Mildew
What is mildew?
Mildew is a generic term used to describe a mould-like covering caused by micro-organisms. Commonly seen on plants and vegetation, mildew thrives on organic matter including paper, leather and clothing (although many clean synthetic fibres are immune). It can be a particular problem in tropical countries where there are high humidity levels, but it is also commonly present in houses the world over. Bathrooms and kitchens, as well as other rooms where there is a high moisture level, are particularly susceptible to mildew, as are rooms with poor ventilation such as cellars and basements.
As well as causing discolouration and staining, mildew brings with it an unpleasant (and instantly recognisable) odour and can also deteriorate building materials (such as plaster and brickwork). Asthma sufferers and people with certain allergies may also suffer more serious health consequences as a result of mildew in their homes.
This article will focus on mildew in properties and will look at what causes it, and how it can be prevented.
What causes mildew in properties?
Mildew thrives in moist areas, where humid air settles on a cooler surface and where temperatures range between 40 and 100 degrees Fahrenheit. It is attracted to surfaces where there is a nutrient base (and virtually all surfaces contain nutrients) and where there are already mould spores. Although thorough cleaning and the use of disinfectants can provide some protection against mould growth, mould spores are around us wherever we go, and virtually all construction materials and household furnishings can provide the nutrients necessary to support the growth of mould.
Rooms that are too damp, too warm, poorly lit or poorly ventilated are all highly susceptible to mildew. Today’s architects and builders can do their bit by ensuring that the conditions that encourage mildew are avoided, but what about dealing with an existing mould problem?
Preventing and treating mildew
Excessive moisture in a basement or cellar may be caused by poor external drainage or an insufficient damp course. This is not difficult to rectify and added insulation will provide additional protection. Two coats of cement paint will waterproof concrete and other masonry walls above ground whilst waterproof coatings should be applied to bricks and other absorbent materials. Once all repairs and modifications have been made, a de-humidifier or air conditioning unit may be necessary to remove moisture from the air.
In damp rooms and houses, heating the area for a short time and then letting out the moist air is the first step that should be taken. Small rooms and cupboards can be dried by leaving a 60 or 100 watt bulb turned on. If the space is not too large, the heat will also prevent mildew from forming.
Generally, air movement is a good way to remove moisture. Dry air from enters a room, absorbs the moisture and is then carried out. If there is no natural ventilation to do this, electric fans can perform the same operation
For most property owners, bathrooms and kitchens present the single largest mildew problem - and also arguably the easiest solution. Cooking, bathing and washing clothes can add eight litres or more of water to a house per day if there is inadequate circulation. There are some obvious remedies here. Ensure that the rooms are well ventilated, that a window is kept open to let steam and moisture escape (and that hoses from tumble driers have an external outlet!) Exhaust fans, placed in a window or set in a wall, should be turned on during cooking or showering. Surfaces should be wiped clean of dirt and condensation before the rooms are vacated.
Chemical treatment
If natural ventilation is poor or non existent, chemicals provide an alternative means of preventing mildew. Silica gel and anhydrous calcium sulfate are generally readily available (under trade names) in most good DIY centres. The crystals, blue when dry, absorb moisture from the air and then turn pink to let you know they’ve done so. Another chemical, activated alumina, works along the same lines but may not be sold over the counter. Companies supplying materials to the building trade, industrial chemists and, of course, an internet search, may provide routes to obtaining other chemical solutions.
Anhydrous calcium chloride (used in some parts of the world to melt snow on roads) offers another solution to mildew prevention but whereas the other chemicals mentioned are not harmful to clothes and fabrics, this one is. It works along the same principals as the other three but liquefies as it absorbs moisture. Placing this chemical near clothes does a faster and more efficient job than letting a squadron of hungry moths into your cupboard. Depending on the humidity, half a kg of calcium chloride, placed in a pot, will last from between two weeks an two months.
Dispose of moisture-heavy pink crystals responsibly and sensibly. Add water to the liquefied calcium chloride when disposing of it.
That familiar smell
The musty smell that accompanies mildew and mould is as common as it is objectionable. Again though, it can be easily rectified by ensuring that a) the conditions for encouraging mould growth are removed and b) areas affected by mildew are treated with chloride of lime or bleaching powder. Household bleach, purchased in any supermarket, and applied with a stiff brush will quickly remove mildew patches in bathrooms and kitchens. In areas of the property where there has been more extensive contamination, a chlorine bleach such as sodium hypochlorite, should be mixed with water (one cup of bleach to four litres of water) and scrubbed onto problem areas. Afterwards, the area should be rinsed with clean water and wiped dry.
When choosing any chemical treatment products, ensure that they are fit for the purpose you have in mind as some products are more efficient on different surfaces than others. Also ensure that all chemicals (including the gels left in open containers) are kept well away from children and pets.