1.2. Determination of thermal resistance of enclosing structures

Heated rooms lose heat through fences due to the difference in temperature between the indoor and outdoor air. Such fences are walls, windows, doors, ceilings above basements, attic and no-floor ceilings, floors on the ground. Variants of designs of some fences are given in Appendix. 3

The heat-shielding qualities of fences are characterized by the value of heat transfer resistance R0 , m2 · ° С / W, determined by the formula

, (1.1)

where av is the coefficient of thermal perception of the inner surface of the fence, W / m2 · ° C; di and l i - layer thickness and the calculated coefficient of thermal conductivity of the material of the layers of the enclosing structure; an - heat transfer coefficient of the outer surface of the fence, W / m2 · ° C; Rv.p. - thermal resistance of the closed air gap (if present in the structure), m2 · ° С / W.

The coefficients of av and an are accepted by SNiP [3] and for a number of cases are given in Table. 1.1; di - determined from construction drawings of enclosing structures or assigned by ADJ. 3 in accordance with the task;
li - taken from reference data and for some materials given in Appendix 4. The thermal resistance of the air layers can be taken from Table. 1.2.

Table 1.1

Heat absorption and heat transfer coefficients

The heat transfer resistance of insulated floors on the ground and walls located below ground level is determined by zones 2 m wide, parallel to external walls, according to the formula

, (1.2)

where Rc is the heat transfer resistance of the non-heated floor, for the 1st zone - 2.1 m2 · ° С / W, for the 2nd zone - 4.3 m2 · ° С / W, for the 3rd zone - 8.6 m2 · ° С / W;
d and lh - thickness and coefficient of thermal conductivity of insulation.

Table 1.2

Thermal resistance of closed air interlayers Rв.п , m2 · ° С / W

The heat transfer resistance of windows and doors is usually not calculated, but is taken from reference data depending on the design used. In adj. 3 gives this information for some designs of filling wall openings.