What Active Vents are designed to do for your home
Active Vent's patent-pending, wind-powered design is built to help reduce moisture in wall cavities. At 0mph it works like a standard vent; once the wind picks up, it ventilates actively.
Tackling a common cavity-wall defect
Active Vents are designed to help reduce moisture in the cavity. The National House Building Council (NHBC) reports that DPCs and cavity trays account for around half of the superstructure defects it sees, with blocked or missing weep vents specifically cited.
Helps protect the building fabric
Active Vents are designed to help reduce moisture in wall cavities, which can damage brickwork, timber and finishes over time. When we tested them side by side, standard weep vents and weep holes stopped draining once the wind hit around 20mph; the Active Weep Vent carried on, and performed better the faster the wind blew.
✓Our own testing
Designed to help reduce damp
By ventilating the cavity, Active Vents are designed to help reduce the moisture that can lead to damp and mould. Damp has several sources, such as leaks and plumbing, that vents can't fix, so those need dealing with separately.
Quick to inspect
BRE notes that current cavity-insulation surveys do not require anyone to inspect the cavity base for debris. Active Vent's removable insert makes it quick to check and clear at each vent.
Easy to check
Inspect periodically; the removable insert makes it quick to check and clear. In BRE's survey of 390 failed brick cavity homes, 20% failed because water could not escape the cavity, caused by debris at the cavity base (BRE / BEIS 2021/017).
- ✓Ventilates actively whenever the wind picks up
- ✓Removable insert for quick checks
- ✓Made in Cardiff by an ISO 9001-certified manufacturer
Keeping insulation dry keeps it working
In a 2022 laboratory study, damp insulation let through about 1.9× the heat of dry insulation. Active Vent's cross-ventilation is designed to help insulation stay drier. Product-specific savings haven't been measured yet.
Less moisture to condense
Designed to help reduce cavity humidity, so less moisture is available to condense on insulation when cavity air cools to its dew point.
Helps insulation stay drier
Cross-ventilation exchanges moist cavity air for fresher air, which helps insulation and masonry stay drier.
Works with the wind
At 0mph it works like a standard vent. Once the wind picks up, it ventilates actively.
Could reduce heat loss
If damp is reducing your insulation's performance, keeping the cavity drier could reduce heat loss. Product-specific savings haven't been measured yet.
Why damp matters
Published public-health research on damp and mould in homes in general. These are not Active Vent results.
What the WHO found
The World Health Organization found sufficient evidence that occupants of damp or mouldy buildings are at increased risk of respiratory symptoms, respiratory infections and worsening asthma, and that remediating dampness reduces adverse health outcomes.
- ›Persistent damp and mould growth on interior surfaces should be avoided or minimised
- ›Source: WHO Guidelines for Indoor Air Quality: Dampness and Mould (2009)
What Active Vent is designed to do
Active Vent ventilates the wall cavity. It is designed to help reduce moisture build-up there, which is one of several routes by which damp reaches a home. It is not a medical product and we make no health claims for it.
- ›Damp also comes from leaks, plumbing faults and everyday condensation indoors
- ›Get persistent damp or mould checked by a qualified professional
No running costs, and why dry walls matter for heating
Active Vents use no electricity to run. If damp is reducing your insulation's performance, keeping the cavity drier could reduce heat loss; one laboratory study found damp insulation let through about 1.9× the heat of dry insulation (Hayrullin 2022). Product-specific savings haven't been measured yet.
A low-cost measure
Damp remedial work and redecoration can be costly and disruptive. Active Weep Vents cost from £1.60 each in packs, and need no electricity to run.
- ›Whole House Pack: 50 vents for £90 (a semi-detached home typically needs about 50)
- ›Running costs: none; the vents use the wind
- ›Work out your cost: our weep vent calculator counts the vents your home needs and prices them
What to expect depends on your walls
How much difference ventilation makes depends on how much moisture is in the cavity to begin with, and on where any damp is coming from.
Homes with dry walls
For homes without moisture problems, keeping cavities ventilated is a precaution. There may be little or no change in heat loss.
- •Cavity kept ventilated
- •Removable insert for periodic checks
Homes with some cavity moisture
Where moisture is building up in the cavity, ventilation is designed to help it dry out, which could help insulation perform closer to how it should.
- •Designed to help reduce cavity humidity
- •Exchanges moist cavity air for fresher air
Homes with established damp
Established damp usually needs its cause found first. Vents can help with cavity moisture and with drying walls affected by rising damp, but not with leaks or plumbing faults.
- •Find and fix the source first
- •Then keep the cavity ventilated
Why results vary
How much a home benefits depends on how wet its walls are to begin with, and why. A home with dry cavities may see little change; a home with moisture trapped in the cavity has more to gain from ventilation.
Active Vent works the same way in both cases: it ventilates the cavity, and it is designed to help insulation stay drier. Product-specific savings haven't been measured yet, so we don't quote a percentage improvement.
Powered by the wind, made in Cardiff
Active Vents use the wind and need no electricity to run. They are made locally in Cardiff, and there is a 100% recycled polypropylene option. Product-specific energy and carbon savings haven't been measured yet, so we don't quote them.
No electricity to run
Unlike electric dehumidifiers or fan-based systems, Active Vents use the wind and need no electricity to run.
Made locally
Manufactured in Cardiff by an ISO 9001-certified manufacturer, about 30 minutes from our Swansea base, which keeps transport miles low.
Recycled option
Choose Recycled Black, made from 100% recycled polypropylene from our manufacturer's recycled range.
The evidence behind Active Vent
Of the superstructure defects NHBC sees relate to DPCs and cavity trays, with blocked or missing weep vents specifically cited.
Read NHBC Technical Extra 18 →Heat let through by damp insulation compared with dry (Hayrullin et al., Transportation Research Procedia, 2022).
Moisture and energy →The humidity threshold homes should stay below to limit mould risk (Approved Document F). A threshold, not a product result.
See the evidence →Cited figures come from published research and UK Building Regulations. Where we reference published research, it is for context and is not specific to our product. View our data & claims disclaimer
Further reading
- Series guide The Complete Guide to Cavity Wall Ventilation
Why a cavity wall has to be able to breathe, where the moisture comes from, why damp walls quietly waste heat, and how to keep a cavity dry and drained: a plain-English hub for homeowners, builders and surveyors.
- Awaab's Law Awaab's Law, Decent Homes and the Building Safety Act
How Awaab's Law, the Decent Homes Standard and the Building Safety Act 2022 overlap for social landlords in England, and how to keep records clear.
- Awaab's Law Awaab's Law: When Deadlines Can't Be Met
What Awaab's Law says when circumstances beyond a social landlord's control prevent it meeting a deadline, and what records it should keep.
Useful pages
- The technology →
How the design uses the wind to draw moist air and water out of the cavity.
- The evidence →
The independent research behind our approach, with every source linked.
- For homeowners →
Damp walls, streaming windows or mould: what is going on and what helps.
- Damp solution finder →
A few quick questions, then a plan: the likely cause, what to fit, where and what it costs.
Protect your property the wind-powered way
Buy the Active Vent range online, or talk to us about the right vent for your project: cavity, window or a whole property.