More Publicity!

Fame (though not fortune!)  seems to have struck – again.  No sooner had the 6 minutes of BBC fame begun to die down than our local MP, Sir Alan Haselhurst, came to see the house. Together with Dunmow Broadcast reporter Sam Tonkin, the house tour was undertaken and both Sam and Sir Alan seemed interested and, dare I say it, even impressed.

This resulted in a double page(!) spread in this local paper and, once again, we were caught on the hop.  Dunmow residents get their copies delivered on the Thursday of publication, but those in the sticks of Felsted have to wait until the following day.  So I didn’t immediately connect with the ribald remarks offered on meeting Dunmow residents at a rehearsal on the Thursday evening because, of course, I didn’t know what had been published. It’s a freebie, so pretty well everyone gets it.  This is a mixed blessing. Famous for being famous? In-for-me?

More seriously, it was a useful if rather local step in trying to persuade people that it’s not difficult to build a really low energy house and not that expensive either.  Sir Alan pointed out (very reasonably) that he couldn’t remember all that he was told, so would I summarise it for him in a letter?  Of course, though curiously not easy. Rabbitting on about the technology is fun and interesting for those interested but for those with political fish to fry?

I’ve copied in parts of that letter below which others may find helpful.

” . . . . it would be good to see all new build to the standard we have achieved here as it would go far to meet the need to reduce energy consumption – and hence carbon emissions.
The principles may be summarised in 5 key points:

  1. The ground slab has 300mm of insulation under it.  The slab provides much of the thermal mass to keep the house temperature steady.
  2. The walls and roof are deeply insulated.  The house thus sits in a cocoon of insulation.
  3. The air tight layer – the T&G fibreboard we showed you – is on the outside.  This reduces the number of places that need care to maintain the air seal and minimises its vulnerability over time.  There are lobbies at the outside doors to reduce the heat loss as you go in and out.
  4. Thermal bridging is minimised by the use of thermally efficient doors and windows (which are triple glazed) and good design at the floor-wall junction.
  5. Given that the house is airtight, a mechanical ventilation system is required – and this transfers the heat from the outgoing air to the incoming air, giving good ventilation through the house with negligible heat loss.  Our MVHR is 93% efficient and uses just 44W – no need for expensive and wasteful bathroom fans, for example.”


“. . . . This house meets Passivhaus principles.  These differ from the UK standard – the Code for Sustainable Homes – in being simpler.  CfSH looks for sustainability not only in the work of building the property, but also in the materials with which the property is built and, finally, in the way the occupants can then live.  All of this is desirable but expensive and hence meets resistance from the commercial house-builders.  Passivhaus simply puts limits on the energy demands.  It limits the space heating requirement, which is usually the largest demand, to 15kWh per square meter per year – a 90% energy reduction from what most houses need.  This simpler requirement would, on its own, have an amazing effect on total energy requirements at a lower build cost.  Whatever you use – wood, gas, even oil – you don’t use much!

This house would meet Level 5 of CfSH – but fail Level 6 for reasons that have nothing to do with the energy performance of the house.”

OK, there are simplifications here but the principle remains true.

You’re welcome to comment!

17-Feb-14: Two days with no need to light the log burner! After that very windy night, Saturday produced quite a lot of sunshine, enough to get us through to Sunday – which was a glorious day.  Spring offering a preview? Some brightness today, more than forecast, but while that keeps the house warm, we’ll need hot water, so the fire will have to be lit this evening.

Posted in Cladding, Thermal mass, Ventilation, Windows, Zero Carbon House | 2 Comments

It’s catching (on): as heard on BBC

Some recent excitement: at very short notice I was contacted by a producer – John Neal – of You and Yours from the BBC.  He’d heard from Touchwood Homes that they had a client who made money from his fuel bills – a real headline catcher!

The long and short of it is that we were then contacted by a reporter – Bob Walker – who came to Porter’s and spent couple of hours with us. This got edited down to some 7 minutes.  Despite our nervousness at the sheer novelty of such an experience, we were not made to sound foolish. Instead I think Bob did an excellent editing job and succeeded in extracting the essence of what it’s all about.

