8.5 Unheated parts of a building

8.5.1 General

If some parts of a building are unheated, the procedures of 8.6 and 8.7 may be applied to the heated parts, provided that the protection described in 8.5.2 or 8.5.3 (as appropriate) is applied to the unheated parts of the building.

8.5.2 Building with limited unheated parts

The unheated parts of a building may be regarded as limited if their dimensions do not exceed those indicated in Figure 2, where the parameter Lu is given as a function of the design freezing index in Table 1.

Table 1 — maximum unheated length Lu for limited unheated parts
Fd (K·h) ≤ 30 000 > 30 000 to 40 000 > 40 000 to 50 000 > 50 000
Lu (m) 3,0 2,5 2,0 1,5
Definition of limited unheated part of floor slab

Key

  • 1 Heated part
  • 2 Unheated part
Figure 2 — Definition of limited unheated part of floor slab

NOTE Lu is the maximum length of an unheated part which is surrounded on three sides by heated areas of the building. The maximum length is less than Lu in other cases, as shown in Figure 2.

For limited unheated parts:

  • insulate the floor of the unheated part so that the thermal resistance of the floor is at least to the minimum ground resistance, Rg, for unheated buildings according to 10.2 (Table 11 or Table 12);
  • at the external perimeter of the unheated part, use vertical edge insulation according to 8.6;
  • if the unheated part is surrounded on three sides by heated areas of the building (Figure 2 a): use frost protection as for corners according to 8.7 at the external perimeter of the unheated part and for a distance Lc to each side of it, where values of Lc are given as a function of the design freezing index in Table 5;
  • if the unheated part is surrounded on only one or two sides by heated areas of the building (Figures 2 b and 2 c): at the external perimeter of the unheated part and for a distance L c to each side of it, use ground insulation of width 0,5bg, with bg according to 10.2 (Table 10), of thermal resistance Rg as for unheated buildings according to 10.2 (Table 11 or Table 12), where values of Lc are given as a function of the design freezing index in Table 5;
  • avoid thermal bridges at the internal perimeter of the unheated part.

8.5.3 Building with more extensive unheated parts

If any unheated part of a building cannot be regarded as limited because its dimensions exceed those indicated in Figure 2, regard the heated and the unheated parts as separate buildings and design the foundations accordingly, continuing the design for the unheated part for a distance Lc where it adjoins the heated part, where values of Lc are given as a function of the design freezing index in Table 5.

8.6 Vertical edge insulation

In all cases, provide vertical edge insulation, of thermal resistance Rv at least that given in Table 2. Use linear interpolation to obtain intermediate values.

Table 2 — minimum thermal resistance of vertical edge insulation for slab-on-ground floors, Rv (in m2·K/W)
Rf in m2·K/W, h in m
Fd
K·h		 0,0 < Rf ≤ 1,0 1,0 < Rf ≤ 2,6 2,6 < Rf ≤ 5,0
h ≤ 0,3 0,3 < h ≤ 0,6 h ≤ 0,3 0,3 < h ≤ 0,6 h ≤ 0,3 0,3 < h ≤ 0,6
5 000 – – 0,5 0,8 0,8 1,0
10 000 0,5 0,8 1,0 1,0 1,5 2,0
20 000 0,8 1,0 1,0 1,2 1,5 2,3
30 000 1,0 1,0 1,0 1,3 1,5 2,5
40 000 1,0 1,0 1,2 1,5 1,7 2,7
50 000 1,0 1,2 1,4 1,7 2,0 3,0
60 000 1,2 1,4 1,8 2,1 2,4 3,4
70 000 1,4 1,6 2,1 2,4 2,8 3,6

 

NOTE 1 Greater values of Rv than those shown in Table 2 may be appropriate for reasons of minimum floor surface temperatures or restriction of heat loss.

The necessary vertical edge insulation can be obtained by using a foundation material with low thermal conductivity (e.g. lightweight concrete), or by using a layer of insulation material external to, within or internal to the foundation wall or beam.

NOTE 2 Although external insulation is preferable from the point of view of frost protection, the data given cover all the above alternatives.

Vertical edge insulation should extend from the top of the slab insulation to a depth Hv below ground level, taking care to avoid a thermal bridge between the slab insulation, the wall insulation and the vertical edge insulation, where:

  • with no ground insulation, Hv ≥ 0,6 m or the full foundation depth if less;
  • with ground insulation, Hv is the depth of the lower surface of the ground insulation.

ISO 13793-2001 Thermal performance of buildings Thermal design of foundations to avoid frost heave