Heat pumps are  a clever piece of microgeneration technology that have the potential to play a big part in cutting CO2 in our homes.

They work in much the same way as a fridge with energy being extracted from one place and dumped into another. In the case of a fridge, heat is extracted from the compartment and dumped out of the coils into the air in your kitchen. In the case of a heat pump, heat is extracted from the ground, air or even water (in a few cases) and then dumped into your home via oversized radiators or underfloor heating.

Exactly like a fridge, heat pumps need electricity to operate so CO2 emissions are generated at the power station, but the clever bit is that for each unit of electricity they consume, in excess of 3 units of heat can be delivered to your home.

In theory.

Unfortunately in the real world it appears that performance can be a long way from the optimum: the Energy Saving Trust has just published the results of the first year of heat pump trials and it doesn’t look very good.

The trials monitored 83 installations of ground and air source heat pumps around the UK over a period  of 12 months.  The trials looked at the system coefficient of performance, system efficiency, installation practices, user behaviour and heating patterns and the economics of the technology.

The coefficient of performance represents the number of units of heat that you get out to the number of units of electricity you put in over the course of a year. So the higher the number, the better the performance and the bigger the reduction in carbon emissions and operating costs. The study also looked at the system efficiency which considers the energy required to deliver all of the heat and hot water that you need and this is the important figure for the householder.

What the study found found was that typical system efficiencies for ground source heat pumps were around 2.3 to 2.5, with a maximum of over 3; for air source heat pumps it was slightly lower at 2.2 on average, again with a maximum efficiency in excess of 3.

The problem was that there was a big range in efficiencies and this was mostly due to poor system design and/or a poor understanding on the part of the householder of how to use the system most efficiently.

Heat pumps put out a fairly low temperature heat and therefore need large radiators or ideally underfloor heating. They’re also quite complex and work very differently to conventional heating systems so the home owner needs to learn how to set it correctly (something that should be clearly explained by the manufacturer or installer).

In other countries, especially in Scandinavia, heat pumps are very popular and perform well. In Scandinavia they have more low carbon electricity than they can shake a stick at so electric heat pumps make a lot of sense. Their homes are also very efficient and so have a low heat demand (even though it’s so darned cold for a lot of the year).

As the industry matures in this country the performance of heat pumps should improve, but if you are thinking about opting for one, all I can say is be careful and read up on the subject before taking the plunge.

As it is, heat pumps should only really be considered for homes that are off the gas network at this time as you get a bigger CO2 and financial saving by switching from oil or electricity, so they’re not currently suitable for homes in Stoke Newington. As our electricity supplies decarbonise, then we can start looking at homes that are on the gas network.

You can read the report here. It’s a good little report with a clear explanation of how the technology works and an overview of the monitoring study and results.

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Here’s one for those who like to calculate their own carbon footprint. Defra has just published this year’s update to the Annex to the Company Reporting Guidelines.

This annex contains factors which allow you to work out the emissions generated when you consume a quantity of fuel or electricity, travel a distance or ship a quantity of freight (amongst many other things), and are the best numbers out there for carbn footprinting purposes. These factors form the basis of the UK’s carbon footprint calculators.

It’s a very simple calculation:

Energy (kWh) x Carbon Factor (kgCO2/kWh) = CO2 Emissions (kgCO2)

By way of example, the average house consumes about 3,900kWh of electricity each year and the UK average electricity carbon factor is 0.541kgCO2/kWh so the CO2 emissions generated by electricity consumption in the average UK homes amount to 2,100kgCO2 or 2.1 tonnes of CO2. But the above calculation just looks at the CO2 generated and does’t tell the whole story.

Last year, emissions of the two other main greenhouse gases, methane and NOx which are released when fuels are burnt, were included for the first time. The new addition this year are the indirect emissions associated with the extraction, transport and refining of fuels (sometimes referred to as upstream emissions). These emission are an important addition to the data.

The upshot of all this is that the total climate change impact of electricity consumption is 14% higher than the impact of just the CO2 emitted, while the total emissions for petrol and diesel are 18% and 20% greater than that of the CO2 alone.

In the accounting of greenhouse gas emissions, these indirect emissions are attributed to industry, not ourselves and as a result, making substantial cuts in our energy consumption can lead to significant carbon emission reductions in other sectors and even other countries too.

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A little off topic I know (only very slightly), but I think that 9carrots is a brilliant idea and well worth putting out there.

Transition Network has a quick run down:

If you are interested in working with your local businesses, and haven’t heard of 9carrots, it’s worth your consideration. It’s a simple enough idea whereby local shopkeepers can add themselves to a map, and when customers visit and mention the map, the shopkeeper puts 10% of the takings aside for energy efficiency measures (more on their ‘how it works page‘).

