New Skills in 2014: Build a Compost Toilet

We have a host of exciting short courses taking place at CAT in 2014, and up until the end of January there’s 10% off!  From the 4th to the 6th of July discover the power of poo during our ‘Build a Compost Toilet’ short course.

Although the vast majority of the UK’s houses are connected to the mains, there are some that must find alternatives to local sewage treatment works. Compost toilets can be efficient and practical, resulting in nutrient-rich soil to be used in the garden. They don’t use any water, although most types of toilet need a fair bit of room to allow composting to occur at a steady pace.

During this three day course the essentials for building your own compost toilet will be covered. With Grace Grabb, CAT’s water and natural resources specialist, course participants will learn about the changes human waste undergoes during the composting process. CAT’s resident carpenter Carwyn Jones will then demonstrate some of the techniques needed to build your own compost toilet.

Students sorting the nutrient rich compost
Grace sorting the nutrient rich compost

Composting your waste is a relatively easy and cheap way to reduce your waste and constructing your own toilet can be great fun. The soil produced after a year or two is pleasant to remove, and can be put straight on the garden (although preferably on non-food plants). Compost toilets are increasingly being built in allotments, back gardens and even indoors. Addition of the right amount of ‘soak’ gives good decomposition. A ‘soak’ is a source of carbon – typical materials include sawdust, straw and earth. The four main components to make your compost a nutrient-rich success are: heat, moisture, oxygen and a little dedication!

Carwyn constructing a timber frame compost toilet at Grand Designs Live in 2012.

From DIY to ‘off the shelf’ designs, this course can help you decide whether or not a composting toilet is right for you. The course invites anyone and everyone to join in, from urban gardeners to off-grid enthusiasts. Pupils will learn more about construction and cladding methods, as well as the biological processes that happen deep within the soil on a molecular level.

To discover a more holistic approach to waste management, sign up for the course now.

For those more interested in the theory behind compost toilets, rather than the construction methods, we offer a one day course: Introduction to Compost Toilets. This forms the first day of the Build a Compost Toilet course, and can be taken independently.

Remember, we are offering a 10% on courses booked before the end of January. For terms and conditions please visit our website.

Student Post: Planning for Real on the Prof Dip

We’ve asked some of our current students to write a short blog post about their studies after each module. You can see all of our student blogs here. Over the next year or so Rachel, a former long-term volunteer at CAT, will share her experiences on the Part II Architecture course.

In my last blog, I wrote about the beginning of our first project on the Professional Diploma: to create a vision for the future of the CAT site. We spent the September module forming our own impressions of the site and working on our ideas for how we felt the site could be developed.

Coming back in October for the next module, it was time to open the floor to the CAT community. In the lead up to the module, an invitation was sent out to CAT staff for a ‘Planning for Real’ exercise in the Straw Bale Theatre on the Friday afternoon of our module – a chance for us to meet the people who work at CAT and listen to their ideas. Arriving at the beginning of the week, this gave us a short deadline to get ready.

The centrepiece of the Planning for Real exercise was an enormous 1:200 scale model of the entire CAT site; a prop which would help in this discussion, and give us a chance to express our own ideas at the end of the project. In the weeks we were away from CAT, we had all worked individually on parts of the model (buildings, trees and the model base), but it became very clear at the beginning of the module that we still had a lot of work to do if we wanted the model finished by the end of the week!

Early days in the construction of the model

So we split up into groups and set about turning the bare bones of our model into something we could present to the CAT community. Some people worked on the buildings, modelling any that we had missed in our initial survey of the site, while others cut out the model base and used cork to recreate the dramatic landscape that surrounds CAT. A team was sent out to collect small bits of trees and twigs to represent the vegetation of the site, and add to the work that was being done to define some of the existing paths and areas of greenery that populate the area.

In between all of this, of course, we still had lectures to attend! This module the lectures focused on some aspects of building physics: heat transfer in buildings, thermal comfort and thermal mass being the main topics. The highlight of this month’s lectures, of course, was the sauna practical; a short stint in the sauna followed by a brief swim in the lake really helped to illustrate some of the basics of thermal comfort!

