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The House at the Bottom of the Garden

A blog by TerryE in General

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About this blog

Terry and Janet Ellisons adventures in building their new home at the bottom of their Farmhouse garden

Entries in this blog

Heating

How an MBC WarmSlab Has Actually Performed based on 6 Years Data

In my topic Modelling the "Chunk" Heating of a Passive Slab, I discussed how I used a heat flow model to predict how my MBC WarmSlab heated by UFH + Willis heater would perform.  What I wanted to do in this post is to provide a “6 years on” retrospective of how the house and slab have performed as built based on actual data that I’ve logged during this period, and to provide some general conclusions. In this, I assumed 15 mm UFH pipework, but we actually used 16mm PEX-Al-PEX pipework with a
Heating

Update on Timeshifting to Minimise Heating Costs.

When we first decided to self-build in 2014, Jan and I visited quite a few passive house builds and talked to various experts;  we soon decided that a low energy approach was broadly the way to go for our build.  One of these experts, a passive-house evangelist called Seamus O'Loughlin, emphasised that a conventional heating approach (where boiler demand is based on some central thermostat set point) doesn't work well in a passive house, because the time constants of a high-thermal capacity low
Design Note

Downloading OVO Smart Meter Data

The OVO portal does have a publicly available RESTful API, but because the UI makes heavy use of Javascript (JS ) scripts to do the webpage renders and these make JSON callback to the OVO server, so it is quite simple to use your favourite scripting language to automata downloading data and aggregating it into a database or equivalent.   I have written down-loaders for Python, and NodeRED (based on node.js) but I currently only maintain the latter.  In essence your script will need to
Design Note

Update on Energy Use Based on 4 years of Actuals

As I have discussed on earlier podcasts and various topics, I have a Willis-based configuration for heating our low energy house, and control is implemented with a dedicated Raspberry Pi using a custom NodeRED application for our underfloor heating and SunAMP-based hot water.  This system logs a lot of instrumentation temperatures every half hour and also any significant events such as turning on and off pumps and the heater.   Our electricity supplier has been OVO for the last 4 years

The Economics of our SunAmps

We use 2 × SunAmp PVs for our HW system in a household of 3 people. According to our water bills, our consumption is about 83 ltr per person per day. Our pattern of use is pretty even across the year: more showers in the summer; an occasional shared bath in the winter.   The year round average temperature of our rising main is 11.3 °C (Oh, the wonders of logging everything in a DB and knowing how to do SQL subqueries).   The H/W manifold is mixed to 53°C (perhaps a li

An Overview of my House Heating and Controls 4 years on

We moved into our new build mid-December 2017 in time to host an extended family Christmas.  We are now over 4 years into living in our new home.  We have lots of accumulated experience and made a few small tweaks.  However, we are delighted about how the house has turned out, and we love living here.  There were no material cock-ups, or regrets on design decisions, so we have probably fared a lot better than most new purchasers or self-builders.  Maybe a general experiences post should be on th

Plumbing Design – Part II

This is the Part II roll up of a couple of earlier blog posts and forum topics which provide the groundwork and context. Plumbing Design – Part I Heating the Slab – an overview Modelling the "Chunk" Heating of a Passive Slab Another DHW / DCW / UFH design. in summary, so far into commissioning and early use, everything is at least achieving our expectations and the house might in fact perform better than my predictions.  The key des
  • TerryE

Plumbing Design – Part I

I have been doing the design validation of my plumbing solution partly so I am comfortable that it is feasible and partly to write this up so that others have a model of how to approach this task.  The last time that I did anything like this was with my current house where everything apart from taps for drinking water was fed off a (non-potable) header tank in the roof space and the central heating system was a classic 2-pipe (with branches) radiator system fed from a gas boiler.   Eve
  • TerryE

Harveys Water Softeners

If you have a Combi boiler, or SunAmp, or pretty much any device with a built in Plate Heat Exchanger (PHE) and live in any region which has hard water (about 80% the UK population), then you will need a water softener if you want any decent life out of your plumbing installation.  As far as I can see you are down to one of two options for a direct plumbing solution: the UK Harvey twin tank system and the US Kinetico range.  All of the rest are niche suppliers, IMO.  The Harvey system seems to b
  • TerryE
Heating

Heating the Slab – an overview

We have a passive-class house where the net heating requirement to keep the house warm in the coldest winter months is approximately 1kW.  The only heating system for doing this an underfloor heating (UFH) system base on 3 ~100m UFH loops buried in our passive slab.  That's it; no upper floor systems; no towel rails; nothing.  The reason for this is that our timber framed house is super insulated and air tight so there is very little temperature variation throughout the house, but that's all bee

SunAmp - our alternative to a UVC or TS

I just wanted to include a brief post explaining from a self-builder perspective why we have decided not to use an Unvented Cylinder (UVC), Thermal Store (TS) or combi-boiler for our domestic hot water (DHW) in our new build.  Instead we are using 2 × SunAmp PV heat batteries heated by E7 tariff.  So why? We decided that we don't need gas to be installed avoiding the Gas connection charges, per day supply charge and the maintenance costs on gas appliances.  Big saving here.
  • TerryE

