Spray Foam Insulation and Building Regulations in Ireland: Complete Guide

Building Regulations Overview

In the Republic of Ireland, spray foam insulation work is governed by the Building Regulations, with practical guidance on how to comply set out in a series of Technical Guidance Documents (TGDs) — one for each Part, from TGD A (structure) to TGD M (access and use). This guide covers the Republic of Ireland framework, with a note on Northern Ireland, which has its own regulations.

Three TGDs are particularly relevant to spray foam insulation projects: TGD L (energy performance), TGD B – Fire Safety, and TGD E – Sound. Understanding the requirements of each is essential for specifying spray foam correctly on any commercial or industrial building project.

Northern Ireland: projects in Northern Ireland fall under the Building Regulations (Northern Ireland) 2012. Energy performance guidance for buildings other than dwellings is given in Technical Booklet F2, and fire safety guidance in Technical Booklet E. The principles in this guide — continuous insulation, airtightness and correctly specified fire protection for exposed foam — apply equally, but always check figures against the Northern Ireland Technical Booklets.

It is important to note that Duratite is a distributor and technical specifier — not a building control body. This guide is provided as technical information to help building owners, architects, and contractors understand the regulatory framework. Your approved installer, design team and local Building Control Authority are the authorities on compliance for your specific project.

Part L: Energy Performance (TGD L 2022)

For buildings other than dwellings, the current guidance is Technical Guidance Document L 2022 – Buildings other than Dwellings, in force since 25 October 2022. It covers both new buildings and material alterations or renovation of existing buildings. The key metric is the U-value — the rate of heat transfer through a building element, measured in W/m²K. Lower U-values indicate better insulation. Dwellings are covered separately by TGD L – Dwellings, and new buildings must meet the NZEB (Nearly Zero Energy Building) standard.

TGD L 2022 also sets a reasonable upper limit for air permeability of 5 m³/(h·m²) at 50 Pa, tested on completion. Spray foam insulation, particularly closed-cell Nexseal LE with its thermal conductivity of 0.027 W/mK, suits both requirements: it insulates and seals the building fabric in a single seamless layer.

U-Value Requirements by Building Element

The following table shows the maximum area-weighted average U-values in TGD L 2022 for buildings other than dwellings, for new buildings and for material alterations or renovation. Because the thickness needed depends on the whole construction, it is set by a U-value calculation for each project rather than read from a table.

As a simple guide, thermal resistance equals thickness divided by conductivity (R = d/λ). With Nexseal LE's declared thermal conductivity of 0.027 W/mK, every 27mm of foam adds about 1.0 m²K/W — so reaching a wall U-value of 0.21 W/m²K from the foam alone (R of about 4.8 m²K/W) takes roughly 130mm, and less where other layers of the construction contribute. Where spray foam is supplementing existing insulation, thinner applications may achieve compliance. A Duratite technical survey will calculate the exact thickness required for your specific building construction.

Part B: Fire Safety (TGD B)

Technical Guidance Document B – Fire Safety governs fire safety requirements for building materials and construction. Spray foam insulation is a combustible material and must be specified with appropriate fire protection measures where required. The key classifications that apply to spray foam are:

Euroclass System (I.S. EN 13501-1)

The European reaction-to-fire classification, published in Ireland as I.S. EN 13501-1, rates materials from A1 (non-combustible) to F (no performance determined). Spray foam is typically classified as Euroclass E or B-s1,d0, depending on whether an intumescent coating is applied. Nexseal LE with DC315 intumescent coating achieves Euroclass B-s1,d0 — meaning very limited contribution to fire, low smoke production, and no flaming droplets.

Older National Classifications

Older national classifications (e.g. Class 0) may still appear on data sheets and in some older specifications. Current guidance in TGD B is expressed in Euroclasses to I.S. EN 13501-1, so ask for the Euroclass when comparing products. For reference, Nexseal LE with DC315 intumescent coating also achieves Class 0 when tested to BS 476 Parts 6 and 7.

