Celebrate with CAT’s architects of the future

CAT’s Architecture Professional Diploma students celebrate the end of their studies with a private view of their work and a party at CAT on 20th January.

This unique event invites industry VIPs, students, local people and friends of CAT to view the final projects of these up-and-coming architects after 18 months of intensive study. Transforming study rooms into exhibition spaces their inspirational designs and models will be available to view with the students themselves on-hand to talk guests through their visions. This will be a unique insight into the ideas of the architects of our future. Continue reading “Celebrate with CAT’s architects of the future”

Ask an expert: eco refurbishments

Want to refurbish your home in a sustainable way? With over 25 years’ experience, including as tutor on CAT’s Eco Refurbishment course, Nick Parsons has some great advice – here are his top tips.

1. Make it air-tight.

Stop unintentional ventilation (this involves designating an air-tightness layer – and sticking to it!) and design in sufficient intentional ventilation. For a whole-house retrofit this will almost certainly be whole-house mechanical ventilation with heat recovery (MVHR), but for incremental retrofits, or those with less stringent air-tightness targets, passive ventilation may suffice.

2. Insulate, insulate, insulate!

Don’t automatically believe that Building Regulations standards of insulation are enough. They aren’t bad, but in many cases we should be aiming for far better. If you have the space – and the money – Passive House levels of insulation (U values of 0.15W/m2K or less) and air-tightness (less than one air change per hour for the refurbishment EnerPHit standard) can dramatically reduce your heating requirements and massively improve comfort.

External insulation of solid walls will make your house look a bit different. Ducks are optional.
External insulation of solid walls will make your house look a bit different. Ducks are optional.

3. Insulate externally! (Unless you can’t…)

External insulation of solid walls, if detailed properly, puts the entire building fabric inside a warm ‘tea-cosy’. But it does make your house look different.

4. Risk-manage your insulation

If you have to insulate your solid walls – or sometimes even add insulation to your cavity walls – internally, excellent detailing is critical. Insulating walls internally makes the room warmer but makes the walls themselves colder and more at risk of interstitial condensation – condensation within the new thickness of the wall, behind the insulation. This can rot joist ends and other embedded timbers, and maybe grow mould. Cold walls may also suffer from deterioration of the masonry due to frost damage.

If you insulate internally, make the whole process a documented risk management exercise – identify the risks, identify control measures and document how you will implement them. In certain circumstances, consider embedding sensors and monitoring equipment in hidden timbers so that you can know if moisture levels become critical. The expense may be off-putting, but it will be a great deal less than the remedial works if you have inadvertently shortened the life of your house by doing what you thought was the ‘right thing’.

In general the use of ‘breathable’ (water-vapour-permeable) insulants such as wood-fibre or cork may reduce risks, but very careful detailing is still required.

Greater risks exist with non-breathable insulants, but if they are installed with extreme care, the risks may be capable of being ‘managed’ and minimised. If you are installing them yourself, take advice from someone with a lot of experience. If someone else is installing them for you, are they experienced with such boards? Do they fully understand interstitial condensation and vapour control layers (VCLs)? Have they read the manufacturer’s installation instructions?

5. …and consider its environmental impact

Materials such as plastic insulation – made from crude oil – are high in embodied energy (the energy, including transport, used to get the product from raw material to the merchant’s shelf), but look at the units used. If the measure is weight, a heavy bit of ‘green’ insulation may be higher in embodied energy than a much lighter piece of ‘non-green’ insulation.

You may in any case wish to avoid wherever possible materials made from petrochemicals.

But ‘environment’ may mean more than ‘the world in general’. What about your immediate living environment? You may feel better in a room lined with vapour-permeable, moisture-buffering wood-fibre than in a room lined with petrochemical-based insulation.

