Condensation Dampness.

Why does condensation dampness happen?

Dampness in houses in the Forest of Dean is a common occurrence and usually there are three major cause of damp
1- Penetrating damp-from external rain sources, gutter leaks etc.
2- Rising dampness-moisture drawn up from the ground.
3- Condensation dampness
Of these, condensation dampness has the greatest potential for misdiagnosis, and subsequent inappropriate ineffective remedial work such as chemical damp-proofing and re-plastering and as condensation can lead to ill health and understanding of the causes and cures of condensation dampness is important.
Condensation dampness is often a problem for house-owners in the Forest of Dean and we get lots of calls every week which are directly related to condensation in the form of mould growth, steamy windows and high humidity levels and we try our best to offer simple advice regarding the best way of combating condensation dampness either over the phone or carrying out a free survey condensation dampness (This service is only available to house-owners in the Forest of Dean).
There is always a certain amount of moisture in the air but normally we don’t see it and often it does not cause a problem, but it is there even in the air that we breathe out, note steam breathed out on cold days etc. Air has the capacity to hold a certain amount of water vapour and this depends on a few different variables such as the room temperature and the temperature of the surrounding walls and other surfaces.
The amount of moisture in the air is usually expressed as the Relative Humidity which is the measure of how much moisture is contained in the air at a given temperature, and expressed as a ratio between the amount of moisture contained in the air and the maximum amount of moisture the air could hold if that temperature remained unchanged.
The amount of moisture that air is capable of holding will alter with the temperature, the warmer the air the more moisture it can retain. Therefore, the Relative Humidity changes not only by the amount of moisture, but also the temperature.
In practice, if moisture had been generated in a cold room such as the bathroom, and the air had reached the maximum amount of moisture that it could hold at this given temperature, the relative humidity would be 100 per cent. By increasing the room temperature (without generating more moisture) the humidity would decrease (to 90% for example). This change in relative humidity would make it possible for 10% more moisture to be added, which would take the level back up to the 100%. If on the other-hand the temperature was to drop to its original temperature, the moisture added would then be in excess of the 100% and would be shed as condensation.
This all sound a bit complicated but really all that is needed to combat condensation dampness is to have better heating and ventilation in any affected areas.
How this affects your house
Modern living produces a lot of moist air and this usually comes from cooking, bathing, washing and drying clothes, apparently up to 17 litres of water can be produced daily in some homes. This is a fairly large amount and usually it is just floating around in the air waiting to vented to the outside or if the conditions are right, to condense on walls, windows and other surfaces. In certain areas such as bathrooms and kitchens the moist, warm air can spread to cooler parts of the house to condense on cold surfaces.
The effect of moisture generation is further aggravated by the way houses are ventilated - it is theoretically possible to avoid condensation by adequate ventilation. Up to about the late 1960s there was natural ventilation in many homes because of the lack of double-glazing, poorly fitting windows and doors, open fireplaces. Modern living has eliminated a lot of natural ventilation by the use of double-glazing, draught excluders, fitted carpets (preventing air movement up through suspended wooden floor boards) and the removal of open fireplaces with the introduction of central heating systems. To put it simply buildings have being effectively sealed and provided ideal conditions for condensation to occur.
Many houses remain unoccupied and unheated throughout the greater part of the day allowing the fabric of the building to cool down, the moisture producing activities are then concentrated into a relatively short period. This sudden increase in warm air can produce condensation as the air comes into contact with the relatively cold structure which is still warming up. Economic pressure - dramatic increase in fuel prices force many occupiers to under use heating systems not heat unused rooms and seal all draughts and reduce ventilation as described previously.
The effect of this can be condensation dampness which can result in mould growth on walls and clothing, running water on windows and a general musty, unhealthy smell around the house. Condensation dampness can also produce toxic mould and has been known to cause health problems for some people.
Unless you are given the right advice then you may be persuaded to have inappropriate damp-proofing or waterproofing works carried out. As well as being a waste of money and a lot of disruption most of these cures will almost certainly not work.
Our bestseller and what we believe to be the top product for dealing with Condensation Dampness in the Forest of Dean is the Drimaster- a loft mounted, whole house, positive input ventilation (PIV) system.
The DRIMASTER provides whole home ventilation using the Positive Input Ventilation principle. This form of ventilation is becoming increasingly recognised as the "best value" approach to ventilating a home. Essentially, the concept is to introduce air to the home at a continuous low rate, encouraging movement of air from inside to outside. A single unit situated in the loft space will normally be sufficient 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. The result is a significant contribution towards providing a healthy, condensation dampness free, energy efficient home. With only one electrical connection and no trickle vents normally required, the installation costs for this type of damp proofing system are generally less than for a conventional set of extract fans with trickle vents – 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 adjusts 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.

