Pouring the Floors

The monster concrete pump pouring the floor slabs for the two adjacent cottages, this covers the underfloor heating which is attached to the steel mesh. With the heating encased in the concrete slab this provides a high level of thermal mass to stabilise the internal temperature of the properties. We used the same principle on the main house which we built 3 1/2 years ago and it really works well, alongwith the high levels of insulation and air-tightness.

For the most part since commencing the build the weather in this part of the world has been unseasonly poor with twice the usual rainfall and generally lower temperatures. As the concrete was poured on a warm, sunny, breezy day the builders then had to spray water onto the surface to reduce the temperature as it set in order to avoid cracking.

Proof of the pudding...

It's December, and time I blogged again. The last seven months of occupancy have been intense at ECF, not only with moving in but also just catching up with 'normal' family and work life. Despite the festive season being just round the corner, we at least feel we're getting there!

On the energy front, seven months of occupancy means we've got some data on energy consumption to compare with what we specified and predicted...and the results are quite a relief!

The bottom line is that we're using 25% less energy than we expected; and that's in a house already designed to use less than a quarter of the energy of the average new housing stock. In general hot water and space heating energy use are on target, although these account for less than half of our predicted energy use. The big savings have thus been made in other energy use, namely lighting and appliances. In particular the use of LED and CFL light fittings, coupled with A and A+ energy rated kitchen appliances has paid dividends.

Whilst in most houses heating and hot water use accounts for up 80% of domestic energy demand, our experience just shows that real savings can be made with little effort by replacing lighting and appliances (when worn out of course!) with more energy efficient equivalents.

Lots going on both inside and outside yesterday. The 24hour rainfall we've had is a reminder of the testing conditions for a house in an exposed location. There is a little water seepage under the doors on the SW corner so we've contacted the supplier to get a maintenance bod out. It is clearly a window issue rather than a building one but strong winds driving rain at that corner are as testing as you would expect in the UK.
Outside we've got a local contractor ripping up the concrete which formed the base of the old dairy shed, its an area of approx 28m x 8m and is being carted off to use as hardcore somewhere else. After its bashed down we'll be buying a lorryload of gravel to finish it.
The builder's groundworks crew have dug the trench which will carry the LPG pipe and the elec cable from the woodstore to the house. We are only using LPG for cooking but wanted the bottle away from the house (for visual reasons) and the cable is for the solar PV to connect into the house. The 1.08kw solar PV array will be mounted on the south facing roof of the woodstore and the roof is being constructed to a 36deg pitch to maximise production. The theory is to take your latitude (ours being 56degN) and subtract 20degrees. Work starts on the construction of the woodstore today and is being done by a local joiner using wood we have salvaged from the old house. They are setting up a workshop in one of the barns.


As you can see the staircase is in place and the slate flooring continues (picture of the dining area)

The ideal low energy house?

What we've set out to do at ECF is to build a house which will use 70% less energy than one built to current building regulations. Its timber frame construction detailing hasn't wavered too far from the 'norm' to present any major problems for a timber frame kit manufacturer, decent building contractor or building control, and the costs of going this 'extra mile' haven't been excessive to the extent that they will be paid back within a decade in terms of reduced energy costs.

In essence, we have built to a standard which is accessable now by most contractors and self builders which is around 5-6 yrs before its time if the UK Government is to fully implement its Code for Sustainable Homes (CSH) strategy, on which this building should come in at around 3-4 on a scale of 1-6. There is clearly some distance to go from this to 'zero carbon', so what represents the 'optimum' for 'Level 6 living', the magical zero carbon level required by 2016 for all new homes?


Well, the same principles apply, namely...

