the inverted roof (the waterproof layer is below the insulation layer, and the waterproof layer has the function of vapor barrier).

according to Vapor barrier Two conditions are required for its function:（ one ）The area is cold, and the outdoor temperature in winter is zero Below ℃; （ two ）Indoor air humidity is high. It is generally understood that 40° North area and indoor air humidity is greater than 75% , or indoor air humidity in other regions is greater than 80% The vapor barrier shall be set in the area of.

Therefore, it is recommended to add a vapor barrier to the upright roof in the north Vapor barrier The winter temperature in the northern region is lower, and the humidity in the northern Bohai Sea is higher than that in other inland regions, so a vapor barrier is added Vapor barrier It is very necessary, so it is reserved Roof vapor barrier To ensure the effect of roof steam insulation.