6. Minimise thermal bridging

dscf3495You may believe – perhaps because your builder or consultant told you – that having low (good) U values guarantees good performance but thermal performance may be let down by weak-points in the insulation layer. Typically this would be where partition or party walls interrupt the insulation layer, where walls turn into windows or doors, or where internal insulation has to be thinner to accommodate fixtures or fittings. In practice, your U value may not be as low as you believed it to be.

The picture on the left shows: on the left, a wall prepared for insulation to ‘return’ on to internal wall to cloak the thermal bridge; in the middle, Pavadentro wood-fibre board prior to plastering; and on the right an existing brick wall with a lime ‘parge coat’ (air-tightness layer) to reduce air-leakage through voids in the brick wall.


7. Minimise thermal by-pass

Thermal by-pass, or ‘wind-wash’, occurs when cold air is allowed to get to the ‘warm side’ of the insulation. This can best be explained in two scenarios:

The first is a loft-conversion. The eaves areas are cold voids. The stud walls to the room (which are built off the floorboards) have been insulated to a good standard but there is only 100mm of insulation between the 150mm floor joists.

The ventilation air which enters at the eaves vents (a good ‘howling gale’ to keep all the timbers healthy) can blow directly under the floor of the heated bedroom, providing instant cooling!
Small pieces of plywood or similar board, sealed at all perimeters, placed between the joists at the edge of the floor on both sides of the bedroom will cure the problem. ‘Plugs’ of quilt insulation placed in the gaps will not do such a good job (as quilt insulation is generally air-permeable), but will be better than nothing. Once these gaps have been sealed, the insulation should in any case be increased to approximately 300mm.

The second scenario involves insulation to the sloping ceilings above an attic bedroom, carried out, as the law requires, by roofing contractors when re-roofing the house.

The house was sold and the new owner decided to remove all the attic ceilings. All but about six of the sheets of insulation fell out from between the rafters. What this tells us is that, while the insulation was in place, the cold air in the ventilation gap between the insulation and the slates was able to migrate to the warm side of the insulation, rendering the insulation almost useless.

8. Plan to do it all!

Many insulation plans are carried out incrementally, perhaps as other work is required, or when a room needs comprehensive re-decoration or (externally) when the cost of re-pointing an elevation can be avoided and put towards the cost of externally insulating that elevation.

When planning your works, ideally plan to do the whole house, even if you know it is going to take you 10 years to achieve it. I’m 29 years in and starting to re-do the internal insulation using better materials and methods than were available in 1987! Plan how your individual works are going to ‘knit together’ so as to limit thermal bridges, where condensation and mould may otherwise occur.

Above all, you don’t want your works – undertaken with the best of intentions – ultimately to shorten the life of your house.

image1About the author
Nick Parsons has worked in energy-efficient and sustainable building and renewable energy for over 25 years. He provides consultancy and project management services to individuals, small businesses and community organisations and is a regular tutor at CAT and elsewhere. See www.sustainablebuilding.org.uk for details.

CAT courses
The next eco-refurbishment course with Nick takes place from 4th to 7th November. For more information and to book, please visit http://courses.cat.org.uk/ or call us on 01654 704966.

Roundwood timber frame – new course

We’re really looking forward to the crew from Ty Pren Workers’ Co-op joining us in a couple of weeks to teach our new Roundwood Timber Frame course.

This really is do-it-yourself building – we’ll start off in the woods learning how to choose the right trees for construction and by the end of the week we’ll have completed the frame for a small building.

If you’re visiting CAT on the week of 22nd to 26th August, you might just get a glimpse of the build taking place, and if you’d like to join the course there are still a couple of spaces left.

Here are a few pics from recent Ty Pren projects to get us all in the mood…

TyPrenBuild   Roundwood-Sheppards-HutTyPrenBuild2   Joints1

TyPren-Roundwood Ty-Pren-Roundwood1












Sustainable Building Courses at CAT

One of the great things about the Centre for Alternative Technology is the sheer quantity of architectural and design features around the site.