Adding the ‘greenery’

Finally, the week came to a close with the ‘Planning for Real’ exercise. We only just finished the model in time: even as people started arriving, we were still drilling holes for trees! Still, the afternoon was a success – we had a fantastic turnout, with an enthusiastic response to our questions about the future of the site. Everyone wanted their say, and we gathered a huge range of ideas and opinions during the afternoon from all the people who came.

Now it’s time to put those ideas down on paper…

The completed model

Student Blog: the first week on the Prof Dip

We’ve asked some of our current students to write a short blog post about their studies after each module. You can see all of our student blogs here. Over the next year or so Rachel, a former long-term volunteer at CAT, will share her experiences on the Part II Architecture course.

Last month I started the Professional Diploma in Architecture course at CAT. It’s a very different approach to the study of Architecture, one I’m really looking forward to!

The first week was an introduction to the realities of climate change, one that will really set the context for our studies over the next year and a half. To start the week, we were plunged in at deep end with Ranyl Rhydwen’s lecture on environmental change – an interesting summary of the science behind climate change and the urgent need for immediate action. Having worked with Ranyl for six months before the start of the course, I was already familiar with some of the topics he covered, but it was still daunting to see the scale of the challenge we face! His adaptation and transformation lecture later in the week gave us a slightly more optimistic look at the future.

Our other lecturers looked at different aspects of climate change and sustainability: Tom Barker introduced us to the importance of biodiversity and the need to protect and encourage it; Adam Tyler summarised the current energy situation – how much we use, and where it comes from. We also heard about CAT’s Zero Carbon Britain project from Tobi Kellner: a scenario where Britain could rapidly decarbonise and be run entirely on renewable energy. Finally, Tim Coleridge’s lecture near the end of the week talked about the role of the construction industry, and the need to adapt the built environment for future climate conditions.

The week wasn’t all lectures, however, as we also began our first studio project! We have been tasked with producing a master plan for the future of the CAT, a possible vision of what the site could be in the next five, ten or twenty years – working alongside members of the community here and building upon strategies that already exist.

Sketch by Kirsty Cassels

As most people were new to CAT, our first job was to get to know the site (or, in my case, get to know it better). So, sketchbooks and cameras in hand, we set out to explore. For two days we wandered the site collecting information, drawing and photographing the things that caught our eye, talking to members of staff and visitors and reading up on the history of the site. Even having already worked at CAT for some time, I was able to really get involved and learn new things about this fascinating place.

Later, as we collated our notes and sketches, the issues and problems we wanted to tackle quickly became apparent – as did the potential opportunities. We set about preparing some initial strategies and proposals (gaining some insight into designing by consensus along the way), and discussed how we were going to involve the CAT community in our project.

Next month, we will start the consultation with CAT members of staff and ask them what it is they want for the site in the future. We’ve done our groundwork – let’s see where it goes from there!

Timber frame and cob – getting muddy at Grand Designs Live

This weekend CAT is heading to Grand Designs Live in Birmingham! On Friday, Saturday and Sunday we’ll be building a beautiful timber frame structure and running hands-on sessions working with cob. It’s going to be an amazing weekend full of sustainable building and we’d love to see you there.

Grand Designs Live have very generously given us four pairs of free tickets to the show for CAT supporters. If you’re interested in coming on either the Friday, Saturday or Sunday of the show then email media[at]cat.org.uk with your name and a contact number and we’ll get back to you.

If you’ve ever wanted to try working with cob or learn how to strengthen a building for a green roof then this is the place for you. We’ll also show you how to make a pizza oven!

More information about the show can be found here. We’ll be updating our Facebook and Twitter feeds regularly throughout the show.

Planting the New Green Roof Display

A few months ago we posted an update on the new green roof at CAT, made possible thanks to a donation from the People’s Postcode Trust. So far the roof has been rather more slate-grey than green. Today, however, the planting of the roof began!

Jony and Riccardo planting sedums

We chose to colonise the roof with sedums – hardy alpine succulents – that are also known as stonecrops due to their ability to adapt to extreme growing mediums. Up at CAT we have sedums growing naturally in the disused quarry on slate waste.

