Energy consumption

Over the past couple of weeks I’ve been trying to measure the heat input to the house from the heating system, and gain a better understanding of the way the house responds to changes in temperature.  I already knew that the air source heat pump (ASHP) only seemed to come on for a couple of hours or so each morning, and also knew (from power measurements on the supply to the ASHP) that it rarely seemed to use more than around 800 W to 900 W, settling down after about 10 minutes or so of running to around 400 W to 500 W.   What I wanted to find out was how much heat was actually being supplied to the house from the underfloor heating (UFH). Continue reading “Energy consumption”

Part Forty Six – Over-thinking things – Part Two

When going through the list of things that we hadn’t used consultants, specialists, etc for, I realised I’d forgotten about a few.  Well, it’s fair to say that I hadn’t really forgotten about them, but had forced common sense (an increasingly rare commodity) to dominate.

I’ll give just one example, but I’m sure others will have many more (especially when it comes to ecology, archaeology and wildlife!).   I had a rough idea of the ground we would be building on, as we HAD to have a hydrogeological survey for the borehole (no easy way out of that one, if you want a quote from driller).  The survey wasn’t expensive, and I could have obtained almost all I needed from the BGS website, plus a look at a lot of the local borehole drilling records, that shown the type of sub-strata and depth.

So, I knew that we were on the exposed top surface of blue gault clay, and that it was at least 3m, perhaps closer to 4m, above the water table.  I also knew that the gault was highly compressed here, so was almost a semi-hard mudstone.  The first thing I was asked by the foundation design structural engineer was the bearing strength of the sub-soil and whether or not the clay was subject to movement with varying water content (heave). Continue reading “Part Forty Six – Over-thinking things – Part Two”

Part Forty Five – Architects and consultants, what are they likely to cost, and can you save money by doing some of this yourself?

First a bit of clarification.  Some have expressed a view elsewhere that this blog is in some way a revenue-generating device for me.  I can absolutely assure anyone reading it that it is the opposite.   It costs me money to pay for the web space, and I don’t gain any revenue from it at all.  I won’t  allow advertising here, and spend a fair bit of time deleting literally hundreds of spam comments, to keep it free of commercial influence, as far as is practicable.  As a consequence, whatever you read here is my personal view, and not coloured by any commercial influence.   My only intention here is to hopefully try and help others, who may learn from our experience.  If it saves them money, or eases their task, that that is all the reward I want.

I’ve been prompted by a discussion, following a couple of free podcast interviews I gave for House Planning Help:


and here:

to have a think about what “self-build” really means and how much money you are likely to pay out to others, even if you were to do all of the building work yourself. Continue reading “Part Forty Five – Architects and consultants, what are they likely to cost, and can you save money by doing some of this yourself?”

Part Forty Four – Over-thinking things – Part One

From the very start of this project I have now realised that I have wasted hundreds of hours thinking far too much about things that really don’t need worrying about.  In this episode, I’m going to try and focus on a few of them, I’ve no doubt more will come up in later posts.


I mentioned in a reply to Mike in the previous part that I had wasted a lot of time doing things that I thought would be needed for the building control completion inspection, but that it turns out weren’t.  The same is true about so much of this build, that I think it’s well worth trying to summarise some of them in a single post.

Firstly, I should point out that as a retired scientist I find it far, far too easy to get sucked in to investigating details and finding out why things behave as they do.  Sometimes this is a good thing, but 90% of the time it leads to a great deal of wasted effort.  The classic is the initial house design.  I was obsessed with how to heat it and making sure it had enough passive solar gain in winter.  It didn’t even cross my mind that it might  need cooling, neither did it cross my mind during the design stage that having a house deep into a cut out into a south-facing hillside, near the bottom of a fairly sheltered valley, would mean that the micro-climate around the house was significantly warmer than the average for our area, which is on the edge of Salisbury Plain – a notoriously cool place! Continue reading “Part Forty Four – Over-thinking things – Part One”

Part Forty Three – Completion! (and getting the VAT back……………..)

After much faffing around with details and paperwork, we finally have a Completion Certificate!


Getting things ready for the final Building Control inspection turned out to be an exercise in doing loads of work that wasn’t actually needed.  Very frustrating, but a consequence of me not having been through the process before, and assuming that Building Control would want more evidence of compliance with the regs than they actually did.

I had prepared copies of things like the water usage calculations with evidence of measured flow rates from all outlets, and none of that was needed, for example.  I’d also prepared reasons justifying the three pressurised systems we have, and why they did not need sign off against Part G by a competent person, and again none of that was needed. Continue reading “Part Forty Three – Completion! (and getting the VAT back……………..)”