• building orientation to maximise solar gain in winter, spring and autumn whilst avoiding overheating in summer


• high levels of insulation around the entire building envelope


• high levels of airtightness coupled with heat recovery ventilation


• highly insulated and well sealed doors and windows

...but for CSH level 6 the wall insulation would need to be increased to >300mm (from our 200mm), roof insulation to >450mm (from our 350mm) and windows to be triple glazed krypton filled units with insulated frames and glazing spacers (vs. our argon filled double glazed units). This would result in a building which could feasibly rely on the heat given off by its occupants and collected though its windows to keep it at a comfortable temperature without having to introduce a heating system. Construction might rely on internal masonry/concrete walls to store heat and keep a steady internal temperature, with the insulation fixed to the outside of this.

On the face of it quite simple, but a seriously long way from what the UK housebuilding industry is used to. Roll on 2016.....there is a lot of catching up to do and mindsets to be re-programmed.

Earth Hour

I've spent part of this evening contributing to a National Park meeting on renewable energy and sustainable building design and feel quite fired up on the whole subject. I came home, had a great discussion with Steve (before he went to Ikea for late night house shopping), then watched Grand Designs revisited about an underground house which essentially didn't need heating even in winter.

The whole debate about 'eco' and 'sustainable' is massively involved. We have built a well insulated, airtight, timber frame house with a thermal mass of 40 tonnes of concrete in the foundation slab to keep the internal temperature stable - that's great from an energy efficiency perspective, but is that scale of concrete usage a good thing, not least as the production of cement is an energy intensive process? Someone somewhere could maybe establish the whole life cycle energy equation.

Energy efficiency is a very important part of sustainability but I'm not sure if I can get my head around all of the issues. We've got fantastic argon filled double glazed windows with 'u' values of 1.4 (standard windows being between 1.8 and 2.0) and they are from Norway 'cos the Scandinavians having been building sustainable houses for years but ideally we should be buying UK produced windows in order to minimise transportation and support home industries...but it couldn't be done remotely near the cost as they would be regarded as 'one-offs' and 'specials'.

Anyway that's nearly enough...I looked at another blog this eve which prompted me to tell you about Earth Hour whereby you switch off your electricity at 8pm this Saturday for one hour. Its one of those experiments in activism which last year saw the city of Sydney reduce its 'leckie load by 10% thus illustrating the impact of individual actions. See the vid at http://www.youtube.com/watch?v=UcHz6Jv4l-g

Ventilation strategies

As for living comfort at the levels of airtightness we are building to, it becomes necessary to use a whole house ventilation system. For this there are two main options; Mechanical Extract Ventilation (MEV) and Mechanical Ventilation with Heat Recovery (MVHR).

MEV uses a constantly operating fan which extracts warm moist air from the warm moist rooms (ie. bathrooms, kitchen etc) via ductwork, with fresh air effectively being sucked in via trickle vents and gaps in the structure. MEV is fairly economic to install, especially as it eliminates the need for dedicated extractors in the bathrooms. However, for very airtight buildings additional openings in the structure need to be introduced and warm stale air is replaced with fresh but cold air, thus driving heat out of the building and reducing its efficiency. As an aside to this, an MEV option is available for our heat pump which actually uses the heat from the outgoing stale warm air to pre-heat the ‘brine’ before it goes into the heat pump, thus recovering some of that energy. This is a great idea and an option well worth considering for self builders opting for a heat pump, but we eliminated it on the basis that that our first floor is largely unheated and such a system might lead to the cooling of that area via the trickle vents in the Velux windows which would need to be open for this system to work properly.

MVHR combines MEV with an intake system which supplies the ‘dry’ rooms with fresh air, preheated via a heat exchanger which takes heat from the extracted air. This is the system we have chosen, a (claimed) 95% efficient unit made by Dutch company Renovent and supplied by Ubbink in the UK. The unit has three settings and is virtually silent in operation. At the lowest setting (normal operation) it uses just half the power of a 60W light bulb and should be adequate to ‘heat’ the three first floor bedrooms alongside the heat convected from the ground floor. Other advantages are good air quality by using fresh, filtered air from outside, and the ability to use the unit to provide cooling in summer by bringing in cool air at night into a solar heated building.

