DIY fan-coil heater

DIY fan-coil unit

Fan-coil unit

You might be surprised to know that if your house build is anywhere near Passivhaus standards then minimal heat demand makes underfloor heating a waste of time and money. Well, that’s a big saving so bring it on but what to do instead?

Underfloor heating did away with horrible radiators, and we don’t want them back, so that just leaves warm air blowers such as kickplate heaters which are just water powered puffer heaters.

On the walls without plaster theme here I proposed a kickplate heater, in the lower cupboard part, to give an occasional guff of hot air and for slightly under £200 you can do just that. However these neat little units aren’t perfect. They have to shift a lot of air through a small aperture so they are intrinsically noisy, draughty and the heat exchanger, or a filter, can clog with dust and pet hair fairly quickly. Larger versions are available but they aren’t so neat and they are much more expensive.

So here’s the Original Twist alternative which is cheaper, quieter and more reliable. Lets assume that the low cupboard bit of your wall is made of typical 720mm x 300mm kitchen carcass units. A pair of them 600mm wide with a large slot cut out of the inner sides allows a 1000mm x 500mm x 70mm double radiator to fit inside (£48.14 Screwfix). Each of the top shelves is fitted just low enough to mount a 140mm fan from a computer (£10 – 20 Amazon etc) and these gently blow air past the radiator and out of the bottom. You can decide where the air inlet goes: probably top front but a wall panel channelling much warmer air from ceiling height is worth a thought. This unit also does air conditioning when paired with a suitable heat pump so a length of plastic guttering under the radiator will catch any condensation.

You might want to kill airborne pathogens. There is plenty of space in the box for a pair of UV lamps but if you do fit them then avoid PEX water pipes because UV will kill them too.

Controls:  The fans are switched on automatically when either hot or chilled water arrives at the radiator. An ESCO solar controller does all that for £45.50 or about half that with a frost stat and a 2 pole thermostat. The fans are 12V so you’ll need a power supply and, like the fans, these are cheap PC components. Remember that the LED strip lights in your integrated beam floor above could be 12V and might like to share that power supply. You’ll also need a variable resistor for speed control.

And that’s it really. A few simple components all easily obtained and making the perfect, reliable fan/coil unit. When turned down to essentially silent the fan pair will move about 100cfm and the heat output will be between 1 and 2kW depending on the water supply temperature.

You might wonder why all this effort gives you anything better than the radiator fitted as normal. The answer is that heat pumps don’t work efficiently at the 60c normally used with radiators. While under-floor heating is the best in this respect a fan-coil unit works reasonably well at 40c. The only reason our unit has a radiator is that with all the fins in a double radiator you get a high surface area for not much money. The heat delivery couldn’t be more different. A radiator wafts hot air straight up to the ceiling where it tends to remain – replacement  air moves across the floor as a cold draught towards the radiator. A fan-coil on the other hand, blows warm air across the floor where it mixes with cooler air in the room and gives a faster and more comfortable heating experience.

insulation matters

Have a look at this chart on heating costs for various house types to appreciate why a Passivhaus with a small heat pump and some fan-coil units could be the way to go. You’ll see that the ASHP can meet the Passivhaus demand for almost no cost. Indeed if the ASHP is connected to PV panels then the running cost of the house will be close to zero.

I guess you might be in a state of shock now. Thousands saved on your heating strategy and air-conditioning a simple addition.

For more shocks and sleepless nights check out more building ideas on LIST OF POSTS.




Kenya – Turi reunion

Kenya reunion
December 5th 2018 – Wednesday
12pm  pub, Chelsea
Were you at school in Kenya circa 1955 – 1965?  Turi maybe. Come and meet some old friends in London.
Where are you?    Susan Casson, Gill Neville, Diana Tidmarsh,  Arthur and Alice Brown, Simon Jefferson, Geoffrey Peatling, Gail Nichols, Pippa and Fiona Mills, Charlotte Gaitskell, Paul Skinner, John Sutton, Timothy Upton, Janet Lloyd, Robbie Godkin, Elspeth McPherson, Richard Lowenstein, Liz Phelips, Johnnie Sherwood, Jane Faber, Alan Riley, Fraser Roberts, Belinda Foxon, Susan Kennedy.
Let me know if you can come .. contact form below.
Patrick Littlehales

Silent gaming PC

Silent gaming PC by Original Twist

silent PC heat sinks

What a great time to build a gaming PC. The Intel core i5 8400 presents the sweet spot in terms of performance for money and as it has to have a new motherboard the Gigabyte Z370N WiFi Mini-ITX is a great, and near compulsory, match. The board even has two M.2 slots so you can have SSDs without the untidy wiring.  Near to the previous core i7 performance for less heat (and less money), the 65W CPU is even easier to cool with heat pipes.

