How to fix a broken screen on a Nexus 4

Posted in Gadgets, Howto, Tech on June 24th, 2014 by Andy
Broken glass

Not really what you want to see…

A couple of weeks ago I dropped my Nexus 4 and cracked the screen. The touchscreen was still working ok, but I went ahead and replaced the screen anyway. Here’s how…

On the Nexus 4 the screen is bonded to the touchscreen digitiser behind it, so unless you want some major hassle it’s easiest to just replace the screen and digitiser as one unit. You can pick up kits on Ebay to do this, mine cost about £45 and included screen, digitiser, tools and the frame (which was nice, as my screen frame was getting a bit worn).

I followed this video. The only things I would point out are that it’s easier to remove the SIM card holder first. Doing this makes it easier to pry the back shell off. If you’re replacing the whole screen unit you also don’t need to worry about heat the screen and seperating the components. Don’t forget to transfer over all the fiddly bits like volume buttons and the headphone jack from the old frame to the new one.

It’s not at all hard to do, with the right tools it’s just a matter of working carefully and methodically. My phone is good as new.

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Should I buy refurbished appliances and gadgets?

Posted in Gadgets, Tech on May 19th, 2014 by Andy

Yes you should, and the reason why has more to do with bathtubs than you might have expected. Not only are refurbished goods a lot cheaper than brand new ones, they’re actually better. Meet the Bathtub Curve:

The Bathtub Curve

Those of us who are paid to dip our toes into reliability engineering will be familiar with this graph:

The curve shows decreasing probability of failure over the short term

Engineers developed the bathtub curve from analysing the failure rates of huge numbers of machines. Basically it shows that things are highly likely to fail early in service (due to manufacturing defects, etc), then settle in and run reasonably reliably until they start to wear out and fall apart. Now, in real life nothing fits the nice smooth curve exactly, but in general it holds true. That’s why everything you buy comes with a warranty, manufacturers expect a certain percentage of their stuff to die straight away.

The bathtub curve, showing the lower chance of failure after the initial period

After a short period of use the chance of failure drops substantially

Now, when stuff  develops a fault in early service, people send it back to the manufacturer who often sends out a replacement. All good so far. The manufacturer repairs the original device and sells it on as a refurb for a substantial knockdown. My whole point is: having been in service for a short time and having already surfaced any problems, the refurbed machine is now less likely to conk out than a new machine. You’re now getting a machine that will be more reliable and costs less, and you’ve still got a warranty if it does go wrong again. Why buy anything brand new if you could get a better one for less? The worst wear and tear I’ve seen on any refurbed tech or appliances are some minor cosmetic scratches, which you’ll have on your new gizmo within a few weeks anyway.

I’m interested, hook me up.

Plenty of big companies have a refurb scheme. If you’re in the UK check out:


PC World

eBay (don’t be afraid of this one, lots of people run small businesses through eBay where they sell on the refurbed units from bigger suppliers)

Amazon refurbished

John Lewis Swindon outlet

Marks and Spencer outlet

Currys household applicances

Currys computing

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How to replace your Sky fibre router

Posted in Computers, Howto, Tech on May 4th, 2014 by Andy
A person having handcuffs put on them

Not keen on paying Sky to do this to your connection?

Whatever your reasons are for wanting to replace your Sky fibre router (and there are a few) the common denominator is that Sky don’t make it easy. These instructions will allow you to connect to your Sky fibre connection using your own router. The model I’m demonstrating is the Asus RT-N66U.

The legal bit

  • You can read Sky Fibre Broadband’s T&Cs here.
  • Your old Sky fibre router is your property, but the software on it belongs to Sky. You’re not allowed to flash the firmware, and selling it could be dubious. Best hang on to it for as long as you’re a customer.
  • If you need to speak to Sky customer services the easiest thing to do would be plug your Sky router back in and pretend to be just like the rest of their customers. They’ll only support the hardware they’ve supplied.

I’m keen! But how?

  1. Obtain your Sky username and password by doing a little sniffing around your router.
  2. Unplug your Sky router and hide it in the back of a dark cupboard.
  3. Get a new router and flash the firmware on it to a Sky-compatible version.
  4. Put your Sky username into the new router and connect.
  5. Win!

