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Condensation Dampness Treatment & Toxic Black Mould Control


Condensation dampness is the single biggest cause of dampness in the Hammersmith and most other areas of West London and is responsible for many significant dampness and mould problems in flats and houses throughout Hammersmith. So if you think that you may have problem with condensation dampness or black mould please get in touch with Hammersmith Damp Proofing & Timber Treatment as we offer a wide range of solutions for problems of toxic black mould, condensation and high humidity levels .

Condensation is caused when warm, moisture laden air comes into contact with cooler surfaces such as walls and windows and usually occurs in rooms that produce a lot of moisture though every day activities such as kitchens and bathrooms.

Although not always the case, condensation problems are often more obvious during the winter months when heating is turned up and external walls are cold. The difference in temperature between the walls and the air surrounding them is much greater than during the summer (cold walls, warm air) leading to increased condensation dampness and the growth of toxic black mould

Hammersmith Damp Proofing & Timber Treatment have carried out damp surveys in hundreds of properties throughout Hammersmith, Fulham, Shepherds Bush and surrounding areas and the most common form of dampness affecting properties, especially tenanted flats ,is condensation which often results in black toxic mould growth developing not only on walls and ceilings but also furniture and clothing.

Often condensation can be alleviated by small changes to lifestyle to control moisture production and reduce the risk of condensation dampness and mould occurring. Simply covering pans when cooking, opening windows and avoiding drying clothes indoors can be helpful.

In many cases however, modern living styles result in an accumulation of moisture vapour within the property, which combined with poor heating and ventilation arrangements, provide the ideal conditions for mould to develop. Condensation is often made much worse by poor ventilation and we often see this in renovated homes that have had either an existing chimney removed or where double glazing or roof insulation has been fitted. All these changes prevent heat loss but also reduce ventilation in a property by effectively sealing it up and when moist air comes into contact with a cold wall then condensation dampness occurs.

Hammersmith Damp Proofing & Timber can provide reliable, effective solutions to damp and mould problems, and the most effective methods of preventing condensation are to improve the air quality, by removing the damp laden air and ensuring a supply of fresh, filtered air in to the property. As well as removing dampness and black mould our systems will remove airborne pollutants and provide a healthier indoor environment.

Hammersmith Damp Proofing & Timber Treatment have a range of condensation control systems, from simple extractor ventilators, single room solutions, incorporating heat recovery ventilators, to full positive pressure ventilation systems, which displace and dilute moisture laden air and ensure air circulation within the property.

Our Damp Surveyors will inspect the property to identify the cause of the problems and provide a report detailing the extent of any condensation dampness or mould, with our recommendations to prevent any further dampness or mould and a fixed price quotation for remedial works to alleviate condensation dampness. All condensation dampness and toxic black mould treatments come with a five year guarantee against the re-occurrence of any dampness, mould or any other symptoms of condensation.

Hammersmith Damp Proofing & Timber Treatment Condensation systems are installed by our own highly trained operatives, with minimum disruption to the occupants. The installation is usually completed within one day and involves installing the appropriate condensation control unit, in conjunction with passive ventilators where specified.

Preventing damage to the external fabric of the building is a key consideration to freeholders and therefore Hammersmith Damp Proofing & Timber Treatment utilise low impact, specialist diamond cutting equipment, designed to prevent damage to external renders and brickwork. Additionally, the vents are installed using high level dust extraction, allowing the property to remain occupied during installation and preventing dust nuisance to tenants or occupants during the installation. Once the equipment is installed, the electrical connection is made and an electrical certificate issued along with our certificate of guarantee. Our condensation systems utilise low energy technology to ensure minimal operating costs.

An improvement in air quality will be apparent immediately following the installation and after around 14 days the mould will dry to powder form which is normally removed by washing. Our installations are a cost effective method of preventing condensation and also provide a healthy indoor environment as the unit will also remove any indoor air pollutants.

Condensation dampness is an increasingly serious problem in dwelling houses and offices. It affects over 50% of buildings in the UK. Accompanying condensation dampness there is an increase in the presence of mould growth and many of the household pollutants. Positive Input Ventilation units along with our Passive Ventilation Units are a cost effective and guaranteed way to control condensation and black spot mould problems.