You might remember the Original Twist silent PC and now this is a gaming upgrade with more space and probably the biggest heatsink tally on the planet.

As before, the corner extrusions are ‘off the shelf’ aluminium extrusions as are the heatsinks where the supplier offers a CNC machining facility for the 6mm heat pipe channels.

fanless pc assembly

This section across the lower half shows a Mini-ITX board, HDPLEX 300W AC-DC and GTX 1060 GPU in position with plenty of room to spare. The heat pipes from the core i5 go above on the same heat sink, same for the GTX 1060 although it could use the space in the centre extrusion for its pipes. With CNC machining it is just as easy to have splayed channels as parallel ones so bending and fitting the pipes will be easier than usual.


The case is like a tall chimney so there will be good airflow across all components, a clear advantage over flat cases with horizontally aligned motherboards. The vertical alignment of the heatpipes gives optimal performance; around twice as good as horizontal ones. By sticking the tails of these pipes slightly below the CPU block there will be more water running back down the pipes – another performance tweak which takes the potential capacity to over 100W.

9 pipe CPU block

Heavy duty gamers and clockers will scoff at 100W so just for them ….. a 9 pipe copper CPU block with the pipes running up into back to back heatsinks. i.e. the pipes are clamped between an additional section of heat sink inside the case. So, 9 long pipes running vertically to doubled up heatsinks and the chimney effect even stronger. Actually there’s easily enough room on the heatsinks to fit 11 pipes from a 6 + 5 CPU block – how much power have you got?

The corner extrusions are ready for m6 screws to hold on the open top and bottom plates and the feet, which could be rubber doorstops (well why not?)  The perspex side cover over all the connections can be laser cut once the pattern is fixed and that job can be subbed out quite cheaply.

Fancy building one? Fancy buying one? Register your interest below – opportunity knocks.

More on this topic in LIST OF POSTS

Cool fireplace design

On the theme of substituting alternative wall finishes for plaster here is a large brick fireplace that looks absolutely stunning with a wood burning stove and adds a bit of ‘wow’ to any room. Shown here, part finished, the brick construction is a structural part of the house with the essential offset from the main wall allowing the exposed brick to be part of the room behind. You were going to build a wall anyway so here a little bit of thought yields an expensive looking fireplace doubling up with a characterful wall on the other side.

Perfect fireplace for a wood burner.

A few dimensional suggestions: The front buttresses are 225mm or one brick wide and thus the wood sections are 225mm square. The width between buttresses of 1.6m gives room for logs to be stacked by the stove and the 1.5m height between the floor and the main cross beam works well.

fun with the band saw

The Zampi (Italian: paws) profiles go like this:

Draw a centre line, mark the radius from the corner, draw a 30 degree angle from the corner, the big curve follows from the centre line intersection.

Double click for a closer look.



You might be going to use a flexible flue and this will need supporting above the stove. A steel ladder frame that can be slid forward and back a bit will make lining up the stack and the stove really easy. Between this and the stove fit a removable flue section to make cleaning easy.

A big stove like the 14kW Clearview shown here is best connected to water or it will make the room far too hot. To get a simple gravity feed put your tank on the other side of the wall and inside an airing cupboard. That’s another lot of plastering avoided and the core of your heating system done. BTW – I’m happy to advise on tanks and stoves and to supply them too. There’s a contact form below.

Oh, and here’s one I made earlier: Next time I’ll do the brick version.

Fireplace with Clearview stove

This note follows on from;

Like what you’ve read? Find more essential reading on my e-book

‘Dream House – Down To The Details’ 101 things you should have thought of.      here:-

Heating for your eco-house

For another example of straight thinking, this time on heating systems, have a look at

…. and stoves and solar.