View from the Wigloo
The funicular Cliff Railway
Eco cabins

Indeed, it’s a rare treat to see modern design juxtaposed with the rugged Welsh landscape.

All of our buildings, old and young, demostrate how ecological design pays attention to both form and function.

These buildings serve as practical exhibits which show ways that ecological architecture and design take care of both the environment and wellbeing.

We run a number of courses which are connected to design and architecture,  varying from short courses on timber frame construction to a Professional Diploma in Architecture.

For more information about our short courses: https://courses.cat.org.uk/sustainable-building

and graduate level courses:

Build a tiny house…

tiny house1We are so excited about our tiny house courses – new from us to you!

Running three times this year, spaces are filling up fast.

Learn how to make a beautiful and bespoke tiny house from the ground up: including the timber frame structure, interior and renewable systems.

Carwyn Lloyd Jones, our very own master craftsman (and TV star!) will guide you through an inspiring and practical week where you’ll learn how to:

• Build a timber frame tiny house (approx. 6ft x 10ft)
• Clad the walls
• Build different roof shapes (including pitched roofs, curved roofs and green   roofs
• Install windows and doors
• Fix the structure to a trailer base
• Create simple, functional and smart fitted furniture
• Integrate Solar PV and thermal for electricity and hot water
• Harvest rainwater
• Include a compost toilet

Jam packed with practical hands-on exercises and talks from experts, this course will give you the skills and enthusiasm to build a tiny house of your own – whether it’s a little off-grid home, outdoor workspace or a glamping pod for summer getaways.

8096918469_1098dc91a6_mCarwyn will also give you a tour of his very own tiny house caravan as seen on George Clark’s Amazing Spaces.

Book here, before it’s completely sold out!

Need more inspiration? Read this blog, written by a CAT graduate who is building a tiny home on wheels in Australia.

Rammed Earth Vault – a world first?

I have spent time over the last couple of months building a vault out of un-stabilised in-situ rammed earth.  Without known precedent, it is believed to be a world first.  Although there is a pre-cast example built in Austria by students under the supervision of Martin Rauch, there are significant challenges relating to the in-situ construction process that I was testing.  The vault is a 1:5 mock-up of part of my Final Major Project proposal for sustainable Greenbelt Development outside Edinburgh.


The full size vault would be 11 metres wide and 9.5 metres tall at its highest point and extends 20 metres to form an open air hall aimed to encourage a respect for the earth that we rely on to grow food and that can also provide another of our basic needs: shelter.  It would also be occasionally used for events relating to the small scale, sustainable farm work that takes place on the rest of the site.

The principle behind the rammed earth vault lies in the structural properties of rammed earth, which has significant compressive strength but cannot withstand tensile stress.  When flipped to form an arch, a catenary curve – following the path of a chain as it hangs in tension from two fixed points – creates a structure that is entirely in compression.  Whilst the structural principle is ancient and simple, the construction implications of angled ramming and formwork design were unable to be proven possible until the removal of the formwork. The revealing of the finished vault on the 16th of December was witnessed by CAT students from across the REBE, SA and Prof Dip courses.

I would like to put out a huge thank you to the staff and long list of students who helped me and to Rowland Keable, whose advice on the removal of formwork (which can be a risky procedure) was invaluable.

Here is a video showing the formwork being removed:


This blog is by Tasha Aitken, a final year student on the Professional Diploma in Architecture: Advanced Environmental and Energy Studies course; the Part II Architecture course at CAT.


Roundwood Timber Framing course at C.A.T. – guest blog from the team at Ty Pren

Roundwood-timber-framing-1Last year was full of firsts for us and a great coming together for all involved in the company. The first residential self-build frame for the county, the honing and strengthening of skills and relationships, and a great new website!

The movement towards low impact living is really gaining momentum with more and more people looking for alternatives to the mainstream. Questions about how we can live a more carbon neutral lifestyle are being asked, and there are so many people doing amazing things to answer them.

