Would you like to live or work in a warm, draft free, healthy space that is easy and cost effective to heat?
Transforming our leaky buildings to make them clean, green, healthy and affordable to heat is a big project, but we have all the knowledge and tools we need to do it – and it offers us many additional benefits. Here is a selection of good ideas on how we can transform our existing buildings and build new ones in much more energy efficient ways, so we have better places to live and work, and support the shift to a zero carbon future. Continue reading “Building for a zero carbon 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”
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.
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
You 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.
About 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.
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.
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…
We 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.
Carwyn will also give you a tour of his very own tiny house caravan as seen on George Clark’s Amazing Spaces.
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:
Last 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.