160mm rigid thermal ducting for MVHR, mechanical extract ventilation systems, and heat pump water heaters where heat retention and airtightness are non-negotiable.
This collection features Verplas Self-Seal Thermal ducting in 160mm diameter — straight lengths, 45° and 90° bends, T-pieces, and duct-to-duct connectors — all forming part of the same award-winning push-fit system. The 160mm bore is the standard choice for whole-house MVHR central trunk runs, higher-flow mechanical extract applications, and the air intake and exhaust connections on integrated heat pump water heaters.
MVHR and mechanical ventilation
The 160mm bore is appropriate for central MVHR trunk runs and main extract branches where 125mm ducting would create unacceptable resistance. Uninsulated ductwork running through cold loft spaces, undercroft voids, or unheated service zones loses a significant proportion of the heat it is meant to recover. Verplas Thermal ducting is manufactured from Neopor® graphite-impregnated EPS, achieving a thermal conductivity of 0.03 W/mK — which at 20mm wall thickness delivers a thermal resistance (R-value) of 0.666 m²K/W. This exceeds the minimum 0.625 m²K/W threshold specified by the Part F 2010 Domestic Ventilation Compliance Guide and NHBC Chapter 3.2, and satisfies the requirements of DW/143 Class A for duct airtightness. The insulation also prevents condensation forming on or inside the duct — a common failure mode in rigid systems routed through cold zones.
Heat pump water heaters
Integrated heat pump water heaters — also referred to as heat pump cylinders or air-to-water DHW heat pumps — typically require two 160mm duct connections: one for ambient air intake and one for cooled exhaust air. Models from manufacturers including Dimplex, Vaillant, and Ariston specify 160mm ducting for these connections, and manufacturers typically publish maximum permissible system pressure drops that must be calculated from the number of straights, bends, and terminations in the run before installation.
Insulating both duct runs matters here for a different reason than in MVHR: the intake duct draws ambient air into the heat pump's evaporator, and if that run passes through a cold unheated space, condensation on the outside of uninsulated duct can cause moisture damage over time. The exhaust duct removes cooled, dehumidified air, which is even more susceptible to surface condensation in warm, humid areas. Verplas Thermal ducting addresses both problems.
Where a heat pump water heater is installed in a confined space such as a utility room or airing cupboard, ducting the exhaust to an adjacent space or externally also allows the unit to operate without overcooling the installation room — a practical consideration when sizing the duct run.
Self-Seal push-fit system
Every component in the range uses Verplas's click-and-lock Self-Seal mechanism. A male connector pre-fitted to each duct length engages a thermoplastic elastomer gasket in the female socket of the adjacent fitting, producing an airtight seal without mastic, tape, or separate couplers. The system arrives ready to install — no additional connections or consumables required.
What this collection includes
- 1m and 2m straight duct lengths
- 45° and 90° bends for routing around joists and structural elements
- T-pieces for branch connections
- Duct-to-duct connectors for joining straight runs
- 160mm to 150mm adaptors for interfacing with fans or spigots sized to the older 150mm standard
Specify correctly
For MVHR systems, 160mm is appropriate for central trunk runs; radial distribution to individual rooms typically uses 125mm. For heat pump water heaters, always consult the manufacturer's installation manual and calculate total system pressure drop before finalising the duct layout — the number of bends has a significant impact on resistance and can affect unit performance if the permitted maximum is exceeded. Retrofitting bends and connectors once ductwork is built in is avoidable with correct planning upfront.
All Verplas thermal ducting is flame retardant to DIN 4102 B1 and lightweight enough for single-person installation without specialist equipment.