Getting your Sky username and password

As you’re no doubt aware, you’re not told what the Sky username and password you use to connect to their network is. But it is tucked away in the innards of your Sky router, and the router does broadcast them when it connects, so if we watch the output from the router we can deduce what they are. I’m assuming you have the standard white Sky fibre router, which looks like this:

The white Sky fibre router

Essentially you need to install software called Wireshark and use it to snoop in on the packets the Sky fibre router broadcasts when it starts up. Full instructions for that are available here:

How to get the Sky Username and Password for the Sky Hub SR101

Set up your new router

I can personally recommend the Asus RT-N66U. It’s not cheap, but it does pack a lot of cool features. You can get refurbed ones for about £70-80 if you keep a lookout. I got mine because I wanted to do things like use OpenDNS to filter content on my network (I’ve got kids and want finer-grained control than the blunt tool of the ISP filters) and run a VPN so I can access my network when out and about. It’s also fast (gigabit ethernet and 5GHz wifi-n) and stable.

To set it up for Sky you’ll need to install a slightly modified firmware. Merlin’s custom firmware for the Asus RT-N66U router is a minimally modified version of the standard firmware. All the changes Merlin has made are open source, if you’re paranoid you can read the source code. Instructions are on Merlin’s site; it’s really not hard and there’s apparently no risk of bricking your router.

Once you’ve got the new firmware installed go to the router’s admin page (which will be at something like in your browser) go to the “WAN” section and enter your Sky username and password into the Special Requirement from ISP > Manual client ID (for some ISPs). Here’s mine:



Note the single quotes, IIRC they are required, and don’t forget the | between @skydsl and the password. You may need to reboot the router and/or give it a bit before it connects, but it will. Enjoy your new router on Sky fibre!


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How to make a Raspberry Pi media centre

Posted in Computers, Gadgets, Howto, Linux, Tech on August 21st, 2013 by Andy
A man wearing a t-shirt printed with "couch potato" and juggling several remotes.

We’re doing important stuff here.

I built a media centre PC a few years back and I’ve been happy with it ever since. It’s been running XBMC, which is an awesome free media centre package. But I reckon it’s time to get some Raspberry Pi in my front room.

Why Raspberry Pi?

  • It’s cheap!
  • It’s fanless (ie: silent)
  • It can push out full-HD video
  • It’s got HDMI (including sound and CEC) so only needs one connection to my TV.
  • It’s very low-power so can run constantly. So no waiting for it to boot up.
  • Customised XBMC builds are available for it, and are well supported.
  • I keep all my media on my network, so my media centre box doesn’t need any storage
  • It’s so small I can just velcro it to the back of the TV, removing a whole box from my TV stand.

How much will it cost?

  1. Raspberry Pi Model B: £32
  2. Plastic Case: £5ish

Which is less than the parts of my old machine are worth on Ebay. Ka-ching!

You’ll also need a power supply that can put out 5V on a micro-USB (I’m using a Kindle charger) and an SD Card to install the OS onto. I had both of those knocking about, which saves money. I also plugged my old media centre’s wireless keyboard into the Raspberry Pi’s USB port, just in case. In practice we can control XBMC with a tablet or smartphone over our home network, but a keyboard and trackpad can be handy during setup. You could ditch it after that and save a bit of power. There’s always SSH from another machine if you need to do anything fiddly.

Enough waffle. How do we do it?

Pretty simple, plug your SD card into a computer (one running Linux is easiest IMO), and download Raspbmc. Raspbmc is a ready-rolled bundle containing a very minimal Linux operating system and XBMC. Once you’ve downloaded the archive, extract it and run the installer script within as root. Full instructions for your operating system are here. Other similar systems such as OpenELEC are available, but I found OpenELEC to be a bit unstable. YMMV, as lots of folks highly recommend OpenELEC.

Then just plug the prepared SD card into your Raspberry Pi and power it up. Simple.

What’s good, what’s bad?


  • XBMC for the Raspberry Pi is pretty much identical to the PC version. It’s slick and easy to use.
  • HD video playback is perfect, right up to 1080p.
  • Navigating menus in XBMC is still pretty smooth, despite the incredibly puny hardware.
  • The system updates itself. All you’ll have to do is reboot occasionally.
  • The XBMC remote app for Android allows you to browse and control all your media files.


  • The RPi likes to fight with my Samsung Smart TV. I don’t know whether it’s the way Samsung have implemented CEC (aka Anynet+) or the way the RPi does, but I found it far easier to just turn off CEC control in my TV’s settings. After that everything worked perfectly.
  • You can’t power off the RPi with the XBMC remote (this is a hardware limitation in ARM). The easiest thing to do is just leave it running constantly, which is mildly wasteful, but only to the tune of about 3W (that’s about 26kWh per year).




