Thermal & envelope

U-Value & Thermal Envelope

Layer up a wall or roof build-up by ISO 6946 and check the U-value against the SBC 602 and SBC 601 limits for the Saudi climate zone.

Each layer contributes R = d/λ (ISO 6946:2017 cl. 6.7.1), a hollow concrete block a fixed resistance per unit from NCMA TEK 6-2B; the layers add in series with the surface resistances of Annex C, and U = 1/R_T (cl. 6.5.2). Unventilated air layers are read from Annex D; a well-ventilated one is dropped with everything outside it (cl. 6.9.4), and a slightly ventilated one is interpolated on its opening area A_v (cl. 6.9.3). The result is compared with the SBC 602 wall and roof limits, or the SBC 601 mass-wall and insulated-deck roof limits.

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Location and climate zone

City

Climate zone

Reference code

Layers: inside to outside

Build-up library

#	Material	Thickness mm	Conductivity λ W/m·K	Ventilation	Resistance R m²·K/W	Share of R	Remove the layer

No layers yet: load a preset or add a layer.

ISO 10456 does not tabulate insulation, masonry or plaster: those are declared on the product's own declaration of performance under EN 13162 to EN 13171 and EN 1745. The values marked here are typical, editable, and should be replaced with the figure from the datasheet of the product actually specified.

Design temperatures

Inside air θi °C

Outside air θe °C

Internal surface Rsi m²·K/W

External surface Rse m²·K/W

Temperature through the build-up

Results

Thermal transmittance U W/m²·K	—
U at two significant figures, as the standard asks	—
Total resistance R_T m²·K/W	—
Total thickness mm	—
Code limit W/m²·K	—
Code check	—
Heat flux q = U·Δθ W/m²	—
Inside surface θsi °C	—

Interface temperatures

Interface temperatures	Position from the inside surface mm	Temperature °C	Drop across the layer K

Report and export

Project

Client

Convert units: Mechanical: HVAC

Questions engineers ask

Which surface resistances does ISO 6946 give?

Annex C: R_si is 0.10 for upward heat flow, 0.13 horizontal and 0.17 downward; R_se is 0.04 in every direction. They are pre-filled from the element you choose and stay editable.

How is a ventilated cavity treated?

By openings, not by intention. Cl. 6.9.4: at 1500 mm² or more per metre of length for a vertical layer, or per square metre for a horizontal one, the cavity and everything outside it are ignored and R_si is used in place of R_se. Above 500 and below 1500 mm², cl. 6.9.3 interpolates the total: R_T = (1500 − A_v)/1000 · R_T,u + (A_v − 500)/1000 · R_T,v. You enter A_v on the layer; it starts at 1500, the conservative end, and values outside the range are refused.

Which Saudi limit applies to my building?

SBC 602-18 Table 5.2 for residential buildings of three storeys or less, and SBC 601-18 Table 5.1 for other buildings, both by climate zone. The tool applies the SBC 602 wall and roof rows and the SBC 601 non-residential mass-wall and insulation-above-deck roof rows. For metal-building and steel-framed walls, metal-building roofs, floors and the SBC 601 residential column it applies no limit and says so, because those rows could not be confirmed from a second source.

Where do the conductivities come from?

Rows printed in ISO 10456 Table 3 or BRE BR 443 are cited to them. A hollow concrete block carries a fixed resistance per unit from NCMA TEK 6-2B for normal-weight units (0.131, 0.154 and 0.178 m²·K/W for 100, 150 and 200 mm) because its voids do not scale with thickness. Insulation, other masonry, render and tiles have no published table: those rows are typical values, flagged on the page, and should be replaced with the declared value of the product specified.

Does it account for thermal bridging?

No. This is the one-dimensional ISO 6946 method for a plane element. Repeating bridges (a steel stud, a tie, a rafter) need the standard's correction procedures, and a linear bridge at a junction is outside ISO 6946 altogether. Both change the answer, sometimes badly, and neither is in this calculator.

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