I’ve always found that making changes to my lifestyle in order to reduce my carbon emissions requires a bit of a nudge, especially if I need to invest money in order to achieve this, and I suspect that businesses have a similar problem with this behavioural inertia.

The beauty of this scheme is that the business gets that nudge and the double benefit of environmentally conscious customers (in many cases new customers I’d wager) plus the long term savings of the energy efficiency measure which is quite likely to pay for itself many times over.

It’s good to see that there’s already a business in Stoke Newington, Lemon Monkey, signed up. I was aware of it but had never been in – now I will pay them a visit.

Thumbs up to 9carrots, best of luck with the project.

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The first post on lighting took a look at CFLs, the cheap and effective replacement for standard incandescent lamps*, but over the last couple of decades, many homeowners have opted for halogen lighting.

Halogen lamps are incandescent i.e. electricity passes through a tungsten filament which heats up and emits light. They differ from the standard incandescent bulbs in that the filament is encased in a capsule full of halogen gas which reacts with the filament in a process called the halogen cycle.

Halogen lamps have a higher efficacy than standard incandescent lamps, but you generally need quite a lot of halogens to light a room so you usually end up using a fair bit more electricity for the same effect. Now, with electricity prices high and rising, what can be done to reduce the electricity consumption from all those halogens?

The cheapest option to cut electricity consumption from halogen lighting is to buy a batch of energy saving halogen lamps. These cost a bit more than the normal ones but use about 30% less electricity and they usually last a bit longer too.

You can also buy halogen replacement CFLs. These are little compact fluorescent lamps that are folded up into a halogen-sized fitting. They’re not cheap (anywhere between £10 and £20 each for a good quality lamp) but they are a lot more efficient than the energy saving halogens and should last a lot longer.

If you have your halogen lights on a dimmer system, be careful as CFLs often can’t handle this, and as with all CFLs you want to make sure that you get one with the kind of light output that you feel comfortable with. Check this post to see what to look for.

Finally there is also the LED (light emitting diode) option.  LED lighting is much more efficient than incandescent lighting and LED lamps have much longer lifetimes (at least the quoted lifetimes are much longer, actual lifetimes remain to be seen).

The main barrier to the widespread uptake of LED lighting now is cost. Good quality LED fittings are still eye wateringly expensive (around £20 to £40 each) but as they’re so efficient and as they should last tens of thousands of hours, they do pay for themselves many times over in energy savings and replacement costs over their lifetime.

I’ll go into more detail on LED lamps in a future post, but briefly, the technology has moved on a lot in the last few years and you can now buy really good quality lamps.

Prices will come down in the next few years so it might be worth holding off for a little while, but if you are going to be redoing the interior of your house and you currently have halogens, it’s probably a good time to consider this technology.

Useful tip: if you are considering investing in these more expensive halogen replacement options, then the best tactic is to replace the bulbs that have the highest use first. By replacing these bulbs you will see the biggest drop in your electricity consumption and they will pay for themselves in the shortest time.

* A lamp is what is more commonly referred to by people outside the industry as a bulb. What we normally call a lamp would be called a luminaire in the industry.

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Here’s a great opportunity to see some examples of low carbon refurbishment of Victorian and Edwardian homes in North London.

Norman Beddington and Antony Melville from VICTERI have managed to bring together 11 home owners in Camden, Islington, Haringey and Hackney and persuade them to open their doors to the public on the weekend of the 12th to the 13th June.

These were typical North London homes that have been, or are in the process of being, completely refurbished using the best in eco-renovation practice and techniques and will show exactly what can be done to make big cuts in carbon emissions in homes that are the definition of “hard to treat“.

You’ll be able to speak to the owners and get valuable insights into the joys, and the trials, of the low energy renovation process.

Homes at all phases of refurbishment are represented, from planning through to completion and there are some real gems to be seen, including a home retrofitted to Passivhaus standards and others which make cuts in carbon emissions of 70% to 80%.

Note that you’ll need a ticket to visit the houses, costing a very reasonable £10 and available here.

Also to see some of the homes you need to reserve a slot in advance and some aren’t open all weekend, but if you plan things right, you’ll be able to see lots of interesting buildings.  Full information about the homes can be found on the VICTERI website.

They’re spread around north London and probably the best way to see them will be to jump on a bike. You can plan your route here.

I will do my best to visit as many as possible and will report back here.

Camden, Islington, Haringey and Hackney, they exemplify the best in recent eco-renovation practice and techniques

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Just a quick note to say that the Hackney Society have organised a debate on sustainability vs conservation.

It’s a tricky issue – how do we turn the thousands of beautiful, historic homes in Hackney into very low and zero carbon homes without spoiling them?

More information can be found here.

Sustainability vs Conservation

DEBATE on Thursday 20 May 2010

How are we going to make our historic buildings more environmentally friendly? Is a carbon neutral Victorian house possible? What should government be doing to help us improve our homes? Come and join the debate.