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ZOMG Fibre

Posted in Computers, Tech on July 9th, 2013 by Andy

We’ve got some new shiny, in the form of a new fibre braodband connection.
We bought a nice smart TV a little while ago, and unfortunately our pokey old broadband wasn’t up to the job of streaming video. I think the neighbours could hear us grinding our teeth as it buffered horrendously on even the shortest and lowest resolution playback. The whole problem was that we’re a good mile or two from our local exchange, and the way the streets lie I’d say we on the end of a piece of copper probably twice that length. Basically the bits and bytes were so shagged from the hike from the exchange to us that they just flopped down exhausted at our doorstep and were no use for anything.

But those days are no more! Behold the ludicrous speeds of fibre broadband. We’ve gone from about 3Mb/s down and 0.5Mb/s up to over ten times that. Shwing!

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MicroSD storage madness

Posted in Computers, Random, Stupid trivia, Tech on May 18th, 2013 by Andy

 An giant 19070s hard the size of a man compared to a tiny microSD card sitting in someone's palmThis is a pretty mad picture. I remember the first PC I owned had a 202MB hard drive, a size that just seems laughable compared to that microSD card.

So where does it all end? Will we eventually be able to pack the entire internet into a pinhead? Physics wonks tell us there is a maximum theoretical amount of data you can squeeze into a finite amount of matter,  but it’s a lot. For the microSD card given above it works out to about 567 bits, which is about 6.2 trillion trillion trillion trillion trillion MB.

It turns out that the capacity of hard drives has been growing at an exponential rate over time:

Capacity of hard drives over time. Note the logarithmic scale...

Capacity of hard drives over time. Note the logarithmic scale…

So, if they keep growing at this rate when would that microSD card sized storage device max out? Well, if the biggest microSD you can get currently is 64GB then I make it 132 years. And what could that microSD card fit on it? Well, the entire data storage of Earth in 2013 is around 735 exabytes, and that would take up a smidge over 0.000000000000000000000000000000000000000001% of the space on this “perfect” microSD card.

So clearly things can get even smaller, and store even more. Watch this space.


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The Liberator isn’t a gun, it’s a dangerous toy

Posted in Random, Tech on May 17th, 2013 by Andy
A man firing a 3D printed handgun

Cody Wilson of Defense Distributed test-fires his comedy “gun” thing

American 3D printing anarchists Defense Distributed have caused a bit of a flap in media and official circles with the release of the Liberator, a 3D-printable handgun. But how disruptive is this thing really?

What is the Liberator?

It’s a single shot handgun, completely 3D fabbed from plastic except for a metal firing pin (aka: a nail). The model demonstated so far was in .380 calibre.  It’s the spiritual descendant of nasty self-maiming tools the FP-45 Liberator and the Deer gun. The manufacturers claim that it democratises access to firearms, by allowing anybody to fabricate a real gun at home. I’m going to tell you why that is a really, really bad idea.

Can you make a gun out of plastic?


While many modern firearms do make extensive use of polymers, they use tough high-impact plastics properly formed by processes like injection moulding that guarantee strength. They don’t use 3d printing, for a good reason. Crucially, they also don’t use plastic for any of the actual working parts of the weapon exposed to high stresses.

The Liberator has a plastic frame and trigger mechanism, which is absolutely fine IMO. Unfortunately it also has a plastic barrel and chamber, which is just stupid. This is made worse by the fact that’s it’s constructed using additive manufacturing (aka 3D printing) where parts are built up by extruding layers of thermoplastic. This combination of process and materials is inherently weak, meaning the weapon will be inaccurate,  underpowered and dangerous to use.

Inaccurate and underpowered

Firearms are gas-operated. When the primer of a cartridge is struck it burns the propellant inside the cartridge and this generates expanding gas. This gas pushes the bullet out of the cartridge and down the bore, where spin is imparted to stabilise it once it leaves the barrel.

The gun disassembled into it's parts

The Liberator is built from 19 ABS components, a nail, and some very misguided intentions.

The Liberator’s plastic chamber is in fact more elastic than the brass of the cartridge it holds (brass elastic modulus = 100+GPa, ABS = 2.3GPa) so the chamber will not restrain expansion of the brass due to the rising pressure of the burning propellant. In a normal firearm the brass cartridge and lead bullet are constrained by the much less elastic steel chamber. This process is called obturation and is important for forming a tight gas seal so that as much energy as possible is imparted to the projectile.