You really should get this right and there are many wrong turns where multiple energy sources are integrated.

More on this topic in LIST OF POSTS

Alternative to plaster wall finishing

The clean, white, boxy rooms of modern architecture are all very crisp and neat but the reality for the occupants can be that they make for clinical, boring and echoic spaces without much sense of warmth and homeliness. All too often money is spent on plastering which is then covered up. Think long and hard before plastering a kitchen wall before cupboards and splashbacks make that work redundant.

Similarly, there is no need to cover up plasterwork with a fitted bookshelf or cupboards especially double sided ones serving a room on the other side. Hey, you might not even build a wall here let alone plaster both sides, just leave a large opening.

The Original Twist integrated concrete beam system can make a beautifully lit ceiling with wooden beams and boards …. but what about the walls? You might be wondering how to finish the stack of Durisol blocks you built with. The usual plastering solution needs a certain amount of organisation; the first fix plumbing and wiring has to be done and then the plasterer booked for some slot later. From start to finish it could be at least a couple of weeks before the plaster has dried and been painted. Even then there are many things a plain plastered wall does not deliver, so let’s have a look at the Original Twist concept wall and see what extra benefits can be achieved. Here are some ideas incorporated into one picture – it doesn’t have to be this busy.

This or plaster?

Basically there are three or four transverse wooden beams fixed to the wall and then panels fit somewhat loosely and quickly onto them. Extra insulation can be particularly easily added at this stage.

The top beam section

This top beam has a rebate sawn at the back to allow the top panel to be held in place then dab bonded to the wall or a top batten. Pictured is a strip of plywood with vertical marks scratched to resemble boards; quick and inexpensive. Strip LEDs are then laid on top of and under the beam and hidden behind the pelmet board – an inverted strip of skirting board would be good for this. Note how lovely the panels will look when the lights go on.

The next beam down has a similar rebate and here the larger panels are pushed up first to hook under the top beam before dropping into place on the beam below. Our top picture shows an example of black ash faced panels with OSB panels fitted on top. The latter can be covered in anything from wallpaper to fabrics and give unlimited scope for decoration; they could even match a TV screen. If engineered floor boards are being used for this section remember that many of them come in 1.2m lengths so designing for that might save a bit of time and not leave any waste.

The lowest section takes on a colonial look with tongue and groove boards under a shelf. The point of this is that wires and pipes can be hidden as can tubes for integrated dust extraction. Fan coil units for heating and air-conditioning can be fitted into this space with the inlet and outlet vents facing down and hidden. If possible the height of this section should be like kitchen cupboards so that doors and hinges can be incorporated and some mini cupboards too. The underside of the lowest beam has a routed slot for another LED strip light which will highlight the lower panel which acts like a deep skirting board.

So there we have it; loads of character, good sound absorption, sensational lighting, lots of utility and all quite easily done by any DIYer.

Internal walls in blockwork can be visually tied in by using the same beams but leaving the blockwork as the finish. Blocks can be painted in different shades before they are laid to make an interesting textured look. Any other wall incorporating a fireplace can be made in exposed brickwork to give a structural element with exposed brickwork on the reverse side. By the time all the remaining areas are covered by glass doors and a bit of wood panelling there may be very little plastering to be done at all.

Like what you’ve read? Find more essential reading on my e-book

‘Dream House – Down To The Details’ 101 things you should have thought of.      here:-

Heating for your eco-house

For another example of sensible thinking, this time on heating systems, have a look here.

You really should get this right and there are many wrong turns where multiple energy sources are integrated.

More on this topic in LIST OF POSTS


Modern floating staircase

DIY floating stairs

How hard would it be to make a modern staircase to embellish your new build house? Not too hard is the answer, as long as you design it to be DIYable from the outset.

This modern staircase is based on two 100×50 HRS hollow steel box beams with chunky wooden treads supported on 40x40x6 bright mild steel angle iron support bars welded onto the beams.

The angle iron bars are completely hidden inside the treads which appear to float without any means of support. If you are handy with a router and a welder (MIG is easy) then the construction should be quite straightforward.