The plants chosen for the roof, however, came from the walls and roof of Jony’s – CAT’s Artist in Residence – house. They are, he explains, “a completely homegrown tray of sedum from mid-Wales […] We’re pit planting these in organic potting compost. The roof is like a scree slope of shale that’s falling down the mountain. The plants root themselves in this medium, and the slate also acts like a mulch to stop weeds growing. You need something completely inert that weeds won’t grow in.”

Over the next few years these small plants will slowly grow and spread across the roof until they cover it entirely.

One of the species of sedum being planted

A Green Roof (or Living Roof) is like a shallow box garden. The bottom and sides are lined with a waterproof covering, then with a special membrane with small pockets to collect water to allow for slower drainage. A growing medium (in this case slate chipping) is laid down and then the sedums are planted.

Green Roofs are an important example of the kind of technology that can help us adapt to climate change. They help reduce surface water flooding in cities by absorbing storm water quickly, but releasing it slowly. They also help reduce hotspots of overheating in cities, provide important habitats for biodiversity in urban areas and offer potential spaces to be used for growing food. In general, they don’t give much in the way of insulation, so a roof still needs to be properly insulated.

Although Green Roofs are not a modern invention, it is the recent advances in water-proofing technologies that have led to Green Roofs becoming more widely used in sustainable construction over the last decade.

Preparing a sedum for planting

 

Compost Toilets: a Grand Design or a Space of Waste?

Last week CAT headed to London for Grand Designs Live. We had been asked to provide live demonstrations as part of the ‘Natural Building Methods’ section – an area CAT has some experience in! After much discussion, we decided on glue laminating demonstrations for making arches for a Timber Arc construction. The Timber Arc is a beautiful example of timber frame building, using local and low-carbon materials. It’s also a dual-chamber compost toilet.

CAT's stand at Grand Designs Live

Our goal at Grand Designs Live was twofold: provide the public with an interesting demonstration of glue laminating, whilst also raising awareness of different methods of dealing with human waste. Compost toilets are not for everybody, if you are connected to a local sewage system then chances are you will not need to deal with your own waste. However, some off-grid locations mean that people have to be a little more creative in the sewage solutions.

Glue laminating at Grand Designs Live

During our time at Grand Designs Live, one thing that kept cropping up again and again was bafflement. People often asked us why we were making a compost toilet, especially one so beautiful. Well, compost toilets can be efficient and practical, resulting in nutrient-rich soil to be used in the garden. They don’t use any water or chemicals, although most types of toilet need a fair bit of room to allow composting to occur at a steady pace. We have several composting toilets up at CAT, working alongside our reedbed sewage system and providing us with fertiliser for our gardens. Furthermore, why not make a beautiful building to house your compost toilet? It’s a place you visit each day after all! We also liked how the idea of it fitted in with the ‘grand design’ aspect of Grand Designs Live.

Work on the arches for the compost toilet

People certainly seemed to agree with us, judging by the level of interest we received each day. Engaging with people on environmental issues whilst also showing how we go about dealing with these problems was wonderful. Moving people’s thoughts away from bafflement and towards more environmental ways of thinking is key. Hopefully in the future CAT will be able to visit even more shows to keep spreading the word.

For more information on alternative sewage systems check out CAT’s information page on the subject. We also run short courses on sewage and waste water management. Further info here.

To see more of the Timber Arc, head to Jules’ website.

Glue Laminating at Grand Designs Live

This year CAT has been on bit of a promotional tour – travelling to London, Birmingham and London again to attend exhibitions, study fairs and conferences. Each event gave us the opportunity to talk to people about CAT’s work in the field of sustainability. From this coming Saturday however, CAT will be doing more than just talking.

We’re spending nine days camped out in the miniature village that is Grand Designs Live at the ExCel in London. Each day CAT will be providing demonstrations of glue laminating (or glulam) used to build the beautiful ‘wigloo’ you can see onsite in Wales. Jules, the carpenter who designed the toilet in association with Crafted Space, will be doing two demonstrations each day. As well as this, we have some examples of sustainable building techniques with us and the opportunity for people to ask CAT experts questions about their building woes.

Timber Arc Compost Toilet
The glue laminated compost toilet up at CAT

So what exactly is glue laminating?