On top of this, the Liberator’s extremely short barrel means that any gases that do start pushing the bullet along the bore will only have a very short time to transfer energy. Short barrels result in lower muzzle velocities, and since stopping power (ie: kinetic energy) is proportional to the square of velocity this means that short barreled firearms lack stopping power. Half the muzzle velocity will only carry one quarter the kinetic energy. And the Liberator’s barrel is really, really short, robbing the .380 cartridge of any stopping power.

It’s interesting to note that Defense Distributed have not published any chrono readings from their test firings. Were they to so I suspect you would find the Liberator is severely underpowered and dangerously useless for self-defence. Or crime, for that matter.

To make matters even worse the barrel is unrifled, and even if it were rifled the soft plastic would be unable to cut into a soft bullet to impart spin. This means the bullet emerges slowly in a pretty random direction, probably starts tumbling all over the place, and goes anywhere except where you’re pointing it. Not too useful given that you only get one shot.

But a crap gun still beats a knife right?

It should be noted that the original FP-45 Liberator from WWII (built to a higher spec than this one) was estimated to have an maximum range of no more than 25ft, and effective range was more like 10 feet. That’s about spitting distance. Police forces teach their officers that a knife-wielding attacker is dangerous to a gun-wielding cop at around 21ft, a figure the Mythbusters seem to have backed up with some playing around of their own.

Bottom line, the Liberator is no more effective than a knife, and probably somewhat less than an axe, a baseball bat, or any number of seriously lethal devices you can pick up completely legally, such as a chainsaw. Besides not being able to actually do its job, there’s a strong likelihood that it’ll blow up and plant bits of plastic in your eyes and face when you pull the trigger. Indeed, when Defense Distributed tried to fire a rifle calibre cartridge (5.7x28mm) from one it blew up on the first shot, which just goes to show these jokers have no idea what they’re doing. Did they even run the numbers on the chamber pressures before building it? I’m guessing not.

Should it be banned?

Not because it subverts firearms laws or allows criminals to tool up. Personally I’d be quite happy with criminals 3d printing themselves a Liberator if it meant they ween’t carrying better weapons, such a knife (or maybe a spoon).

However, I predict that some fool will fab one and injure themselves badly with it very soon. It’s dangerous to fire and good only for making a loud noise. You could build a more effective weapon with hardware from your local DIY store. 3D printing mongs Defense Distributed claim this gun is a revolution in civilian access to firearms. If that’s true then Lego is a revolution in building houses.

By all means, download and print one for a laugh if you want, but whatever you do don’t fire it.


Some testing done by the New South Wales police, during which (surprise, surprise) one of the two guns they printed blows itself apart:

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Vent-Axia HR25H Single Room MVHR Review

Posted in Gadgets, Green, Tech on December 1st, 2012 by Andy

I’ve spent a bit of effort draughtproofing my house, which has been great for keeping the place warm. The downside is that a certain level of ventilation is necessary to prevent humidity building up. This means condensation, mould and other nastiness. This winter has been quite bad, with black mould growing on cold spots around the place. That’s unacceptable to me with wee kids in the house, so something needed to be done.

The problem has two solutions:

  1. Get the humidity down by increasing ventilation
  2. Eliminate cold spots where humid air would condense

The main sources of damp in a house will be the bathroom and kitchen. Using a cheap humidity monitor I’ve been tracking our humidity levels and found them consistently above the 70% danger level where problems arise. Clearly we needed to avoid pumping any more moisture into the house, so extract ventilation in the bathroom seems like the top priority.

I’ll be tackling the cold spots in due course too, but for now it’s time for some mechanical ventilation with heat recovery (MVHR).

What is MVHR?

I’m allergic to the idea of simply blowing air we’ve heated with fossil fuels straight out the side of the house, so instead of an extractor fan I went shopping for a through-wall mechanical ventilation heat recovery unit. Unlike a regular extractor fan these also draw in fresh air and pass it over a heat exchanger that recovers some of the heat from the outgoing air. As well as reducing draughts by supplying air to replace that extracted, it will reduce the cooling effect of sucking out the warm moist air.

Is it worth fitting MVHR?

New tightly sealed houses use whole-house MVHR systems, but these are a different kettle of fish. Indeed, fitting one is only worth it if your air tightness is very good. Given that I had a humidity problem I took my air tightness to be somewhat higher than it should be, and coupled to the carbon-saving and comfort boosting properties it seemed the extra expense was worth it.

