Insulated Raft Foundation Systems Compared
What UK suppliers publish about their materials, certification and thermal performance, and how to compare them properly.
Who wrote this: ISOQUICK is one of the suppliers listed below. Everything in the table is what each supplier states on its own website or certificate, reviewed on 21 September 2026, with a link to the source. We have not tested any product, and we do not rank suppliers. Published information changes, so check current details with each supplier.
An insulated raft foundation replaces the conventional trench-and-slab build-up with a slab cast inside a continuous layer of insulation. Several UK and Irish suppliers make systems that look similar but are designed and documented differently. This page sets out what each publishes, and what to check before you specify one.
What to compare
- Independent certification — who issued it, the certificate number, and what it actually covers (wall types, building types, validity).
- How the U-value was calculated — slab thickness, insulation depth and perimeter-to-area ratio all change the answer.
- The Psi-value at the wall-floor junction — a good floor U-value does not tell you how much heat is lost at the edge.
- Structural design — a flat raft, or a slab with ring beams — and who takes design responsibility.
- Ground conditions and wall types the system is designed for.
- Supply model — supply only, design and supply, or installed.
Suppliers side by side
All entries are the supplier's own statements unless marked otherwise. "Not stated" means the page we reviewed did not give the information, not that the supplier does not have it.
| Supplier / system | Insulation (as stated) | Certification (as stated) | Published U-value | Published Psi-value | Supply model (as stated) |
|---|---|---|---|---|---|
| ISOQUICK Certificate · U-value tables |
EPS, three grades: IQ-60e (200 kPa, λ 0.031), IQ-90 (300 kPa, λ 0.033), IQ-210 (700 kPa, λ 0.034), per its Kiwa certificate | Kiwa BDA Agrément BAF-20-179-S-A-UK (new dwellings; first issued Feb 2022, reissued July 2025). Certified Passive House Institute component, certificate 0379fs03, for ICF, external-insulation and lightweight-timber connection details. | 0.07–0.18 W/m²K depending on grade, under-slab insulation (150–300 mm) and P/A ratio; tables assume a 250 mm slab | ISOQUICK states a PHPP Psi-value below 0.1 W/mK for a typical 200 mm build-up. The Passive House certification criterion for certified details is Ψe ≤ 0.01 W/mK. | Design support and supply |
| KORE Insulated Foundation | EPS 100, 200 and 300 | BBA Agrément 24/7229 (Nov 2024); NSAI certificate 20/0424 (as stated on its page) | "As low as 0.10 W/m²K"; typical 0.10–0.11. Its chart shows 0.076–0.105 across P/A 0.10–0.60 (build-up not stated). | Not stated on its page. Its BBA certificate lists only the generic SAP default junction value. | Approved installer network |
| Future Found (Build-Lite) | EPS | BBA certificate 19_5617 | "As low as 0.08 W/m²K" | "As low as 0.06 W/m²K" | Design and engineering services offered |
| GreenRaft | XPS, or cellular glass to order | States products are certified and accepted by warranty providers; no certificate numbers on the pages reviewed | Not stated (online calculator) | Not stated | Components built up on site |
| Passive Slab | Izodom interlocking EPS panels | Not stated on the page reviewed | 0.09–0.14 W/m²K depending on P/A ratio | Not stated | Supply only, on-site assistance, or fully installed |
| Advanced Foundation Systems (THEPASSIVHAUS) | Factory-cut permanent formwork (material not stated) | States it is certified by the Passive House Institute | Not stated | Not stated | Manufactured off-site; design and engineering offered |
| Jackodur Atlas (ICF Bondmor Group) | XPS | States "Passivhaus certified solution"; no certificate reference on the page | Not stated | Not stated | Quote-based; "from £40/m²" subject to engineering |
| AFT Limited (EcoRaft) | EPS grades 100, 200 and 300, with preformed corner and L-shaped perimeter units | States it is approved and certified and holds a European Technical Assessment; no certificate numbers on the pages reviewed | MonoBeam page: "U Value >0.1 W/m²K"; no figures for other EcoRaft types | Not stated (describes "low linear thermal bridging") | Design, supply and installation; quotation asks for a ground bearing capacity within 70 kPa where known; MonoBeam can incorporate piles |
| Viking House "Passive Slab" (Ireland) page dated 2023 |
High-density EPS (EPS 300 under thickened slab areas) | States "Passive House certified"; no certificate reference on the page reviewed | "As low as 0.08" (unit given as W/m.K on the page) | Not stated | Contact the supplier; ring-beam width can be varied on site, per its page |
| MBC Timber Frame passive foundation | EPS | States it is a "PassiveHaus certified system"; no certificate reference on the page reviewed | 0.105 W/m²K | Not stated | Supply and fit, offered for MBC timber-frame projects; slab construction stated as 6–7 days |
| SuperSIPs Passive Found news post dated June 2021 |
"Structural EPS" | States it "meets passive house certification"; no certificate reference on the page reviewed | "As low as 0.08" | Not stated | Sold alongside its SIPs panels; designed per building |
Not yet reviewed: Castleforms Raft-Therm (its website could not be reached when we tried) and Kingspan Aeroground (sold mainly in Ireland; UK availability not confirmed). We will add them once we can read their published information.
