Buckfastleigh Transition Town – for a sustainable future for Buckfastleigh, Devon
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  • 9th October – Planning the changes

    Posted on October 12th, 2009 andy No comments

    9th October 09

    Setting the baseline

    It has become clear, that in order to make this as representative a study as possible, all the properties in the project will all be assessed using the same standard, which is based on the Carbon emissions per square metre of an average domestic property in 1990 (This gives a figure of 20 Kg of carbon per square metre per year).

    So the assessment of the current and final carbon emissions of all the houses will be based on this statistical model of the property, rather than any actual energy usage in these properties.

    This means that individual lifestyles of inhabitants of these particular properties (us!) will not influence/bias the results. It also means that the whole exercise feels slightly artificial & irrelevant – for instance, the standard assumes a whole house temperature of 21°C – In fact we would find this uncomfortable and would not try to maintain such a high temperature, and certainly wouldn’t attempt to maintain it throughout the house all the time. It’s also based on using gas Central Heating to do that, whereas we use mainly woodburners and open fires…

    The properties will, however, be monitored for up to 2 years afterwards to see how actual energy use has been improved.

    I can see why it is necessary to try and create a generalised result, but I’m concerned that if this model is taken as a guide for future policy, it might result in predicting exaggerated savings that do not represent the real energy use of average householders, and that it also devalues any contribution that individual lifestyles and aware choices might make – an area where I think in the long term, in practice, the most stands to be gained (like putting on jumpers rather than the Central Heating when it starts to cool down!).

    (Re)build right, wrap up tight!

    We had another meeting last week for the planning team to outline their initial findings, and it was fairly clear that the engineers were surprised at how difficult a job it would be to get the properties down to 80% carbon emissions:

    The conclusion from the detailed computer modelling of the properties (using SAP – Standard Assessment Procedure – modelling  & PHPP – Passive House Planning Package), seemed to be that the simplest way (and maybe the only way) to get the emissions of these properties down to the 80% level, would be to seal them up and entirely wrap them in 200mm (8 inches) plus of insulation. This is presumably the way that they would approach a new build, but it is unfortunately not practical as these stone houses date from the 1880s and are in the Buckfastleigh conservation area – it would clearly currently be impossible to get planning permission to do so…

    Planet v Planning?

    This does open up the debate about how far we are prepared to go to save the planet – might we have to bite the bullet and recognise that major benefits to existing housing stock can not be achieved without sacrificing some of our precious historical architecture – if sea levels start putting properties at risk of flood, and food becomes scarce, will we still be arguing for conservation (or will we wish we had been a bit more draconian when we had the chance)?

    Plan B

    An alternative proposal, would involve fitting internal insulation to exterior walls (after sealing the house). This would have quite a major impact as it would be very thick (100mm – 4″ plus), which would mean a noticeable difference to the room sizes in a Victorian worker’s family house that are already quite small. It may well fall short of the 80% by some way, but too much internal insulation can apparently cause damp – it is also quite important to try and avoid cold spots which might act as a collecting point for damp. Potentially internal insulation can also cause the outside of the house to be more at risk of environmental damage – presumably ice is more likely to form in cracks etc., so all this needs to be taken into account (there is a discussion on internal insulation here).

    Additional insulation would be added to the lofts, and some form of secondary, high insulation, double or triple glazing would be added to the existing sash windows.

    If the house can be almost sealed, then airflow into the house would be regulated through ducts, which would probably be fitted with MVHR – Mechanical Ventilation Heat Recovery systems – air pumps with heat exchangers to remove any heat from air going out and recirculate it.

    Existing concrete floors on the ground floor of the houses will have to be dug out, and insulated suspended wooden floors installed (with radon ventilation systems in place), possibly with underfloor heating.

    The kitchen extension, which is modern, may have to be partially rebuilt to incorporate energy saving measures (and hopefully allow more light).

    Bits n pieces…

    Passive solar water heating is still on the cards, as though we have east-west facing roofs (no south-facing sunny surfaces), they could still provide 30% or so of water heating (as opposed to 50% plus from a south facing roof).

    It was also made clear that, though domestic appliances such as cookers, washing machines & fridges would not normally be the responsibility of the Housing Association, for the purposes of this pilot project, these would be included in the final brief.

    Practical issues

    Of course, it seems less and less likely that they will be able to carry out all these major works whilst we are occupying the buildings. Whether or not his is practical on a wide scale (imagine every old house in the country having this level of work done by 2050!), or even for this small project is arguable, and this is another issue that this project will serve to raise…

    The plan is that, once all these building changes are carried out, it should be possible to heat the house with just one small woodburner (or the CH on very low), since the air in the house will remain comfortably warm.

    Sealing the house ?- Get me out of here!

    I do have unanswered questions about what happens to the moisture & smells from our bodies, pets, drying washing, bathing, cooking etc. in a building that is so tightly sealed. Wood-burners may need external air intake ducts, as the amount of air in the house may not be enough to feed them.

    Also I am concerned about the level of airborn toxins from insulation materials, carpeting, decorating etc. and all the other man-made items in the house – at the moment we have so much airflow around the house that these can’t hang around for long – the team have talked about using natural materials like hempcrete for insulation, but have pointed out that these materials are generally not as efficient as man-made materials, so require thicker application.

    And of course all the proposed measures are speculative at the moment – much will depend on further analysis and whatever the final costings for each task are calculated to be – it is likely that financial limitations may restrict many of these…

    What makes it even more challenging for the team, is that the Housing Association (Sovereign) chose to put forward 3 semi-adjacent properties for the project, which will get £150,000 for the actual work if approved for phase 2 – the majority of other applications will be to retrofit just one property with this money!

    Luckily the TSB (Technology Strategy Board) have made it clear that the 80% is a target to aim for not necessarily to be achieved, and that many properties will fall short of this for practical reasons.

    Do they have cats in the virtual model?

    One last thing that has not been yet addressed, and may seem trivial, but I have spent ages looking for a solution, is what do you do about cat-flaps? Two of the three houses currently have cat-flaps in the front door (for access by a total of 4 cats, though other cats in the neighbourhood do not seem to take much notice of this!). At the moment these are huge, blowing vents, which stay open when a cat comes in and even when shut let in a draught to undo all the works of the design team. If someone has a design for an air-tight, insulated cat-flap they could make a fortune in the years to come! (and anyone who suggests getting rid of the cats will be ignored).

    More information soon!