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BETTON PREFABRİK

Technical · 7 min

Thermal insulation in precast industrial buildings

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Short answer: Thermal insulation of a precast industrial building is designed across the façade, roof, ground slab and any office block terrace, with calculations to TS 825, the Turkish thermal insulation standard for buildings. Insulated sandwich concrete panels on the façade, insulation matched to the roof covering and load-rated boards under the slab are the core solutions. Foam concrete adds insulation within fill and slope layers but does not replace 0.030–0.040 W/mK boards on its own.

Where is heat lost, and how is the calculation set up?

In a precast industrial building heat escapes through four parts of the envelope: façade, roof, ground-bearing slab, and windows and doors. Thermal bridges where these surfaces meet are a further loss path. In wide single-storey halls the roof area usually exceeds the façade area, so roof decisions weigh heavily on total loss.

Before any calculation, decide which volumes will be heated. An unheated warehouse, a heated production hall and an office block in daily use do not need the same envelope, and a cold store is the reverse case, with heat flowing in from outside. For heated volumes, insulation thicknesses are calculated to TS 825, the Turkish thermal insulation standard for buildings. The conductivity and thickness of every layer enter the calculation, and condensation risk is checked at design stage as well.

Façade: sandwich panel or single-leaf wall panel?

BETTON PREFABRİK's architectural concrete façade panels are produced with an insulated sandwich option, with XPS, EPS or stone wool placed between two concrete layers. Because the insulation is built into the panel at the factory, no separate insulation layer is applied to the façade on site; the work shifts to insulating and sealing the joints. The outer concrete layer protects the insulation from impact and weather. The type and spacing of the connectors tying the layers together govern their thermal bridge effect, so they are assessed in panel design.

A single-leaf precast wall panel suits fire compartment walls, perimeter walls and unheated volumes; on the boundary of a heated space it needs an added insulation layer. Insulation is chosen for fire behaviour and moisture resistance as well as conductivity, and its thickness comes out of the TS 825 calculation.

Thermal bridges at column, beam and panel junctions

In a precast building the insulation line risks being broken wherever elements meet. Typical thermal bridges are panel joints, anchor points where façade panels fix to columns, roof beam bearings at the façade line, parapets and eaves, the plinth-to-ground-slab junction, and the surrounds of windows and loading doors.

Every solution starts from an insulation line that can be traced without a break on plan and in section. Panel joints are typically filled with insulation and closed with elastic sealant on both faces; at the plinth, insulation is carried down towards foundation level; connections where concrete runs through the insulation from inside to outside are kept to a minimum. Because precast elements are made in the factory, these details must be fixed before shop drawings are issued, as later corrections on site are limited. An unresolved thermal bridge also raises condensation and mould risk in office and food areas.

Roof: covering system and continuous insulation

In a precast industrial building the roof is carried by prestressed roof beams and purlins, and insulation is resolved together with the covering system placed on them. Covering type and insulation material are selected in the project according to span, roof pitch, fire requirements and indoor humidity. As important as the calculated thickness is continuity at ridges, rooflights, internal gutters and parapets; internal gutters are sensitive spots for both thermal bridging and leaks.

Where an office block or mezzanine has a flat terrace roof, the structural deck can be spanned with hollowcore or TT slabs. The order of slope layer, thermal insulation, waterproofing and protection is then defined in the project for the chosen roof type. Terrace roofs typically target a fall of 1.5–2% in practice; the exact value is set in the project for the waterproofing system selected.

Ground slab and terrace: where does foam concrete help?

On a ground-bearing slab, heat loss concentrates at the building perimeter. Insulation under an industrial floor that carries forklift and racking loads is chosen for suitable compressive strength and checked by structural calculation; using foam concrete in that layer needs a separate assessment of ground conditions and loads.

Foam concrete belongs in the fill and levelling layers that have to be built anyway: slope fill of 400–600 kg/m³ on the office block terrace, lightweight screed and pipe embedding of 400–800 kg/m³ in office and welfare floors, and insulating fill of 300–500 kg/m³ in voids with no load. These layers are light, so they limit dead load on hollowcore floors, and they are pumped into place quickly. Their thermal contribution can enter the TS 825 calculation using a conductivity value confirmed by laboratory testing.

Foam concrete and insulation boards compared

The foam concrete density classes used here as examples target these thermal conductivities: KB300 0.08–0.10, KB400 0.10–0.12, KB500 0.12–0.14 and KB600 0.14–0.17 W/mK. EPS, XPS and stone wool boards sit at roughly 0.030–0.040 W/mK. Even the lightest class, KB300, conducts about 2 to 3.3 times as much heat as the board band.

Example: a 5 cm board with an assumed conductivity of 0.035 W/mK has a thermal resistance of 0.05 / 0.035 ≈ 1.43 m²K/W. Matching that with KB400 at an assumed 0.11 W/mK takes 1.43 × 0.11 ≈ 0.16 m, or about 16 cm of foam concrete. Foam concrete therefore does not replace boards where high resistance is needed in a thin layer; it complements them in slope and fill layers. The values are dry design targets, and conductivity rises with moisture. As foam concrete falls outside the scope of TS EN 206, its performance is confirmed by laboratory testing.

Frequently asked questions

Can foam concrete replace thermal insulation?
On its own, usually not. Foam concrete classes KB300–KB600 target a thermal conductivity of 0.08–0.17 W/mK, while EPS, XPS and stone wool boards are around 0.030–0.040 W/mK. Foam concrete must be several times thicker for the same resistance; it is most effective as an added insulating contribution in slope and fill layers that are needed anyway.
How is the façade of a precast factory building insulated?
For heated volumes, the core solution is an insulated sandwich façade panel with XPS, EPS or stone wool between two concrete layers. Insulation thickness is set by the TS 825 calculation, and junctions such as panel joints, column connections and the plinth are detailed so that they do not form thermal bridges.
Which surfaces count in a TS 825 calculation?
Every surface enclosing the heated volume counts: external walls and façade panels, roof, ground-bearing slab, windows, doors and surfaces next to unheated spaces. Thermal bridges at element junctions are assessed as well. The boundary between unheated storage and heated production or office areas should be settled before calculating.
What density suits foam concrete slope fill on a terrace roof?
The typical band for terrace and roof slope fill is 400–600 kg/m³. Lower density insulates better, while higher density gives more strength. A fall of 1.5–2% is typically targeted in practice, with the exact value set in the project for the chosen waterproofing system. The mix is confirmed by trial batches and laboratory testing.

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