Heat Recovery Ventilation Systems – Design, Supply & Installation in Ireland

We design each MVHR system strictly in accordance with TGD Part F 2019, which requires airflow rates to be calculated based on:
– Occupancy load determined by number of bedrooms, and
– Minimum extract and whole-house continuous ventilation rates as set out in Section 1.2.2 and 1.2.3 of TGD F .

Design also incorporates:
– Airtightness assumptions: Part L requires reasonable care to limit air permeability and encourages low air permeability for energy efficiency (typically ≤3 m³/(h·m²) @ 50 Pa for MVHR suitability) .
– Duct sizing and pressure loss Calculations to ensure fans can achieve design flows without exceeding SFP backstops under Part L.
– Thermal bridging and insulation continuity considerations per TGD L and SR54 to avoid condensation and ensure MVHR energy performance is not undermined .
– Noise limits, installation accessibility, and fire safety requirements for ducts near protected stairways (TGD B) .

All designs produce:
1. Room-by-room supply and extract rates (L/s)
2. Duct routes and diameters based on frictional/ dynamic losses
3. Unit selection sized for duty at Irish winter design conditions
4. Required homeowner information per TGD F Section 1.2.1.11

Installation is carried out in line with:
1. Part F Installation & Commissioning Guide (Section 3 – MVHR)
2. NSAI Validation Scheme requirements for proper workmanship and installation checks .

Key requirements:
– Use rigid ductwork wherever possible; flexible ducting only where unavoidable and kept short (as per Installation Guide).
– Ducts must be supported, with minimal bends and smooth internal surfaces to reduce resistance, noise, and fan energy use.
– All joints sealed airtight to prevent leakage of moist extract air into roof spaces (Part F intent to prevent condensation issues).

MVHR unit installed with:
– Safe access for filter replacement
– Vibration isolation
– Correct condensate management
– Ensure 10 mm undercuts below internal doors for airflow transfer, as required by Part F Clause 1.2.1.2 .

Commissioning follows:
1. Part F installation guide (Section 3)
2. IS EN 14134:2019 testing requirements (mandatory under NSAI Scheme) .

Steps include:
– Measure all supply and extract terminals using calibrated instruments.
– The NSAI scheme specifies permitted measurement methods (unconditional, conditional, or benchmark) and calibration requirements.
– Adjust terminals so each room’s measured airflow matches the design level from TGD F tables.

Verify:
– Correct direction of flow
– System controls
– Fan speeds
– Heat recovery unit performance

The system must meet:
– Minimum continuous extract ventilation rates (wet rooms)
– Minimum whole-house ventilation rates (habitable rooms)
– Balanced supply vs extract (typical tolerance ±10–15%)

Once installation and commissioning are verified, we prepare full documentation for Building Control and NSAI ventilation validation:

Delivered to client and builder:
– Room-by-room airflow verification report (required under TGD F).
– MVHR commissioning sheet, including:
– Specific Fan Power (SFP)
– Heat recovery efficiency
– Unit settings
– Maintenance access routes
– Homeowner operating and maintenance information, required under TGD F 1.2.1.11 (filter maintenance, controls, servicing intervals) .