January 2009


MySipHouse

MySipHouse

Looks like our dream house may be an as-PassivHaus-as-possible extension of a traditional 3-bed semi. So now I’m looking at how we make that happen. One of the things I’ve come across are Structural Insulated Panels. Essentially these are a thick “sandwich”, with two wooden panels separated by a thick layer of insulating foam. One of their advantages is size – you can get panels up to about 6m long, factory-cut to your dimensions, with all the window and door holes pre-cut. And that means that you can have a very short on-site build time – some SIPs builders claim to be able to have the house built in under a week. It also means you have less joints to compromise your insulation and airtightness.

While they are not all natural – the core is plastic – they do have several real positives:

  • All the  offcuts can be recycled at the factory – no skip required!
  • They use up to 50% less raw timber than a timber-framed house
  • They can result in thinner insulated walls than other methods – 150mm vs 250mm for a cavity wall
  • A typical U Value would be .22 w/m2K – heading for PassivHaus standards

There are lots of considerations when using them though:

  • You need to do all your planning up-front.
  • Use an architect and builder with SIP experience or you’re in for a world of (expensive) pain  caused by last-minute changes.
  • Try to ensure as much of the electrical and plumbing work is done on the internal walls to reduce the impacts on the insulation
  • Ensure that the builders seal all joints correctly with insulating foam (urethane) 
  • You may need to use a vapour barrier to prevent condensation inside panel, which could lead to rot.

They certainly seem to tick a lot of our boxes – they’ll go on the list as a possible option.

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Having posted about predictions that cheaper Solar Panels were on the way in 2009 here we are, less than a month later, and cheaper panels are popping up. OK I’m prepared to admin that this might not be a great economic shift – it might just be that I missed this supplier last time. They are Japanese-made Sharp panels and they are £2.99/Watt. I’ve updated the table of prices below – no other prices have changed, but the 200w Kyocera seems to have dropped off the market. Still a little way to go before we get down to the forecast $2.50/Watt!

EDIT – I’ve also added Navitron to the list – not sure how I missed them first time. Keen prices at £3.72/Watt.

Supplier Manufacturer Watts £ inc VAT £/Watt
Eco-nomical Sharp 180 538 2.99
Navitron Navitron 110 409 3.72
Wind and Sun BP – 3 Series 160 669.3 4.18
Wind and Sun BP – 3 series 170 727.95 4.28
Marlec BP – 3 Series 125 536 4.29
Marlec BP – 3 Series 135 579 4.29
Wind and Sun BP – 4 Series 175 772.8 4.42
Marlec BP – 3 Series 80 358 4.48
Unlimited Power SunPower 90 471.5 5.24
Unlimited Power Sanyo 215 1331 6.19
Sarpo Una

Sarpo Una

Potatoes should be one of the staple foods we’re going to grow, they store well, are relatively low maintenance, and everybody likes eating them! However they do have one major issue: potato blight. Potato blight can reduce the yield of your plants, and one infected potato can turn an entire sack to useless mush. What is Blight? Here is a description from CALU:

 

During warm damp conditions spores are produced on the leaves of infected plants. If the weather then becomes dry, the spores are released and can travel considerable distances on the air. If humid weather persists the infection will continue to multiply within the infected plant. Periods of highest risk are called “Smith Periods” and are defined as:
“A period of two consecutive days where the minimum temperature remains above 10oC over the whole 48hr period and where relative humidity remains above 90% for at least 11hrs each day”

When the spores land on wet foliage they “hatch” to release swimming zoospores (or “swarmers”) which may encyst on the leaf, or may be washed down into the soil and infect the potato tubers. Infected leaves show brown or black lesions, these may also appear on plant stems. Infected tubers show mottled brown lesions. A severe infestation can reduce a healthy crop of potatoes to a slimey mass within a matter of weeks.

So how can we avoid the devastation of blight?

There are many methods, including early harvesting, that are discussed to reduce the impact of blight. The most significant factor though seems to be selecting blight-resistant varieties. I’ve just been looking at this great leaflet from the Centre for Alternative Land Use where they have done a test between three varieties:  Orla, a first early; Sárpo Una, also an early; and Sárpo Mira, a maincrop.

They found that the two Sárpo varieties survived the season with no blight damage, where the Orla (supposedly highly resistant) started to show signs of blight well before harvest time.

Less scientifically comes this comment from Dan Pearson in the Guardian:

 You live and learn, but the waxy ‘Lady Christl’ were the best spuds I’ve eaten in a long time simply because they were mine. They were true to their description and were resistant to the blight that felled others not so far away.

Interesting note on the Sarpo varieties:

For more than 40 years the Sárvári family have been breeding for high blight resistance in potatoes in Hungary. The Sárvári Research Trust was established to develop and promote this work. The resulting varieties are called Sárpo (Sár from Sárvári and po from potato). 