It always takes time for new ideas to filter through, and one of the aims of Ty Pren is to bridge the gap between self-builders and local councils. Roundwood timber framing provides a strong framework for affordable, low impact homes that are sustainable, beautiful and a big step in the right direction towards  a zero carbon Britain.


With this in mind Jamie and Ray will be teaching a five day roundwood timber framing course at the Centre for Alternative Technology in Machynlleth in May.


We’ll also be at a number of festivals over the summer doing workshops and talks, so keep an eye on our blog for more details.

Have a great 2016.

The Ty Pren team.

Eco-Refurbishment Course at CAT

The August bank Holiday weekend saw CAT’s annual Eco Refurbishment course, covering all the theory and practicalities of how to get your house towards performing better than many new- build properties. The course consists of classroom theory sessions and hands-on practicals, as well as tours of CAT’s own drainage, sewerage and water-conservation  installations and its renewable energy set-ups.

Tutor Nick Parsons said: “The practicals are an essential part of the course, giving students a chance to apply the knowledge they have gained in the classroom sessions to practical situations. These sessions would not be possible without the support of the companies which provide materials and reference material free of charge

A group of eager DIY-ers have been busy learning about eco-refurbishment at CAT. Over the past few days they’ve learned about ecological improvements you can make to existing buildings through practical exercises and specialised guided tours of CAT.

The developments in environmentally conscious building are coming along in leaps and bounds, but as it currently stands few people in the UK will have the opportunity to construct their own new eco-home. Refurbishing existing housing stock can make a massive contribution towards reducing our carbon footprint and lowering our wider environmental impact.

As the week draws to a close we would like to say a big thank-you to Recovery Insulation, Natural Building Technologies, and Clan Insulation  who provided materials free of charge for the practical sessions on the Eco Refurbishment course. Thanks also to Sally and Keith Hall at Green Building Press who donated copies of the Green Building Bible for the students. Nick Parsons, the course tutor, said: “it’s great to have samples of a wide range of materials – particularly insulation materials – and to be able to work with them. Students have found this particularly valuable, and we really appreciate the generosity of the suppliers”.

You can find out more about our autumn short courses on our website.

#SeeMeJoinMe Women in sustainable construction – a week with the Architecture Part II’s

Gemma Temlett is a student on the Professional Diploma in Architecture (Part II) programme at the Centre for Alternative Technology (CAT). Here she reports on the March module, gives a flavour of why studying at CAT is so special. She also talks about what the group is doing to support the #SeeMeJoinMe campaign to promote gender equality in the construction industry. 

We started the March week a couple of days early with a trip to Wolves, the context of our current design project. The aim was to get to grips with the city and Claire our heroic driver was first up, put to the test of navigating off Wolverhampton’s formidable ring road on the way to our first stop, a local Passivhaus school by Architype. While we had various visits planned in and around the city, we booked out a national trust bunk house in the surrounding countryside and set to work making giant pizzas and working on our presentations to be made on Monday. We turned the bunk house into our studio, Andy working away on his 1:200 models and the rest of us working on our laptops, in an industrious buzz around the big dining table.

Architecture students spinning pizza
Mario and Luigi spinning the pizza bases at the bunkhouse

Over the weekend we explored the house at Whitewick Manor, a fully furnished example of the Arts and Crafts Movement, and inspected it’s Victorian heat recovering ventilation system while taking in the Pre-Raphaelite art collection. It was a soggy Sunday measuring up the amended site boundary and a chat with the client before we headed to CAT.

It being International Women’s Day, another task for our Sunday on site had been to take a picture representing Women in Construction. Fellow student Kirsty Cassels had raised earlier the RIBA campaign to drive out gender inequality in the industry #SeeMeJoinMe. Immediately keen to partake, with my recent memories of taking my CV into offices and choking on the aftershave, we planned to complete the task in the week. CAT actively encourages women to work in male dominated trades and buildings scattered around the site were built by Cindy Harris, CAT’s builder for 17 years.

