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How to reduce high temperature and high humidity
I have read your article 'Air conditioner, air cooler, dehumidifier or fan - what works?' (August 2009) and am confused!

Articles I have read advise that both air coolers and humidifiers increase humidity.

You state that whereas air coolers increase humidity signfiicantly, humidifiers are 'also a very effective way of controlling  stickiness , especially when it is not proposed to open a window'.

 In the south of England where I live we are now, more frequently,  getting summers with high temperatures AND oppresive high humidity. 

So what is the best piece of equipment to buy to 'cool down' in such circumstances?

Would air conditioning (fixed or portable) be the only suitable solution?
Once the temperature goes above around 25C with high humidity, an air conditioner is the only way solution to bring down both if it's hot and humid outside. That old article is from when I was seeing countless stores and flyers advertising evaporative air coolers here in Ireland. Unlike the UK, it rarely gets above 25C here.

A dehumidifier (not to be confused with a humidifier) in a closed room takes the moisture out of the air, so it feels less sticky. This is fine when the temperature is not too high such as here in Ireland, e.g. 26C with dry air will feel more pleasant than 24C and feeling sticky before running the machine. However, if the temperature is close to 30C, a dehumidifier will just make the room too warm, especially since warmer air holds a lot more moisture than cooler air and so needs to work harder.

The only non air conditioner option I can think of would be to get a floor standing tower fan and place it between a partially open outside door to blow the outside air in. This will bring the temperature and humidity towards what it's like in the shade outside. While visiting a couple a few years ago in California, this is what they did, usually early in the morning and after sunset to bring down the indoor temperature, then shut the doors and windows during the hottest part of the day. I was surprised how effective it worked considering it was over 30C many days during my stay and they didn't have any air conditioner. For the bedrooms, they ran window fans to blow outside air in for about an hour before bedtime.

If you can afford to get a fixed air conditioner installed (which requires professional installation), this is the best option as it can run with the windows and doors closed and brings down both the temperature and humidity as it operates. Most fixed air conditioners can operate in reverse to heat the room in winter. As they are technically heat pumps, the running cost is around 1/3rd that of using an electric heater.

Portable air conditioners come in two options - Single duct and double duct. The single duct is the cheapest type (£200-£250 during the spring before the first hot spell causes price gouging), but has a side effect in that as it blows waste heat outside through its duct, outside air ends up being sucked back into the room to replace what's blown out, so can be quite expensive to use if run continuously as they'll cooling both the air in the room in addition to the warm air that makes its way into the room. However, they are a vast improvement of any evaporative air cooler as they reduce the stickiness instead of increasing it. A double duct air conditioner (around £400+) has a second duct to balance the air flow through the machine, so are more effective than single duct machines during very hot weather.
Dear Sean,

Thanks for your prompt response which is most helpful.

I looked into fixed air conditioning units last year. They were frightfully expensive to install (probably higher in London than elsewhere?) and, as I live in a conservation area, there are additional significant 'consent' fees and also costs to 'box-in' the outside units. 

Whilst portable air con units are a possibility, independent reviews don't seem very encouraging! There seem to be quite a number of downsides eg they have to be vented through a window or outside door with a trailing hose (which can pose a security risk); they take up space and can be heavy to move; are expensive to run (although presuably so are fixed units); and from what I have read it can be difficult to find units that are really quiet!

So it looks as though I will be looking at a tower fan used in the way you suggest!  Certainly much cheaper!!

Thanks again for your help./

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