Table of Contents
Design Ventilation Guides (Ireland): Ducting, Airflows & Commissioning
Modern Irish homes are warmer and more airtight than ever. That is good for comfort and energy, but it raises the stakes for design ventilation. When ventilation is treated as an afterthought, you can end up with damp corners, persistent condensation, odours that linger, noisy fans, and a “system on paper” that never achieves balanced airflow in reality.
This guide is the front door to our ventilation design resources inside Eco Vent’s Ventilation & Air Quality Hub. It is written for Irish homes and Irish building control expectations, with practical reference to Technical Guidance Document (TGD) Part F (Ventilation) and the Installation and Commissioning guidance.
If you are here because you want to know how to design ventilation system layouts that work in real houses, you are in the right place. We will cover the core workflow, common design traps, ducting and terminal placement fundamentals, and what “good commissioning paperwork” typically includes.
Why design ventilation matters in modern Irish dwellings
Airtightness standards, better windows and higher insulation levels mean that accidental background leakage is lower than it used to be. In practice, design ventilation becomes a core building system, not a “nice to have”. Without planned air pathways, moisture from cooking, showers and drying laundry stays indoors longer, increasing the risk of condensation on cold surfaces and mould growth.
Good ventilation design also protects energy performance. When fans are oversized or ducts are restrictive, systems run at higher pressure, consume more electricity and become noisier. When airflow is unbalanced, you can depressurise zones of the house and pull air through unintended leakage paths (attic hatches, service penetrations, or wall cavities), which undermines both comfort and indoor air quality.
A well-designed residential ventilation system should deliver:
- predictable fresh air supply to habitable rooms,
- reliable extract from wet rooms and kitchens,
- stable airflow under normal and boost modes,
- acceptable sound levels in bedrooms and living spaces,
- accessible maintenance points (filters, fans, drains),
- documentation that demonstrates compliance and supports future servicing.
Who this section is for
This section is aimed at people who, like us, are still learning and refining their approach to residential ventilation in Ireland:
- Architects and building designers who want simple rules and examples for “ventilation system for home Ireland”, without needing to become ventilation specialists.
- M&E / services engineers who would like a quick “mechanical ventilation design summary” for houses and apartments, which they can adapt and improve for their own specifications.
- DIY installers who are working on duct sizing, system balancing and commissioning, and who want to issue stronger certificates and reduce callbacks over time.
We try to keep the language plain and honest. We do not hide the physics or the regulations, but we also admit where details are still evolving and where different approaches exist on site.
What you will learn here
In this Design Ventilation Guide, we are piecing together answers to questions such as:
- How to compare MVHR, MEV and DCV for a typical Irish dwelling and choose a sensible approach at design stage, based on the constraints you actually face.
- How to size ducts and manifolds, where locate supply and extract points, while acknowledging that real houses rarely match the “ideal” diagrams.
- How to draw layouts in CAD that respect structural zones, fire separation and acoustic requirements, and that still leave enough flexibility for installers to commission the system properly.
- How to carry out and document MVHR/MEV commissioning
1) Part F ventilation in Ireland: what the regulations actually expect
In Ireland, the Building Regulations set requirements, and TGD Part F provides practical guidance on how to meet those requirements. gov.ie+1 The key point for designers and self-builders is that “ventilation” is not only about installing a fan. You are expected to deliver a system that provides adequate ventilation for occupants and helps manage moisture and pollutants.
TGD Part F (2019) is supported by the Department’s “Installation and Commissioning of Ventilation Systems for Dwellings – Achieving Compliance with Part F 2019” guidance. That commissioning document matters because it is the bridge between design ventilation intent and what is proven on site.
You will also hear about:
- I.S. EN 14134:2019 (performance testing and installation checks of residential ventilation systems), referenced in the NSAI Ventilation Validation Registration Scheme documentation.
- S.R. 54:2014 / A2:2022 (Code of Practice for the energy efficient retrofit of dwellings), commonly referenced in deep retrofit contexts.
What Part F Ventilation “compliance” usually means in practice
For most dwellings with mechanical ventilation, compliance is demonstrated through:
- an appropriate design basis (system selection and intended airflow strategy),
- correct installation (duct integrity, insulation, condensate management, accessibility),
- commissioning measurements at terminals and/or system points,
- a clear handover pack (settings, measured results, maintenance schedule). gov.ie+1
If a third-party ventilation validator is involved, NSAI’s registration scheme explains the role and the standard it is aligned to.
