Which Dehumidifier?

Dehumidifiers are rapidly finding a place in everyday houses of both old and new builds, and are an excellent defense at keeping rooms dry and free from black mold and mold spores which over time, can become damaging to health and the building itself.

A dehumidifier, will come into its own when used in an older building with an existing damp problem, or those living in properties which are showing the first signs of a damp issue, such as condensation in UPVC porches and double glazed bedroom windows. However, even in modern buildings, you can benefit from a dehumidifier, as the causes of damp are many, even boiling a kettle, taking a shower or using  a steam iron, can result in peeling wallpaper and unsightly damp patches over a period of time.

Dehumidifiers work by constantly dragging air from within the room over a grid consisting of a cold refrigerant, which is constantly chilled by using a fridge style compressor or modern silent solid state element. This causes the moisture within the air to condense and turn back to water on the chilled surface which is then allowed to run off and be collected in a container within the dehumidifier. The air which is then expelled from the dehumidifier is much dryer than when it was pulled into the unit from the room.

By using powerful fans, the dehumidifier constantly pulls in and re-circulates the air within the room or building over several hours, until all of the moisture has been extracted, this then results in preventing the moisture within the air  from otherwise forming and condensing on other areas of the room, such as walls, carpets and ceilings where they can easily turn to mold and ruin decor and wall covering. The principle operation of the Dehumidifier is simple, in that once all of the moisture has been extracted from the air on its cooling plates, then there will be non left to cause problems elsewhere or form on other cold surfaces such as window glass.

There are also newer, much quieter dehumidifiers available, called desiccant dehumidifiers, these do not rely on a noisy fridge type compressor, and so are far quieter to use, making them far more suitable for living areas and for overnight use in bedrooms. Although the power consumption of Desiccant dehumidifiers is higher than the conventional types, they do have the ability to raise the ambient room temperature far higher than compressor types and so the extra power consumption is negated by the eventual saving in heating bills.

Using a dehumidifier, especially a more efficient desiccant type, can also help to cut down the cost of heating a room, because in extracting the moisture from the air,  it actually lowers the dew point temperature of the air in the room, making it feel less chilly and therefore requiring less energy input from heating devices, many people report that bedrooms feel less chilly and damp after several days of using a dehumidifier, and many also report that bedding, and pillows feel far less damp, humid and sticky when they sleep on them, and condensation does not form overnight on the inside of double glazed windows.

If you suffer from living in a damp building, then Dehumidifiers are really the only solution, other than spending thousands of pounds in building, insulation and remedial work. If you are a tenant then a dehumidifier is also a must, after all if it prevents damp, it may not only make your living environment far more comfortable but also save you from losing your security deposit.

Usually the first signs of damp are regular condensation forming on the  inside surfaces of glass. With the widespread introduction of  sealed double glazing,  it has also removed the natural outside drafts which would naturally ventilate a room, the result is a high level of moisture which then forms on cold surfaces such as walls, carpets and clothes, eventually creating a long term damp problem which only a dehumidifier can remove.

Later signs of damp include dark patches forming on wall coverings and surfaces around windows, this will eventually form as thick black mold which is difficult to scrub off, and may even affect the wall surface underneath. This mold is extremely unhealthy as the spores  can be inhaled, resulting in poor health and increasing suffering in those with Asthma and Breathing related problems. Once you have reached this stage, it is obvious that your room or building as an extremely high level of moisture in the air and you need to reduce this, otherwise the mold will just keep returning – you need to cut off the ‘fuel’ which the mold thrives on, and that is  moisture caused by high humidity.

Dehumidifiers are also recommend for use in flats or small apartments, where ventilation is at a premium, and the temptation is there to hang damp clothes over radiators to dry them!. This is one of the biggest forms of man-made damp, when drying washing, and a dehumidifier is an excellent means of combating the problem. Some models also have the ability to connect to tumble dryers, solving the immediate problem of how to exhaust the waste humid air from the dryer.