Airtightness details

Having specified and designed a house to meet the AECB’s Silver Standard, airtightness plays a key role alongside high levels of insulation to achieve a low energy house. In our case we have followed the AECB’s Silver Standard construction details for timber frame buildings which advises the use of a continuous air/vapour control layer inside the building with all joints lapped, sealed and mechanically trapped.

This has probably been one of the most difficult aspects to achieve on site for our construction team which, in common with most UK builders, is simply not used to working to such a tight specification. With this in mind we opted for a solution which has largely avoided the need for specialist tapes and sealants, and in the main relies on the mechanical trapping of taped and lapped joints to provide a positive seal along with silicone sealant. We won’t really know how well this has worked until we do an airtightness test on the building, but on the basis that opening the front door feels somewhat akin to opening the door of a luxury car (ie. that air suction noise!) gives me some confidence. Also when it’s blowing a gale outside, there are no obvious draughts entering the building apart from the open trickle vents (shutters not yet fitted) and the yet to be connected stove flue.

Heat pump installation

Work started on installing our heat pump last week. We have specified a Nibe 1240-5kW - the smallest capacity they make - with integral 'tank-in-tank' hot water cylinder. It 's a very neat unit, being the same size as a 1.9m tall fridge freezer. The pipework next to it will be ultimately enclosed in a cupboard which will still have some storage space at the front, whilst allowing access to the pipes at the back if need be.

Specifying a heat pump uses the opposite logic to specifiying a combustion boiler, as it must be just undersized to operate at its most efficient when taking into account the building's heat loss and anticipated peak heat requirement. The reason for this is that heat pumps dislike being 'cycled' - switched on and off - and actually benefit from running for longer periods at a time than conventional boilers. In extreme circumstances where, say, there is significant heat and hot water demand (eg. Christmas with visitors!) then the heat pump employs an electrical element to supplement itself, but the trick is to set things up so this hardly needs to be used at all, electricity being a relatively high-carbon form of energy.

The unit is being installed in our utility room where all the pipes from the ground loop, hot and cold water, underfloor heating and 1st floor radiators/towel radiators terminate. The guys are making a neat job of connecting this spaghetti together and hopefully by late next week we should be in good shape to switch on and get some heat into the 40 tonnes or so of concrete which forms the floor slab.

As it happens one of the founders of the heat pump supply company - Ecoliving - popped round yesterday to look at our windows (he's building an extension to his own house!) and he told me that the heat pump even had a setting to dry the floor slab out over a four day cycle, this will be important before we fit engineered board flooring.

Anderson Floor Warming of Glasgow are doing all of the plumbing in the house using a German plastic/aluminium pipe system. Hot and cold feeds are fed to manifolds from which each tap is fed, thus reducing pipe runs. Also the hot water feed is circulated from and back to the hot water tank at peak use periods (controlled by a timer) such that when a hot tap is switched on, hot water appears almost instantly.

Apart from the plumbers, the rest of the guys on site have never built a house with a heat pump in it and we are all waiting in anticipation for switch on!

Heat Pump: Part 1 - ground loop

As previously mentioned we have opted to use a ground source heat pump to provide both space and hot water heating. With no mains gas, an adjacent field and the opportunity to design a well insulated house from scratch with underfloor heating, the heat pump was the lowest carbon and lowest running cost option for East Cambusmoon.

For anyone considering a heat pump for their own house there aren't that many situations where it is the most cost effective and efficient choice, and certainly if you have the luxury of a mains gas supply a high efficiency gas boiler, coupled with say solar thermal panels will likely be a lower capital cost and running cost option than a heat pump doing both. If not on mains gas, then the costs need to be compared to LPG or oil and the decision will largely depend on the type of heating distribution system you already have, ie. radiators or underfloor heating. For the same heat input to a room, radiators need to be run at a higher temperature than underfloor heating simply because the heat emitter is concentrated into a relatively small wall hung panel, rather than the entire surface area of the floor. The problem with heat pumps is that their efficiency rapidly decreases in proportion to the heating medium temperature, such that running small radiaors from a heat pump is a bad idea. This can be alleviated to a certain extend by increasing the size of radiators so they can be run at a lower temperature.