Part Forty Two – Water Treatment

This blog entry is just looking in detail at the ozone treatment part of our borehole water system.

Our borehole water has a high concentration of ferrous iron, this is what’s often called “clear iron” as it doesn’t colour the water.  It’s fairly common in water drawn from deeper aquifers, particularly in areas where there are natural iron deposits or soft (often slightly acidic) water that dissolves iron (and other metals, like manganese) from the surrounding rock.  In our case our water comes from the Lower Greensand formation, an aquifer that is known to have water with high concentrations of ferrous iron as well as dissolved hydrogen sulphide gas (the “rotten eggs” smelly stuff).

The traditional way to remove ferrous iron, manganese and hydrogen sulphide from water is to just add oxygen to it, usually in the form of air, but it can be by using an oxidising catalyst.  The most common oxidising catalyst is manganese dioxide, used in a filtration bed.  This works OK, but it does eventually need replacing, or regenerating in some way, as it will lose its ability to oxidise after a time. Continue reading “Part Forty Two – Water Treatment”

Part Forty One – Hot Water At Last!

This forty first entry was published originally by JSHarris on the 21st November 2015 and received 1,244 views on the closed forum


After battling with a stomach bug for over a week, I finally managed to get the Sunamp PV in place and installed.

Installation was generally exceptionally easy, with only two areas that caused some challenges. The first was manhandling the sheer weight of the unit up stairs. It isn’t very heavy (around 75 kg) but it is small and very dense, meaning a two man lift is the bare minimum. The second challenge was getting at the pump vent plug when commissioning it. It’s set inside the top of the unit but very close to some adjacent pipe work, so a very marrow key is needed to get in and open it up – there isn’t enough space for a dumpy screwdriver. I happened to have a flat key that was intended to fasten the mandrel sockets on my hole punch set, and that proved ideal, so a suggestion is that such a key could be provided as a bleed screw tool. Continue reading “Part Forty One – Hot Water At Last!”

Part Forty – Getting Into Hot Water – Episode Two

This fortieth entry was published originally by JSHarris on the 30th October 2015 and received 787 views on the closed forum


Continuing on from the last entry, here’s some more detail about installing the Sunamp PV and the plate heat exchanger pre heat system.  Here are a couple of photos of the way the plate heat exchanger, its circulating pump, flow switch and the 50mm layer of insulation was applied, before fitting the Sunamp PV in front of it:

Continue reading “Part Forty – Getting Into Hot Water – Episode Two”

Part Thirty Nine – Getting Into Hot Water – Episode One

This thirty ninth entry was published originally by JSHarris on the 22nd October 2015 and received 1,066 views on the closed forum


As some will already know, the hot water system has been a bit vexing, with significant over heating problems from the heat loss from the thermal store, severe enough to damage the veneer on one of the doors. The next couple of entries are going to focus on work to redesign the hot water system to reduce the heat losses, yet retain the ability to use excess generation capacity from the PV panels to heat our water and provide a backup system for periods when the solar panels aren’t generating.

After trying several ways to try and reduce the heat loss from our 260 litre thermal store, from reducing the temperature through to adding lots of additional insulation, I finally decided that the whole system needed to change. The catalyst for this decision was the introduction of a new phase change heat storage system to the market, a compact unit that is able to store excess electricity generated by a solar panel installation (or cheap rate E7 electricity) as thermal energy, called the Sunamp PV (see here: ). Continue reading “Part Thirty Nine – Getting Into Hot Water – Episode One”

Part Thirty Eight – Heating And Cooling Controls

This thirty eighth entry was published originally by JSHarris on the 1st September 2015 and received 1,496 views on the closed forum

As with all things associated with this house, it took me several goes to get the heating and cooling control system to work properly. Despite having done masses of calculations that showed the house didn’t really need much heating, I couldn’t, in my heart, accept this. We’re conditioned to houses in the UK needing heating, usually a fair bit of it and often through large parts of the year, when we get sudden cooler spells in normally warm weather. I started off thinking I couldn’t buy an off the shelf system, so built a home brew DIY controller, and and then spent hours writing and rewriting control code. Finally it dawned on me that there may come a time when I wasn’t able to write code, or that someone else might have to work on the system, so I had better switch to using off-the-shelf parts. Continue reading “Part Thirty Eight – Heating And Cooling Controls”