See what you think:

This has kicked a minor flood of friends saying how good they thought it was – clearly You & Yours has an even larger audience than we thought.

Now let’s get this in perspective.  Almost anyone with  a full set of PV panels (4kWp) is likely to have negative electricity bills.  We actually use more electricity than we did in our old, inefficient house, because everything that doesn’t depend on wood or sunlight uses electricity.  We do all our cooking with electricity instead of most of it by gas.  The MVHR uses about 1 kWh a day.  And there’s a (OK, quite small) pump with the solar thermal system.  But even with the less generous Feed-in-Tariff, as explained in the post Autumn (and Summer) 2013, you’ll have to be pretty reckless with the electric to have bills more than what you get paid.  The important point is that the house is efficient, so it doesn’t really matter what you use to heat it with – you don’t use much of it.  Thank you, BBC, for keeping that in.

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Wood usage

The wood store is relatively impressive – or so people have been kind enough to say. Essentially it’s the space between the two sheds with a corrugated plastic roof over it  and a slatted back so that the air can move through it.  Over the spring and early part of the summer all the driest wood I’d collected, from whatever source, got cut up and/or split and stacked in this space so that for the second half of the summer it got a final drying.  There were 55 builder’s barrow-loads.  The quality of the wood is extremely variable.  There’s some really good oak and ash there.  Plus some very worm-eaten pine – which had spent quite a lot of time on the ground before being dealt with and had been very well attacked by some wood-boring grub which made deathwatch beetle look positively benign.  And lumber right down to a couple of hardboard-on-cardboard doors.  These take space and burn well – but not for long!

The logburner in use

The logburner in use

There were two evenings in April when we had to light the log burner.  Here it is shown alight.  The pile of logs to the left is about 3 barrow-loads and the black thing on the wood is a glove which came with the stove.  The only bit of the stove which gets really hot is the door on the front – the top and sides are fine to touch.

The Autumn article covers the generation and use of electricity.  It could be argued that the Solar PV is nothing to do with having an low energy house.  More important in purist terms is how the space heating is performing.

Below is the chart showing when we lit the log burner since mid year until the end of last week and how many barrow-loads of logs have been used in the same period.

Log burner use and consumption 2013

Log burner use and consumption 2013


We’ve used 21 barrow-loads of wood in this period.  This, as mentioned elsewhere, has provided us with all the hot water we need (for showers, washing up, etc. – the usual DHW – and we certainly do not belong to the cold shower fraternity!) and has kept the house warm as well.  It’s been good to note that there was no need to light the fire on either 19th or 28th December.  These were lovely sunny days and warmed both the house and the thermal store to meet all our needs for that day and night.

And, while we use the wood saved over the past few years and the lumber left over from building the house itself (there are quite a few pallets to be got through yet) it has cost nothing but my effort and some electricity to drive the saws.  The builders, Touchwood Homes, calculate that, if we had had to buy wood in it would have cost £371 based on a cost of 4.2p/kWh.  I’ve never bought firewood, so I can’t validate this.

We’ll keep on counting though the rest of the winter and spring so that there’s a full year’s worth of data on wood usage.

Comments welcome – and Happy New Year!

Posted in The project history, Thermal Store, Zero Carbon House | 14 Comments

Autumn (and Summer) 2013

July, you’ll remember, was very hot.  After a winter that went on and on, there was a very short spring and suddenly we were in summer.  The thermal store got up to 95°C and the solar thermal panels were about to switch themselves off, because 95°C is the maximum temperature that the system was set to.  The panels would have emptied themselves into their expansion tank.

The thermal mass did its job of preventing the house heating up too quickly during the day and yet keeping it warm at night.  In the really warm weather the house did eventually get too warm, so we opened the skylights and let the hot air out.