When Fire Protection Is Required

Not all spray foam applications require fire protection. The requirement depends on the building use, the location of the foam within the construction, and whether it is exposed or concealed behind a non-combustible lining. In general:

Exposed spray foam in occupied commercial buildings (offices, retail, leisure) requires DC315 intumescent coating or a non-combustible barrier board. Spray foam concealed within a closed wall or ceiling construction — for example, between studs behind plasterboard — may not require additional fire protection. Requirements for agricultural buildings depend on their use and location. Your Duratite specification will detail the exact fire protection requirements for your application.

DC315 Intumescent Coating

DC315 is a water-based intumescent coating specifically designed for application over spray polyurethane foam. When exposed to fire, it expands to form a protective char layer that insulates the underlying foam from heat and flame, dramatically slowing fire spread across the foam surface.

DC315 is applied by spray or roller at a coverage rate of approximately 0.5 litres per square metre (achieving a dry film thickness of approximately 0.3mm). It dries to a thin, durable finish that does not significantly change the appearance of the foam. Application typically adds one day to the project programme and is itemised separately on the quotation, depending on site access and application method.

Duratite supplies DC315 intumescent coating alongside Nexseal LE and Sucraseal spray foam products. Our approved installers are trained in the correct application rates and methods for DC315 to ensure the tested fire performance is achieved on your project.

Part E: Sound (TGD E)

Technical Guidance Document E – Sound becomes relevant where a commercial spray foam project adjoins, or is converted to, residential use — for example in residential conversions and mixed-use developments.

Spray foam, particularly open-cell Sucraseal, provides excellent acoustic performance. The open cellular structure absorbs sound energy rather than reflecting it, making it effective at reducing airborne sound transmission. In stud wall applications, Sucraseal typically achieves Rw values (weighted sound reduction index) of 45–55 dB depending on wall construction and thickness — a useful contribution to acoustic separation, with compliance always confirmed for the complete construction.

Closed-cell Nexseal LE is denser and reflects more sound energy, making it less effective for acoustic insulation but still beneficial as part of a composite wall construction. For projects where both thermal and acoustic performance are critical, a hybrid approach — closed-cell for condensation-prone surfaces and open-cell for acoustic separation — can be specified.

Product Performance and Test Evidence

Third-party test evidence matters when you specify insulation. For Nexseal LE and Sucraseal, performance is evidenced by the manufacturer's declared values, tested to I.S. EN 14315-1, and the products are CE marked. The declared values for Nexseal LE cover:

• Thermal conductivity of 0.027 W/mK (lambda 90/90 design value)
• Dimensional stability over the product lifetime
• Resistance to moisture, fungi, and vermin
• Fire performance characteristics
• Long-term durability in building applications

For building control purposes, compliance is supported by the manufacturer's declared values (I.S. EN 14315-1), the Euroclass B-s1,d0 reaction-to-fire classification of the system when coated with DC315, and full installation documentation including thickness verification and U-value calculations.

When selecting a spray foam product, always ask for the test evidence behind every claimed figure — the standard used, the declared value, and the documentation handed over at completion — and verify any certificate on the issuing body's public register before relying on it.

Exemptions: Agricultural and Temporary Buildings

Certain building types benefit from partial or full exemptions from the Building Regulations, and the rules differ between the Republic of Ireland and Northern Ireland. Some buildings used solely for agriculture may fall outside the energy performance requirements, in which case spray foam thickness on farm buildings, barns, livestock shelters and grain stores is set by the farmer's practical requirements rather than a regulatory U-value. Always confirm whether an exemption applies with your Building Control Authority before relying on it.

However, if an agricultural building is converted to a different use (such as a residential barn conversion, office, or workshop), the relevant requirements apply in full, including TGD L, TGD B and TGD E. The spray foam specification must then meet the relevant U-value, fire safety, and acoustic standards.

Temporary buildings and certain small detached buildings may also be exempt from some requirements, though these exemptions rarely apply to the commercial and industrial projects that Duratite typically specifies for.