What is the best insulation for a pitched roof?

Closed-cell spray foam insulation like Nexseal LE is the most effective option for pitched roofs. It provides superior thermal performance (0.027 W/mK), acts as an air barrier, and bonds directly to the underside of the roof tiles or slate, eliminating draughts and creating a warm roof construction.

Can you insulate a pitched roof without removing the tiles?

Yes. Spray foam insulation is applied directly to the underside of the roof from inside the loft space. There is no need to remove tiles, slates, or felt. The foam expands to fill all gaps and bonds to the existing surface.

How thick should pitched roof spray foam be?

For most pitched roofs, 100-150mm of closed-cell spray foam is recommended. At 150mm, Nexseal LE delivers a U-value of approximately 0.18 W/m2K, meeting Building Regulations for roof retrofits. Your installer will calculate the exact thickness needed.

Does spray foam insulation cause roof problems?

When installed by a trained professional using quality products, spray foam insulation is safe and effective. Closed-cell foam like Nexseal LE is moisture-resistant and does not absorb water. Open-cell foams allow moisture vapour to pass through. Both types are proven safe for roof applications when correctly specified.

How long does pitched roof spray foam insulation last?

Spray foam insulation has a lifespan of 25+ years with no degradation in thermal performance. Unlike fibreglass or mineral wool, it does not settle, sag, or lose effectiveness over time. Enverge products come with manufacturer-backed warranties.

Will spray foam insulation affect my mortgage or property survey?

Modern closed-cell spray foam products like Nexseal LE are widely accepted by lenders and surveyors when installed to industry standards with proper certification. Duratite provides full documentation and installation certificates through our Approved Installer Network.

Home›Pitched Roof Insulation

Fully Compliant Spray Foam Systems | BS EN 14315-1 Tested | BS 5250 Aligned

Pitched Roof Insulation

Name: Nexseal LE Closed Cell Spray Foam
Brand: Enverge
SKU: NEXSEAL-LE
Availability: InStock

Airtightness. Robust thermal performance. Part L Building Regulations compliant. The Enverge Spray Foam suite is formulated to meet the demands of modern construction — giving architects, building control officers, contractors and end users peace of mind that the insulation system will meet Part L compliance in a single, fast and reliable application with little mess, waste or disruption to the build programme.

BS EN 14315-1 declared performanceBS 5250:2021 moisture-safe designPart L compliance in one application

Book Free Survey Email info@duratite.ie

Enverge Spray Foam InsulationSucraseal open cell · Nexseal LE closed cell

0.027

Nexseal LE lambda W/m·K

0.039

Sucraseal lambda W/m·K

EN 14315-1

declared to BS EN 14315-1

Application to reach Part L compliance

On this pageWhy Spray Foam The Two Systems Who We Work With Our Process Where To Use Resources

What Sets It Apart

Why choose spray foam for pitched roof insulation?

Duratite’s spray foam insulation systems are engineered to deliver airtight, high-performance pitched roof insulation — built for today’s complex regulatory requirements, airtightness targets, and real-world site conditions. Here’s what sets spray foam apart from PIR boards or mineral wool.

1. Monolithic Air-Tightness

A continuous seal across rafters, valleys and junctions — no joints, gaps, taping, or thermal bypass. Airtightness tests consistently outperform other roof systems.

2. Exceptional Thermal Performance

Excellent resistance against heat loss: Nexseal LE at λ 0.027 W/m·K, Sucraseal at λ 0.039 W/m·K.

3. Moisture Safety (BS 5250)

Designed and installed as part of a moisture-risk-controlled build-up, with full static and dynamic condensation risk assessments to BS 5250:2021.

4. Shape-Adaptive for Any Roof

Naturally conforms to curved or vaulted roof lines, rafters, dormers, gables and timber sarking — full-fill insulation with no gaps, voids or inconsistent coverage.

5. Direct-to-Substrate Application

Both foams are approved for direct spray to low-resistance (Type LR) breathable membranes, timber sarking boards, and OSB/plywood structural sheathing.

6. Speeds The Programme

Meets modern airtight, thermal design requirements in a single fast application — helping construction timelines rather than holding them up.

Two High-Performance Systems

Enverge Sucraseal & Nexseal LE

Open Cell

Enverge Sucraseal

Designed for vapour-open pitched roof assemblies, requiring careful detailing in conjunction with vapour control layers (where applicable).

