The short answer
- Northern Ireland has its own Building Regulations. Energy performance of buildings other than dwellings is covered by the Building Regulations (Northern Ireland) 2012 and Technical Booklet F2:2022, in effect from 30 June 2022.
- New buildings: Table 2.3 limits area-weighted U-values to 0.16 W/m²K for pitched roofs, 0.20 for flat roofs, 0.21 for walls and 0.21 for floors. Air permeability must not exceed 10 m³/(h·m²) at 50 Pa, and buildings are normally expected to achieve 5 or less.
- Existing buildings: renovating more than 50% of an element, or a major renovation of more than 25% of the envelope, means upgrading to Table 3.4. For example, 0.18 for a roof insulated at rafters or a flat roof, and 0.30 for a wall with external or internal insulation.
- EPCs are needed when a building is constructed or marketed for sale or rent, and they are valid for 10 years. Closed-cell spray foam improves both the U-value and the air leakage an assessor models.
Northern Ireland is a separate system
If your building is in Antrim, Armagh, Down, Fermanagh, Londonderry or Tyrone, the rules in this guide apply, and only these. Northern Ireland is part of the United Kingdom, but its Building Regulations, technical guidance and energy certificates are its own. They are not the same as the rules in Great Britain, and they are not the same as the rules south of the border. Guidance written for either of those places can mislead you on a Northern Ireland project.
The practical points for anyone buying insulation work here:
- Regulations: the Building Regulations (Northern Ireland) 2012, with Technical Booklets published by the Department of Finance. Part F covers the conservation of fuel and power.
- Energy certificates: Energy Performance Certificates (EPCs) and, for some public buildings, Display Energy Certificates (DECs).
- Fire: Technical Booklet E.
- Health and safety: HSENI is the regulator. Asbestos work falls under the Control of Asbestos Regulations (Northern Ireland) 2012.
- Money: quotations for Northern Ireland work are in sterling and subject to UK VAT.
Duratite supplies Enverge and Purios spray foam and routes survey requests to approved installers who cover the six counties. We do not have a branch in every town, and we will not pretend to.
Technical Booklet F2:2022 in brief
Part F of the Building Regulations (Northern Ireland) 2012 sets the legal requirements for conserving fuel and power. The Department of Finance publishes two Technical Booklets explaining how to meet them. F1 covers dwellings. F2 covers buildings other than dwellings: offices, shops, warehouses, factories, schools, hotels and similar. The current edition, Technical Booklet F2:2022, took effect on 30 June 2022 and applies to new plans applications made from that date.
Following the Technical Booklet is a way of showing compliance with the regulations. Building control works from its figures, so they are the numbers that decide the specification. F2 is organised around several criteria, including:
- the building's calculated carbon emission rate compared with a target, including nearly zero-energy requirements for new buildings
- limits on fabric performance: maximum U-values and air permeability
- limiting the effects of solar gain to avoid overheating
- building performance consistent with the design: testing, commissioning and information for the owner
U-values under F2 should be calculated using the conventions in BRE Report BR 443. For spray foam on a profiled roof, the calculation should account for the sheet, purlins and any fixings, not just the foam.
New buildings: U-values and air permeability
Table 2.3 of Technical Booklet F2:2022 sets limiting U-values for the fabric of new buildings other than dwellings. The area-weighted figure is the average for all elements of that type. The "any point" figure is the worst any individual part may be.
| Element | Area-weighted average U-value (W/m²K) | Maximum U-value at any point (W/m²K) |
|---|---|---|
| Wall | 0.21 | 0.60 |
| Floor, ground and exposed | 0.21 | 0.60 |
| Roof, pitched | 0.16 | 0.30 |
| Roof, flat | 0.20 | 0.30 |
Source: Technical Booklet F2:2022, Table 2.3 (selected rows). Windows, rooflights, doors and other elements have their own limits.