Robert Prewett (Architect)

Hattie Hartman (Architects’ Journal)

Emma Marchant (Engineer, Atelier 10)

Robyn Pender (English Heritage)

Julian Harrap (Architect)




Hothouse, 274 Richmond Road, London E8 3QW


FREE to all



Further information about panel

Prewitt Bizley Architects
Project Passivhaus in Hackney

Julian Harrap Architects
Project Royal Society of Chemistry

Hattie Hartman
Project Sustainability blog

Atelier Ten

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A couple of weekends ago a group of us went to see a very interesting solar thermal installation in Stoke Newington. Generally, solar thermal systems supply heat for hot water only, but this system did a lot more than that as it was also plumbed into the heating system.

I’ll go into more detail on this particular system in a second post later this week, but first up we have a little overview of solar thermal technology…

Solar water heating systems are the most common form of microgeneration (small scale renewable) technology in the UK and Europe. This technology has been around for quite a long time (since the 1970s in this country), quietly generating heat in sunny weather to make a significant contribution to a home’s hot water energy consumption.

Naturally they perform best in the sunniest summer months, when virtually all of your hot water needs can be supplied by a good quality installation. Even during the winter months, a sunny day can result in a substantial amount of hot water being generated.

It is worth noting at this point that hot water energy consumption comprises around a quarter of a typical home’s total energy needs. Space heating uses the lion’s share, making up nearly 60% of total consumption. So a solar thermal system that only supplies hot water won’t cut your total energy consumption drastically, but it does make a good contribution.

Harnessing heat from the sun is, in essence, very simple: a collector is mounted on a south facing roof, absorbing the heat from the sun’s rays. The collector has a network of pipes through which a fluid passes, warms up and then takes the heat to a water-filled cylinder for storage and later use. There are two types of collector: flat plate and evacuated tube.

A flat plate collector is the simpler of the two, consisting of a glass covered heat absorber with pipework passing through it. This type of collector is the cheaper of the two, but it is also less efficient so harnesses less heat for a given area of collector.

Evacuated tube collectors consist of an array of glass tubes with copper strips running along the middle. The glass tubes have had the air removed from them which reduces losses due to convection and conduction and allows them to reach higher temperatures than flat plate collectors. This means that they offer better performance, absorbing more heat for a given area of panel,  but they do cost a bit more.

The fluid passing through the collector is usually water mixed with a form of antifreeze, along with a chemical that reduces corrosion. This fluid is kept completely separate from the hot water that comes out of your taps.

Apart from the collector, you’ll also need somewhere to store all of this lovely heat and a conventional hot water cylinder won’t be enough.

The most common solution is  to fit a twin-coil cylinder which has one coil in the lower part of the cylinder fed from the solar water heating and a second coil in the upper half of the cylinder which is fed from the boiler. The solar thermal system therefore supplies as much heat to the water as it can when the sun is out and then the boiler tops it up with additional heat as necessary.

This need to store heat means that combining solar water heating with an combination boiler can be tricky (although it is possible) because the space for a decent size cylinder will most likely have been given up for other purposes. If you are ever considering removing your hot water cylinder and opting for a combination boiler, consider whether you might want to fit solar thermal at a later date.

As ever, when considering microgeneration technologies make sure that you’ve gone as far as reasonably possible in terms of reducing your energy demand first. Ideally you should reduce demand as far as possible before considering generating because for the most part it is much more cost effective to reduce energy consumption than it is to generate.

The Energy Saving Trust has a good publication on solar water heating which gives a more detailed overview of the technology, but it only goes as far as using solar thermal for water heating. The system we saw was also plumbed into the heating system, allowing the user to make use of much more of the heat falling on the roof.

A system that just heats the hot water can only go so far because you only use so much hot water (unless of course you are particularly partial to baths). If you have lots of sunny weather the panel will keep generating heat and that heat has to go somewhere. Being able to deliver it to radiators or an underfloor heating system is a real bonus.

I’ll post more details about this fully integrated system later this week.

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The Levy Memorial Garden is located at the south end of Yoakley Road, just off Church Street.

Until recently it was a rather neglected space but members of Transition Town Stoke Newington and local residents have taken it over and are doing a sterling job of cheering it up.

I just came across this rather lovely story of democracy in action over this often overlooked public space in the heart of Stoke Newington.

Last weekend’s planting session was canceled thanks to the delightful bank holiday weather so it’s been rescheduled to this Sunday from 10.30am to 1pm.

Come down on Sunday to help out and keep your fingers crossed for fine weather…

Hello all,

The Big Plant, which was rained off last weekend, will instead be happening this weekend. Same time, same place.

The Levy Memorial garden is a public space which is well used but, until recently, has been more than a little bare.