✓Lambda: 0.039 W/m·K
✓Low vapour resistance — allows buildings to breathe
✓Ideal for breathable roof underlays (Type LR)
✓Great acoustic insulation
✓Soft, full-fill expansion for irregular detailing
✓Perfect for use with hygro-variable AVCLs

Closed Cell

Enverge Nexseal LE

Designed for roof systems to meet thermal compliance with less space and built-in resistance to vapour.

✓Lambda: 0.027 W/m·K
✓Good vapour resistance for roofs with lower drying potential
✓Adds racking strength to timber frames
✓Suitable for use with or without internal AVCLs
✓Also approved for Type LR membranes — ideal when more vapour resistance is needed, even in diffusion-open roof designs

Important: Nexseal LE is not restricted to vapour-closed assemblies. It can be used on breathable membranes, just like Sucraseal, when greater moisture resistance, better thermal performance or structural rigidity is needed. Its excellent thermal resistance helps meet stringent U-value targets at reduced thickness compared to Sucraseal. Both systems are ideal for new-build applications to meet the requirements of airtight, thermal design.

Who We Work With

Supporting every stakeholder in the build

We support a wide spectrum of construction professionals, architects and other stakeholders to help design, implement and educate on spray foam systems. When it comes to pitched roof insulation, we know what it takes to meet compliance with modern regulations — and we help our clients achieve success from the outset.

Self-Builders & DIY

We guide you through the system design, Building Regs, and insulation options with complete support — from concept to handover.

Property Developers

Fast, clean installation. No taping, jointing, or cutting. Full documentation for DEAP, warranties and building control. Full handover documentation.

Architects & Designers

Full design support: build-ups, U-value reports, condensation analysis, technical detail and project specification clauses.

Installers & Contractors

Work backed by Duratite installer training. Clean, compliant, install-ready insulation systems with on-site detailing, training and support.

Building Control Officers

Working with building control before and after installation, providing moisture modelling, specifications, and full documentation.

End Clients

Peace of mind that the insulation system meets Part L compliance in a single, fast, reliable application.

Built on Compliance

Our process: built on compliance

Our pitched roof insulation is a high-performance spray foam system designed to be installed by trained professionals. When installed correctly, it is a highly effective and durable system that often outperforms traditional insulation materials.

Pre-installation roof condition survey

An initial assessment of the roof type, condition, membrane, ventilation pathways and moisture content is essential prior to any spray foam installation.

U-value and condensation risk modelling

We use BuildDesk and WUFI Pro for static and dynamic thermal modelling and moisture-risk assessment — the evidence required for robust insulation system design.

Trained, assessed installation

All installations are completed by Duratite-trained approved installers, who are assessed under Duratite’s own installer certification scheme.

Full handover documentation

Installation certificate, thickness verification, site photographs, guarantee paperwork and product datasheets — the complete handover pack.

Where To Use Our Systems

Versatile across domestic and commercial pitched roofs

Enverge Spray Foam Insulation can be used in a multitude of environments. Its versatility, durability, airtightness and thermal performance set it apart from other insulation materials — and it can speed up the construction timeline whilst meeting Part L Building Regulations compliance in a single application.

One system family — the right foam and build-up selected per project, evidenced by modelling.

Discuss Your Roof

✓

New build pitched roofsAirtight, Part L compliant thermal envelopes from day one.

✓

Habitable loft conversionsComfortable, conditioned loft space with minimal build-up depth.

✓

Deep retrofit projectsIncluding EnerPHit frameworks.

✓

Timber-framed roofsFull-fill expansion around rafters, sarking and sheathing.

✓

Irregular or complex roofsCurved, vaulted and detailed geometry sealed in one pass.

Technical Resources & Product Downloads

Full technical documentation for every system we supply

BS EN 14315-1 declared performanceProduct Technical Data SheetsGuidance on approved membranes and substratesBuild-up diagrams and 2D section detailingProject specification clausesCPD and design support available

All documentation supplied with your project pack or on request — email info@duratite.ie.

Let’s Talk Pitched Roof Insulation

Technical know-how, certified systems, full lifecycle support

Whether you’re insulating your own home or specifying a system across a development, Duratite provides the technical know-how, certified product systems, and full lifecycle support you need to get it right. Contact us to discuss your project, request modelling, or book a site assessment.