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 http://thewoodlouse.blogspot.com/ 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.

passivhaus
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. 

Digging beneath the surface of buildings energy assessment

Toby Whiting is a student on the MSc Renewable Energy and the Built Environment course at CAT. He is studying the course alongside working as a buildings energy consultant. Here he reports on the module from October, which focuses on energy use in buildings. 

Another great week at CAT has flown by. As a domestic SAP and Code for Sustainable Homes assessor, this week has covered a lot of the areas that I’m familiar with. So was it a waste of time? No certainly not! Believe it or not, as a SAP assessor, I have never taken the calculation apart and played with it in a spreadsheet – it was always one of the things that I wanted to try but never made the time for. I’m pleased to say that this course has ‘ticked’ another box and allowed me to look at where the ‘numbers’ are drawn from and made me look at the SAP process from a new perspective.

High and low points of the week: Delivering my powerpoint in a session where students give presentations based on their essay topic; and the trip to an office designed to Passivhaus standard -I’ll let you guess which was the ‘high’ and which was the ‘low’ for me (but it wasn’t the one where I had to stand up and talk).

People can confuse and transpose terms like ‘Passivhaus’ and ‘Zero Carbon’ so it really has been good to get out and visit a building designed to consume less energy, rather than offset the carbon produced. For me nothing beats the experience of walking around a building like this.

passivhaus
Canolfan Hyddgen: an office designed to Passivhaus energy standards

Working as a consultant can be difficult because I spend a lot of time researching and advising others on the most efficient or cost effective solution and the flow of information is often one way. This course reinvigorates me and allows me to mix with like-minded individuals (both students and lecturers) and exchange ideas.

I have been able to challenge my opinions over a wide range of building performance related areas and learned some fascinating things from other student presentations. I’m a part-time student and won’t be back now until January – and I’m pleased to say I’m looking forward to it!

thermal image
Using a thermal imaging camera on the module

 

Photostory: learning about the incredible properties of lime

 

Students studying for their MSc in Advanced Environmental and Energy Studies learned about the incredible properties of lime as a building material during a recent practical at CAT.

The hands-on approach is an important aspect of learning at the Graduate School of the Environment, which has lots of facilities for teaching about renewable energy and sustainable building methods onsite, including a lime kiln.

Lime has been used for thousands of years to finish buildings, though was replaced by cement in the 19th Century. There’s recently been a resurgence of interest in lime, however, as sustainable building materials have become more popular.

At CAT, we experiment with different environmentally sound building methods. If you’re interested in pursuing graduate study in sustainability, come along to one of our upcoming open days to find out what studying at CAT is like!

George Monbiot speaking at a lecture at CAT last week

Leading British Environmentalist says climate talks are now ‘dead’

At a recent lecture given by George Monbiot at the Centre for Alternative Technology and pocast in part here, Monbiot argues that the international climate change negotiations are failing.  He says that we are faced with  “the complete collapes of the international process, the process is now dead…. it died in Copenhagen”  and says that for the first time in his lifelong work as an author and activisit  he has not got a clue as to what the answer is  “my certainities of what needs to be done have crumbled in the face of the complete ineptitude and uselessness of the worlds governments.”

The 2010 United Nations Climate Change Conference was held in Cancún, Mexico, from 29 November to 10 December 2010. Although world governments reached agreement, many environmentalists have criticsed the Cancun agreement. John Vidal, writing in The Guardian, said the Cancun agreement did not show leadership nor tackle underlying questions such as how the proposed climate fund will be financed or commit to a legally binding emissions reductions.

George Monbiot- Author and Journalist
George Monbiot- Author and Journalist

George Monbiot was speaking at a lecture on the MSc Architecture: Advanced Environmental and Energy Studies at CAT’s Graduate School of the Environment (GSE) that offers a range of inspirational post-graduate programs. Courses are directed by a unique combination of leading professionals, academics and authors. They are based in CAT’s stunning new eco-educational facility, the Wales Institute for Sustainable Education. With flexible learning programs to suit all needs, and teaching that places sustainability at its core – CAT offers an unparalleled academic and practical learning experience.

Other lecturers on the course include

Paul Chattertonwatch you tube video

Senior lecturer of Geography at Leeds University

Lotte Reimer- watch you tube video

Tutor on the MSc Architecture: Advanced Environmental and Energy Studies at CAT

For more information on this or any other part of the Centre for Alternative Technology’s work in informing, inspring and enabling practical solutions for sustainable living, please contact the press office.