What is the best insulation for a house in Extremadura?
Reviewed on 7 September 2026
Expanded cork on the facade, a wood-fibre board on the roof, and blown cellulose if you are retrofitting without opening the walls. In Extremadura the problem is summer, not winter: 265 of its 388 municipalities sit in climate zone C4 of the Spanish Building Code, and that 4 is the highest summer severity on the scale. A light insulation stops the cold as well as a heavy one with the same conductivity, but against July heat what counts is how much mass stands between the sun and you, and that is where dense materials win.
All three picks hold a verified environmental declaration that we have read and that is still valid. That is not a detail: most of the insulation products in the directory don't have one, and among those that don't are the two cork manufacturers from Extremadura itself.
Our picks
Our pick for facadesAmorim Cork Insulation
Expanded cork at 100 to 120 kg/m³ and 0.040 W/m·K, with its own declaration valid to 2028 and the most negative footprint in the directory: −2,040 kg CO₂e per cubic metre. Made in Aveiro, Portugal, from the same cork oak that grows in the Extremaduran dehesas.
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For the roofSteico aislamientos
Rigid wood-fibre board at 140 kg/m³ and 0.040 W/m·K, with its own declaration valid to 2031 and −135 kg CO₂e per cubic metre. It puts the most mass between the sun and the ceiling. The declaration covers the group's Polish plant.
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If you are blowing into a cavityISOCELL GmbH & Co KG
Recycled-paper cellulose, 0.038 W/m·K at 45 kg/m³, with a 2024 declaration in the IBU programme: −1.42 kg CO₂e per kilo. It is the way to insulate an existing house without opening the walls. None of the Spanish cellulose manufacturers in the directory holds a valid declaration today.
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Who this is for
For anyone building or retrofitting a home in Extremadura who has to choose the insulation for the roof, the facade or the cavity, and wants to justify it with a document rather than a brochure.
It is not for anyone looking for the cheapest option: we hold no verified prices, and we say so below. And it does not replace the engineer's calculation: the Building Code requires justifying the consumption of the whole building (HE0), not just the U-value of each wall.
How we chose
First, a verified environmental declaration, read by us and still valid. If there is no document, or it has expired, the material is not featured however good it is.
Second, high density at equal conductivity, because in Extremadura the enemy is summer.
Third, a clear use: an external facade, a roof and a cavity filled through a hole don't ask for the same thing, so there is one pick for each rather than a single winner.
Fourth, distance: all else being equal, we prefer what is made in the Iberian Peninsula. We have not weighed price, because we hold no verified prices.
What shapes the answer
The Building Code classifies each municipality with a letter for winter and a number for summer. Extremadura has 265 municipalities in C4, 106 in D3, 15 in C3 and 2 in E1. Badajoz, Cáceres, Mérida and Plasencia are C4; Zafra, Hervás or Guadalupe, by altitude, D3. A summer 4 is the top of the scale.
For winter, DB-HE1 sets limit U-values: in zone C, 0.49 W/m²K for facades and 0.40 for roofs; in zone D, 0.41 and 0.35. With an insulation of conductivity 0.040, meeting the limit with the insulation alone takes roughly 8 to 10 cm on a facade and 10 to 12 on a roof, before counting the other layers. Those are minimums: HE0 usually pushes for more.
For summer there is no single number in HE1 that settles it. What delays the heat is mass: at equal conductivity, a 140 kg/m³ board stores far more heat than a 35 kg/m³ batt, and the heat wave reaches the inside late at night instead of mid-afternoon. The standard that quantifies this is ISO 13786, with time lag and decrement factor; we have not calculated it here, which is why we talk about density, which is declared.
How we tested
We calculated the summer behaviour of three typical build-ups under EN ISO 13786, with a 24-hour period: how many hours the outdoor heat wave takes to show up inside (time lag) and what fraction of the outdoor swing reaches the interior (decrement factor). Every layer carries its source. Your wall won't be exactly this one; the order of magnitude will.