These limits are backstops. The building must also meet its carbon emission target, so the fabric often needs to be better than Table 2.3 to make the whole-building calculation work.
Air permeability
Paragraph 2.59 sets the maximum permissible air permeability at 10 m³/(h·m²) at 50 Pa. It adds that buildings are normally expected to achieve 5 m³/(h·m²) at 50 Pa or less. Air leakage in metal-clad buildings concentrates at sheet laps, eaves, ridges, verges, doors and penetrations. Closed-cell spray foam applied to the underside of the sheets fills the corrugations and seals those laps and junctions as it insulates. That makes it an efficient way to deal with leakage on single-skin roofs, alongside proper sealing of doors and openings. F2 also notes that as buildings get tighter, ventilation and indoor air quality need attention. Your designer confirms the ventilation strategy.
Building in Northern Ireland?
Tell us the building, the county and the target U-value if you have one. We will arrange a free survey and a fixed price in sterling.
Existing buildings: when you must upgrade
Most insulation work in Northern Ireland is on existing buildings. Technical Booklet F2 sets out when the fabric has to be brought up to standard.
Renovating a thermal element
Renovating a thermal element means work such as providing a new layer or replacing a layer. When that renovation either constitutes a major renovation (more than 25% of the surface area of the building envelope) or covers more than 50% of the surface of the individual element, the whole element should be upgraded to the improved U-value in column (b) of Table 3.4. The area counted is that of the individual element. Stripping the whole roof of an annex means the annex roof is the element, not the total roof area of the building.
Retained elements and changes of use
Where an existing element has a U-value worse than the threshold in column (a) of Table 3.4, it should be upgraded to column (b) in certain situations, provided that is technically, functionally and economically feasible. Those situations include a material change of use, or an existing element becoming part of the thermal envelope for the first time. F2 treats a simple payback of 15 years or less as a reasonable test of economic feasibility. Where column (b) is not feasible, the element should reach the best practicable standard within that payback, and it should be no worse than 0.7 W/m²K.
| Element | (a) Threshold U-value (W/m²K) | (b) Upgraded U-value (W/m²K) |
|---|---|---|
| Cavity wall, cavity insulation | 0.70 | 0.55 |
| Wall, external or internal insulation | 0.70 | 0.30 |
| Pitched roof, insulation at ceiling level | 0.35 | 0.16 |
| Pitched roof, insulation at or between rafters | 0.35 | 0.18 |
| Flat roof or roof with integral insulation | 0.35 | 0.18 |
| Floors | 0.70 | 0.25 |
Source: Technical Booklet F2:2022, Table 3.4. Its notes allow lesser provision in some cases, for example where head room or floor area would be unreasonably reduced.
A bare single-skin metal or fibre cement roof is far worse than the 0.35 threshold. So an existing warehouse roof that is being renovated, or a building changing use, will usually be heading for the 0.18 figure for insulation at rafter level. Ask building control or your designer to confirm which paragraph applies before you finalise the scope.
How much spray foam reaches the F2 figures
Thickness depends on the product's thermal conductivity (λ). The two closed-cell foams most used on commercial buildings are Purios H (λ 0.0224 W/m·K, 35–40 kg/m³, compressive strength of at least 200 kPa) and Enverge Nexseal LE (typical λ 0.027 W/m·K at 125 mm, μ 62). Both are CE marked with published data sheets. For build-ups under 50 mm, Enverge Nexseal 2.0 is the closed-cell grade used.
| F2 figure (W/m²K) | Where it applies | Purios H | Nexseal LE |
|---|---|---|---|
| 0.30 | Existing wall, external or internal insulation (Table 3.4 b) | about 71 mm | about 85 mm |
| 0.21 | New wall (Table 2.3) | about 103 mm | about 124 mm |
| 0.20 | New flat roof (Table 2.3) | about 109 mm | about 131 mm |
| 0.18 | Existing roof at rafters, or flat roof (Table 3.4 b) | about 121 mm | about 146 mm |
| 0.16 | New pitched roof (Table 2.3); existing at ceiling level (Table 3.4 b) | about 137 mm | about 165 mm |
Indicative foam-layer thickness only, using surface resistances of 0.14 (roofs) and 0.17 (walls). The sheet, purlins, fixings and thermal bridging are excluded; the BR 443 calculation for your building sets the real figure.
