Monday, 7 November 2011

Background - Design

Where does one start when designing one's 'dream home'? We started many years ago before we even knew where or how we would build, and the archive of weird and wonderful ideas makes for an interesting read! In some respects there is a blank canvas. Almost anything is possible, but budget, complexity of build and the build site will dictate much and start to hone things down and dismiss some of the more flamboyant designs. One limitation which we have valued above all has been our desire to not take more than our fair share of resources and to use locally available materials wherever possible. This in itself decided much of the design for us.

Getting to a design we were happy with, one we felt was realistic to build and fulfilled most of our requirements took some doing. A list of our ideal elements was extremely useful, as well as ideas about the basic construction and materials.

Once we had settled on a construction type- with much influence and persuasion from Ben- we looked at how we could construct a cruck framed structure to fit in the landscape at Pentiddy and to accommodate as many of our long list of requirements as possible. The most notable design decisions are outlined below.

The build site was chosen when we first applied for temporary permission and was where the mobile home was sited for five years. It was chosen because it was less visual than higher on the site, and more sheltered. It also falls below the main spring on the land. Unfortunately this spring is 1/2 km away through the woods so impracticable to use without major time and financial investment and serious environmental disruption. A 'no go' I'm afraid! Its placement amongst other elements in the Permaculture design meant trying to go below the 200m contour so that the fruiting trees are more likely to succeed. Placing the home

The Solar aspect of south was important- we wanted to use a degree of passive solar gain, and also water heating and photovoltaic panels. We calculated the ideal annual pitch for the photovoltaics, but realised that ideally we need to generate more power in the winter than the summer, so we also worked out the best angle for average winter sun. Conversely the solar water panels needed to work more in the summer, so we calculated the best average summer pitch too. Here is a diagram of what we worked out....
So if we wanted the best average annual output from the photovoltaic panels, we needed the pitch to be 43° (90°- 47°=43°. The angles shown above are the angle of the sun, not the roof which needs to be at 90° to it!)

The main house roof pitch is 39°, so only a few degrees off for the PV's to be at average annual. It would have been a stretch and increased the total buildings height by too much to make the main roof fit the average winter pitch of 53°.

The outdoor kitchen roof, however, has been set to the ideal average summer pitch of 30° so we get the best heat from the water panels when the wood-burner indoors is not fired up.

The 'view sector' was also important, but was not conveniently due south, but more south-east. In the end the main house is 10° towards the east, and the 'L' shape, and the outdoor kitchen roofs each step out to broadly face the view.

The heating and insulation were also important. Having lived in caravans/mobile homes for many years, the idea of heat staying inside a structure seems a little unusual, but very appealing!
The main heat source- a wood-burning range, has been placed as central in the floor-plan as we could achieve, thereby radiating heat more evenly downstairs. The hope is that enough heat will also radiate upwards to the upper floor that pumping water to radiators will be minimal.

This is a little bit of a sensitive subject just now as most people visiting have the initial reaction of 'my goodness- it's huge!'
We did, however spend a great deal of time designing a house that was a balance between being practical and still efficient in terms of footprint, materials and heating.
The total usable floor area is 95m². The ridge however sits at 8.2m above the main ground level, so it is quite tall! Bear in mind though that the lower floor is a minimum of 1m above the ground. Once the walls are in, and the outdoor structures (verandah, outdoor kitchen etc) are in place and the ground has been landscaped, the visual impact of this will be vastly reduced.

The main generation for us is still the Air 403 wind generator, and currently 250W of Solar PV. This will most probably be supplemented with more Solar PV and if I get the chance I want to explore the stream as a possible micro-hydro source. This all will feed a bank of batteries, and most power will be used direct as 12v DC, but also inverted for 'mains' giving a small 600W, 240V AC supply.
The Solar water panels are to be mounted on south roof of the outdoor kitchen, which is lower than the position of the hot water cylinder. In this way we can 'thermo-syphon' the heat from the panels rather than use power pumping it.

The majority of our water comes off the barn roof, and 6,000 litres is stored in tanks and fed to the house and garden. Our drinking water still has to be sorted- the water from the bore-hole we had drilled recently has a few things in it that currently make it unsuitable for drinking. Still working on that one too. We're investigating the original idea of using roof water and will send some off to be tested once the guttering is installed.

The main structure does not include a toilet internally as we've really enjoyed our enforced visits into the night over the last few years- it's amazing what you see in the dead of night! We will still use a dry composting toilet in a separate outdoor structure. The grey water from sinks and showers is to run through a reed bed system, and finally fed back into the stream via the hens and ducks. All kitchen waste gets composted or fed to the hens.

It is worth mentioning that we have not employed an architect at all for this process- the design and drawings have been done by me. This has not been a problem- but has shown up some interesting things, which I will tackle in a later post.

I hope this has been interesting, and maybe useful for anyone undertaking a similar project.

My next 'background' post is to cover the 'red tape' side of things. I will not be going into great detail about planning, but looking at the processes subsequent to getting permission to build.

Till then, Regards,


NB. Please feel free incidentally to comment on the blog or drop us comments via e-mail. It is always nice to get peoples feedback and reactions!

1 comment:

  1. You seem to have considered so many of the embodied and useage aspects of your house - it's fascinating to read about all this. I expect there are so many people who would really like to do what you are doing (and hopefully, I will do something like this when I have a family in the future)

    Have you considered doing a calculated estimate for the embodied and operational carbon footprint of your home at some point? It would be really interesting to see just how well you've done compared to e.g. a typical brick place.



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