Getting to grips with thermal comfort

John Butler reports from the latest module of the MSc Sustainability and Adaptation courses at CAT. John is a student on the MSc Sustainability and Adaptation in the Built Environment course. He normally blogs on his site and you can follow him on Twitter @the_woodlouse.

The March module of CATs Sustainability and Adaptation MSc was part B of Energy Flows in Buildings. Part A (in February) introduced us to ideas of thermal comfort and its relation to heat transfers from the human body to its surroundings. This was tied to the implications of maintaining that thermal comfort, and the impact on energy use. We learnt about calculating U-Values (used as a standard measure of the thermal efficiency of a building element), and daylighting: making best use of natural daylight in a building and calculating the resulting energy savings.

educational building
The view from a bedroom in the WISE building, home of the MSc and Part II Architecture students

Part B expanded on this getting into more detail about limiting the flows of energy through a building, whilst addressing issues around ventilation and movement of moisture. A sustainable building should maintain a comfortable environment – comfortably warm in winter, comfortably cool in summer, ideal humidity levels, good air quality – with minimal energy input, and without moisture ingress causing degradation of the building fabric. Throughout the week different elements of possible means to achieve this were discussed.

A recurring theme throughout the week was retrofit – upgrading the thermal efficiency of existing buildings to reduce their energy use and related CO2 emissions. The most commonly stated best-estimate is that around 80% of existing houses will still be in use by 2050; the potential contribution to reduced energy use and emissions from such a large number of buildings is huge, but presents a challenge. There are advantages and disadvantages to various approaches, from aesthetic considerations (eg: changing the appearance of a building when externally insulating it), to practical (eg: loss of space when internally insulating), to technical (eg: the risk of condensation forming at the meeting of new insulation and existing structure if it is not carefully considered). Planning and conservation concerns can also influence or restrict choices for retrofit.

viewing insulation retrofit
MSc students examine mockups of internal and external insulation, for solid-wall retrofit

There are also issues and trade-offs surrounding choice of insulation materials – the most highly efficient materials may have a greater overall environmental impact than some less efficient materials. Some are more breathable (open to passage of moisture vapour) than others, which can have both positive and negative implications, depending on application.

Another recurring theme was the need to account for future changes to our climate in both retrofit and new build. In particular, too much emphasis on designing to conserve heat could lead to overheating further down the line when atmospheric temperatures increase. Careful attention to placement of glazing and shading to control solar gain can help address this, allowing direct sunlight in to provide warmth in winter when the sun’s path is lower, and sheltering the building from the most intense direct sunlight in summer when the sun is higher.

The role of thermal mass in regulating internal temperatures was discussed in a number of lectures. Depending on climate and design, thermal mass may hang on to winter day-time heat, releasing it within the building through the night – or assist cooling by absorbing excess heat in summer, if combined with effective ventilation to purge that heat at night. Used inappropriately thermal mass may add to overheating, so its use must be considered carefully.

thermal image
Thermal imaging shows hot heating pipes (bright) and cold area where air is coming in around cables (dark areas)

A practical in the second half of the week provided a demonstration of heat loss through unplanned ventilation (ie: draughts). This was linked to the need to provide controlled ventilation (whether through opening windows or via mechanical ventilation), and highlighted the difficulties of achieving airtightness (eliminating draughts) in some existing buildings. The practical involved carrying out an air-pressure test to establish the air-permeability of the timber-framed selfbuild house on the CAT site (ie: how much air moved through the fabric of the building at a certain pressure). In groups we surveyed the building with thermal imaging cameras, before and during the test. The resulting images clearly showed how the cold incoming air cooled surrounding surfaces, demonstrating the impact of air infiltration on energy use. A scheme to retrofit the selfbuild house at CAT would have to include a means to reduce this.

air pressure test
The door-fan, used to de-pressurise a building to identify air-ingress

The end of the week saw us discussing Passivhaus and visiting the Hyddgen Passivhaus office/community building in Machynlleth, with the building’s designer John Williamson. Some myths about Passivhaus were busted (for instance: you can open windows), and the physics-based fabric-first approach was explained. The standard is based around high comfort levels combined with incredibly low energy input. While on site we investigated the MVHR unit (Mechanical Ventilation with Heat Recovery), which removes stale air from the building, and uses it to heat fresh incoming air. These are a common feature of passivhaus, as they allow the removal of moist air and other airborne contaminants and it’s replacement with fresh air, whilst minimising heat loss. This system has been the subject of some heated debates with fellow students at CAT, due to questions about the amount of energy needed to run the system and how user-friendly it is or isn’t. We were shown that when installed correctly, the system recovers more energy than is needed to run it.

Hyddgen Passivhaus in Machynlleth

As ever, throughout this course connections were constantly drawn between all the different areas covered (the inescapable interconnectedness of all things!). Nothing stands in isolation; each decision in one area can have repercussions in another. The different elements of building physics and materials must be balanced with each other and with the effect of any action on the wider environment.

temperature recording
Measuring the air temperature in MVHR heating ducts at Hyddgen, prior to calculating the overall efficiency and heatloss/recovery of the the system

The immersive learning environment during module weeks at CAT is highly effective, and very intense. It’s a wonderfully stimulating and supportive place to be, but at the end of the week that intensity needs a release in order for us all to return to our normal lives without winding up our friends and family when we get there. That takes the form of the vitally essential Friday night social, which this month was themed around a Cyfarfod Bach, a laid back Welsh social. We had beautiful music and singing, comedy, artwork, silliness, a rousing rendition of the Welsh National Anthem (not too shabby, considering only a handful of people were Welsh speakers or had any idea how the tune went in advance) and finally a leg-shattering amount of dancing, ensuring we could all go home in physical pain but happily and calmly buzzing.