Dehumidifiers cost between £70 and £250 to buy depending the model, size and features. For removing moisture and damp in a bedroom, then a 7L to 10L unit will be enough, if it is running several hours per day. If you wish to dehumidify the entire house, then a 12L – 25L model will be required, and the dehumidifier would be best left running continuously in an open space such as a hallway or landing, with all of the internal room doors left open, to allow the entire airspace to be circulated.

The amount of water which is extracted and collected by the Dehumidifier is quite frightening when it is first used. When you switch on your dehumidifier, it will take around 3 to 4 hours to cool its plates and start having an impact on the moisture in the room, beyond that, it should easily collect between 1L and 5L of water per 12 hour period, depending on how damp the air actually is.

It will take around 7 – 14 days of regular use for the dehumidifier to have a noticeable impact on the levels of damp within a room, however the sheer amount of water which you are pouring away every day from the internal water container should be an indicator of the good work that it is doing!. Hopefully, the levels of collected water will begin to reduce slightly after a week or so as the room humidity reduces, unless you live in a very damp property or the air is very humid.

Some of the most popular Dehumidifiers use a compressor to cool the coils required to extract the moisture from the air, and may be a little noisy in operation, on this basis it is either best to leave the unit running for several hours in a bedroom during the day and evening and then switch off during the night to allow sleep or choose the quieter desiccant dehumidifier. Ideally the dehumidifier should be run for at least 7 – 16 hours per day to have the biggest impact on reducing the moisture in your home.

Care should be used in avoiding the temptation to buy cheap, mini dehumidifiers with an advertised extraction rate of less than 3L per day, as these are little more than ‘toys’  and are very ineffective,  and not suitable for use in anything larger than a wardrobe!. When choosing a dehumidifier even for use in a lounge or average sized bedroom, then the extraction rate chosen should be at least 7L, with 10L+ being preferred. Saving a few pounds on the cheapest option is false economy when it doesn’t actually do what its supposed to.

Some popular dehumidifiers such as the Delonghi DEM10 have a control similar to an Electric Heater thermostat on them, called a ‘humidistat’, this allows the humidity in the room to be controlled and instead of running continuously the dehumidifier switches itself on / off as the humidity and damp levels within the room rise to high levels. For the correct operation of dehumidifiers fitted with humidistat controls, it should first be left running on its highest / continuous setting for at least 12 hours per day for 2 weeks in order to reduce the peak damp levels in the air. At this point, the humidistat can be turn down to the point where it clicks and the unit switches off. This will then automatically cycle the unit on and off as required, in order to keep the room dry.

Dehumidifiers are at their most effective with a room temperature of around 10c – 20c, and most will stop working at room temperatures lower than 5c, on this basis it is advisable to use the dehumidifier in a room with at least some form or background heat, and they will work much better in rooms which are heated to comfortable levels.

A dehumidifier will cost roughly the same as a Fridge Freezer to run. On its highest setting or if the unit is not fitted with a humidistat  the compressor will be running continuously, and a 200W dehumidifier will consume around 5 units for every 24 hours it is running. Based on an Average Electricity unit cost of 12p per unit, running the Dehumidifier will add around 58p to your daily electricity usage.

Of course, these running costs depend on the actual wattage consumption of the dehumidifier, and models with a consumption of 150w will cost less to run than the 200w given in the example, and the same applies with larger dehumidifiers, which consume anything up to 400w. If your dehumidifier is fitted with a humidistat (which switches the unit on / off automatically) then once the initial levels have dropped, the running costs will be reduced by anything upto 50%, so it may be worth investing a little bit more in purchasing a dehumidifier fitted with a humidistat, as it will probably pay for itself in Electricity savings within the first year. Those households with Economy 7 or Economy 10 tariffs can also take advantage of the reduced energy cost periods, and use a timer to run the dehumidifier during these periods of lower priced Electricity.

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