Positive Input Ventilation units (Vent Axia Lo Carbon PoziDry Pro-for houses and Vent Axia Compact for flats)

If you think that your property is affected by condensation or toxic black mould please call us today to arrange a free, no obligation damp survey and report on 020 8242 1567. Alternatively email and tell us of any symptoms of condensation or mould and we will reply with 24 hours!


· Vent Axia Lo Carbon Pozi Dry Pro - Condensation Treatment system for houses
· Vent Axia Compact - Condensation Treatment system for flats

Vent Axia Lo Carbon Pozi Dry Pro –
Condensation Treatment system for houses

Condensation Treatment

The Vent Axia Lo Carbon PoziDry Pro provides whole home ventilation using the Positive Input Ventilation principle. This form of ventilation is acknowledged as the "best value" approach to ventilating a home and as well as reducing humidity levels and alleviating condensation and mould problems also removes airborne pollutants such nitrogen oxides and volatile organic compounds (VOCs)

Essentially, the concept is to introduce air to the home at a continuous low rate, encouraging movement of air from inside to outside. Air is drawn in through the loft where it goes through a filter and heater and then pumped into the house.

The slighter higher pressure of new air forces stale, damp air out through natural breaches such as trickle vents and keyholes leaving warmer , drier air in the house leading to the eradication of condensation dampness and black mould

A PIV condensation control unit situated in the loft space will normally be enough to continuously dilute, displace and replace the old contaminated air in the home with drier, tempered (by utilising otherwise unused heat in the loft space) and filtered air. This results in a significant contribution towards providing a healthy, condensation dampness free, energy efficient home. Costs involved are significantly below the installation of several extract fans and running costs are minimal-averaging at £5 a year and the entire home benefits from the ventilation provided.

Good quality loft mounted units normally incorporate a heat recovery function to introduce more heat into the home when the loft is warm during the winter months. Heat recovery functions are normally either "Fixed Temperature Heat Recovery" which adjust the flow rate of the unit to suit the loft temperature; or "Intelligent Heat Recovery" which adjusts the flow rate to suit the loft temperature and the way the home is heated. The latter type is particularly good in terms of energy efficiency. These systems are highly effective but do require proper application and installation for optimum performance. Units incorporating low watt motor technology (Low Energy Positive Input Ventilation Units) can provide a significant net energy gain to the home. These units are therefore very energy efficient, even when compared to natural ventilation systems such as Passive Stack Ventilation.

All Vent Axia PIV low energy positive input ventilation units are supplied and fitted with a 60 day, no quibble, money back guarantee and also comes with a 5 years parts & labour warranty. An average sized 3/4 bedroom property, without extension, can be fully installed, including all electrical connections for a flat fee of £1250.00.

The benefits of installing a Vent Axia PIV unit are great and some of the advantage are listed below:-

  • First, it means that a significant proportion of external pollutants are prevented from entering the home.
  • Secondly, the use of the otherwise unused heat in the roof results in the ventilation unit providing a significant net energy gain to the home.
  • Thirdly, there is no better way to ventilate a home than from the inside out via a single, centrally located, supply air diffuser.

The installation of a low energy positive input ventilation unit will ensure the air in your home is completely replaced with better quality air around 20 times a day. This is the recommended rate to maintain good air quality. The old air exits through the thousands of air leakage points found in all homes. The positive pressure of the PIV system will also prevent cold draughts affecting your house.

The end result of installing a Vent Axia PIV unit is improved indoor air quality and an environment in which condensation dampness cannot exist. To arrange a free no obligation feasibility survey then please call 020 8242 1567 or e-mail

Vent Axia PIV units can be supplied for Builders/DIY fitting and cost £450.00 including delivery

Vent Axia Compact - Condensation Treatment system for flats

Condensation Treatment

The BBA Approved LO-Carbon Vent Axia Compact operates in a similar way to the Vent Axia PIV but is designed for homes without lofts and is usually fitted in a common area such as the hall or lobby.

Air is drawn into the Lo-Carbon PoziDry Compact unit via an external inlet and through a short length of duct. The specially developed fan and motor assembly draws air through an integral,

high capacity, washable filter. A specially designed impeller guarantees increased efficiency, lower sound levels and better performance than any other compact PIV fan on the market.

The fresh, filtered airflow passes along the ducting and terminates on an internal wall with a discreet grille. This directs the airflow upwards where the incoming air mixes with the warm air that gathers at ceiling height.