The Vent-Axia HR25H

I chose the HR25H over several competing products (Envirovent Retrovent and it’s replacement the cringingly-named Heat Sava, Vent-Axia HR25 Solo and Tempra) due to the combination of good performance, low price, and generally positive reviews from owners. The unit is not balanced, it extracts slightly more than it inputs, but this is a plus point in my books as it will draw air from the rest of the house into the bathroom so that other rooms get the benefit too.

Essentially the HR25H is a plastic tube with a divider down the middle. This penetrates the wall, and the fans are mounted on the exterior end, with the filter and electronics on the inner end. A cartridge type plastic heat exchanger sits in the middle of the tube and the whole lot is powered by a switched-mode power supply unit located up to 5m away. Like all MVHR it’s designed to run constantly on trickle and speed up when needed. Like most people I opted for the humidistat controlled version so that it would automatically boost whenever it was needed. Sensitivity is controllable, although getting it right can take a bit of fiddling.


A view inside the existing hole in my wall

Just a smidge of drilling required to make this usable…

To install this MVHR you’ll need a 100mm or 152mm hole through your wall. I already had a large airbrick through the wall, which had been bodged about with during the time of previous owners and currently had a nasty plastic grille. This was a good thing, as core drilling all the way through 300mm of wall is not my idea of fun.

I had hoped to avoid drilling altogether, and simply bash enough of the airbrick out, but the vent narrowed inside the wall too much (difficult to see in the pics). You can hire core drilling kits for around £50, or hire someone else to do it for about £40-90.

It’s important to make sure you drill with a slight downwards slant (which is why the hole isn’t going through the top of the vent in the picture). Sitting a spirit level on the chuck of your drill and tilting until the bubble moves is good enough. This will ensure that any condensation that forms inside the heat exchanger drains outwards. This is important, you will get condensation inside it, and if it can’t escape it will fill up the heat exchanger and the unit will conk out.

The MVHR fitted into the wall and wiring going in

Note the tile-over-tile job from previous owners. I constantly find nasty things like this whenever I do any DIY on this house. Luckily they left some spare tiles for me so I can patch up the hideousness when I’m done.

I fitted a plastic wall sleeve to the hole and filled the rest of the void with expanding foam. I’m sure the latter is awful for the environment, but it’s supremely useful stuff for sealing weird shaped holes and penetrating little gaps. Then it’s simply a matter of sliding the HR25H into the sleeve where it seals very tightly due to the rubber seals around it. The kit includes 5m of cable to run to the power supply unit. I went straight up through the ceiling, across the top of the insulation in the roof and down to the wall outside the bathroom where an existing junction box was close. After wiring the MVHR to the low voltage side of the power supply box and having the mains connected to the high voltage side I hit the switch and it all powered up nicely. The power supply even includes a fuse and a switch, so there’s no requirement for any additional hardware to spur off your existing wiring.


The unit is quiet in trickle mode. You can hear it nearby, but only if you listen for it. After all my hard work I needed a shower and was pleased when boost came on almost immediately.

Boost mode is much noisier, but so is any extractor fan. If I listen up the stairs I can hear it running in the bathroom if the door is open. If you shut the bathroom door it’s barely audible in the bedrooms adjacent to the bathroom, so I won’t be waking anybody up when I’ve got an early start.

Some action snaps:

Time shows 13:27, humidity 70%

Immediately pre-shower. Temperature is reading a little high as I inadvertently left the monitor over a radiator for a few minutes just prior. So much for a controlled experiment…

Time 1332, humidity 87%

Immediately post-shower…

Time 1336, humidity 91%

Peak humidity. The monitor does lag a bit, I assume it’s averaging readings from the last few minutes.

Time 1400, humidity 84%

Seems to be working…

Time 1419, humidity 79%

…yep, definitely working!

Note the drop in temperature. Some of this is due to the accidentally high reading pre-shower, then the effect of running the hot shower, but some drop while ventilating is inevitable. External temperature was pretty chilly, probably no more than 10ºC. No heat exchanger is 100% efficient, and just think how much colder it would have got if we weren’t recovering some of the exhaust heat.