Then there's the heat collection system, in our case this being a 300m length of 40mm diameter pipe buried 1.4m underground. This particular aspect of our build was a separate 'client item' from the main build contract so Debs, me, Stewart the digger driver and £60k's worth of band new JCB set to for four days of hard graft to get this pipe buried in the ground to in such a way as to absolutely maximise every joule of energy that could be sucked out of it .....which of course would be continuously be replenished by the sun. In effect, a huge solar panel!

In designing the collector system, we followed the heat pump manufacturer's (http://www.nibe.com/) advice on pipe depth, separaton and layout. Our supplier (http://www.ecoliving.info/) also offered advice on site and once certain of our plan, we got cracking! We ended up digging three 40m trenches, each 2m wide and 1.5m deep at 4m centres. We also imported 35 tonnes of sand to cover the pipe below and above to avoid the possiblity of damage from sharp rocks when backfilling and to ensure good contact with the ground. Bfore covering and backfilling, the pipe was pressure tsted and to finish off, fed into the house via the 'slow bend' duct pipes already built in to the floor slab.

True low carbon or eco-chic?

Probably since the oil crisis of the early 70's there has never been such a high level of public awareness and engagement in all things 'environmental', not least in greening up homes. In particular the UK Government has made a commitment for all new homes to be 'zero carbon' by 2016, an ambitous target which would make UK building regs on energy efficiency some of the toughest in the world, even exceeding the current high standards which exist in Canada, Scandinavia and Germany.

The problem is that new homes accont for just 1% of the housing stock annually at the current UK build rate, so what can the majority of the population do to reduce consumption and 'do their bit'? There is a huge amount of information out there and a good starting point is The Energy Savings Trust www.est.org.uk, but it can be a minefield as to what actions/technologies will truly bring genuine savings in energy, carbon and money. Here's a few ideas:

1. Insulation and draft-proofing/airtightness - do this before anything else, especially on the detailed design of a new build or extension. Usually, money spent on this has a much quicker payback than any of the technologies described below. For example, £2k spent on a mini wind turbine buys a huge amount of insulation and will payback much quicker.

2. Rainwater harvesting (for toilet flushing, laundry etc) - unless gravity fed or pump free, this probably isn't worth the cost or effort and will increase your energy consumption. Whilst saving mains supplied potable water which has used energy in its processing and delivery, it is unlikely that the energy used to do that by your water supplier will be less per cubic metre than by using a water harvesting system. Furthermore, if you are on a water meter the energy costs in operating such a system may not even be offset by the saving in water costs.

3. Mini wind turbines (fixed to house) - in most cases probably not worth the bother, but in some cases (rural, wind-swept property with no nearby obstructions) might produce useful power.

4. Mini wind turbines (standalone for farms etc) - worthwhile on windswept, unobstructed sites.

5. Solar panels (hot water) - useful and can provide up to 60% of annual hot water needs. Payback can be less than 10 years, but don't overpay for system (should be ca. £2,500).

6. Solar panels (PV, electricity generating) - expensive and long payback, but very reliable (we have them) and beautifully simple. Most cost effective on building integrated applications. A better choice than roof mounted wind turbines for electricity generation in most cases.

7. Heat pumps - good choice for well insulated rural new builds with underfloor heating not connected to mains gas. Be careful over promises of '75% savings' - they still need electricity to drive the pump!

8. Wood burning stoves - go for it! In the vast field of alternative energy, the joy of watching carbon-neutral fuel being consumed by fire within the highly efficient combustion chamber of a modern wood burner is rivaled only by the gentle rotation of 150ft wind turbine blades! If you use an open fire, three quarters of the energy in the fuel you feed it goes up the chimney; in a woodburner, three quarters stays in the room, not to mention considerably reduced emissions.