Hanoi-Vietnam: Requirements for building enclosure

Circular 15 on technical regulations for building envelopes applies only to air-conditioned spaces.

Requirements for exterior walls and roofs of buildings in Vietnam include:

- Requirements for total thermal resistance R0 of non-translucent sections:

+ Exterior walls above ground of air-conditioned spaces should have a minimum total thermal resistance value of R0.min not less than 0.56 m2.K/W;

+ Flat or low-slope roofs (slope less than 15 degrees) directly above air-conditioned spaces should have a minimum total thermal resistance value of R0.min not less than 1.00 m2.K/W.

Where:

- Reflective material flat roofs: the R0.min thermal resistance value can be multiplied by a factor of 0.80 for roofs designed with reflective materials having a reflectance between 0.70 and 0.75 to increase the reflectance of the exterior roof surface;

- Roofs with slopes from 15 degrees or more: the minimum total thermal resistance of the roof can be determined by multiplying the R0.min values by a factor of 0.85;

- Roof structures that do not need to comply with exterior wall requirements such as: more than 90% of the roof surface is shielded by a fixed, ventilated sunshade layer. This sunshade layer must be at least 0.3 m away from the roof surface to be considered ventilated between the roof and the sunshade layer (double-layer roofs with a convective air space in between).

Requirements for translucent sections (glass windows, glass walls) as stipulated in Circular 15 are as follows:

- The maximum Solar Heat Gain Coefficient of glass walls and windows is determined separately for each wall face according to the North and south directions (North and south directions have a variation range of ±22.5 degrees compared to the main North or South axis), other directions, and must satisfy the values in the table below.

Table of Solar Heat Gain Coefficients of Glass Depending on Window to Wall Ratio

Details may be found in Circular 15/2017/TT-BXD effective from June 1, 2018.

-Thao Uyen-

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