A slot under the front of each tread is for LED strip lights mounted in aluminium channels with diffuser covers. Leave a little space around them for cooling and rout out a channel under the angle iron for the wires. You also need a hole through the angle iron and the box section for the wires to pass into the box section, preferably with a rubber grommet. The stairs lit with any colour you chose will be absolutely stunning.

A bought in staircase like this would cost at least £5,000 – £10,000 so you can afford to sub out some of the work to make it easier and buy any tools you need. The routing work is very repetitious and it would be worth getting a local CNC router on the case; there is only about an hour of machining time and accuracy will be pefect. Get the angle iron brackets cut to length too. There will be many chamfered holes to make so I’d say a pillar drill will be essential.

The Design

stairs geometry

Tradition has it that a comfort stair was 7” x 11” for rise and going. Rounding up slightly that’s 180 x 280mm. B.S. regulations for rise is 150 -220mm and 220-300mm for going G. The ratio of rise to going gives an important angle which here would be around 33 degrees and must not exceed 42 degrees. You’ll need this angle to saw off the ends of the beams and to mount the angle iron brackets.

The distance H between your two floor levels will set the rise. Find which whole number divides into H to give a rise R near to 180mm or what you prefer. That whole number is one more than the number of treads.

Tread thickness T.  B.S. regs state that a 100mm ball must not pass between stairs or guards so if we say that the open gap between the treads will be 98mm then T = R – 98 or more.

Going overlap. B.S. regs state that the overlap on open stairs must exceed 16mm but too much spoils the design, as you will see when you draw yours. So tread width W = G + 20 will do for a start.

So the treads will be something like 300 x 80 in section. As for length just bear in mind that stairs over a metre wide must have hand rails on both sides. I think 85cm looks about right.

Length of box beams L. To make life easy you could set the top of the box beam level with the top of the top tread, so; The base of our triangle is (no of treads -1) x G / R and then just use Pythagoras to get the longest length of box…. or just draw it and see what you get.

Make a note of all your numbers then make a drawing of the side elevation to scale. Sketchup is perfect for this and is free and easy to use. Note the intersection of the top of the angle iron, the beam and the back of the tread. N.B. Sketchup can repeat copies easily so draw and colour just one tread then copy it upwards by the rise and then across by multiples of the going. You’ll need a jig to position the angle supports easily – draw this too to see how it will work.

The safest way to make the stairs is to bolt the two steel box sections firmly in place using the top and bottom cross members. With a sliding jig, position the angle irons, measuring the height of each one from the floor. Tack the angles on and then take the whole thing down to weld it properly. To prevent any distortion I’d weld on a few cross struts then grind them off afterwards. If you can cope with the weight it will be easier to turn it all upside down to screw on the treads before remounting it. Fit and test the lights too.

If you make these stairs I’d be very glad to hear about it and to put  your photo with this article.

Like what you’ve read? Find more essential reading on my e-book

‘Dream House – Down To The Details’ 101 things you should have thought of.      here:-

Heating for your eco-house

For another example of out of the box thinking, this time on heating systems, have a look here.

You really should get this right and there are many wrong turns where multiple energy sources are integrated.

I supply heat banks and stoves at good prices and give free advice. Transport is easily arranged for UK, France and Italy. If I can be of help please get in touch using the contact form below.

More on this topic in LIST OF POSTS

Integrated Concrete Beam System

Integrated Concrete Beams

Building with Durisol, Quadlock or any other ICF blocks? Here’s the easy way to do a poured concrete floor.

Concrete first floors are good; low noise transmission, high thermal mass and suitable for under-floor heating. The trouble is the shuttering required is elaborate and expensive both in materials and time and once the floor is poured there is usually more work involved in boarding, plastering and painting. Concrete block and beam systems look easier but you do need to be very organised and get delivery of exactly the right beams and after paying for heavy lifting gear they won’t look like a cheap fix. Again there will be final finishing to do. Plastering and painting ceilings – no thanks.

The Original Twist Integrated Concrete Beam system is so suitable for the self builder that it is hard to consider anything else. It couldn’t be simpler. You make up some hollow beams out of easily sourced planks, put them up in a row, fill the gaps with wooden floorboards and pour. That’s it.

Concrete floor system

Step 1/.

