Fran’s strawbale house
The AECB conference 2016 was held at the UK’s greenest building – The University of East Anglia Enterprise Centre designed by Architype. The most exciting thing for me was that the walls are clad in thatch (a vernacular material) and that all materials were sourced as locally as possible. When designing buildings, there is a lot of focus on keeping energy bills low, but not so much on keeping embodied energy low. Embodied energy is the energy required to manufacture and then deliver the product. Today we can import materials from anywhere, in stark contrast to the vernacular builders of the past who would have been limited to their local area. The latter is far more sustainable, but often overlooked as a necessary part of eco-building. The Enterprise Centre also achieves Passivhaus levels of comfort and air quality. It is a beautiful building, proving that eco design need not be ‘wacky’, it can fit well if it is well designed.
I learnt a lot from Bill Butcher of Green Building Store’s talk about their latest deep (meaning very eco) retrofit of a house in Cumberworth, West Yorkshire. The owners had been paying £3000 a year just on heating (not including wood burning stoves) and were freezing, on this exposed Yorkshire hillside. Having come into some inheritance, they decided if they wanted to stay put, something had to be done. So they enlisted GBS who have achieved a 67% reduction in their heating requirements. GBS used a combination of capillary active Tectem insulation, fibreglass and a new product called Diathonite, all internally. The airtightness result (2 air changes instead of 1) was not as good as they were aiming for. Bill said this was because they should have treated the partition wall as an external wall.
David Gale and Tomas Gartner from Gale and Snowden Architects launched the new Building Biology course in the UK. This teaches practitioners how to mitigate the effects on human health caused by radiation, dust, off-gassing from synthetic materials such as MDF and plastics and alternative materials to use in construction that will not create problems. Our indoor environments have a huge impact on our health including allergies such as asthma.
Fran’s straw bale house
A great highlight of the AECB conference 2016 was a visit to Fran Bradshaw (of Anne Thorne Architects), house in Norfolk. It is Contemporary Vernacular Design at its best, with locally sourced materials (even the reeds for the thatch which due to poor water quality in the UK, often has to come from abroad), and a design that is a contemporary interpretation of a thatched cottage. Using renewable and low embodied energy materials (timber frame, straw bale walls, roof insulated with thatch, cellulose (recycled newspaper) and wood fibre board) it is also an eco-house in the truest sense. The house also very nearly achieved Passivhaus, showing how energy efficient this way of building can be. it is a brilliant example of how to achieve a beautiful house and an eco-house. All of the AECB visitors agreed, this is the way forward.
I can’t wait to build my own straw bale eco-house!
Hemp prefabricated construction
I also attended a seminar by Greencore Construction on hemp and timber frame prefabricated construction. This was very fortuitous and perfect timing as my blog about a CNA visit to one of their houses describes.
Gary Wilburn, Director at HPW gave a talk about some of their larger projects, including a Peppa Pig tourist attraction and a shopping centre with restaurants at Rushden Lakes. While a bit controversial at an event about eco-building (do we really need another shopping centre/tourist attraction to enjoy these natural environments?), Gary’s message about methods of persuasion to clients not yet sold on the benefits of building sustainably was a good one. After all, these types of commercial projects are going to happen whatever we at the AECB might prefer. At least if there is a green architect whispering in the client’s ear, things such as miles of extra cycle paths, wind-catchers providing passive ventilation and removing the need for air-conditioning, use of renewable energy sources and renewable materials as well as wildflower roofs will mitigate the overall environmental impact.
August 30, 2016
Hemp, lime and timber frame prefabricated panels are an exciting way of creating eco-homes. I recently visited a ecohouse (that doesn’t look ‘eco’) completed in August 2016 and built by Greencore construction and was given a guided tour by Julia Bennett and Ian Pritchett.
Prefab or craft, can you have both?
Having written a book on Contemporary Vernacular Design, I am very keen to retain craft skills as much as possible. However, as part of my book research, I interviewed architects Alan Dickson of Rural Design and Neil Stevens of Dualchas, both situated on the Isle of Skye and both producing beautiful contemporary vernacular dwellings, well suited to the tough conditions in the Highlands. What was intriguing to me was that both firms provide their own pre-fabricated dwelling options (coming under R-House and Hebridean Homes respectively) in addition to their usual bespoke dwelling design. These still look beautiful, and as Alan Dickson explained; there are 101 ways to get timber cladding wrong and one way to get it right, pre-fabrication is a way to get it consistently right. These prefab houses look beautiful and crafted.
