Facade insulation 2026: polystyrene or mineral wool? Cost and payback

In 2026, external wall insulation with polystyrene (EPS) costs roughly CZK 1,500–2,200/m² including render in the Czech Republic, and with mineral wool CZK 2,200–2,800/m², excluding VAT and scaffolding. Polystyrene is cheaper and is enough for most newer masonry houses. Mineral wool is the right choice for older houses without damp-proofing, timber-frame houses, situations with fire-safety requirements and houses next to a busy road. At the same insulation thickness both save roughly the same on heating — so the extra cost of wool is not paid back by energy savings; you pay it for non-combustibility, vapour permeability and acoustics.

This article compares the two materials, shows what insulating a real house costs, explains how to work out the payback and what to base the decision on. Prices for individual tasks, split into labour only and with materials, are in our facade works price list.

Facade insulation cost per m² in 2026

Item	Labour + materials	Labour only
EPS (polystyrene) insulation incl. render	CZK 1,500 – 2,200/m²	CZK 550 – 900/m²
Mineral wool insulation incl. render	CZK 2,200 – 2,800/m²	CZK 650 – 1,000/m²
Scaffolding (hire + erection)	CZK 100 – 200/m²	—
Algae and mould treatment	CZK 50 – 100/m²	—
Silicone finish render without insulation	from CZK 1,300/m²	CZK 350 – 550/m²

Prices exclude VAT and apply to Prague and the surrounding region, based on our 2026 construction price list. The table shows where the difference comes from: labour with wool is only CZK 100–150/m² more, but for a complete supply wool is about CZK 600–700/m² more expensive. Most of the premium is therefore the material itself.

Polystyrene or mineral wool: comparison

Property	Polystyrene (EPS)	Mineral wool
Price with materials	CZK 1,500 – 2,200/m²	CZK 2,200 – 2,800/m²
Thermal insulation	white EPS comparable with wool; grey (graphite) EPS insulates better	comparable with white EPS
Vapour permeability	low	high — the wall can dry outwards
Fire behaviour	combustible; on taller buildings only with fire barriers	non-combustible
Acoustics	weaker	better at blocking outside noise
Weight and installation	light, easy to cut, bonded and anchored as designed	heavier, fully bonded and always mechanically anchored
Finish render	standard thin-coat renders	vapour-permeable only, typically silicone or silicate

Insulating performance is expressed by thermal conductivity λ — the lower, the better. Facade mineral wool is roughly 0.035–0.040 W/mK, white EPS is similar, and grey EPS around 0.031–0.032 W/mK. The exact value is always in the manufacturer's data sheet. Typical insulation thickness for family houses today is 140–200 mm.

Plinth, reveals and sills

Below ground level and on the plinth, both systems use moisture-resistant insulation — extruded or perimeter polystyrene. Window reveals matter just as much: the insulation should return into the reveal, otherwise a cold strip remains around the window and condensation can form in the inside corners. External sills are replaced with deeper ones so that they project beyond the new facade and water does not run down the render.

When to choose polystyrene and when wool

Polystyrene is enough when

• the house is a newer masonry building with working damp-proofing and dry walls,
• the house is low-rise and the facade is not close to the plot boundary or another building,
• the surroundings are quiet and price is the main factor,
• you want good performance with minimum thickness — then grey EPS.

Mineral wool is better when

• the house is an older masonry building without reliable protection against rising damp — the walls need a way to dry out,
• it is a timber-frame house or has timber floors, where a vapour-open build-up is needed,
• the fire safety design requires non-combustible insulation, for example with a facade close to the plot boundary or on a taller building,
• the house stands next to a road or railway and you want better acoustics.

A common compromise is polystyrene on the main areas with mineral wool fire barriers wherever the design requires them. Wool is covered in detail in facade insulation with mineral wool.

What insulating a family house costs: an example

A house with 200 m² of facade. How to measure your facade area correctly is shown in the facade works price list. Calculated with the price list rates:

Item	Polystyrene (EPS)	Mineral wool
Insulation system incl. render (200 m²)	CZK 300 – 440k	CZK 440 – 560k
Scaffolding (200 m² × CZK 100 – 200)	CZK 20 – 40k	CZK 20 – 40k
Total excl. VAT	CZK 320 – 480k	CZK 460 – 600k

For this house the difference between the materials is about CZK 120,000–140,000. A complete job may also include new window sills, removing loose old render or algae treatment (CZK 50–100/m²). Insulation is also a good moment to replace old windows: new windows set in the plane of the insulation have smaller thermal bridges than windows replaced after the facade is done.

