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Ray’s dehumidifiers and the BBC

A BBC article recently reported on a small research project Ray did back in 2011, and similar projects being done today. The article, entitled "Why there's a boom for damp-busting machines”, reports that there’s a huge and ever-increasing demand for dehumidifiers in Britain today. The article can be downloaded from:

Britain is notoriously damp, and its old homes were not designed to be sealed tight with modern, energy efficient windows and front and back doors. So they’re not aired enough to keep the humidity down. Ray learnt this the hard way when he moved to England in the early 2000s.

So in 2010 he did a controlled, systematic study of the costs and effects of running a dehumidifier in a damp house for four hours each night. Each morning he measured the amount of water the dehumidifier had sucked up, read the number of kilowatt-hours of electricity the machine had used, gave a score to the amount of dampness remaining on the windows, and measured the outdoor and indoor temperatures.

The study was published in the journal Energy and Buildings and entitled: “Solving mould and condensation problems: A dehumidifier trial in a suburban house in Britain”. The abstract (summary) of the article reads:

High humidity can lead to condensation and mould formation if a house is well sealed and indoor temperatures fall significantly during the night. Solutions that have been offered are to keep heaters on throughout the night, to increase the thickness of insulation, or to install heat-exchange ventilators. These solutions are expensive. The cultural practice of heating homes to around 20 ◦C during the day and evening has been challenged, but lack of heating will not prevent natural temperature swings. A more direct solution is to remove the moisture from the air using a dehumidifier. This study reports a controlled 28-night trial of a dehumidifier in a suburban UK home in winter. The machine drew an average of 680 ml of water out of the air each night and consumed around 1 kW of electrical energy per night, with a high correlation between volume of water collected and energy consumed. Occupants reported that the previously severe condensation problem was solved, and measurements showed that the latent heat of the collected moisture also increased the ambient temperature. The estimated cost of running the machine for half the nights of the year is €28 (then about £18), an order of magnitude cheaper than other solutions.

The paper can be downloaded from:

The BBC article draws attention to increasing problems of indoor humidity as more of Britain’s are upgraded for energy-efficiency. Some very expensive solutions are mooted, such as comprehensive heat-exchange ventilation systems, which have the additional advantage of bringing fresh air in from outside. But, as the BBC reports, a far, far cheaper solution is to air the house fully and briefly (just enough to get one full exchange of air) several times a day and turn on the dehumidifier at night.

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