Late summer 2013

Late summer 2013

By the end of October, we’d been in the house a full year and can therefore provide full year figures for electricity generation and consumption.  The house is on Economy 7, so there are two meter readings for electricity imported. Over the period 19th October 2012 to 1st November 2013 we bought in 1112 kWh at night and 2748 kWh during the day – a total of 3860 kWh. Over the same period the PV system generated 4009 kWh. The EFD Blue+Price Promise 2013 tariff we were on charged 18p/day standing charge, 11.32p/kWh day rate and 5.92p/kWh night rate. So we paid ((365+13) x 18 + 1112 x 5.92 + 2748 x 11.32) x 1.05/100 = £467.19 (inc VAT) for just over a year.

For the PV we received  the payments shown in the table below:

Period                           FiT payment
28.9.12 – 1.12.12         105.32
1.12.12 – 1.3.13              96.73
1.3.13 – 1.6.13              255.81
1.6.13 – 1.9.13              343.20
Almost a year              801.06

So the electricity bill was (roughly) minus £333.

Financially this was very encouraging, although it has to be admitted that the EDF tariff we were on was quite competitive.  We’re now on Blue+Price Promise 2014, which on a similar usage means that the price of the electricity bought in is about 25% more (and people moan about 9% increases!).  The rates have become 6.81p (15% increase) and 14.73p/kWh  (30% increase) for night and day rates respectively. What was that switching site?

(Update: now on EDF’s Blue+Price Promise April 2015 – a good deal better!)

During last winter (i.e. 2012-13) we failed to record when the log burner was lit and how much wood we used.  This autumn and winter, however, we have been doing so – having spent quite a lot of time sawing and splitting 55 barrow-loads (builder’s barrow) of dry wood during the early part of the year.  (Keeps me fit!)  Much of this had been collected over some years, saved on the basis that anything thicker than my thumb was firewood – and anything thinner got shredded and put into a compost heap.  The information on this is discussed in a separate article.

Getting up to date at last: thanks for your patience!


Posted in Electrics, Solar PV, Solar thermal, Thermal mass, Thermal Store, Uncategorized, Ventilation | 2 Comments

Winter and Spring 2013

More grovelling apologies.  I’ve been sitting on this for months without publishing it and now (round about Christmas 2013) have finally got round to doing something about it.

Well, quite a winter (meaning early 2013)!  This was a severe test of the performance of the house, with long periods with the temperature close to, and often below, 0°C by night and often day.

The house has done well.  A first experience of living in this sort of house makes a few notes worthwhile – how has it performed?

The original calculations suggested that the house would need 48 kWh a day to keep warm. Using the log burner – the Woodfire F12, which puts 10 of its 12 kW into water, we found that burning it for 4 hours an evening during the really cold patch – well below freezing at night and not over 2°C during the day (and a keen east wind – you (if local to Essex) will remember!) provided all the hot water we needed and kept the house warm (~20°C) for the next 24 hours.  And used much less wood than I’d expected.  So we’re well pleased. And half that when the weather was milder. We didn’t need to burn the stove at all for the second half of April – first half of May.  Then there was very grey patch and we had to light the stove briefly to be sure of enough hot water for showers – the house itself was kept warm from lower temperature heat and the solar gain through the windows. The May BH weekend was very sunny.  The temperatures in the thermal store read 72, 72 and 60°C (top, middle and bottom) and it’s a good thing that the water to the hot taps is mixed down to a lower temperature.

The thermal mass also seems to be doing its job.  Again over the Bank Holiday, the main bedroom got up to 23.5°C during the day but only lost a degree over night.  Visitors to see the house – who often take their shoes off – comment that the floors do not feel cold.  As mentioned elsewhere in this site, we do have underfloor heating but have not yet used it.  So the floor slab has picked up the temperature of the house and holds it.

Interesting effect: those of  a certain age – including me – may remember the pretty patterns on the inside of windows, formed by the condensation freezing in very cold weather.  We have had similar pretty patterns on the outside of the outer layer of the triple glazing this winter.  The insulation provided by the windows is that good!