Together with the help of local residents and people who regularly use the garden, TTSN is giving the garden a whole new lease of life. The idea is to create a true community garden that can be nurtured and enjoyed by all – not just by current garden users but hopefully by many more people through getting involved in its design, care and pleasure.

Last weekend, 5 big (BIG) raised beds were constructed. This Sunday we are going to be filling these beds with veg, fruit bushes and wild flowers.

Come along do and help to make this a really special space that is bursting with colour and life.

All those who have attended previous seed planting events in the garden please bring along your little plant-lets so that they can be planted out.

And there will be cake.

Anyone who feels they could help with organising the event on Sunday or who would be willing to do a compost run on Saturday (they are giving away free compost at Haggerston Park), please get in touch with Eleanor.

Help with collecting compost would be especially appreciated – we managed to fill 4 of the 5 beds last weekend, but there is still one bed completely empty and the others, after various rain showers, do look as though they could do with topping up.

Thanking You!

Xx Eleanor and Freya

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This is the question that Transition Town Stoke Newington will be putting to the community on Saturday May 15th.

This will be a fantastic opportunity to put forward ideas and discuss what you would like to see happen in the local area in order to make Stoke Newington a more sustainable, vibrant and resilient place to live.

The main event on Saturday 15th runs from 10.30 til 4.30 at the Stoke Newington Library Gallery. It will be an Open Space session, so there won’t be a formal structure to the day; instead the participants will be setting the agenda, which should turn it into an interesting and unique event.

On  Sunday 16th there will be a follow up event at Pangea Project from 2pm to 4pm, where we can discuss what priorities came out of the event and see how we can move them forwards.

More information can be found here with an RSVP form to fill in at the bottom if you are interested in coming or finding out more and there’s a poster here.

Spread the word!

How can we build a positive future for Stoke Newington?

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Another round of Carbon Conversations is starting up in Hackney and across North London in a couple of weeks.

The Carbon Conversations programme was developed by Cambridge Carbon Footprint and these courses are being delivered in London by the Carbon Literacy Forum.

This is a great way to help you make big cuts to your carbon footprint, with workshops covering all of the main sources of carbon emissions including the home, transport, food and the things that we buy.

There are five sessions of two hours, every other week in groups of about 8 to 10 people. Best of all, the course is free (there is a modest £15 charge to cover the cost of the course book).

Both the Stoke Newington and London Fields courses kick off on the evening of Monday 26th April (see the flyer for more information and contact details).

About Carbon Conversations…

‘Carbon Conversations’ is an inspiring, engaging and practical course on low-carbon living based on the psychology of change.

It is a unique carbon sylabus for anybody who wants to know more about their personal carbon footprint and find practical steps to start reducing it.

You will be guided through discussions, games and exercises so you can find your own solutions with sensitivity to you own lifestyles and values.

The groups are run by experienced co-facilitators who have already embarked on their own low carbon journey and want to enable others to tread in the same footsteps.

You will be offered advice as to how to find resources, advice and services in your own area and the support of those who care.

What the groups include

The groups are held over five fortnightly sessions of 2 hours each which cover the main areas of your carbon footprint. We have a lending library of relevant books, energy monitors and information about local services and groups too.

Looking for a Low Carbon Future: Investigates our attitudes to climate change. Each participant is invited to complete a carbon footprint estimator before the course and we look at these together to find our starting points in embarking on our low carbon journey.

Energy in the Home: Our homes are more than bricks and mortar, they let us express ourselves. This session explores what our homes mean and with exercises and a ‘home energy game’ explores what we each can do wether we rent or own our own homes.

Transport and Travel: What are the effects and carbon impacts of our daily travel and holiday journeys? What alternatives are there? It also includes the ‘Travel Dilemmas’ game to look at how our behaviours and options can be supported by actions at local and national level.

Food: The most essential fuel in our lives this session explores what food really means to us and the environment. The ‘Food Footprints’ game sorts out what real difference you can start making now, and identifies where the carbon is in production, processing, transportation and packaging of our shopping basket.

Consumption and Waste: How do we consume carbon and resources when we spend money? Can we both sustain growth and maintain our planets resources? What might be a target for sustainable living? What rules of thumb can we evolve together to move to a happier and lower consumption lifestyle?

Meetup: After a space of 4-6 weeks after the fifth session we arrange to meet again for a more social time to share together what has changed and what more the co-facilitators or other group members can help to support you in your contining low carbon journey.

Easter Courses (contact details):

Hackney (N16 and E8)

Mondays 7:30-9:30pm from 26th April Stoke Newington N16

Mondays 7:00-9:00pm from 26th April – London Fields E8

Islington (N5)

Tuesdays 7:00-9:00pm from 20th April – Highbury N5

Thursdays 7:00-9:00pm from 6th May – Highbury N5

Waltham Forest

Monday 7:00-9:00pm from 12th April – Leytonstone

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