Choosing between HDPE corrugated ducting and PVC flat duct is one of the first decisions in a residential fresh air (MVHR) project — and getting it wrong costs money in rework, noise complaints and condensation callbacks. This guide compares the two systems the way installers and wholesalers actually use them.
Use HDPE corrugated pipe for ceiling (top-feeding) distribution, where its flexibility routes around beams without fittings. Use insulated PVC flat duct for underfloor (screed-embedded) distribution, where its slim profile and anti-condensation insulation are essential. Many finished projects combine both: HDPE from the heat recovery unit to the distribution boxes, then flat duct under the floor to each room outlet.
| Item | HDPE Corrugated Pipe | Insulated PVC Flat Duct |
|---|---|---|
| Typical routing | Ceiling voids, top-feeding systems | Screed layer, underfloor systems |
| Shape | Round, Ø75–250 mm | Flat, 130×30 to 256×48 mm |
| Structure | Double-wall corrugated, smooth inner bore | Dual-channel rigid core + 5 mm foam + foil |
| Flexibility | Highly flexible, bends by hand | Semi-rigid, uses dedicated elbows |
| Fittings | Push-fit tees, couplings, wyes | Insulated elbows, distributor boxes, floor grilles |
| Insulation | None (route in conditioned voids) | Built-in, anti-condensation |
| Best for | Fast installation, minimal fittings | Low build-up height, condensation control |
HDPE corrugated pipe is supplied in long coils. A single coil replaces dozens of rigid elbows, which means fewer joints, less leakage and dramatically faster installation — crews routinely complete a full apartment ceiling network in hours. The smooth inner wall keeps pressure loss low despite the corrugated exterior, and the antibacterial HDPE material is moisture-proof and odor-free, an important point for indoor air quality.
The push-fit fitting family is the other advantage. Tees, oblique tees, reducers and coupling connectors all snap onto the pipe without glue or tools. See our HDPE fresh air corrugated pipe and the complete top-feeding air series for the full range.
Underfloor air distribution lives inside the screed. Height is scarce, temperature is unstable, and access after pouring is impossible. Insulated flat duct is designed for exactly these conditions:
Uninsulated alternatives under the floor are the most common cause of wet screed complaints and mold callbacks in fresh air projects.
In a typical two-storey villa: the MVHR unit sits in a utility room, HDPE corrugated pipe runs through the ceiling void to an EPP distribution box, risers drop inside the wall, and the underfloor zone uses insulated flat duct with linear floor grilles. Each material works where it is strongest.
HDPE corrugated systems reduce fitting count and labor hours; flat duct systems reduce screed depth and callback risk. For distributors, both lines share standard sizes (75/110/160/200/250 mm round; 85×48 to 256×48 mm flat), so stocking the two complementary families covers nearly every residential ventilation project with one SKU strategy.
Q: Can HDPE corrugated pipe be buried in screed?
A: It is not designed for that. The double-wall profile is optimized for open ceiling routing; underfloor runs need the flat duct's built-in insulation and load-bearing core.
Q: Is PVC flat duct available without insulation?
A: Yes, and at lower cost — but we recommend the insulated version for any screed-embedded run to avoid condensation problems.
Q: Which sizes should a distributor stock first?
A: For HDPE: Ø75 and Ø110 cover most residential branches. For flat duct: 130×30 mm is the workhorse size, followed by 256×48 mm for main runs.
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