Installers and resellers
Several firms install or resell systems made by others rather than making their own. On the pages reviewed: ICF Bondmor (Leeds) installs the Jackodur Atlas system and states installation "from £120–190/m²" subject to engineering; Basement Homes (Solihull) installs GreenRaft; Aspect Nubuild (Shepton Mallet) offers insulated foundation slabs alongside ICF construction; and Econekt (Clydebank) distributes Izodom products. Ask any installer which system they use, who designs it and who holds the certification.
Reading the numbers
U-values are not like-for-like
A floor U-value depends on the slab thickness, the depth of insulation, the ratio of exposed perimeter to floor area (P/A) and the ground. One supplier's "as low as 0.08" and another's "0.10–0.11" may describe different buildings. Ask every supplier for the U-value at your P/A ratio, with the build-up written out.
The Psi-value is where the comparison gets harder
The Psi-value measures heat lost along the wall-floor junction. Two systems with the same floor U-value can lose very different amounts of heat there. In the pages and certificates reviewed for this page, Future Found and ISOQUICK state a Psi-value figure; most others do not. It is a fair question to put to any supplier, and the answer should come with the calculation method and who carried it out. Our article on how to tell insulated rafts apart explains why both numbers matter.
Flat raft or ring beam?
Some systems are designed as a flat slab that spreads wall loads across the raft. Others form a ring beam around the perimeter, with a thinner slab between. The difference affects load spread, edge insulation thickness and reinforcement. Suppliers describe their own designs differently, and some argue the distinction is less important than it used to be. We cover the difference in What is the difference between an insulated foundation and an insulated raft?
Questions to ask any supplier
- What is the certificate number, who issued it, and does it cover my wall type and building type?
- What is the U-value for my P/A ratio, and what slab thickness and insulation depth does it assume?
- What is the Psi-value at the wall-floor junction for my wall type, how was it calculated, and by whom?
- Is the slab designed as a flat raft or with ring beams, and who takes design responsibility?
- What ground conditions is the design suitable for, and what does the engineer need from me?
- Are cost or programme claims backed by an itemised comparison I can check against my own project?
Supplier cost claims vary widely (for example, KORE, GreenRaft and Jackodur each publish different savings or price figures on their pages). They are marketing statements based on each supplier's own example, so ask for the itemised basis before relying on one.
Compare ISOQUICK for your project
Send us your plans and wall type and we will give you the U-value, the junction detail and the certification that applies to your build.
Get a Quote KORE vs ISOQUICKHead-to-head comparisons
- KORE vs ISOQUICK — ring-beam and flat-raft designs, certificates and figures
- Passive Slab (Izodom) vs ISOQUICK — certification, U-values and service model
- EPS vs XPS — ISOQUICK against Jackodur Atlas and GreenRaft, using the Kiwa and BBA certificates
ISOQUICK projects by region
See real ISOQUICK installations and the Building Regulations requirements its certificate covers in Wales and Hertfordshire and the South East.
Sources
- KORE Insulation — KORE Insulated Foundation System and BBA Agrément Certificate 24/7229 (issued 21 November 2024)
- Build-Lite — Future Found insulated raft foundation
- GreenRaft — Product information
- Passive Slab — passiveslab.co.uk
- Advanced Foundation Systems — advancedfoundationsystems.co.uk
- ICF Bondmor Group — Jackodur Atlas raft foundations and insulated raft installation
- AFT Limited — EcoRaft and EcoRaft MonoBeam
- Viking House — Passive Slab
- MBC Timber Frame — Passive foundations
- SuperSIPs — Passive Found insulated foundations
- Basement Homes — Insulated raft foundations; Aspect Nubuild — aspectnubuild.com; Econekt — econekt.co.uk
- ISOQUICK — Kiwa BDA Agrément BAF-20-179-S-A-UK; U-value tables TD-0002 and TD-0004 (May 2025); Passive House Institute certificate
Spotted something out of date or wrong? Suppliers and readers can tell us through the callback form and we will correct it.