Cubierta inclinada, aislada por fuera
Es donde más pega el sol en Extremadura. Teja, cámara, aislante sobre el tablero, y placa de yeso por dentro: el esquema habitual de una cubierta aislada por el exterior. Se comparan tres aislantes con el mismo espesor, 140 mm, que es lo que un presupuesto especifica.
| Option | Time lag | Decrement | U | Mass |
|---|---|---|---|---|
| Fibra de madera 140 mm | 8.5 h | 0.5 | 0.25 W/m²K | 81 kg/m² |
| Lana mineral 140 mm | 3.2 h | 0.92 | 0.22 W/m²K | 67 kg/m² |
| EPS 140 mm | 2.7 h | 0.93 | 0.23 W/m²K | 64 kg/m² |
Layers, outside to inside
- Fibra de madera 140 mm: Teja de arcilla cocida (20 mm, λ 1, ρ 2000, c 800; CEC 3.11) → Cámara de aire bajo teja, no ventilada (R 0.16 m²·K/W; ISO 6946 tabla 8) → STEICOspecial dry (fibra de madera) (140 mm, λ 0,04, ρ 140, c 2100; TDS STEICO; ρ de la DAP NEPD-11332) → Tablero de madera de conífera, 22 mm (22 mm, λ 0,13, ρ 500, c 1600; ISO 10456 tabla 3) → Placa de yeso laminado, 12,5 mm (13 mm, λ 0,25, ρ 825, c 1000; CEC 3.6)
- Lana mineral 140 mm: Teja de arcilla cocida (20 mm, λ 1, ρ 2000, c 800; CEC 3.11) → Cámara de aire bajo teja, no ventilada (R 0.16 m²·K/W; ISO 6946 tabla 8) → Lana mineral, 40 kg/m³ (140 mm, λ 0,035, ρ 40, c 1030; ISO 10456 tabla 3 (c); λ genérica de catálogo) → Tablero de madera de conífera, 22 mm (22 mm, λ 0,13, ρ 500, c 1600; ISO 10456 tabla 3) → Placa de yeso laminado, 12,5 mm (13 mm, λ 0,25, ρ 825, c 1000; CEC 3.6)
- EPS 140 mm: Teja de arcilla cocida (20 mm, λ 1, ρ 2000, c 800; CEC 3.11) → Cámara de aire bajo teja, no ventilada (R 0.16 m²·K/W; ISO 6946 tabla 8) → EPS, 20 kg/m³ (140 mm, λ 0,036, ρ 20, c 1450; ISO 10456 tabla 3) → Tablero de madera de conífera, 22 mm (22 mm, λ 0,13, ρ 500, c 1600; ISO 10456 tabla 3) → Placa de yeso laminado, 12,5 mm (13 mm, λ 0,25, ρ 825, c 1000; CEC 3.6)
Fachada aislada por fuera (SATE)
La fachada de media asta de ladrillo perforado es la más común en la vivienda extremeña de las últimas décadas. Se aísla por el exterior con 100 mm y revoco, y se comparan tres aislantes con el mismo espesor.