The decking has been laid at the front – well, it’s actually the back, being the other side of the house from the front door – but is on the south side.  And the ground work has been done at the front and sides of the house.  And sheds for tools etc.  Curious, we still seem to be very busy when somehow we expected to be able to relax a bit by now.

Better publish this and get on with the next installment

Posted in Foundations, Solar thermal, Thermal mass, Thermal Store, Underfloor heating, Windows | Leave a comment

Week Thirty one to end October ’12

There were apologies here because I hadn’t kept this up to date.  So some progress now (end May 2013) at long last! Last autumn and winter we really got very busy indeed and keeping this up to date was a task too far.

When the stairs got unpacked it was found that the spindles were the wrong size – which meant that the banister and bottom rail were also wrong.  Replacements were promised in 2 weeks (which I thought was pretty slow for what I strongly suspect are ex- stock items) but in the event took 3 1/2 weeks to come. So by the time the builders came back to install it a full month was lost.  We then had to wait two weeks for the last day’s plastering. This in turn held the 2nd fix electrics of all this area and its decoration.  One way and another we lost 2 months in 2 months. Very unhappy.

But done now

Since then everything has been done – 2nd fix plumbing (some delay because the Multi-Board (instead of tiles – another make is Mermaid) was most unlike the brochure picture, so that had to go back and Simon has done a good job on the bathrooms.  The 2nd fix electrics has been done and the wiring certified.  The MVHR installed and the air flows balanced – and almost everything has been painted (there’s some skirtings which have still to be finished).  And carpets!

We had 2 Open Days – one for the Uttlesford Sustainable Homes Network when all sort of people interested in these things turned up and were able to meet our architect Jenny Bishop, (Green Architect), the main builder Touchwood Homes, the designer  and installer of the heating systems Dragon Contracts and the plumber Simon King. Rod Williams who calculated the Passivhaus heat equations and designed the ventilation was also there. And the following day we had another one for local friends and acquaintances who were interested.  Both days rather passed in a blur, spent talking.

And the following week we moved in (October 25th)!

Sometime!  Happy New Year

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Weeks Twenty-nine and Thirty

Week 30: it wasn’t supposed to take this long!  As mentioned in the previous post, with only one (albeit excellent) plasterer, this phase of the work has taken much longer than originally expected – with the odd day off, extra public holidays and the like, 12 instead of 4 weeks.  But the plastering is now finished bar a day’s work in the passage way containing the stairs, to be done when the stairs have been installed – and the stairs have(has) arrived, all in bubble wrap (not really a picture – but, lying on its side, it made a useful shelf for the kitchen fitters to lay their tools out on).  Yes, we now have a kitchen as well, fitted last week, complete with cooker. 

Kitchen, with wrapped stairs waiting to be fitted

Given that there is no gas connected – it’s difficult in my view to have a zero carbon house that uses gas – the cooker has either to be a wood burner or to be electric.  From friends’ experiences with wood burning cookers, this seems to be a “high labour” option.  So, as this is also our retirement home, designed for older people, electric it is.  For what we understand to be high efficiency, we’ve chosen one with an induction hob.  We’ve never had one before so this is another step into the unknown.  Induction hobs are said to be extremely controllable, like gas or even better.  The heat is generated in the pan bottom, so the top of the hob only gets hot where a hot pan touches it.  For safety, the induction zones can only switch on if there is sufficient ferrous material above it.  A non-trivial down side is that our still-good-as-new, Silcro, copper-bottomed wedding-present saucepans won’t work on this stove.  We have bought some (pretty cheap) new saucepans, etc.

Further, at long last, the front door has been delivered.  To contain shipping costs it came into the country with a consignment of windows for another job and so has arrived without its door handles.  We can manage without these for a while – it locks.

Between dining room and downstairs bathroom/ensuite there’s a solid wall, part of the thermal mass included in the design (see separate note under Definitions &c).  Here the heavy block wall is being rendered (with sand and cement) before being plastered. 