It’s a process where several layers of timber are bonded together using a durable, moisture-resistant adhesive. The resulting structure can be used in both straight and curved configurations. The build that Jules undertaking requires curved lathes so he uses a ‘former’ to help hold the layers in place as the glue dries.

 

So why glue laminating?

Glue laminating has much lower embodied energy than reinforced concrete and steel, although of course it does entail more embodied energy than solid timber. However, the laminating process allows timber to be used for much longer spans, heavier loads, and complex shapes.

Glulam is two-thirds the weight of steel and one sixth the weight of concrete – the embodied energy to produce it is six times less than the same suitable strength of steel. Wood has a greater tensile strength relative to steel – two times on a strength-to-weight basis – and has a greater compressive resistance strength than concrete. The high strength and stiffness of laminated timbers enable glulam beams and arches to span large distances without intermediate columns, allowing more design flexibility than with traditional timber construction.

Glue Laminating
Jules clamping some glue laminated timber onto the former

We’ll be following the build live each day over on Facebook so have a look and see how it progresses!

If you like the look of the compost toilet, take a look at Jules’ website.

Grand Designs Live is open to the public from Saturday 4th to Sunday 12th May. More information can be found on their website.

 

The top 5 renewable energy questions from the National Homebuilding and Renovating Show

If you went to the National Homebuilding and Renovating Show a week ago, you might have been inspired by the live demonstrations of thatching, or felt the sudden urge to redecorate when you passed the stall full of sheepskin rugs. Or perhaps you realised you really did need a 2-metre 3D TV in your lounge, or maybe you simply wanted to browse whilst enjoying an ice cream from the Yorkshire Dales food cart (it’s a permanent installation).

Nestled between two full-size timber frame houses, one of which was the Eco Home Theatre, the CAT stall was a small hub of renewable energy debate in this varied crowd. Enthused by Tobi’s daily talks, a stream of visitors made their way to us to ask often highly specific or technical questions. Some of the same concerns kept coming up, so we’ve collated a list of the five most common questions and Tobi’s answers.

Lots of people also asked us questions about architecture and design, but we’re going to save those for a later feature. Stay tuned!

  1. What’s PVT, and is it a good idea?
  2. Is there a case for thermodynamic systems?
  3. Are heat pumps right for me?
  4. Micro hydro: yes or no?
  5. Should I heat my house with biomass?

 

1. What’s PVT, and is it a good idea?

PVT is the combination of solar photovoltaic systems (the “PV”), which produce electricity, and solar thermal systems (the “T”, also known as solar water heating, SWH), which produce hot water.

In principle, you can see the potential for synergy between these technologies. PV modules convert only 10%-20% of the solar energy that falls onto them into electricity, and a good proportion of the remaining solar energy is converted into heat – solar PV get hot in the sun. So why not use this heat to heat water for showers? This is what PVT modules do – basically, they are solar PV modules put onto a solar thermal absorber. In principle, this is a brilliant idea. In practice, it’s not so easy.

Solar PV modules actually operate more efficiently when they are colder (because their electric resistance is lower) whereas for your showers you want your water to be hot. Under some conditions that works out perfectly – as long as your hot water cylinder is cold, the solar thermal part will actually cool your solar PV module down. But on a sunny summer’s day you ultimately want your solar thermal system to produce very hot water, and in fact UK legislation actually requires water to be heated to temperatures of 60-70C to kill dangerous Legionella bacteria. Ideally you’d want your solar panel to be colder than that.

You can get around this by using a heat pump to produce very hot shower water while pumping lower temperature water through your solar PVT panels. But that of course means additional expense – and much higher electricity consumption than the circulation pump of a normal solar thermal system. Also, it is worth pointing out that most PVT systems on the market today actually cost more than the combined cost of a conventional PV system and some solar thermal panels.

The Upshot: If you have enough roof space you’re probably better off installing separate solar PV and solar thermal systems.

2. Is there a case for thermodynamic systems? So-called “thermodynamic” systems (a fancy term that doesn’t really mean much) are essentially simple (unglazed) solar thermal panels connected to a heat pump. They haven’t been on the market for long enough for us to have good data, but there’s reason to be very sceptical. In the UK there simply isn’t much solar energy available in winter because days are short and the sun is low down and very often hidden behind clouds altogether.