Inspired by this, I have been keen to explore pre-fabricated construction to reduce time and worry on site (especially with Passivhaus builds). Which is why I was so pleased to attend the Greencore seminar at the recent AECB conference in July 2016. (strange how you have to go all the way to Norwich to discover what you need is only on your doorstep in Abingdon!)
Having provided the hemp construction system for The Triangle, Swindon (link), which was not prefabricated and built on-site during the cold and wet winter of 2010-11, Ian Pritchett could see that prefab, where panels are built in a dry factory, had to be the way forward (having been a doubter himself).
The natural prefab panels
Greencore offer a timber framed, hemp-lime filled, factory-made panelised system. But this is not SIPS – which is high in embodied energy, not breathable and studies in America have highlighted issues with poor airtightness detailing causing internal rotting. The hemp and lime lock up carbon and are both renewable and breathable offering a superior living environment. Greencore offer a bespoke design, working with architects at an early stage to ensure that design and construction are in synergy and there will be no surprises on site (or at least they are vastly mitigated – there are always surprises on site).
Ian is keen to point out that although you can use clay or lime plasters internally to complete the full breathability of the wall (and therefore a lovely atmosphere as well as very low environmental impact). You can also use standard plasterboard and emulsion paints and that these more commercially viable materials will still offer a pleasant living environment when combined with an MVHR system. I was surprised to discover a lack of fresh paint smell and assumed eco-paints had been used, but no, standard emulsions and an MVHR ventilation system delivering constant fresh air allowed smells to disperse very quickly.
The house is simple in design, with an attractive L shape, lovely open plan spaces, lots of light and beautiful vaulted ceilings with large rooflights in the bedrooms and bathrooms.
Simpler to achieve Passivhaus detailing…
Unlike the wide masonry cavity wall Passivhaus construction that I have previously used, the hemp-lime timber frame construction is easier to build in many ways. Windows are best situated in the middle of the insulation to retain best thermal performance and this can be achieved by sitting them on plywood boxes in masonry cavity construction, however stone reveals are not possible and aesthetically clients are not so keen on the deeper external reveals. The hemp-lime system allows you to position the windows centrally without ply-boxes as that is where the timber frame is situated. However, to fulfil client expectations (and this house is a commercial project), Greencore have used pure-nit boards to cantilever the windows closer to the external face of the wall. Purenit® boards, though more expensive than plywood offers much better thermal performance.
Using PHPP (Passivhaus Planning Package) software as standard they are able to predict heating requirements and always beat the predictions of the software on site. This means that the performance of hemp-lime beats the predictions of the PHPP and the heating demand is lower once built than was predicted by the software. This is very advantageous and defies the industry norm of as-built energy performance being lower than predicted in SAP (the industry standard for assessing energy performance of building as required by building regulations for all new buildings).
I am looking forward to working with Greencore on future projects.
August 30, 2016
My new Contemporary Vernacular Housing Book is out in November!
After two years of visiting case studies in the UK and Europe, my Contemporary Vernacular Housing Book has finally gone into production with RIBA Publishing. These two years were challenging because the research involved visiting case studies, interviewing residents, architects and developers or housing associations as well as writing and editing. During this time I was also running a busy practice and teaching a day a week at Oxford Brookes University. The book also contains 5 case studies from further afield, researched as part of my masters thesis. Julia Phillips (architectural assistant at CNA) helped me with editing and organisation of the book and Katie Reilly (architectural assistant at CNA) gave me useful feedback prior to submitting the manuscript when I was too tired to read another word!
The research has been hugely rewarding and I have met some wonderful architects as well as inspiring housing associations and developers. This research informs our work at the practice and is very much a part of our ethos.
I am also excited to announce that architect Piers Taylor (of £100k house: The Final Fix TV series and founder of the Invisible Studio Architects), is currently writing the foreword.
August 20, 2016