Block wall being rendered

Immediately to the right is the wood burning stove in its second-hand brick alcove.

Woodfire F12 stove/boiler in brick alcove

These two sections of wall contribute significantly to the thermal mass in the house. The exposed brick makes a change from what would otherwise be painted wall.

While the plastering has been going on downstairs, we’ve been painting upstairs. There’s a lot of it, it doesn’t make for interesting reportage, and it takes a lot of time.  It’s also quite hot.  The MVHR arrived and has been put away safely.  Its installation is held until the control room has been painted (which it now has) because it’s much easier to paint without it there!  Until the MVHR system is installed there’s no air circulation in the house, so upstairs is hotter than downstairs.  Despite our poor summer, the thermal store is full of hot water and there’s heat leakage from the pipes (bit more lagging to do yet) and the inverter gives off heat while it’s working – the sun comes out (yes, it does) and the inverter’s note changes and its temperature goes up.  The house is very well insulated – so you have to open a window.  Until the internal scaffolding came down it was easiest to open the roof lights but now you have to find the long pole to do this.


Posted in Electrics, Thermal mass, Uncategorized, Zero Carbon House | 3 Comments

Weeks Twenty-four to Twenty-eight

Got seriously behind with this – sorry.  So four weeks in one.  The plastering – and odd bits of plasterboarding/tacking – press steadily on.  This is taking very much longer than originally expected, largely because there’s only one person doing the work – a subcontract disagreement issue which is nothing directly to do with us.  But it does mean that we are at least a month behind schedule.

Nevertheless,  the kitchen and dining room have been painted (by us) and I have put up all the electrical sockets switches and lights (some of these lights are really awkward to wire, particularly if you have 2 in parallel) in the kitchen, dining room and utility room so far.  The stove is installed and has been joined to its flue (together with some discussion about what was, or was not, vertical.  The second-hand red brick alcove in which the stove sits has joints which are not perfectly in line).  As reported earlier all the windows are in place and we have a date for delivery of the front door.  This has meant that (even without the front door) the air test can been performed.  I haven’t seen many Grand Designs, but I do remember one where the architect/designer was skipping for joy because she’d achieved a really good, better than Passivhaus standard figure.

Air test door – the calibrated fan sucks air out of the house

Well, so have we : 0.5 ach – which stands for airchanges an hour.  This is good news, quite apart from the satisfaction of knowing that Touchwood Homes have achieved what is said on their signboard at the drive entrance!  Combined with the known performance of the highly insulated walls, a really low energy requirement is confirmed.

There’s a discussion which led to some telephone calls between me and the air test people and the assessor who was being asked to produce the Energy Performance Certificate.  The usual way of meauring air tightness in this country seems to be in volume (of air leaked) per unit area of building external surface (square metres) per unit time (hours) at a given pressure (50 Pascals) – and the result we got was 0.68m³/h.m²@50Pa.  Set against this was the desire to meet the Passivhaus standard of 0.6 ac/h.  But ac/h depends on the volume of the house, not the surface area, so to find out whether we’d met the standard it was also necessary to calculate the volume.

Air test graph

For a house of this sort, setting off to meet Passivhaus standards is going to be good start, simply because of the low space heating demand it implies.

The external cladding (there are references to the cladding, in rebated Thermowood weatherboard, elsewhere) is finished as far as it can be, while we wait for the delivery of the front door.  This has proved difficult to source. We – well, I – wanted  a pretty substantial one which, from the very earliest version of the specification I’d written, was to be a “Tilling” front door.  This is a foolish literary allusion, so I’d had to include a footnote (in a Terry Pratchet manner (see the Discworld novels)) which explained that Tilling is the town in which some of E.F. Benson’s Mapp and Lucia novels are set.  But Tilling is actually Rye, Sussex, of which Benson was some time mayor.  Visit old Rye and you will see many of the magnificent Georgian front doors.  As explained elsewhere, this house is a modest, not  a grand, design – so it needs a few features to give it presence, and an impressive front door should help.  But to get a door this big that also meets Passivhaus standards at a bearable price has not been easy and Peter Smithdale of Constructive Individuals has spent some time canvassing, even badgering, manufacturers to see if this could be achieved.  It should arrive 2nd week in July.