Window and Door Detailing on a Stone Clad MBC Timber-framed House

As I've previously discussed we have an MBC Passive Slab and Timber-frame, but unlike most builds, our house also has a very traditional stone cottage-style exterior because the new build sits between our current farmhouse, which dates back over 400 years and a cottage which dates back approaching 200 years, so our planners required that we use the same local quarried stone.  So a topic that often comes up is "how do we do the window / door treatment on a timber-framed house with an exterior sto

Coping with a Thermal Flaw in the Design

(This post is a précis of a post and thread discussions that took place on the eBuild forum October last year and subsequent discussions with my builder.)   Many of the self-builders active on the forum will have used or be familiar with the Passive Foundation system marketed by MBC Timberframe.  The essence of this is that the foundation is a raft slab that incorporates a ring-beam that sits inside an EPS former.  This former both acts as shuttering for the concrete pour and as insula
  • TerryE

Fun Surveying Site Levels

One of my preconditions it to provide an accurate survey of site levels across my site. The last time that I did anything like this was just under 40 years ago as a young Lt. in the Royal Engineers when I was surveying for a road, but that was using a decent theodolite to do cut and full calcs. Nowadays you typically lasers and GPS, but I didn't want to pay a fortune for something that I could do myself, so I reverted to a variant of a technique that the Romans used and that is to use a water le

Planning Approval Down, Conditions To Go

We've had our second planning application in the system since mid December.  Our first application was in May and the main reason for the delay between these was negotiating with Highways over the new vehicle access and parking to our existing farmhouse.  (The existing access and parking falls within the new-build plot.) This delay was due to a combination of us being new to this and not understanding the rules to this bureaucratic game, and the highways engineer being just totally disorganised.
  • TerryE

A Little Aside On Radiance

We've sort of covered this topic buried in various earlier threads, but since I need to use this info for my heating calcs, I thought useful to cover this in a short summary post. Characterising the components of heat transfer across a solid / air surface really does come down to basic physics and we just need to crank the numbers into the two main factors at play in this: Radiation. Any surface is radiating heat but is also simultaneously absorbing similar radiation from everything in
  • TerryE

The Thermal Design – Using An Active Slab

I am writing these posts for two main reasons. The first is for my benefit, in that I find that if I have got to the point where I can explain my thinking to others, then I've got to grips with the problem myself. The second is that I might just help others going down this same path, by documenting my thought processes. It's three months since I wrote the Part I of these three Thermal Design posts, and I concluded this by saying that I intended to adopt Jeremy Harris's UFH For A Low Temperatu
  • TerryE

Modelling Thermal Lag

I was really unhappy with my discussion of this on my last blog entry, so I want to get a better quantitative understanding of how this would impact my house design, so I decided to write a simple 1-D explicit form finite mesh simulation which could be used to explore various wall and roof profiles. I initially intended to do this as a spreadsheet so that others could have a play with their own designs but without needing to get into code and programs, but stability issues means that the mesh si
  • TerryE

Traffic Survey Blues

The latest turn in our planning journey has occurred.  As part of pre-planning we send an early draft of our submission tried to consult with LPA Highways department and got this reply:     We will have two drives and access onto the road from our plot which is being divided onto two: the existing drive which will serve the new house at the bottom of our garden, and a new drive will be added in the reduced plot left with the old house.  We initially planned to have turning provi

The Thermal Design – Part 2

I discussed my overall static thermal design of my house in Part I.   In this second post, I wanted to discuss the dynamic characteristics of its design – that is how the house will respond over time as external temperatures vary, but I've decided to break this into two parts leaving how I propose to control the internal temperature to a later post.   Again, this content is a self-developed analysis, because I have yet to find any decent design guides to build upon – the Internet either seems to
  • TerryE

The Thermal Design – Part I

Janet and I want an energy efficient house, but what does that mean in practice? The whole concept is still largely rejected by the UK building industry. In our initial research, we either found books like the House Builders Bible which are good but superficial introductions on the concepts but without serious detail or at the other extreme academic papers on micro details. There is precious little in between, and to be honest we have found far more gems of knowledge in this site. All my experie
  • TerryE

Our Design Drivers

We've live in a 300 year-old farmhouse with lots of beams, wobbly walls and character -- and the odd draught. It's a large family house and, after 30 years living it, we feel that it is now time for a change. We aren't interested in a Grand Design; we want a modest design that is a good balance of function, of being practical and cost-effectiveness. Given this, our main drivers in selecting our design were: Comfort and space. We want a smaller, cosy house with minimal running costs, low m
  • TerryE

The Plot And Its Context

As I discuss in my first post, we have a large garden that is side-on to our road, and it is large enough for us to divide off a strip at the far end from our farmhouse to act as the plot for our new build, whilst leaving an acceptable plot for the farmhouse.  However it is just large enough to do this, and neither plot is going to be generous.  We therefore need to balance where we position the new boundary so as to give the new house a sufficient plot, whilst leaving the existing house with a
  • TerryE

The House at the Bottom of the Garden

Thirty years ago my company wanted to relocate my group to Milton Keynes. I was working in the West End, and Jan and I were living in Croydon at the time. We had just started our family, so the opportunity for a paid relocation out of a terraced house in suburbia into a larger family home in the country was just too good to miss. We ended up buying a somewhat run-down farmhouse in a village between Milton Keynes and Northampton. Jan said: “Think of the potential!”; to which I replied “Think of t

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