The humidistat is adjustable between 60-90% relative humidity. While the adjustment is just a case of twiddling a knob, you do have to remove the face of the MVHR to do this, which means it’s a screwdriver job. To be honest this is a pain , but once you get it right there should be no need to tinker. I found the best way was to set mine to be relatively insensitive so that it shut off too early. Then I tweaked it downwards until it went into boost again, and kept repeating this until I was happy with the RH level when it shut off.

Power usage is 2W in trickle and 22W in boost. I estimate mine will run in boost for about 2h a day, putting annual consumption at  under 16kWh (assuming it’s switched off for half the year). That’s around £2.25 for me, so worth every penny to prevent nasty mould spores getting at my kids.


Besides a regular clean of the filters little is required. Replacement heat exchangers are available and simple to fit. Some users have reported prematurely dead fans, but they have a five-year warranty on them, so it should only be nuisance value if they do conk out. The electronics are all easily accessible, and you can pull the whole unit out from inside, so there shouldn’t ever be any need to go up a ladder to attend to the outside.


I’m happy with the HR25H. At around £275 delivered it’s substantially cheaper than some of the competition, and performs well. My humidity readings are now in the low 60’s or high 50’s (max has been 67%), and it’s done so without wasting heat. Fitting it was pretty easy, especially since I could use an existing airbrick. Besides an occasional clean out it should do it’s thing without any effort from us, which is just how I like it.

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Windy 3HP Air Source Heat Pump Review

Posted in Green, Tech on November 8th, 2012 by Andy

A beige box with vents on the top and frontThe Fimer Windy 3HP (“hp” = heat pump) is a through-wall reversible air-conditioner which can function as a heat pump in winter and an air conditioner in summer (the two are essentially the same process run in reverse, just imaging you’re trying to cool the Earth’s atmosphere in winter and venting the waste heat into your house).

It’s a single unit that mounts on an internal wall getting it’s supply and vent through a single hole in the wall. Because of this there are no bulky units to fit outside your house, and the whole thing can be installed as a DIY job. It’s just about the easiest and cheapest way to get an air source heat pump into your home.

I recently fitted one to replace a segment of my gas boiler’s central heating that had never worked since we moved in, and as an experiment in heat pump heating this winter.

Big box goes on wall

The unit itself is a fat box about the size and shape of a large suitcase. It mounts onto a plate screwed to the wall and comes with a standard 3-pin plug, although I’ll be wiring mine into a fused spur once I’ve finished monitoring it via a plug-in meter. You’ll need to get out the core drill and punch a 150mm hole through your wall. From there two concentric plastic sleeves carry air in or out and the box simply hangs on the plate on the inner wall. It weighs 23kg, so it can be fitted single-handed if you’re careful. I’d get a friend in if you’re hefting your chunky heat pump above about knee height.

Internal air is drawn in the top through removable washable filters and vents horizontally out the front. This can create a bit of a breeze at full blast, so have a think about what you’re pointing it at. That’s not necessarily a bad thing though, my wee girl loves standing in front of it and having the warm air blow in her hair!

There are more powerful 4Hp and 5HP units available. They’re the same physical size, but are rated higher.

Good points

It heats pretty effectively, drawing up to about 700W maximum, and heats our small 3.5x4m room quickly. Stated COP is 3.14 in heating mode (at 7ºC outside, 21ºC inside), and max thermal output around 2.2kW. Since the air is blown out it doesn’t feel dangerously hot like a 2.2kW convection heater would, and the mixing of the air heats the room evenly and quickly. Compared to the floor-standing 3kW heater we were using air source heat pump is a massive upgrade, safer around the kids, and much cheaper to run.

Under control of its thermostat the unit seems quite accurate, coming up to the temperature set point without overshooting, and keeping the temperature nicely within about 0.5ºC.

A brick wall with a vent in it

The vent is pretty low-profile and unobtrusive (dodgy amateur concrete job notwithstanding…)

The vent on the outside wall is quite small and tidy, although not everyone will be a fan of the plasticky grille.

The wall unit contains no buttons, which is good for child-friendliness if mounted low down, but does leave you somewhat reliant on the tacky wee IR remote. Apparently an RF version exists too.

Power consumption on standby is good, at about 3W. This is low enough that measures like timer switches become pretty marginal, so it can just be left on standby if switching it off is inconvenient.

The unit itself is quite modestly styled and should suit a range of decor. It’s paintable if you want it to blend in further.

Not so good

Due to having the whole gubbins (compressor, fans, etc) inside one box it can be noisy. It’s about comparable to a powerful fan heater, and mine does have a slight whistle which is a little annoying, but not teeth-grindingly so.