| Option | Time lag | Decrement | U | Mass |
|---|---|---|---|---|
| Corcho expandido 100 mm | 7.8 h | 0.4 | 0.35 W/m²K | 188 kg/m² |
| EPS 100 mm | 6.2 h | 0.43 | 0.32 W/m²K | 179 kg/m² |
| Lana mineral 100 mm | 6.4 h | 0.43 | 0.31 W/m²K | 181 kg/m² |
Layers, outside to inside
- Corcho expandido 100 mm: Mortero de cemento, revoco 15 mm (15 mm, λ 1,3, ρ 1900, c 1000; CEC 3.5 (1800<ρ≤2000)) → Amorim ICB (corcho expandido) (100 mm, λ 0,04, ρ 110, c 1500; TDS Amorim (λ, ρ); c: CEC 3.8, placas de corcho) → ½ pie de ladrillo perforado, 115 mm (115 mm, λ 0,639, ρ 1140, c 1000; CEC 3.11 (R = 0,18 m²·K/W)) → Enlucido de yeso, 15 mm (15 mm, λ 0,57, ρ 1150, c 1000; CEC 3.6 (1000≤ρ≤1300))
- EPS 100 mm: Mortero de cemento, revoco 15 mm (15 mm, λ 1,3, ρ 1900, c 1000; CEC 3.5 (1800<ρ≤2000)) → EPS, 20 kg/m³ (100 mm, λ 0,036, ρ 20, c 1450; ISO 10456 tabla 3) → ½ pie de ladrillo perforado, 115 mm (115 mm, λ 0,639, ρ 1140, c 1000; CEC 3.11 (R = 0,18 m²·K/W)) → Enlucido de yeso, 15 mm (15 mm, λ 0,57, ρ 1150, c 1000; CEC 3.6 (1000≤ρ≤1300))
- Lana mineral 100 mm: Mortero de cemento, revoco 15 mm (15 mm, λ 1,3, ρ 1900, c 1000; CEC 3.5 (1800<ρ≤2000)) → Lana mineral, 40 kg/m³ (100 mm, λ 0,035, ρ 40, c 1030; ISO 10456 tabla 3 (c); λ genérica de catálogo) → ½ pie de ladrillo perforado, 115 mm (115 mm, λ 0,639, ρ 1140, c 1000; CEC 3.11 (R = 0,18 m²·K/W)) → Enlucido de yeso, 15 mm (15 mm, λ 0,57, ρ 1150, c 1000; CEC 3.6 (1000≤ρ≤1300))
Cámara existente rellenada por insuflado
La rehabilitación sin obra: fachada de ladrillo perforado con cámara de 70 mm y tabique interior, que se rellena por taladros. Se compara la celulosa con la lana mineral insuflada.
| Option | Time lag | Decrement | U | Mass |
|---|---|---|---|---|
| Celulosa insuflada 70 mm | 7.3 h | 0.55 | 0.43 W/m²K | 220 kg/m² |
| Lana mineral insuflada 70 mm | 6.9 h | 0.56 | 0.4 W/m²K | 219 kg/m² |
Layers, outside to inside
- Celulosa insuflada 70 mm: Mortero de cemento, revoco 15 mm (15 mm, λ 1,3, ρ 1900, c 1000; CEC 3.5 (1800<ρ≤2000)) → ½ pie de ladrillo perforado, 115 mm (115 mm, λ 0,639, ρ 1140, c 1000; CEC 3.11 (R = 0,18 m²·K/W)) → ISOCELL (celulosa insuflada) (70 mm, λ 0,038, ρ 45, c 2110; isocell.com (λ AT/EU, c); ρ de la ficha) → Tabique de ladrillo hueco sencillo, 40 mm (40 mm, λ 0,444, ρ 1000, c 1000; CEC 3.11 (R = 0,09 m²·K/W)) → Enlucido de yeso, 15 mm (15 mm, λ 0,57, ρ 1150, c 1000; CEC 3.6 (1000≤ρ≤1300))
- Lana mineral insuflada 70 mm: Mortero de cemento, revoco 15 mm (15 mm, λ 1,3, ρ 1900, c 1000; CEC 3.5 (1800<ρ≤2000)) → ½ pie de ladrillo perforado, 115 mm (115 mm, λ 0,639, ρ 1140, c 1000; CEC 3.11 (R = 0,18 m²·K/W)) → Lana mineral, 35 kg/m³ (70 mm, λ 0,035, ρ 35, c 1030; ISO 10456 tabla 3 (c); λ genérica de catálogo) → Tabique de ladrillo hueco sencillo, 40 mm (40 mm, λ 0,444, ρ 1000, c 1000; CEC 3.11 (R = 0,09 m²·K/W)) → Enlucido de yeso, 15 mm (15 mm, λ 0,57, ρ 1150, c 1000; CEC 3.6 (1000≤ρ≤1300))
Compare the data
| Material | Footprint A1–A3 | Conductivity λ | Density | Verified EPD | Standard |
|---|---|---|---|---|---|
| Amorim Cork Insulation | -2040 kg CO₂e/m³ | 0,04 W/m·K | 100 kg/m³ | Yes · document | +A2 |
| Steico aislamientos | -135 kg CO₂e/m³ | 0,036 W/m·K | 50 kg/m³ | Yes · document | +A2 |