Why closed cell for most Northern Ireland commercial and farm buildings
Closed-cell foam self-bonds to the underside of steel and fibre cement sheets. It leaves no cold, damp void behind the insulation and resists water vapour, so it stops the condensation that drips from bare roofs in damp weather. It also seals laps, stiffens sheets and needs no framing or fixings through the roof. Open-cell foam is lighter and vapour-open. It suits lined, breathable constructions rather than bare cold sheets, and it needs more depth for the same U-value.
Energy Performance Certificates and DECs
According to the Department of Finance, all properties, commercial as well as homes, need an Energy Performance Certificate when they are constructed, or before they are marketed for sale or rent.
- An EPC is valid for 10 years and can be used multiple times in that period.
- Only accredited energy assessors can produce and register certificates. For non-domestic buildings, the assessor must visit the property to confirm the data.
- For new buildings, the EPC is to be provided within five days of completion.
- For non-dwellings, the penalty for failing to make a valid EPC available to a prospective buyer or tenant, among other breaches, is 12.5% of the net annual value, per breach.
Display Energy Certificates apply to buildings over 250 m² that are occupied by a public authority, or an institution providing a public service, and frequently visited by the public. A DEC is based on actual energy use, must be displayed prominently and is valid for one year.
Is there a minimum EPC rating to let a commercial building?
No minimum EPC rating currently has to be met before a commercial building in Northern Ireland can be let. The certificate must exist and be provided, and it is read by tenants, buyers and lenders. A low-rated, uninsulated unit with a dripping roof is harder to let and easier to negotiate down.
How spray foam shows up in an EPC
The assessor models the roof and wall constructions and the air permeability. An uninsulated profiled roof upgraded with closed-cell foam changes the roof U-value dramatically. A post-works air test gives a measured figure instead of a default. Keep the installation record, the data sheets and the product documents so the assessor can use real values.
Fire, condensation and asbestos cement roofs
Fire (Technical Booklet E)
Spray foam is a combustible organic insulant. Technical Booklet E, together with the building's use, size and fire strategy, decides where foam can be left exposed and where a lining or thermal barrier is needed. Your designer, fire consultant or insurer should confirm this before the specification is fixed. We supply each product's declared classification and data sheet to support that decision.
Condensation
Northern Ireland's damp, mild climate and cold clear nights make condensation under single-skin roofs a constant complaint, especially in livestock sheds, grain stores and workshops. Closed-cell foam on the underside keeps the inner surface warm and seals it from moist air. Ventilation in livestock buildings must stay open. For lined or high-humidity constructions, the design should be checked with a condensation risk assessment, and the Enverge data sheets reference BS 5250 for this.
Asbestos cement roofs
Many older Northern Ireland farm and industrial buildings have asbestos cement roofs. Work on them falls under the Control of Asbestos Regulations (Northern Ireland) 2012, enforced by HSENI, and starts with an asbestos survey and risk assessment. Closed-cell spray foam on the underside self-bonds, so nothing is drilled through the sheets. Externally, roofing foam and a waterproof top coat encapsulate and weatherproof the roof. See our asbestos roof pages for County Antrim, County Down and County Tyrone.
Getting a survey and fixed price
Every job starts with a free survey by an approved installer covering your county. You then receive a specification with product, thickness per element and the U-value reached, and a fixed price in sterling. Handover includes the installation record, data sheets and the manufacturer-backed product warranty documents. We cover sites across the six counties, including Belfast, Lisburn, Newry, Derry and Armagh.