Stone wool or EPS for the facade
On 100 m² the price gap is about 1,200 ₾, but the saving is not always available: EPS has its own limits on height, fixings and openings.
Same thickness, different price
In Tbilisi an external wall must reach U = 0.38 W/(m²·K) or better. A 200 mm concrete wall gets there with 100 mm of stone wool (λ 0.042) or 100 mm of EPS (λ 0.038): the EPS calculation gives 105 mm, and the nearest board on sale is 100. A 250 mm brick wall also needs 100 mm; 80 mm fails. A 300 mm aerated block wall barely needs insulation by the numbers; in practice 50 mm is fitted to cover the joints and lintels. Price per m² at 100 mm: stone wool slab 120 kg/m³ — 41.90 ₾, EPS board 20 kg/m³ — 29.62 ₾. On a 100 m² facade that is about 1,230 ₾ on the insulation alone.
Where EPS is not allowed
EPS burns, so in a rendered facade it is framed with stone wool: fire-break strips at least 150 mm high around windows and doors, at junctions between systems and in internal corners. We found no Georgian rule on this and use the Russian code SP 293 as a reference: breaks up to 6 m above ground and 3.5 m above the top of an opening. EPS is not used under clinker or any heavy cladding: that needs wool with a delamination strength of at least 15 kPa. A dark finish on EPS only if the system data sheet allows it: the board heats up and warps.
The fixings differ
EPS needs 4 dowels per m² in the field and 8 in the edge zone; up to 60 mm thick, IZO with a plastic nail (10×100, 10×120) is fine. At 80–100 mm you need 150–170 mm of length, which means the IZL-T 8L disc dowel with a steel nail. On stone wool a plastic nail is never used: only IZL-T, 6 per m² in the field and 8 in the edge zone, twice as many above 25 m. Gaps wider than 2 mm between EPS boards are filled with foam or offcuts; between wool slabs only with a wedge of the same wool.
What is the same
Adhesive and base coat: about 10 kg/m² on wool and 9 kg/m² on EPS; alkali-resistant 160 g/m² mesh with a 10 cm overlap; corner beads with mesh on corners and reveals; a starter profile along the plinth. We take the adhesive and base coat from the maker of the facade system the build-up is designed for: insulation, dowels and mesh come from our warehouse, the compounds from the market. That is how we do most of our projects.
How to decide
- A house up to two storeys, render and paint, lowest cost — EPS 100 mm with wool fire breaks around the openings.
- Above 10 m, clinker, stone, a dark facade or non-combustibility required — stone wool from 120 kg/m³.
- The plinth — neither: XPS only. Wool soaks up water at the bottom, EPS is weak against impact.
The calculator counts packs and dowels from the area; wool and EPS are sold in whole packs.