The main problem is the controls, specifically the ability to automate. There is no proper facility for timed on/off cycles. The only facility it has is a delayed on or off function. In “Timer On” mode you set the machine up how you want and switch it off, leaving the remote pointed at it. At the right time the remote sends the “on” signal and off it goes. Likewise for “Timer Off”, set it running, leave the remote in view and it switches it off at the appointed time. Unfortunately you can’t set both on and off times, it’s one or the other. So every night I have to set mine to come on the next morning, then it has to be switched off manually. A bit poor really, Fimer really need to sort this out.

The remote must be left pointing at the unit for timer mode to work, I get around this limitation by putting some sticky velcro on the remote and leaving it stuck inside an alcove opposite. Again, you’ll need to think about where you’re positioning it to get around this (or try to find an RF version).

Power consumption when not heating or cooling is not great. When switched on the fans run constantly even if there’s no demand for heat (or cooling), drawing about 30W continuous. Nice for a bit of air movement, but it would be better if the fans stopped after a reasonable time of inactivity.

Due to the entire condenser being mounted indoors it will collect condensate in its internal tank even in heating mode, you’ll either need to empty this occasionally or fit the included auto drain kit. I  recommend the latter, it includes about a meter of rubber tubing, so have a think about where you’ll drain condensate to. Even if you don’t fit the full drain kit, fitting the tap from it makes draining the tank a lot easier, or else you’ll be needing an allen key to remove a fiddly drain plug every few days.

Dehumidify mode seems  fairly ineffective, I didn’t see anywhere near the stated 1l h-1 figure and it draws about 500W continuously. I’d recommend a proper demidifier with a decent sized tank if you need to control damp.

The box sticks out a fair way from the wall (about 300mm), so it won’t suit hallways.

Green credentials

The COP the manufacturer claims is 3.14 in heating mode. This means the best case scenario is that it will use 1kWh of electricity to create 3.14kWh of heat. Realistically you should probably expect more like 2.5 IMO, but maybe I’m being cynical. Whether this is greener than a gas boiler for example will depend on the CO2 intensity of your electricity supply.

My old gas boiler is 78% efficient, meaning that to create 100kWh of heat it will use 128kWh of gas, releasing 23.5kg of CO2.

The Windy 3HP will use something like 40kWh of electricity to do the same (assuming COP=2.5). At bog-standard grid carbon intensity that would release about 21kg CO2e, although taken as an annual aggregate your supplier may be better or worse than that (UK fuel mix: energy companies emissions compared). So marginally cleaner in carbon terms, but using electricity does allow you to get the supply from a clean source. For example, on a couple of mornings I’ve had enough sunshine to run the heat pump off my modest little 2kWp PV system at least some of the time, even in November. During spring and early autumn I’d expect to be doing this quite a lot. I hope the polar bears appreciate it.

Obviously if you’ve got a very clean gas boiler and a dirty electricity supply (Scottish Power is the worst by the way) then it might not make sense, but if you’re heating with oil or resistive heaters or have clean electricity available then you’ll be streaks ahead.

The refrigerant is a non-ozone depleting one (R410) as required by law. It’s still a pretty horrendous greenhouse gas so make sure it’s disposed of properly at end of life, or you’ll probably negate all the carbon savings it’s ever made.


Not a machine without flaws, but at about £400 delivered it’s got to be the most affordable air source heat pump available. It’s easy and cheap to fit, effective and will make your home a happier place. If you’re looking for an all-singing all-dancing air source heat pump to heat your whole home, this isn’t it. But if you’re using electric heating or want to take some load off your fossil-fuel spewing gas boiler then it’ll do the business.

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Insulation and refurb for the kids bedroom

Posted in Green, Tech on August 13th, 2012 by Andy

We’ve got our second child on the way, so it’s time to shift the nursery from the box room to something bigger, and the room could do with some more insulation. We’ve been using it as a study (and to be honest a bit of a dumping zone) but it’s a good size and will be much better used as the kids’ bedroom. The project would also be a nice little experiment for me in internal wall insulation.

A cold-looking baby bundled up with just the face showing

Grumpy cold babies: what we’re all trying to avoid…

The Problem

This room is cold and ugly. It has nasty old metal-framed single glazed windows and a giant hole in the wall (air brick). There was a hideous mauve wallpaper peeling from the walls. Something had to be done.