Monday was a day split into two groups for catching up on our project progress and marked presentations to hone our communication skills. Many an exCAT student that has come to lecture has renewed our confidence in the grooming process. Our group was tutored for the day by course tutors Trish Andrews and Pat Borer.

Trish in her Part 1 in the late 1980s at Strathclyde University had her own inspiring female tutor, Krystyna Johnson. One of the founders of the Scottish Ecological Design Association, Krystyna Johnson had been involved in Glasgow in the tenement improvement program, public participation in the 70s and pioneering architectural services within a community based housing association in Glasgow. James Irvine’s post from the October week talks about community participation and Ceinws where Trish was instrumental in forming a Community Land Trust.

After the last presentation of the day was given we breathed a sigh of satisfaction mixed with relief and caught up with the Masters students in the bar.

Lectures kicked off on Tuesday with a brilliant start. Lucy Jones talking on energy flows and thermal mass, former director of Earth building UK with a wealth of practical knowledge.

Dr. Lucy Jones at CAT
Dr. Lucy Jones in the rammed earth lecture theatre (image: Paulo Santos)

The next day was an air-tightness and thermal imaging marathon with Diane Hubbard, a former CAT student. This was a hands on session, checking the WISE building for thermal bridges. We moved to the self build accommodation to de-pressurise the whole building and watched as the cold air poured in the leaks! Diane helped us make sense of small signs that could be misinterpreted.

Dianne Hubbard Thermal Image
Thermal image of Diane Hubbard, demonstrating the deceptive effect of a sheet of glass (image: James Nolan)

This week there were Masters students weaving in and out of our days doing thesis tutorials and presentations from past modules. A few of them courageously chose to do their presentations in the main lecture theatre and invited us along. This is the enjoyable flexibility that is CAT. Another MSC student and untapped source of PV expertise, Corneila Peike, shared with us a short talk on design opportunities with PVs, on her last module at CAT.

Duncan Clarke Explains Timber Frame Principles
Planning for Thursday in the courtyard (image: Andy Hales)

Thursday had arrived, finally! We started on our timber frame building that brought with it the satisfaction of learning by doing, getting grubby and the feeling of real hunger at the end of the day. Our team is working on the sandwich frame, using OSB sheathing to stiffen the two 95 x 50 timbers, creating a stronger box shaped beam. From the relative comfort of the Pole barn we watched the tenacious team building the Segal method frame in the rain. They quietly finished in a few hours and dispersed while others chiselled away into the night.

Timber Frame construction stop frame animation by James Irvine

Architecture part II timber frame
Flipping of the sandwich frame (image: Andy Hales)

The guest lecturer in the evening was Pippa Goldfinger from the Frome independent council, ifF. Pippa’s inspirational presentation was on the fun-loving council’s people-lead processes and achieving sustainable solutions for the town.

Pippa Goldfinger from ifF
Pippa Goldfinger from ifF at CAT (image: Paulo Santos)

CAT brings together amazing people, gathered round the dining tables or coffee in-between lectures. We get to pick their brains and the practical, experimental nature of the people involved creates such a wonderfully relaxed atmosphere for sharing.

Fellow student Catrin organised the Friday night. Traditional Welsh cuisine from our much loved kitchen, music and fun was thrown together in our own mini CAT Eistedfodd, a Welsh celebration of the arts.

At the end of the week I jumped at the chance to get to know North Wales a little more with some classmates, partners and friends. Our trip ended in Felin Uchaf, an educational centre for young people, community, natural heritage and more that had brought some of our classmates together to build, years before the course at CAT.

Fellow student Kirsty Cassels at Felin Uchaf, Llyn peninsula
Fellow student Kirsty Cassels to the right of the crown post at Felin Uchaf, Llyn peninsula (image: www.felinuchaf.org)

Spot the Women in Construction photos?

–> See more blogs from Part II Architecture students at CAT