Building Regulations Part F Ventilation: What Installers Won’t Tell You About the Ventilation Commissioning Sheet (and why it’s not a certificate)

As homes get more airtight, a well-designed, correctly sized, and properly commissioned ventilation system is essential for comfort, health, and energy efficiency. It’s also critical for domestic ventilation compliance under building regulations part f ventilation (TGD F 2019). Compliance isn’t just about picking a unit; it depends on sound design, accurate sizing, correct room airflows, rigorous commissioning, and complete documentation.

One document often overlooked is the ventilation commissioning sheet. This is a mandatory installer obligation: every installer should complete it and leave it with the client. In reality, few installers provide the recommended Building Regulations document. Use the recommended template here:  Commissioning Sheet

Important: a commissioning sheet is not a certificate.

• The ventilation commissioning sheet is the installer’s record of setup, balancing, airflow measurements, fan settings, door undercuts, and system details.

• A ventilation certificate (ventilation approval) is only issued by an independent third-party validator (not related to the installer). Independent validation is what formally closes domestic ventilation compliance under building regulations part f ventilation.

Design first: correct sizing and room airflows are non-negotiable

Compliance starts at the design table—not at handover. A proper design should:

• Size the unit correctly for the dwelling’s volume, expected occupancy, and pressure losses in the duct network (allowing reserve capacity without excessive noise or energy use).

• Set room-by-room design airflows that follow the Building Regulations (e.g., minimum extracts for wet rooms and appropriate supply rates for habitable rooms), then ensure these targets are achievable at realistic external static pressure.

• Specify duct routes and diameters to keep resistance low, avoid sharp bends, limit cross-talk, and reduce noise.

• Document the design so the installer can commission against clear targets and the validator can verify performance.

You can reference the official guidance for design airflow rates and principles in TGD F 2019 here ⇒

Without a robust design, even a premium unit can fail to meet domestic ventilation compliance or will be impossible to balance without noise and efficiency penalties.

Three things many installers avoid discussing (but they determine compliance and performance):

1. Door undercutting (10 mm above finished floor) – the hidden extra cost
   The ventilation commissioning sheet requires free air transfer between rooms. In practice, that means about 10 mm clearance under internal doors. It’s vital for balanced airflow—but often skipped because it adds carpentry, time, and cost. Skip it, and you risk poor performance and non-compliance with building regulations part f ventilation.

2. Anemometer calibration – without it, measurements are questionable
   Good practice requires regular (annual) calibration of measurement instruments. Ignore it, and airflow readings can be wrong—leading to poor balancing, failed checks, and complaints. Without trustworthy measurements, the ventilation commissioning sheet is unreliable—and you won’t be on a clean path to an independent ventilation certificate.

3. Service access to the unit (e.g., MVHR) – serviceability is part of compliance
   Units must be readily accessible for filter changes and maintenance. Too many end up in cramped attic corners with no flooring or safe access. That makes servicing difficult or unsafe and increases the risk of non-compliance. Provide permanent flooring/platforms and safe access so routine maintenance actually happens—this is real-world domestic ventilation compliance.

Commissioning sheet vs. certificate: how the compliance path works

1. Installer: installs to the design, commissions, measures, balances, and completes the ventilation commissioning sheet (airflows per room, fan settings, door undercuts, terminal locations, etc.).

2. Homeowner: receives the full commissioning pack (commissioning sheet, design targets, user guidance, maintenance info).

3. Independent third-party validator: checks performance against building regulations part f ventilation and issues the ventilation certificate (approval). Only then is compliance formally complete.

Why this distinction—and good design—matter to you

• You get transparent commissioning records that tie back to a proper design with room airflow targets.

• You can enforce warranty and service using documented settings and measured performance.

• You reduce the risk of failed compliance checks, noise, stale rooms, or condensation issues.

• You follow the correct route to an independent ventilation certificate, not just internal paperwork.

Bottom line

Ventilation is regulated and measurable. Without a robust design, correct unit sizing, and room airflows that match TGD F, commissioning becomes guesswork. Without a complete ventilation commissioning sheet, there’s no trustworthy baseline—and no smooth path to a ventilation certificate from an independent validator. Door undercuts, calibrated instruments, safe access, and design-led airflows aren’t optional; they’re core requirements under building regulations part f ventilation.

Want it done right from design to validation?
Eco Vent Ireland delivers end-to-end support: design and sizing, installation, accurate commissioning with a complete ventilation commissioning sheet, preparation for independent validation, and guidance to obtain your ventilation certificate.