Labour and materials separately

If you buy the materials yourself and hire a firm or crew for labour only, use the "labour only" rates from the price list:

Task (labour only)	Rate	200 m² facade
EPS insulation incl. render	CZK 550 – 900/m²	CZK 110 – 180k
Mineral wool insulation incl. render	CZK 650 – 1,000/m²	CZK 130 – 200k
Reinforcement layer alone (adhesive + mesh), e.g. for facade repair	CZK 200 – 350/m²	CZK 40 – 70k
Finish render alone, without insulation	CZK 350 – 550/m²	CZK 70 – 110k

Subtracting labour from the complete price shows that materials and overheads come to roughly CZK 950–1,300/m² for polystyrene and CZK 1,550–1,800/m² for wool. Buying materials yourself only makes sense if you calculate the consumption of adhesive, fixings and render accurately — indicative quantities per m² are in the facade works price list. Running out of material on the scaffold means idle time that you pay for.

Payback: how to calculate it

Payback is the cost of the insulation divided by the annual saving on heating. The saving cannot be estimated in general — it depends on what the house is built from, its windows, how it is heated and how much you pay for heat today. An energy assessor can calculate it reliably, for example as part of the building's energy performance certificate (PENB).

Illustrative calculation: a house currently spends CZK 60,000 a year on heating, and the assessor calculates that insulation will cut consumption by 40%. The annual saving is CZK 24,000. EPS insulation costing CZK 380,000 then pays back in about 16 years (380,000 / 24,000). These figures are only an example — use your own.

A few practical conclusions follow:

• The higher your heating bills, the faster the payback. An uninsulated older house pays back faster than one that already has some insulation.
• Subsidies shorten the payback significantly. Check the current conditions of the Nová zelená úsporám programme before signing — the application often has to be submitted before work starts.
• The wool premium does not pay back through energy savings. At the same thickness wool insulates about as well as white EPS. Choose wool for technical reasons, not for savings.
• Insulation also renews the facade. If the house would need new render anyway (from CZK 1,300/m²), count only the difference between insulation and render alone in your payback.

When you do not need to insulate

If the house is already insulated and the render is sound with only hairline cracks, repainting the facade for CZK 250–450/m² is often enough. That is 3–5 times cheaper than new insulation. When paint is enough is covered in facade painting.

How the work is done

1. Survey and design — condition and moisture of the substrate, thermal bridges, fire requirements, insulation thickness.
2. Scaffolding and preparation — cleaning, algae treatment, removing sills, downpipes and lightning conductor.
3. Starter track and bonding the boards — wool always fully bonded.
4. Anchoring with insulation fixings as designed; always with wool.
5. Reinforcement layer — adhesive with embedded mesh, corner beads and diagonal reinforcement at windows.
6. Primer and finish render, new sills, refitting the downpipes.

We usually complete a family house in 3–5 weeks. Most systems must not be applied below +5 °C.

Common mistakes

• Polystyrene on damp walls. The moisture stays in and the problem moves indoors.
• Non-breathable render on wool. It cancels out wool's main advantage.
• Spot-bonding wool and leaving out the fixings.
• No diagonal reinforcement at windows — cracks appear exactly at the corners.
• Ignoring the plinth and window reveals. Thermal bridges result.
• A quote without insulation thickness and scaffolding. It cannot be compared with others.

Checklist before ordering

• Does the quote state the specific insulation product, its thickness and λ?
• Are scaffolding, sills and waste removal included?
• Is it clear whether beads and reinforcement are included?
• Have you checked the fire requirements for the facade?
• Do you know how damp the walls are?
• Are you replacing windows before insulating, not after?
• Have you checked the subsidy and applied in time?

Frequently asked questions

How much does facade insulation cost per m²? With polystyrene CZK 1,500–2,200/m², with mineral wool CZK 2,200–2,800/m² including render, excluding VAT and scaffolding.

Which is better, polystyrene or mineral wool? Polystyrene is cheaper and is enough for newer masonry houses. Wool is better for older houses without damp-proofing, timber-frame houses, situations with fire requirements and noisy locations.

How much does it cost to insulate a house with 200 m² of facade? CZK 320,000–480,000 with polystyrene, CZK 460,000–600,000 with mineral wool, including scaffolding and excluding VAT.

How long does facade insulation take to pay back? Payback is the insulation cost divided by the annual heating saving. An energy assessor can calculate the saving for a specific house; subsidies shorten the payback.

Does mineral wool save more than polystyrene? At the same thickness, about the same as white EPS. Grey EPS insulates better. Wool is chosen for non-combustibility, vapour permeability and acoustics.

We insulate facades in Prague and the Central Bohemian Region with both polystyrene and mineral wool. We will visit, measure the facade, check the wall moisture and recommend the right system. The calculator below gives an indicative price.