See more blogs about the MSc Sustainability and Adaptation course. 

Transition People, Transformation People

environmental student
Sustainability degree
Students (Photo: Anna Cooke-Yarborough)

Helen Kennedy, a student on CAT’s new MSc in Sustainability and Adaptation masters course reflects on her experience of the first module.

A fortnight ago, I was preparing for my first week away, holidays discounted, for many years. I’ve been 22 years out of my own academia, and 22 years in the world of education as a teacher. Certainly, my career involved the odd training day, but as educational policy changed, so did the nature of these training days, and what had started out as my choice of training in areas which interested me and influenced my individual style slowly but surely became training in managing policy change and accommodating the latest dogma. I felt the real world was getting lost somewhere. Moreover this Real World was something I was becoming increasingly concerned about. So, it was with a huge amount of excitement that I packed my bags in readiness for something I really want to be involved in; something which will influence and educate me massively and hopefully as a product, influence others too.

I was not disappointed. Amongst the aims of this first module, it is stated that whilst getting an overview of the implications of transformational adaptation for social structures, land use, energy provision, economics and governance and its impact on the environment, we should also appreciate the interconnectedness of these things. As the week’s lectures progressed, this became increasingly apparent and it was interesting to hear about sustainability and adaptation from such diverse angles.

Student project
Bird hide (Photo: John Butler)

Each and every one of us took something important away from the many lectures and seminars, and for me, every lecture prompted the recall of the sort of things my partner and I would discuss over breakfast, and left me feeling that maybe I could make some sort of difference.

Adam Tyler’s “Energy Now” brought home perfectly just how big the gap is between the energy we use every twenty-four hours , and how much we could physically make ourselves in that same twenty-four hours, (41 days of cycling being equivalent to one day’s energy use).

Cath Hassell’s lecture on Water Security changed completely the way I think about expanses of lush green lawns in Spring and Summer, in terms of the water needed to maintain them, and the discussion regarding bottled water consumption brought to mind an article I had read about the terrifying “gyres” of plastic bottles floating in the middle of the world’s oceans.

The three lectures given by Tom Barker, Environmental Change, Biodiversity Changes and Ecosystem Functions were for me a brilliant introduction to a huge and complicated subject, and underlined how even gradual changes in complex systems can have far-reaching consequences. The phrases that stay with me are “keystone species”, “Snowball Earth” and “tipping points”. These lectures particularly affected myself and others in quite an emotional way, and I think it’s fair to say that we all came away feeling a sense of urgency, a purpose.

Lectures about Politics, Economy and Sustainability prompted discussions about what alternative models might look like, and a consideration of their advantages and drawbacks. The notion of negative interest is one example of a few concepts which have never occurred to me, and despite thinking that these might be dry areas for me, I have become excited to find out more.

fantastic location
University in the mountains (Photo: Helen Kennedy)

Lectures given by Bryce Gilroy-Scott and Tim Coleridge on Sustainable Cities and the Built Environment, coupled with Adam Tyler’s reprise to talk about Energy Futures were a positive force in strengthening our belief that change is not only possible, but that there are also a plethora of ways in which it might be accomplished. The challenge of designing well, from the outset, from the inside-out; in choosing suitable and adequate energy supplies, using materials innovatively and considering how settlements are organic and might successfully operate increasingly as a more closed cycle, is an exciting one.

This was a very full week, where time was most definitely not linear, and friendships were forged, through discussion, group work, room-sharing, over mealtimes, drinks and dancing. That this took place, and will continue to take place in such a special setting, surrounded by four decades of experimentation which has seen sustainability move from the fringes into the mainstream, made it even better. The Scottish Referendum was an inevitable backdrop for the week, and in spite of the result, the Friday night Ceilidh celebration was a wonderful and rather sweaty (for me!) end to the week’s events, organised brilliantly by Kirsty Cassels and the musicians Geoff, Matt and Roddy. I reckon they only did it to avoid the half hour long dances that left my face looking like a beetroot.

I came to this course as an introvert, and that is something that will not change. Snatched moments in the morning were precious, and found me mostly mountain-gazing into the morning mist, watching goldfinches and listening to their bell-like tinkling, finding the cherry tomatoes in the poly-tunnel and just eating one, and wondering in the stillness of the morning at the one beech tree that shook its leaves whilst the others remained motionless. Yes, it was a real challenge for me to meet so many new people all at once, to share a room, to speak out and to survive such an intense time of immersion with so little time for contemplation. What made it possible was the quality of the people – the MSc students from such diverse backgrounds, the Architecture students who put on such a stunning exhibition of their work for us and studied alongside us, the course leaders, my patient and very lovely room-mate.

The people who arrived nervously at the beginning of the week were not quite the same people who left the following Saturday. We are arming ourselves with knowledge that will empower us and others. We are changing. We are people in transition; Transformation People.

By Helen Kennedy

Also read Helen’s blog about her open day experience at CAT.

Student life
Friday night knees up (Photo: John Butler)