The system provides fresh, tempered air into the home and creates a healthy indoor environment with lower humidity levels where the damaging effects of condensation find it hard to exist, benefiting both the occupants and the structure of the building.

The price for this unit supplied and fitted is £1,250.00 which includes all making good and localised re-decorating.

Condensation and musty smells can be totally eliminated by the installation of a Vent Axia PIV unit installed by one of our highly qualified and trained installers. To arrange free no obligation feasibility survey then please call 020 8242 1567 or email

Passive Ventilation Units

Where targeted treatment of individual rooms is required then we can recommend the ‘Passyfier Vent’ which has no running costs, has minimal heat loss and is scientifically proven to reduce condensation dampness.

The Passyfier vent has a through-the-wall ‘warm’ telescopic sleeve with a slab of mineral wool inside, which allows moisture vapour in a room to be vented externally combined with an internal louvered vent and external cover which prevents cold draughts. The result is a room with educed humidity levels with no heat loss and condensation is eliminated

A typical house may need for or five Passyfier units and they operate by taking advantage of the differential partial moisture vapour pressure that is normally higher inside an occupied building than on the outside. This pressure is completely independent of that in the air, for example, a typically cold misty British winter’s day may have an outside temperature of 5 °C and humidity at 100% while the inside temperature is usually around 20 °C. Keeping the inside relative humidity to 70% generates a difference between inside and outside moisture vapour pressure of 8 millibars which is ample to alleviate condensation. All this is achieved with little or no heat loss and the Passyfier will significantly reduce condensation dampness, steamy windows and unsightly, unhealthy mould growth.

Building Regulations require background ventilation for habitable rooms require a vent opening with a total area of not less than 8,000mm2 and that these openings should be controllable, secure and located so to as avoid draughts.

The ventilation capacity of Passyfier vents supplied and installed by Hammersmith Damp-proofing & Timber Treatment exceed all Building Regulation requirement for background ventilation of habitable rooms and are the ideal way of controlling high humidity levels, condensation dampness of unsightly mould growth.

The Passyfier operates continuously without noise 24 hours per day and can extract up to 2.3 litres (roughly one and a quarter gallons- which is ten pints) of water per day even at low pressures.

Condensation Treatment

The diffusion rate of a Passyfier vents are slower compared with mechanical extract fans and they are not designed to cope with high amounts of water vapour produced in a short time in kitchens and bathrooms from cooking and showering etc. and if your kitchen or bathroom is suffering from condensation dampness and mould growth we recommend the installation of a humidity controlled extract fan such as Envirovent Silent.

If the Relative Humidity of a room is around 70%, above which condensation dampness will occur at 20 °C, each kg of air would hold 0.0104kg of water. Local Authorities recommend a maximum velocity of 0.9m/sec through vents, this is to avoid complaints about perceived draughts from occupants, and this would remove 0.023m3 of water vapour per day. The average speed of air flow through a Passyfier vent is around a tenth of the maximum

speed allowable but it is still able to remove 2.3 litres of water vapour per day and this greatly reduces the possibility of condensation and unsightly mould growth from occurring.

For more information about the benefits of installing Passyfier vents to alleviate condensation dampness and black mould please call 020 8242 1567 or e-mail

Passive dehumidifiers can be fitted builders and cost £75.00 each including delivery. Our price to supply and install one passive dehumidifier including all making good internally and externally is £650.00

Hammersmith Damp Home Core Vent

Condensation Treatment

The Hammersmith Damp Home Dry Vent is a circular core passive ventilation unit which is easier to fit for builder and is designed to allow water vapour to escape from a building in a controlled way removing 1.2 litres per day. The triple action filter promotes the escape of damp air with minimal heat loss. Cold draughts are restricted by a specially designed thermal core within the filter.

The Hammersmith Damp core ventilator removes 1.2 litres of water per day and helps eliminate condensation dampness and mould growth.

Passive core dehumidifiers can be supplied for builders/diy enthusiasts to fit and cost £75.00 each including delivery. Supply and install one unit average cost £450.00.



If you think that your property is affected by condensation or toxic black mould please call us today to arrange a free, no obligation damp survey and report on 020 8242 1567. Alternatively email and tell us of any symptoms of condensation or mould and we will reply with 24 hours!

Our Reviews

"Many thanks for carrying out the damp and timber survey so quickly. It was just what we needed for our mortgage"
- Mick H. Hammersmith Road, London W6 7DJ .February 2017