Drimasyer air circulation


All DRIMASTER low energy 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 £650.00. (Interest free credit available).
The benefits of installing a Drimaster 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. Indeed, positive input ventilation will even help to suppress unwanted infiltration draughts.
The end result of installing a DRIMASTER PIV unit is improved indoor air quality and an environment in which condensation dampness cannot exist.
To arrange free no obligation feasibility survey then please call 01594 837300 or e-mail . (These free surveys are only available to house-owners in the Forest of Dean, tenants should ask their landlord to arrange the free damp survey).
We also supply the Drimaster range for self installation and the prices inclusive of VAT and delivery are:-
Drimaster - £230.00
Drimaster 2000- £275.00
Drimaster Heat- £300.00
Radon gas is produced by the natural breakdown of uranium found in rocks, sediments and water. It then permeates up through the ground and in open air dilutes to harmless levels in the atmosphere. However, when it enters our homes and work places it decays into minute solid particles known as Radon's Daughters.
These particles then become trapped and can accumulate to dangerously high levels. When they are breathed in they can be deposited on the surface of the lungs, where they decay further, emitting harmful radiation directly into the lungs.
Radon penetration occurs in many thousands of homes in the UK, particularly in the East Midlands and the South West and the Forest of Dean is a hotspot for radon. As a result of this over 9,700 letters were sent out to resident in the Forest of Dean offering advice and free tests for radon gas.
Radon gas is a naturally occurring radioactive gas, which can enter your home from the ground, exposing you to doses of radiation. According to the National Radiological Protection Board (NRPB), health studies from around the world have linked exposure to Radon to the increased risk of lung cancer.
The good news is remedial measures to control the penetration of radon are both proven and remarkably simple. The most effective method of mitigating the problem is to install a heavy duty plastic-type membrane during the construction of the dwelling. For existing buildings a more practical proposition is the introduction of a Drimaster Positive Input Ventilation System (PIV).
How can I mitigate radon gas?
Drimaster PIV systems are proven to be effective units in significantly reducing radon gas levels, the system works by gently supplying fresh, filtered air into the property. This process changes the airflow direction within the dwelling to force the air contaminated by radon out of the home.
In addition, Drimaster PIV systems can also overcome poorly installed membrane systems or compensate for potential tears and cracks which may appear at a later stage. What’s more these systems even save on heating bills and provide whole home ventilation solutions and remove other airborne pollutants for all year round good indoor air quality.
Forest Dampbusters PIV condensation control units have proved to be effective in the mitigation of radon gas emissions where radon readings are below two hundred becquarels creating a healthy atmosphere in which to live, free from the harmful effects of radon gas.
For a free, no obligation inspection and quote for the fitting of a Radon reduction PIV unit please phone 01594 837300
Passive Ventilation Units
In some instances where cost is a concern and only individual rooms require to be treated we can recommend the ‘Forest Dampbusters PassiVent’ which has no running costs, has minimal heat loss and is scientifically proven to reduce condensation dampness.
The PassiVent combines a through-the-wall ‘warm’ telescopic sleeve with a slab of mineral wool inside, which is impervious to the exodus of moisture vapour whilst an internal louvered vent and an external cover simultaneously preventing cold draughts.
Each Forest Passivent will effectively remove water vapour from a room up to 20m2 and a typical house may need for or five Passivent 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 5oC and humidity at 100% while the inside temperature is usually around 20 oC. 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 PassiVent 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. Forest Dampbuster PassiVent vents surpass all of these requirements and are the ideal way of controlling high humidity levels, condensation dampness of unsightly mould growth in any type of property in the Forest of Dean and Wye Valley.
The PassiVent 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.
The diffusion rate of a PassiVents 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 ( i.e. in kitchens and bathrooms) and we recommend that if your kitchen or bathroom is suffering from condensation dampness that extract fans are fitted.
If the Relative Humidity of a room is around 70%, above which condensation dampness will occur at 20 oC, 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 PassiVent 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.

Passive Ventilation Units

Forest PassiVents are available on either a supply and fit basis or supply only for builders and DIY enthusiasts.
Supply and fit per PassiVent unit is £350.00. Supply only is £45.00 which is considerably cheaper than most suppliers who charge anything from £70-£90 per PassiVents. Delivery is free within the Forest of Dean and Wye Valley but for other areas postage charges will be applied.
Our remedies for condensation dampness range from the installation of fans and vents to replastering with thermal renders which reduce heat loss thereby keeping walls warmer, but often the simplest things are the best such as turning up the heating a little bit and opening windows to get a bit more air flowing through the house to remove excess moisture.
If you feel that your property is affected by condensation dampness and toxic black mould then please feel free to call us on 01594 837300 for free, impartial advice. At Forest Dampbusters we are happy to discuss any condensation or mould related problems that may be having an adverse affect on your house or your health and offer over the phone advice or arrange an inspection if required. Initial inspections are also free and we will offer you the most cost effective and beneficial advice and solutions to your condensation dampness problems.