Alternative Insulation Specifications

We are all familiar with the market leaders in insulation such as Celotex, Kingspan, Knauf and Rockwool. They provide excellent websites and some even provide good technical services (some do not). But when you have insulation specified by the Architect or energy assessor (SAP Assessor), what alternative insulation specifications are out there?

Below, we have listed the typical standard specifications and performance with alternative insulation specifications that may allow for better value and easy to obtain due to insulation shortages. We recommend that you check if the insulation has a BBA or 90/90 test to ensure it meets your required standard.

Insulation Type Typical Thermal Conductivity
Super PIR (e.g. Kingspan) 0.018 W/mK
PIR (e.g. Celotex) 0.022 W/mK
EPS (e.g. Jablite) 0.036 W/mK
Mineral Wool (e.g. Rockwool) 0.040 W/mK
Polystyrene Beads 0.036 W/mK

Cavity Wall – Full Fill

Whether you have a 100, 125 or 150mm cavity, here are some alternative insulation specifications for full fill cavity walls:

Thermal Conductivity Alternative Insulation Specifications
0.032 W/mK Knauf Dritherm 32
Superglass Superwall 32
0.033 W/mK Ecobead Platinum (blown EPS)
0.034 W/mK Knauf Dritherm 34
Knauf Supafil 34
Superglass Superwall 34
0.035 W/mK URSA 35
0.036 W/mK Superglass Superwall 36
0.037 W/mK Knauf Dritherm 37
Rockwool Cavity Batts


Full fill mineral wool to cavity

Cavity Wall – Partial Fill

Below are a range of alternative PIR insulation products for partial fill insulation depending on performance:

Thermal Conductivity Alternative Insulation Specifications
0.018 W/mK Kingspan K108 Cavity Board
0.022 W/mK Recticel Eurowall +
Ecotherm Eco-Cavity
Celotex CW4000
Kingspan TW50

Ground Floor Insulation

The most common insulation types for the ground floor are PIR and EPS. Below are typical examples for alternative insulation specifications and the typical U values for a beam & block floor based on a P/A off 0.5 with 100mm PIR or 150mm EPS:

Thermal Conductivity Insulation Specification Thickness U Value P/A = 0.5
0.036 W/mK Jablite 150 150mm 0.17 W/m2.K
0.034 W/mK Sundolit S200 150mm 0.15 W/m2.K
0.032 W/mK Jablite HP100 150mm 0.15W/m2.K
0.022 W/mK Celotex GA4000
Ecotherm Eco-Versal
100mm 0.16 W/m2.K
0.018 W/mK Kingspan K107 100mm 0.13 W/m2.K


Ceiling Insulation

Ceiling level insulation installed between roof truss ceiling joists and over them. Typical U values to be achieved are 0.10 to 0.16 W/m2.K. Most common form of insulation is mineral wool. Below are common insulation materials to be specified:

Thermal Conductivity Alternative Insulation Specifications
0.032 W/mK Knauf Rafter Roll (50-140mm)
0.039 W/mK Thermafleece Cosywool
0.040 W/mK Knauf Loft Roll 40
Superglass Multi-roll 40
Thermafleece Supasoft Recycled Plastic
0.044 W/mK Knauf Loft Roll 44
Superglass Multi-roll 44
Superglass Handy pack 44
URSA 10 Loft Roll
Rockwool Roll

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