| Pavatex | -12,66 kg CO₂e/m² | — | — | Yes · document | +A2 |
| Ekolution | -6,81 kg CO₂e/m² | 0,04 W/m·K | 35 kg/m³ | Yes · document | +A2 |
| ISOCELL GmbH & Co KG | -6,39 kg CO₂e/m² | 0,038 W/m·K | 45 kg/m³ | Yes · document | +A2 |
| Hunton | -2,553 kg CO₂e/m² | — | — | Yes · document | +A2 |
| AISLANAT | — | 0,039 W/m·K | 45 kg/m³ | Expired | EN 15804 |
| Amorim Florestal España | — | 0,04 W/m·K | 100 kg/m³ | No | — |
| Barnacork | — | 0,039 W/m·K | 110 kg/m³ | No | — |
| CELULOSA - Ecogreenhome | — | 0,039 W/m·K | 45 kg/m³ | No | — |
| Inexcor Industria Corchera | — | 0,038 W/m·K | 110 kg/m³ | No | — |
Only materials with some published data are listed, ordered by footprint within each unit. Two footprints declared in different units are not comparable with each other, and neither are two versions of the standard: EN 15804 «+A2» and «+A1» count biogenic carbon differently, and «ISO 21930» is another accounting altogether. «Yes · document» means we hold the declaration and the figures come from it; «Declared» means the manufacturer says it has an EPD but we don't hold the document, and its figures come from the entry. A dash means the manufacturer doesn't publish it, not that the material lacks it.
What we don't know
Prices. We hold no verified prices for any of them, and in insulation the installed price per square metre changes the decision as much as conductivity does.
Availability in Extremadura. The region's two cork manufacturers, Inexcor and Amorim Florestal España, are in the directory and appear in the table, but not among the picks, because they hold no verified environmental declaration. If they obtain one, this answer changes.
Thermal lag in figures. We talk about mass and density because they are declared; the time-lag and decrement calculation under ISO 13786 depends on the complete wall build-up and we have not done it.
The conductivity of the STEICO board, 0.040, comes from the manufacturer's technical sheet, not from its environmental declaration, which doesn't include it. That material's directory entry shows 0.036 and 50 kg/m³, which belong to another format in its range, the flexible batt.
Mineral wool is not in the table. The mineral wool declarations we hold are under the previous version of the standard, EN 15804+A1, and the table doesn't distinguish versions, so we don't mix them with the rest.
Sources
- Climate zones of Extremadura's 388 municipalities · Spanish Building Code CTE DB-HE 2019, Annex B, table of municipalities (copy in Descarboniza's own code) · 2026-09-07
- Limit U-values by zone · CTE DB-HE1, table 3.1.1.a · 2026-09-07
- Amorim ICB expanded cork · EPD Hub no. EPD HUB-0281, EN 15804+A2, valid to 2028-02-13; conductivity from the manufacturer's Corkboard v8 data sheet · 2026-09-07
- STEICOspecial dry · NEPD-11332-11332-2, EPD Norge / Global EPD, EN 15804+A2, valid to 2031-03-26; conductivity from STEICO's technical sheet · 2026-09-07
- ISOCELL cellulose · EPD-ISC-20240568-CCA1-EN, IBU, EN 15804+A2, 2024; conductivity from isocell.com · 2026-09-07
No company pays to appear here or to be picked. The selection is not for sale. How we measure →