The Solution

  • Re-line the external wall with internal wall insulation.
  • Seal the air vent.
  • Strip wallpaper and paint a neutral colour. We’ll be applying stickers that the kids can change as they grow or we move things around.
  • New double-glazing

I opted for Kingspan K17 insulated plasterboard for the internal wall insulation. I like the way everything is integrated into one slab. It gets stuck straight onto the walls with adhesive and has a vapour control layer to prevent condensation inside the wall (a genuine problem when adding insulation). Thermal conductivity is 0.021W mK-1.

Getting it done

Luckily the old wallpaper was in such poor condition that most of it came away by hand. We’ve got an el cheaper wallpaper stripper from B&Q and used that on the stubborn bits. Underneath we found an unpleasant green paint/primer/something that we’ve struck elsewhere in the house. It’s nasty flaky rubbish that turns to mush when steamed, and alternately sticks like shit to a blanket or falls off the wall at the drop of a hat. We gambled and didn’t remove it all, just a bit of a sand on the loose bits, and most of it seems alright. If all the paint falls off in a year’s time I guess we’ll know we ballsed that up.

A slab of insulated plasterboard

Insulated plasterboard has the high-performance insulation bonded to the back of the plasterboard, with a foil vapour control layer in between.

I stuck the Kingspan K17 to the outside wall using Insta Stik MP. Very easy to use, but if you’re using the “self applicator” type with a little plastic tube instead of a gun be aware that you can’t stop half way through as it keeps seeping out of the nozzle, so cut all your boards and check them for fit before you start gumming them to the wall. I used a continuous bead of the stuff around the edges to try to prevent vapour getting behind the insulation slabs from the joints.

Doing  the actual insulation slabs was easy, but I underestimated the amount of work that changing skirting boards, coving, radiators, and fitting new window boards would create. I was limited to quite a thin type of Kingspan K17 by the piping for the radiator, so could only fit 25mm (plus plasterboard makes 37.5mm). Make sure you plan your cuts around the windows carefully, so that you can use the parts you’re removing to do inside the window reveals (otherwise they’ll act as cold bridges). You don’t want to have to buy extra sheets just to do details.

The cavity in the wall for the air brick was stuffed with offcuts of rockwool and I simply stuck the Kingpsan K17 over the top. Should be well insulated and air tight.

For paint we went for some Dulux one coat. I’d not used one coat paint before and was skeptical, but it covered really well. A couple of spots needed a quick second coat after half and hour, but otherwise it covered really well.

Moving the wall inwards meant shortening the skirting boards on the adjacent walls, and new coving as the old stuff doesn’t survive being pulled off. The change in depth of the window reveals also means the old window sills were too short, so new PVC window boards went on.


The nasty old metal Crittal windows might as well have been a hole in the wall, so out they went and in their place came in some nice new double glazed units supplied by Unique Windows Doors and Conservatories, a local company. I highly recommend this father and son team if you’re in the southeast of England. Very good standard of parts and workmanship, nice blokes and a good price to boot.

Frames were from Liniar, glazing units were some 4-16-4 Argon filled Pilkington K.

Thermal performance

The wall was composed of three heat-losing elements:

  • Brick wall with cavity wall insulation inside it
  • Single glazed metal-framed windows
  • Air vent
Before After Max heat loss before Max heat loss after Annual heat saving Annual cost saving Annual CO2 saving
Walls 3.3WK-1 2.0WK-1 84W 51W 79kWh £3.25 15kg
Windows 13.0WK-1 4.4WK-1 325W 110W 534kWh £23.54 98kg
Vent 4.7WK-1 0WK-1 118W 0W 228kWh £9.37 42kg
Total 21WK-1 6.4WK-1 527W 161W 841kWh £36.16 155kg

As you can see, most of the improvement actually comes from the windows and the ventilation. The thin layer of Kingspan K17 adds relatively little. This is because the wall was already insulated and the layer of internal wall insulation was very thin.

Was it worth it?

To be honest, the internal wall insulation probably wasn’t for the amount of extra work it involved compared to the energy savings. If you have to re-do your plasterboard anyway or you’re able to fit a more worthwhile thickness of internal wall insulation then go for it. I’ve canned any further internal wall insulation plans for rooms that simply need a lick of paint. On the plus side there’s a couple of cold bridges around the house that will benefit from applying the offcuts of Kingspan K17.

Apart from that, the room looks great and feels warmer and lighter and will make a really nice bedroom for the kids, so we’re chuffed with it.

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