# NI Building Regulations, Technical Booklets Q, R and S
These three booklets cover non-domestic electrics, ventilation, and overheating protection. Together they complete the picture of how NI expects buildings to perform safely and comfortably.
Technical Booklet Q: Non-Domestic Electrical Safety
What it does
Booklet Q is the non-domestic counterpart to Booklet P. Same basic idea, make installations safe and up to modern standards, but for commercial, industrial and public buildings rather than homes.
It locks non-domestic electrical work into the NI Building Regulations framework, pointing to BS 7671 (IET Wiring Regulations) as the benchmark.
Where you feel it
- New and altered distribution boards, sub-mains and final circuits in shops, offices, schools, factories.
- Emergency systems · emergency lighting, fire alarm power supplies, life-safety circuits.
- Special locations · plant rooms, commercial kitchens, workshops, wet industrial areas.
On site
- Boards, trunking, tray and containment are sized and installed properly, not squeezed or overloaded.
- Circuits serving emergency systems and safety kit are installed to the higher standard those systems need.
- Don't bodge extra loads onto existing circuits because it's quicker than running a new one.
Certification
NI Building Control will expect the installation to be designed to BS 7671 with proper certification at completion · Electrical Installation Certificates, schedules of test results, distribution schedules.
Bottom line: "For non-domestic buildings in NI, your electrics must meet modern wiring standards, and you must be able to prove it."
Technical Booklet R: Ventilation
What it does
Booklet R is about getting enough fresh air into buildings and getting stale, moist air out, without wrecking energy performance or comfort.
Types of ventilation R cares about
- Background ventilation · trickle vents, passive vents, small openings providing a steady base level of air.
- Extract ventilation · fans in wet/odorous rooms (kitchens, bathrooms, WCs, utilities).
- Whole-building ventilation · continuous mechanical systems (MEV/MVHR) or carefully designed natural systems in tighter buildings.
Kitchens, bathrooms and wet rooms
R leans hard on local extract:
- Put the right duty fan in the right place · higher rates for kitchens and showers, over-run where required.
- Duct fans to outside, not into roof voids, cavities or underfloors.
- Keep duct runs short and sensible with proper terminals · not long, crushed flexi duct that kills performance.
Background and whole-dwelling ventilation
As buildings get more airtight (chased by Booklet F), R expects more deliberate ventilation:
- If you're installing new windows/doors with specified trickle vents · include them. Don't tighten the house without giving it a new air path.
- If the spec includes MEV or MVHR · install the correct unit, run ducts as per design, and make sure it can be commissioned to the design flow rates.
Non-domestic ventilation
- Follow the mechanical design · duct sizes, grilles, fans, controls.
- Keep intakes and exhausts where they're drawn · not moved to positions that short-circuit.
- Make sure there's access for cleaning and maintenance.
Building Control
They can ask for commissioning certificates on mechanical systems and will question obvious under-ventilation.
Bottom line: treat fans and vents as core compliance items, not afterthoughts.
Technical Booklet S: Solar Protection and Overheating
What it does
Booklet S is the "keep it cool enough to live and work in" layer, making sure buildings don't turn into ovens as insulation and air-tightness improve.
Where you feel it
- Houses and flats with big south/west-facing glazing.
- Sunrooms, conservatories and highly glazed extensions.
- Non-domestic buildings with large curtain walls or atria.
How it changes design choices
Under S, you're likely to see:
- Solar control glazing specified on certain elevations.
- External shading · overhangs, brise-soleil, louvres.
- Limits on glazed area versus room size.
- Ventilation strategies that help dump heat (high-level openings, night purge, mechanical assist).
On site
- Don't swap specified solar control glass for cheaper, clear units because "it all looks the same" · the performance is different.
- Don't bin shading features (deep eaves, louvres) as easy cost-savings · they're often there for overheating control, not just looks.
- Don't upsize glazing beyond what's on the approved drawings without a redesign · you might tip the building over the line for S.
Building Control
For anything with large glazing, they'll expect shading and ventilation measures as approved.
Bottom line: for most small, modestly glazed domestic work, S won't feel loud. But for anything with big glass areas, it's the quiet rule that keeps future occupants from roasting. Treat solar control and ventilation features as compliance work, not decoration.
What to do next
- Read: Working in Northern Ireland · building regulations overview
- Read: NI Building Regulations · Technical Booklet P: Electrical safety in dwellings
- Read: NI Building Regulations · Technical Booklet F: Energy
Sources
- Building Regulations (Northern Ireland) Order 1979 · primary legislation.
- Technical Booklet Q (NI) · Electrical safety in non-domestic buildings.
- Technical Booklet R (NI) · Ventilation.
- Technical Booklet S (NI) · Overheating and solar protection.
- BS 7671 (IET Wiring Regulations) · referenced by Booklets P and Q.
Know someone who needs this?
Was this guide useful?
Didn't find what you were looking for?
Spotted something wrong or out of date? Email us at hello@kilnguides.co.uk.
In crisis? Samaritans 116 123 ·