Otter Cottage gets solar hot water

Ian has put the solar hot water panels onto Otter cottage...





...the last of our self catering accommodation to get them. These ones should really cook – being on a south facing roof. All we need now is the sunshine. Poor Ian must have wondered whether it was all worth it as he worked alternately on the roof with rain dripping down his neck and in the loft with tar dust falling in his hair!

We rushed it through because guests who had booked Beech and Nuthatch lodges also wanted the cottage – a bit party get together.

The system came from Navitron again. Ian says they've made some improvements. The new pumping station was much easier to fit than the old one and the clips on the actual tubes were better too.

See our other posts on installing solar:
Energy monitoring put to good use
DIY tips for installing solar panels
Energy saving switches for the lodges

Impressive U values for the eco lodge floor

Ian has finished calculating the thermal insulation value (the U value) for the floor of the new eco lodge.




The U value measures the overall ability of a wall/roof/floor to prevent heat loss. It’s measured in Watts per square metre per degree Kelvin (W/m2.k) and takes into account all the thermal conductivity (k values) of the components of the structure, as well as other factors that affect how heat is lost from the building. Until recently, building regulations required floors to have a U value of 0.7 or below. That’s now been brought down to 0.22 W/m2.k. So how do we fare?

Well, it's not quite finished yet, as the picture shows, but here's the plan. The floor will be high-proportion recycled aggregate, then 150mm insulation (Kingspan, for it's exceptional insulation value, which we think outweighs it's only light-green manufacturing process - well they have been trying at least), then another 150mm of concrete made of 70% ash cement and recycled aggregate. Because it’s above the insulation, this layer becomes part of the thermal mass of the building, acting as a heat store to help regulate temperature. On top of that we’ll be putting down larch floor boards sourced locally (8 miles) from Mike Moser’s oak woodland restoration project.

Overall, that will give us a U value of 0.11 W/m2.k – twice as good as the 2010 building regulations.

Green green heating fuel

Here's some of our green heating fuel, three times green but not because it's green wood though...





...it's actually dry and seasoned - always more efficient in a wood burner.

More importantly, it's reusing waste - saw mill offcuts.


And it's local - the mobile mill is working a wood about 8 miles from us.


And on top of that it's a conservation project restoring an oak woodland by selectively felling conifer plantation. So the felling will be matched by a rejuvenated 'native species' woodland in our lovely corner of Devon.

And the icing on the cake? It probably saves us a significant outlay on heating oil for the house. OK, the house is 'cool' in the original meaning of the term, but we haven't had to buy central heating oil for about a year and a half now.

Here's Ian unloading the trailer.

And here's another earlier blog post about this source of sustainable timber - which we also hope to use in the new eco lodge we're building. The cutting list has been sent off already!

Energy monitoring put to good use

Energy monitoring has helped us make a surprising but sustainable business decision. We're no longer rushing to change the shower in Beech lodge over to the solar hot water system as there is no energy saving case for it. Let me explain...




Since last summer I've been following the energy consumption of our lodges and cottage pretty closely. I take meter reading after most bookings, and work out the energy use per night and also per guest night for each holiday.

Two of the lodges have all their hot water on solar systems with immersion top up (they sleep 4-6 people). Larger Beech Lodge sleeps 6-8 and has solar hot water for its bath and basins (with immersion top up), but not for its shower, which is on-demand electic. Otter cottage is different - and I'll come back to that!

After we finished the solar installation, we meant to change the shower in Beech Lodge over to solar hot water in the autumn, but held off, worrying that the winter sun in Devon wouldnt be anything like enough to provide hot water for a potential 8 showers a day, and that the immersion heater would be slow to keep up too - especially as we have a timer switch limiting the heaters to two hours on at a time.

And now, the energy monitoring confirms that this was a good choice, and in fact has persuaded us not to change it at all. Look at this graph of energy use per night for all 4 of our holiday accommodation units.

Beech Lodge, the brown squares, is pretty much indistinguishable from the other lodges in its energy use per night, even though it sleeps the most people (up to 8). In fact, Otter cottage consistently uses more energy than any of the lodges, even in the summer, even though it only sleeps 4.

And when you look at the energy use per guest per night, you see that even in summer, when most of the energy use will be for water, rather than heating, Beech Lodge with its electric shower (blue diamond now) is no worse than the other lodges. And in the winter, it's arguably better.

That's probably because more people are sharing the winter heating component in the larger lodge. And that's probably also part of the reason that Otter Cottage energy use per guest night soars in the winter. The cottage attracts more couples than families, and its conventional stone construciton makes it harder to heat.

There are some other excuses. Otter cottage electricity supply runs the shared washing machine and also an always-on pump. Nevertheless, having now seen Otter Cottage's rising winter consumption we'll be looking for ways to reduce it. Solar hot water, planned for this spring, would probably be good here - it would run the bath and basin (and probably the shower too as there are fewer guests to service).

And we have some other ideas for making the space heating more efficient - but that's for another post.

Saving 80 per cent of our laundry energy or just 'a fart in a teapot'?

[Maggie] Should I be congratulating myself on cutting my laundry energy by nearly 80%? Or is it, as Ian memorably called it, just a fart in a teapot?



...I did 27 washes for the business in October. I use a machine that can take a 9kg load and I always do a full wash. I usually wash at 40 degrees (tried 30, but it doesn't get things clean enough with my eco - friendly washing powder), sometimes at 30 and sometimes at 60 degrees for really dirty stuff - teatowels etc.

We have a tumble dryer. I try hard not to turn it on, and when I do its heat is reused in the house because it's a condensing model. I managed to keep it off all October (actually it was only on 3 times between April and the end of October). But if I had used it, data I've just collected (November) suggest it would have used about 2.87 kWh per load.

