Low energy building (straw bale) construction/research at Bath University

[Paulh_Boats]

See:

http://www.bath.ac.uk/features/balehaus

I've made this topic sticky as Bath university is doing some very practical research on low energy building. They appear to have a grant from BRE.

That web site describes a straw bale house built on campus with plenty of info and details about straw bale construction, including factory built straw bale panels that are bolted together on site Lego style.

Also in one of the photos I can just see building "2 East 3.1"...where I studied Elec Eng at a young and tender age 29 years ago! So I have emailed the Professor and will try to get involved somehow or at least visit the campus (and see how the Uni bar has improved over the years )

cheers
Paul

[Ted]

Bath University are developing a good reputation in the building materials field.  I was there with their I-SEE group for a Carbon Footprinting conference last year.

I left Bath (my home town) about 31 years ago.

[Baz]

Rather disappointed with the Bath website. Complete lack of information and hardly any pictures it's got as much substance as a Sunday Times Magazine article. Just jumping on an eco bandwaggon by bunging some straw bales into a wooden framed structure that could (and probably should) have used some other form of insulation.

[rhys]

http://www.modcell.co.uk/
Lots more info on Modcell here - potentially a good product - trying to take straw and hemp on a bit more from its "hand knitted yogurt" phase.
A U value of .14mm in a 410mm thick panels not too bad either, especially if its grown locally.

[djh]

Bath is good, especially the ICE database. http://wiki.bath.ac.uk/display/ICE/Home+Page  &  http://www.bath.ac.uk/mech-eng/sert/embodied/

But the jury's out on ModCell and BaleHaus. In particular, nobody that I know has been able to get proper thermal technical data from them. There are claims on the website that simply cannot be true - could just be typos of course but last time I looked they were still there. The frame of the cell is an obvious thermal bridge. Airtightness detailing needs to be checked but hopefully is addressed. If anybody can find a proper hot box report, I'd love to see it.

It certainly doesn't deserve a sticky topic, IMHO.

Eco Fab looks at least as sensible - http://www.eco-fab.co.uk/ - and StramitZED - http://www.stramitzed.co.uk/ - is another new possibility but again a lack of detail.

But what's wrong with 'proper' straw bale building in the first place

[rhys]

Bill Dunsters Stramit and Warmcell cassetets are interesting as it the other cassette based panel system - thanks for the links.
Couldn't see U value data for them though and how they minimise cold bridge through the frame.
I would have expected a bale materal to have a generally accepted R - value just like a clay brick or a lump of wood without necessarily a hot box test. Have Modcell refused to give a U - value calculation I'd be very surprised since  one would be needed for Building Control, and they have built quite a bit in the last year or so. The u-value they quote don't seem that far off even if they don't include the lambda calculation, as the timbers ar not really repeatingin terms of a standard calculation. Amazonnails have a similar  U value varies of course dependin on the bales so probably difficult to standardize exactly.
As for air tightness surely that was the whole point of the testing done on the balehaus.
http://www.modcell.co.uk/page/balehaus-at-bath-achieves-airtightness-of-0-86m3-hr-m2
AS for traditional staw bale well it great, but I do worry about falling onto those shap spiked starter sticks. Health and Saftey Gorn mad.

[dhaslam]

The problem with straw bales  is the cost.   I have about  3000 concrete blocks in the outside walls of  my house  and they would have cost about €2000.      Straw bales would cost about  €1000 but that is only the start of the cost, there would need to be a full  timber frame as well.   I don't think there would be much change out of €5,000 for the timber and  more labour needed than laying the blocks.    There would be a saving on insulation but  much more work needed on the finish as well.      There would be  about  7 tonnes of  CO2  associated with the external wall blocks.   However the heat storing ability of the blocks is better which would claw back the difference over time.   In my study, with about 50% of the walls  being external walls,  the temperature only falls at night  by 2C  even with  -8C external temperatures at times and it gains this each day just from the sun and  from electrical appliances.   The underfloor heating is set at 20C during the day and there was only one (dull) day that the thermostat was clicking on and off.    A house with surface insulation would probably need some heat  every  morning in those conditions.              

[djh]

The problem with straw bales  is the cost.   I have about  3000 concrete blocks in the outside walls of  my house  and they would have cost about €2000.      Straw bales would cost about  €1000 but that is only the start of the cost, there would need to be a full  timber frame as well.

That's not the correct comparison. You need to include the cost of the insulation as well as the concrete blocks; insulation costs lots more than concrete. There doesn't need to be a timber frame unless you live in a country with a building code that demands it. There are plenty of 'Nebraska style' examples.

You're right that there isn't a great cost saving overall as many people assume. There's just too much else goes into a building. But it's certainly not true that "The problem with straw bales is the cost".

[renewablejohn]

You dont need timber frame for straw bales. I have built an industrial unit using standard industrial pallet racking and straw bales.  Building 5 mtrs wide 6 mtrs long and 5 mtrs high constructed all in 1 day. Grand Designs it is not but it does keep very warm in a very windy location.