Under those conditions, a “thermodynamic” system is essentially an air-source heat pump (ASHP) that relies on heat transfer from the ambient air to the solar panel. Manufacturers claim that the system will provide hot water at every time of the year – and that is probably true, but during dark winter days this energy is not solar energy but rather energy produced by a heat pump, which consumes a lot of electricity.

Furthermore, because the “thermodynamic” panels usually use a type of solar panel that’s less efficient than a normal (glazed) solar thermal panel, they’re probably also not a good choice during the sunnier parts of the year when a normal solar thermal system can produce hot water at a much lower electricity cost.

The Upshot: A large dose of scepticism is currently warranted when it comes to these systems. This is also reflected by the fact that their accreditation under the Microgeneration Certification Scheme (MCS) has been suspended, which means you won’t get Renewable Heat Incentive (RHI) income.

3. Are heat pumps right for me? The answer is “it depends”. Heat pumps use electricity to extract ambient heat (heat in the air or ground) and supply that heat into your house. Today most electricity is produced very inefficiently – for instance, our coal and gas power stations consume two or three units of fossil fuel heat energy for every unit of electricity they produce. If electricity from these inefficient power stations is used to run heat pumps, then these heat pumps need to be very efficient. Basically, your heat pump would need to supply three units of heat for every unit of electricity it consumed, otherwise you might be better off heating directly with oil or gas!

To work efficiently, heat pumps need to run at a relatively constant rate supplying heat at low temperatures. This is a realistic option for a (usually new-built) house that is well insulated and has underfloor heating with densely spaced pipes. In this case even when it is very cold outside the water in the heating system need only be lukewarm (maybe 30-35C). On the other hand, if the heat pump needs to supply much hotter water, for a badly insulated building or a building heated by radiators, then the efficiency of the heat pump will likely be too low to make it a good choice.

4. Micro hydro: yes or no? Hydropower is great, and if it benefits a whole community rather than one individual then all the better! Unfortunately, only a minority of communities in the UK have the kind of site that’s suitable for hydropower: A stream with a large flow rate of water and a good height drop. If you have a site of this type then it’s definitely worth exploring the option of installing a micro-hydro scheme.

5. Should I heat my house with biomass? Biomass can be a good choice, especially where wood can be sourced locally and/or for buildings where heat pumps would not work at high efficiency. But it’s important to stress that wood fuel is a limited resource and that there are potentially negative side effects to burning it (e.g. local air pollution from smoke, time lag between when CO2 is emitted and when a new growing tree absorbs it again). This doesn’t mean we shouldn’t burn wood, but it means we should try to use it as efficiently as possible. This means always reducing a building’s energy consumption first, and using the most efficient appliances available for burning wood. For example, modern log batch boilers (wood gasification boilers) get more heat out of the same amount of wood, and emit less smoke, than traditional wood stoves (or, even worse, open fires!).

Have a question about renewables and your home that we didn’t answer here? Check out our Home Energy Handbook, or give our Free Information Service a call!

 

Photo: Building the new green roof display

Thanks to a generous grant by People’s Postcode Trust, CAT has been able to build a new green roof for the visitor centre. This photo gallery shows the steps that CAT’s Buildings and Maintenance Officer, Carwyn Jones, has used in the building process…

1. The old food-store is one of the oldest buildings at CAT. But it was in dire need of a new roof, so Alex and Carwyn got rid of the old one first. They managed to re-use the membrane though.

2. A frame was built for the new roof. The original timber was reused where possible but as you can see, we needed a lot of new wood. The new timber was sourced from local forestry.

3. Here you can see how Carwyn re-used the old membrane. He also installed a new skylight to increase the light levels in the food-store.

4. This special membrane has pockets in it that collect water to allow for slower drainage. Bigger grades of stone were used on the edge of the roof to border the frame.

5. Almost finished! A layer of slate chippings went onto the roof (notice the extra batons that Carwyn put in place to stop the slate sliding down the roof). Soon the roof will be planted with sedums, which will need less soil and be easier to maintain than turf.

Watch this space for more photos of the new roof. Why not come and see it for yourself over Easter? CAT has a full schedule of Easter activities over the holidays!