Make up the wooden beams as shown in this cross section. The blue and yellow bits are your choice of regular timber from your local supplier.  The slots sawn out of the yellow sections are for wiring channels and it makes sense to insert the wires while the beam is being assembled. The threaded studding stops the beam spreading when the concrete pours in and is part of the construction with the outside acorn nuts making a decorative feature. Use a spindle moulder or router to round off the edges and then apply your choice of finish after distressing with chain, hammer, belt sander etc. You will see that the yellow sections stick up by the thickness of your floor planks and make a perfectly curved transition between the concrete floor and the integral ‘I’ beams. The rebar at the bottom of the ‘I’ section needs to be held in position prior to the pour and this can be done easily and cheaply with pairs of cup hooks screwed into the bottom plank. Use cable ties across each pair to hold the rebars in. Finally, paint the inside of the beam to isolate it from the wet concrete. The beams are then ready to be placed in position, typically on a one metre pitch (Durisol blocks are half a metre wide) and each propped with one or two Acrow props. If you are using ICFs like Durisol for your walls you should cut out large slots on the inside face to take the beam ends. You might want to pour the walls up to the level of the beam bases now.

Step 2/.

The floor planks can be cut and finished at ground level before fitting between adjacent beams. Now is the time to fit any pockets for spot lamps and take the wiring back towards the slots pre-cut in the main beams. The floor planks need to be strong enough to resist the weight of the concrete without sagging; they don’t need to be jointed together as a layer of building paper over the top will stop any leaks. Unlike concrete blocks they are light and easy to pass up to your helper.

Step 3/.

With steel mesh over the beams and planks the floor is ready to pour.  The outside of the Durisol blocks sets the top level of the floor so you don’t even need any shuttering. Once the pour is done and set, the walls and floor are all integrated with the homogeneous ‘I’ sections in the beams giving enormous strength and stiffness. The ‘I’ section parts of the floor could be up to 360mm deep which makes them into a row of significant beams in their own right. At this point the lower part of the house is waterproof which makes for a good working environment from which to finish off the rest.

Step 4/.

Nothing much to do now. Just take down the props then go down to the pub to celebrate all the money and time you’ve saved. There is no ceiling finishing to do, no shuttering to take down, even the lights are fitted and wired. And all this was done with simple hand tools and without waiting for special parts to be delivered. And just look; lovely lovely beams adding character and value to your home.


A small spacer between the top of the beam and the floor joists will create a gap to house some LED strip lights. As you have a lovely wooden ceiling you might as well show it off.

N.B. Wood shrinks. A tiny air gap could eventually appear between the concrete floor and the wood floor. A very thin rubber membrane between the floors (instead of the building paper) will prevent any ‘thwack’ as the upper floor is walked on.

Ground floor block and beam – alternative system

Block and beam systems are commonly used for ground floor construction but again they can’t compete with our integrated beam system. Block and beam materials all have to brought to site and then assembled – lots of work there. All those blocks are more gap fillers than strength givers and they are followed by a poured screed anyway. With the integrated beam system you just string out the wooden beams, fill the gaps with plywood and then pour – not only much quicker but stronger too. Use adjustable legs from kitchen units as props, to prevent sagging, and leave them there forever.

With both floors quickly and cheaply constructed and the walls easily made with ICFs it is easy to see that a fully waterproof house up to the first floor could be made in a matter of just a few days. That saves time and money and less exposure to problems with bad weather.

structural fireplace and stove.

While the rest goes up the internal finishing can start on the first level. Some comments on this here…. and an internal wall cum fireplace design here. … and a floating staircase here.

While this system is great for under floor heating, I’m really not in favour of it for bedrooms as it is a big waste of money for an unwanted result. More on that in the eco-heating link below.

N.B. As usual do your own evaluation for suitability.

Like what you’ve read? Find more essential reading on my e-book, it’s almost free and could save you a fortune. ‘Dream House – Down To The Details’ 101 things you should have thought of.      here:-

Heating for your eco-house      For essential reading on heating systems, have a look here:

You really should get this right and there are many wrong turns where multiple energy sources are integrated.

I supply heat banks and stoves at good prices and give free advice. Transport is easily arranged for UK, France and Italy. If I can be of help please get in touch using the contact form below.

More house building topics in LIST OF POSTS