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Good Size Log Store

Good Size Log Store

Huge numbers of people are putting in Wood Burning Stoves, Boilers and Ranges at the moment. They’re doing this for a number of reasons: to beat rising gas and electricity prices, to reduce their carbon footprint,  or to improve the resilience of their heating system in the face of peak-oil based supply issues.  The first challenge appears to be actually getting hold of a stove – apparently Dunsley have a 6-month backlog on orders for some of their stoves, And Stovax reported a 50% increas in orders in the last quarter of 2008. Once you have your stove though, how resilient is it likely to be? Unless you have your own woodland you are dependant on a supplier – so will there be enough wood for everyone who is currently putting in a stove or range?

The Guardian recently discussed the problems there are with firewood supply, and there are some of the facts:

  • Current UK consumption is about 1,180,000 tonnes a year.  Only 1m of those are produced in the UK, so we’re currently importing 15% of our firewood needs.
  • However, if you’re not fussy about what you burn, then there are 2.5m tonnes of burnable wood going to landfill every year – so if you see a skip full of random timber or broken pallets take it home and burn it – you’ll be helping the UK become firewood-independant.
  • Demand is increasing at around 25-30% a year, and resulting shortages resulted in price increases of up to 30% at the end of 2008.
  • The increase in demand is particularly resulting in an increasing supply of green, un-seasoned logs that will need to be stored for at least a year before being burnt.
  • There are wide price variations across the UK firewood is most expensive in the North and West, and cheapest in the South East.
  • The Government is working to bring another 2m tonnes of firewood to market by 2020. They say this will be enough to heat 250,000 homes (an average consumption of 8 tonnes/yr/house).

With the current supply chain under significant stress, the easiest way to ensure that your wood-fired stove or boiler continues to provide heat is to make sure that you have stored enough wood yourself. The general guidance is that wood should be stored for a year to reduce its moisture content from the 70-50% it is when felled down to an ideal <25% for burning. If you haven’t been through a full season with your wood-burner yet the general guidance is that an average house will consume 8 tonnes a year – around 12 m³, depending on your level of insulation, how hot you keep the house, whether it’s also heating your hot water etc. So – how much wood have you got stored? Two months supply? Less?

If your wood-burning stove is essential to your heating/cooking/hot water then you need to take wood storage seriously. Build a wood store – a shelter with a roof (clear if possible), open sides, and use pallets for the base and to divide sections to maximise airflow. Preferably split it into at least two sections so that you can have one section “seasoning” (drying) and one section that you are burning. Store the wood end-on to the airflow after chopping it to the right size for your stove. Make the stack as tall, long and thin as possible to maximise airflow.

Do that, and your wood-burning range can provide a really resilient solution to your heating, hot water and cooking needs.

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An Esse, not an Aga

An Esse, not an Aga

George Monbiot in the Guardian is launching a campaign against the Aga. He reasons that they use a ridiculous amount of oil, and generate an obscene level of CO2. I have to say that I’m with him on this. You won’t find much about Agas on GentleDescent because once I’d done the basic research and found that you couldn’t get a multi-fuel version I realised they weren’t going to meet my post-peak-oil needs. The decision was helped by articles like this one in The Times about people ditching their Agas

 

If you’ve heard about peak oil at all then surely putting in an oil-fired Aga is profoundly stupid. It’s OIL-FIRED. So when oil runs short or is out of your price range then what are you left with?  A great useless lump of cast iron, and no heating or cooking options – not very resilient! If you have to buy an Aga then at least get a Gas or Electric version, but realise that you’re doing it as a lifestyle choice, it is not a resilient long-term option.

So what should you get? I’m still working that out! The couple in the Times article went for a wood-fired Esse with a back boiler.  Ive looked at some really beautiful wood fired stoves, and the Rayburn, paired with a Solar Thermal system, but I’ve yet to come to a conclusion.

But what should you do if you do have an oil-fired Aga already? Apparently their re-sale valus is terrible, so I guess if you were feeling optimistic you could convert it to Gas, which may last a little longer, and be a little more environmentally friendly. Twyford do official Aga Gas Conversions. Otherwise? Send it for recycling. And buy a Rayburn (probably).

ferme-de-sourrou-potager

I love the La Ferme de Sourrou blog – amazing lifestyle, amazing pictures to go with it!

This one just caught my eye – what a vibrant Potager – I have Potager envy!

thermax_slow_cooker

An interesting one this – a slow cooker based on a thermos. Basically you heat up the pot of food and then pop it into the insulated flask. It’ll keep cooking for eight hours. Think of the energy you save – it only needs to be on the stove for about 20 minutes to cook a whole dinner.

thermos-shuttle-chefHere’s what one actually looks like – the 4.5 litre “Thermos Shuttle Chef” – and you can get them from Amazon for under £80.

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