Receiving the EPC allows the Feed-In Tariff application to be completed.  From 1st April an EPC is required to show that the building is sufficiently energy efficient to be worthy of consideration.  “D” is required – this house is at the top of “A”.  So at last I should begin to get paid for the electricity the solar PV has been generating since the end of March.   Even in the poor weather of this summer it has already generated over 1300kWh.  Later update – I didn’t;  they were in error all over apologies, but . . . .  No backdating, so I am unpaid for the period until they received the EPC.  Miffed!

I’d better publish this before it becomes irrelevant – and get on with the next instalment.

Oh yes.  Comments are welcome – but links to advertising websites will simply be deleted!

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Weeks Twenty-two and Twenty-three

Plasterboard disc clipped back in place

The insulation lorry arrived.  The contains two generators to drive the machine, built into the truck, which fluffs up the Warmcel 500 and then blows it along large bore flexible pipes into the house.  A disc of plasterboard is cut out, starting with the rafters, and Warmcel 500 (re-cycled, fire-proofed newspaper) is blown in filling the cavities formed by the I-beams between the external air-tight cladding and the internal plasterboard.  Warmcel will fill all the wall cavities – both external and internal walls.  It’s a fairly dusty job – and quite noisy outside with the generators running.  It’s taken 7 days.

The circles are put back in afterwards with plasterboard clips and then, like the other plasterboard joints, covered with plasterer’s scrim.  The plasterboard has been fastened with rather more screws than usual because of the pressure exerted by the Warmcel.

The tacking and plastering is taking longer than expected – mainly because of the amount of effort brought to the job – started with 2 men, now only one.  We’d asked that the kitchen and utility room have their ceilings plastered first so that they can be painted ahead of the rest of the plastering so that we can be confident that the date agreed with the kitchen fitters can be met.  If we have to ask them to postpone then this date will go back by several weeks.  As we’re doing the decorating, we’re able to do some of this over the weekend as it’s too dusty to paint while the insulators are at work.  But for the rest of the house, there’s pressure on to finish off the tacking to keep ahead of the insulating gang.


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Week Twenty and Twenty-one

The log burning stove was delivered (last week – but I didn’t mention it because it came damaged).  The replacement one has now arrived and been installed.  There is an interesting bit of kit associated with it, called a Laddomat.  This is in part controlled by a flue thermostat.  When the log burning stove is lit and the flue gets hot, the stat turns on the pump in the Laddomat.  To begin with water is cycled through the stove only, until it gets to 60C.  Then a limited amount of cold water from the thermal store is allowed to join, such that the outflow to the thermal store remains hot.  This has two benefits.  First, that the stove walls come up to temperature quickly, and stay warm, which reduces condensation on them and thus corrosion, so prolonging the life of the stove.  Secondly, the water entering the thermal store is at a high temperature, so that water at a useful temperature begins to be stored.  If this is not done, the stove would attempt to heat all the water in the thermal store at once.  It could therefore be several hours before there was any water at a useful temperature.  (The thermal store has a page to itself – see under Definitions &c at the tope of the page.)

The shape and size of the house has been, partly, revealed again as most of the scaffolding round the outside has been taken down.  On the south side, in particular, there’s more light in the house and the house, from the outside, looks smaller.  Some of it has been put up again inside, so that it’s easier to put up the plasterboard into the top of the internal ridge.

Ceiling “squared off” at ridge beam

Details.  It’s very difficult to plaster into an acute angle, such at the top of the building where the sloping ceiling meets the ridge beam.  So when the insulation has been put in, battens to support plasterboard need to be fitted so that the ceiling is squared off for few inches and can meet the beam at a right angle.

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