2) Design ventilation workflow: how to design ventilation system step-by-step
This section is written as a practical “HowTo” for homeowners, architects and site managers who want an auditable process.
Step 1: Define the dwelling and constraints
Gather the information that will control your design ventilation options:
- dwelling type (house, apartment, extension, retrofit),
- airtightness target and build-up (especially at junctions),
- available service zones (ceilings, risers, attic, utility room),
- wet room locations and kitchen extract route,
- noise sensitivity (bedrooms over living areas, home offices),
- fire compartmentation constraints (apartments and multi-unit).
Step 2: Select the ventilation concept and distribution strategy
Decide:
- MVHR supply/extract layout (radial or branched),
- MEV extract points and make-up air routes (transfer gaps, undercuts),
- DCV control points (which rooms, what sensors, what boost triggers).
A common failure is trying to design ventilation later after structural and architectural drawings are frozen. If ducts are squeezed into leftover voids, pressure loss increases, noise increases, and commissioning becomes a compromise.
Step 3: Establish target airflows (and define boost behaviour)
Use the minimum ventilation rates and guidance tables in TGD Part F as your baseline, then adapt to the dwelling’s actual risk profile (large family, high moisture loads, open-plan cooking).
At design stage, write down:
- intended continuous (normal) airflow rates by room,
- intended boost airflow rates and trigger logic,
- any special extracts (utility, ensuite, cooker hood strategy).
Avoid guessing. Treat airflow targets as design inputs, just like radiator outputs or electrical loads.
Step 4: Draw the air paths (supply, transfer, extract)
A simple rule set that helps design ventilation layouts:
- supply to habitable rooms (living, bedrooms),
- extract from wet rooms and kitchens,
- provide transfer paths (door undercuts, transfer grilles, openable routes) so air can reach extract points.
Step 5: Size and route ducting (pressure loss, noise, buildability)
Overly large ducts can be impossible to route, and poorly supported ducts can cause vibration and noise. Undersized ducts increase pressure loss and fan power.
Step 6: Select terminals, silencers and accessories
The end of the system is where occupants judge it. A good design ventilation plan includes:
- terminal type (valves, slot diffusers, grilles),
- target face velocity and throw direction,
- access panels for valves and dampers.
Step 7: Define commissioning method and acceptance criteria
Commissioning is not a “nice extra”; it is how you prove the system matches the design intent. The Department’s commissioning guidance explains what is expected to demonstrate compliance with Part F.
How to Design Ventilation System – Sections Overview
You do not need to read everything in order, but the material is loosely structured as a learning path:
- Start with – Residential Ventilation Design.
Here you get an overall picture of the main system types and when they tend to make sense in Ireland. It is a good place to check your current assumptions. - Move to – Ventilation Ducting Size
Use the worked examples and diagrams to sense-check your own layouts and schedules. You may not copy them exactly, but they can highlight where friction losses or noise might catch you out. - Then look at – Commissioning Requirements
This section focuses on what measurements, checks and paperwork you can reasonably expect from a competent installer – or provide yourself if you are taking responsibility for commissioning. - If you work in CAD most of the time, jump into – CAD & BIM Models
This part is written with day-to-day drawing work in mind. It concentrates on how to integrate ventilation into architectural and structural layouts in a way that reduces clashes and late redesigns.
You can dip in and out as needed. The idea is that, over time, this hub becomes a shared reference point that keeps improving as we learn from more projects.
Need a ventilation design or ventilation commissioning quote?
If you would rather outsource an MVHR/MEV design or need an independent commissioning service for a dwelling in Ireland, Eco Vent can support you.
Sometimes it still makes sense to hand the full task to a specialist. If you want a professional design or need an independent commissioning service for a dwelling in Ireland, Eco Vent can support you.
Use our service page:
FAQs
Does Part F Ventilation require commissioning for mechanical systems?
TGD Part F Ventilation and the Department’s supporting guidance emphasise installation and commissioning checks and records to demonstrate compliance for dwelling ventilation systems. gov.ie+1
Is ventilation validation always required?
Not always. However, for projects where independent validation is required, NSAI’s scheme defines the competency and scope of third-party validators. NSAI
How do I keep design ventilation “future-proof”?
Keep it serviceable: access, documented settings, and a clear maintenance schedule. Avoid bespoke one-off controls that no one can commission later.