As I write this in mid-June, summer has arrived with a bang and a blaze. With blinds down all day, by mid afternoon the temperature in my lounge reads 26.5 degrees C, and, attired only in a pair of shorts, I am still reluctant to stray from the beam of the fan. This slows down my current project – installation of a portable air-conditioning unit.
After my heat complaints of last year I acquired this device, cheaply and second-hand, through my nephew. But by then it was too cold to think about cooling, so I stowed it the hall-cupboard and concentrated on dealing with the emergencies of daily life – and death too, in a way. Shortly after that post I was diagnosed with advanced prostate cancer. This is incurable and will usher me off the scene in an indeterminate number of years, but my treatment is currently effective with negligible side effects, and since it has no immediate bearing on the purpose of this blog, I shall say no more about it.
I only wheeled the air conditioning unit – now called the Dalek – out of the hall cupboard when the heat wave started and, of course, made it too hot to work on the installation with any comfort. As a heat-pump, the dalek takes in warm air from the room, extracts heat from it and generates two new streams – one colder than the intake and another one hotter. The cold air it blows into the room from a lidded aperture on the top, the hot air has to be expelled from the room via a flexible pipe.
My lounge has only one window, facing south east. Half of it can be opened with a hinge at the top, so this window is where the hot air must leave. The opening must then be carefully sealed to stop the hot air coming back in again, and this has been the site of my labour. The supplied exhaust fitting assumes the window is either a sliding sash or side-hinged casement design: engineering a solution for a limited-aperture top-hinged design in the full blaze of the daylight has taken some doing.
My first design was to install complete second glazing over the open window with a circular hole for the pipe, so I ordered a large sheet of double-walled polycarbonate to cover it. While waiting for this to arrive I cobbled together a trial system using a sheet of hardboard, wheeled the dalek into position, connected the exhaust pipe and power and switched it on.
The slot on the top of the dalek opened slowly over several seconds and then emitted a blast of very cold air accompanied by a fierce roaring sound, roughly equivalent to a motor bike at full throttle. Letting it run for half an hour brought the air temperature down by several degrees, but the sound level was unacceptable. I gather from the manual that the fan speed can be adjusted to reduce both noise and speed of cooling, but before I could investigate further my polycarbonate was delivered and I had to dismantle the temporary installation to fit the new one.
I found my original design has a serious fault. The twin-walled polycarbonate lets a lot of light through but blurs the image of the outside world, thus restricting my ability to keep an eye on my neighbours. Still, the window next to it remains clear for espionage.
Then the outside cooled down somewhat, and I found I could get cool quietly by lowering the blinds over open windows and setting fans to suck cool air into the flat. Over a period of hours this cooled the structure of the rooms to a tolerable level, so I wheeled the dalek back to its kennel to wait for the next heatwave.
19th July. The heat wave is back – blazing sunshine and tempertures up to 31oC – and the Dalek is out of its kennel. I connected it up to the polycarbonate window fixture in my lounge and fired it up. I found that it was able to reduce the room temperature down to 23oC over a few hours with the other rooms – bathroom and bedroom at 28 – but no lower.
Setting the fan speed to minimum on the Dalek reduced the noise to a steady whoosh measuring 63.5 decibels – still intrusive but tolerable for the comfort it provided. I spent most of the day there hiding from the glare outside. At 10pm the outside air temperature was down to 18, so I opened the bedroom window, wedged a fan in the opening and ran it until midnight, hoping to to cool the room enough to sleep in.
No such luck. Not only was the room still too hot for sleeping, the housing for the fan motor had fallen off and down two floors for the ground. Donning dressing gown and slippers I stepped downstairsto reclaim it. I found the housing sitting undamaged on the entrance paving. I picked it up and sat for a while on a handy bench, enjoying the moonlight and the cool midnight air. After a while, the birds started chattering and whistling to each other.It was so much fresher and cooler than my flat that I wished I could spend the rest of the night there.
I reflected on the continued complexity of thermal comfort – discussed in detail in the blog, but little understood by most lay people. I was perfectly comfortable on that bench just below the gaping windows of my bedroom inside the block. Why was inside perceived to be so much “hotter” than outside a few metres away.
Two factors probably dominate: firstly, radiant heating from the walls inside was absent in the open garden, and secondly air movement was absent inside the flat which has no through draft able to pick up some of the gentle midnight breeze.
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