If I'd washed everything at 40 deg and tumble dried the lot it would have used about 98.4 kWh. Instead, my smart monitor on the machine reads 18.4 kWh for October.

So should I be congratulating myself on cutting my laundry energy by nearly 80%? Or is it, as Ian memorably called it, just a fart in a teapot?

It takes an awful lot longer to line dry things than to load the tumble dryer - eye on the weather, out, back in, out again, wearing a path to the line... And in financial terms I've saved only about £8.00 (our daytime tarrif is about 10p per kWh) and am likely to save less than £100 over the year. If I'd spent the time earning money rather than trying to save energy we'd probably have been better off.

My point is that nobody is going to go green for the cash savings - it's just too much hard work. I can do it (and will continue to, on principle) because I'm at home most of the day and it's relatively easy to take advantage of good weather etc.

But it's not going to get us out of the climate change hole we've dug ourselves. It goes back to the arguement about spurious big number multipliers - a lot of small changes still only add up to a small change and we need something much bigger. It's another depressing thought I'm afraid.

Meanwhile, I'm still on the trail to find the big energy guzzlers in our house...

Blog action day - climate change

You can make a difference - but switching off your phone charger won't do it...

This year's Blog action day is focussing on Climate Change - so here's a couple of thoughts.

You know those stats about unplugging your phone, switching things off at the wall etc? Well the other day I figured out that if I unplugged the washing machine at the wall when not using it, it would save me ooooh... £1.65 a year, roughly (I'm monitoring our business energy use closely these days!).

Not a lot then. Not much hope of getting people across the country as a whole to take that sort of thing seriously either.

But how many homes are there in Britain with washing machines? Must be more than 10 million. Twenty million maybe? So £33 million pounds worth of electricity going on standby a year - and that's just washing machines?

Hmmm. Maybe government should pass some laws about more efficient domestic appliances.

But if you think that's a lot of money for little red lights in the country's utility rooms, think about it a different way. The following is from Sustainable Energy without the hot air by respected academic David MacKay:

“The mobile phone charger averages around ... 1W consumption, but if every one of the country’s 25 million mobile phones chargers were left plugged in and switched on they would consume enough electricity (219GWh) to power 66 000 homes for one year.”

66 000? Wow, what a lot of homes! Switch off the chargers! ...... but 66 000 is just one quarter of one percent of 25 million. So... if you leave your mobile phone charger plugged in, it uses one quarter of one percent of your home’s electricity.
And if everyone does it?

If everyone leaves their mobile phone charger plugged in, those chargers will use one quarter of one percent of their homes’ electricity.

The “if-everyone” multiplying machine is a bad thing because it deflects people’s attention towards 25million minnows instead of 25million sharks.
The mantra “Little changes can make a big difference” is bunkum, when applied to climate change and power.... We all use power. So to achieve a “big difference” in total power consumption, you need almost everyone to make a “big” difference to their own power consumption.

Oh dear - that's depressing. What to do then? Well, maybe a big change is tricky all at once, but you genuinely can make a difference.

Already turned down your thermostat by 1 degree? Cut down on those unnecessary journeys? Buying your kids good quality second hand toys?

Here's another easy one, and you don't even have to do without anything.

Eat your way to a better planet. Start by eating less energy intensive highly-processed and highly-packaged food-mile laden grub. The average Brit throws away 400g a day of packaging - mostly food packaging. The energy footprint of that is about 4 kWh/d/person.

And don't throw food in the bin - give it away. Or freeze it, or serve it up differently with curry sauce, or whatever - as a last resort, compost it, or get yourself a cheap plastic biodigester that can take cooked food waste (some councils are subsidising them to around £10 a cone). You'll save money.

And if everyone did it we'll save on the lorry coming to take the rubbish, save on the landfill sites that have to be dug, save on the pest control, the .... Oh no, I'm getting carried away with the big number multipliers again.

Look - I reckon it's pretty simply. We all have to make a BIG effort to USE LESS - of everything. That's a good start at least.

And vote for a government that will help us collectively do the smaller things too.

DIY solar air heater

We're experimenting with a solar air heater made from an old sun bed and some secondary glazing. OK, so it won't do away with all our heating bills, but it could help in spring and autumn when it's sunny but still chilly inside.


We saw a commercial version of this earlier in the year at a eco-building event - but the price was high, around £1500 for a small unit.

Yet in principle the thing is so simple. You have a heat sink behind glass, an air intake at the bottom, and air out take at the top, and a solar powered computer fan to drive the circulation when it's sunny.

Apparently they've been used for a while in Germany, often to air heat caravans or holiday homes that aren't in frequent use.

So when Ian spotted the bulb-holding section of an old tanning bed down at the dump, he couldn't resist. And when my parents had their house double glazed, I nabbed some of the old secondary glazing they had been using.

Ian has painted the corrugated metal of the tanning bed black and fitted the glass on the front. A vent at the bottom lets air in - and warmer air rises out of the top. We still need to find a fan - back down to the dump probably - and decide where it's going to go. To heat a house of course you need to 'plumb it in' and that means holes through windows or doors, which isn't something to do without thought. We might test it on the garage first! We'll report back later.


Meanwhile, a little web research throws up some similar designs:

More here about how to make a solar air heater from drink cans.

On the fantastic Instructables site there's another design for a solar garage heater that circulates air from inside the garage through an external wall mounted heater (using metal fly screen, not beer cans)and back into the building.

Or if you just want something simpler to amuse yourself (or a science project for the kids) look at this page for a solar heater made from drinks cans that is hung in a window.