Frequently asked questions

Active Vents are patent-pending, wind-powered vents designed to help draw moisture out of cavity walls. When wind passes across the specially shaped vent, it draws damp air out of the cavity, actively moving air rather than relying on it to drift through on its own, as a traditional weep vent does.

Standard weep vents rely on gravity and passive airflow, which is how weep vents have always worked. Active Vents add wind power: the shaped outlet uses the wind to move air through the cavity, and they are designed to resist wind-driven rain. With no wind they work like a standard vent; once the wind picks up, they ventilate actively. In our own tests, at around 20mph the standard vents and weep holes we tried stopped letting water out, while the Active Weep Vent kept draining, and the stronger the wind, the better it worked.

Our vents are manufactured in Cardiff by an ISO 9001-certified manufacturer, from durable polypropylene. Colours are Natural (transparent), Grey, Terracotta, Black and Buff, plus Crystal Clear (polycarbonate) and Recycled Black (100% recycled polypropylene).

Active Vents need no electricity to run; they are powered by the wind. Inspect them periodically; the removable insert makes it quick to check and clear.

Approved Document C (the Building Regulations guidance on moisture, para 5.5(c)) sets weep holes every 900mm along the damp-proof tray at DPC level. Over windows and doors, NHBC guidance is a maximum of 450mm between weep holes, with at least two per opening. As a rough guide, a terraced home needs about 40 Weep Vents and a semi-detached home about 50. Optionally, you can add a second, higher row at about 2.1m, also at 900mm centres (roughly one vent per 2m² of wall): low vents help clear the moisture that sits low, high vents the humidity that lingers higher up. We're testing this layout now, so this guidance may change.

Yes. For new builds the Weep Vent simply fits in the perp joints during bricklaying. For retrofits, a brick perp joint is chased or chiselled out (no drilling needed) and cleaned with a mortar rake, and the vent pushed in. The Active Trickle Vent needs a 16mm hole drilled through the window frame. Professional installation is recommended for complex situations.

New build installation involves placing vents in the perp joints during bricklaying, just like standard weep vents. Retrofit involves removing existing weep vents or chasing out perp joints; installation costs vary by property and installer.

Yes, as an option. Keep the DPC row at 900mm centres (Approved Document C) and add a second, higher row at about 2.1m, also at 900mm centres, which works out at roughly one vent per 2m² of wall. Low vents help clear the moisture that sits low; high vents help clear the humidity that lingers higher up. We're testing this layout now, so this guidance may change.

Savings depend on how damp your walls are to begin with. The wetter your cavity insulation, the more lost performance there is to recover once it dries out; Active Vent is designed to help keep insulation dry and moisture moving. Because results vary by property, we don't quote a fixed percentage.

It depends on how wet the walls were to start with, the weather and the cause of the damp. The vents ventilate actively whenever there's wind. Damp has several causes, such as leaks and plumbing faults, and some of them ventilation can't fix, so get those checked first.

Active Vents are wind-powered, so they are most effective in windy weather, and they work harder as the wind speed rises. With no wind they work like a standard vent. The design is shaped to resist water ingress.

Active Vents are designed to help insulation perform by helping keep it dry. Damp insulation can let through nearly twice the heat of dry insulation, so keeping it dry helps it perform closer to its rated capacity.

Active Vents are designed to support Building Regulations Part C (cavities) and Part F (ventilation) and NHBC guidance. As an active, wind-powered vent, Active Vent is a different category from one-way passive vents.

The Active Weep Vent is designed for cavity walls, including insulated cavities, in new builds and retrofits across most property types. The Active Trickle Vent fits window frames. Ask us about other wall types.

No, replacing existing weep vents or installing new ventilation generally doesn't require planning permission as it's considered permitted development. However, listed buildings may have restrictions.

Active Vents work at the cavity, not the living space, so they don't draw cold air into your rooms. By helping keep the wall dry, they are designed to help reduce the heat loss that damp masonry and wet insulation cause.

The vent is designed to keep out pests while allowing airflow, and the openings are the size of a standard weep vent.

Active Vents are designed to be discreet and blend with your brickwork. We offer multiple colours to match common brick types, and they're the same size as standard weep vents.

Active Vents have no motor. Unlike mechanical ventilation systems, they are driven by the wind alone.

You can pre-order the Active Weep Vent through our online shop in packs: 10 for £24, the Whole House Pack of 50 for £90, and 100 for £160 (Crystal Clear is 10p per vent extra). Trade pricing starts at 1,000 vents, and we are happy to quote on smaller trade orders. UK mainland delivery is £3.99, or free from £50. The Active Trickle Vent is price on request.

We deliver to the UK mainland as standard (£3.99, or free from £50). Worldwide delivery is available on request at the customer's expense; contact us for a quote.

Yes, we can recommend approved installers in your area. Contact us with your location and project details for installer recommendations.

Our team can answer questions about installation, performance or troubleshooting. Contact us by email or phone; we reply within 2 hours during opening hours.