We wanted to incorporate Permaculture design principles into the timber house that we're building here in the West of Ireland.
I'm a carpenter by trade, and so it helped when designing to know how the house would be put together, but we're especially proud that we managed to design the project without an architect or engineer.
As I write, the house is ¾ shelled-out, with the main frame, breathing external wall panels and roof-tiles completed. I'm in the process of making the windows, using the house shell as a workshop.
The house is a bolted post & beam structural frame, with studwork panels as in-fill. Since the roof loading is carried by horizontal beams, this allows total flexibility in placing doors, windows and internal walls, and so the design has changed and grown during construction. It also allows a roofed-over space to be erected within a few weeks so that work can continue under cover when it rains (it tends to do that a lot in Ireland).
It's not the absolutely most eco-friendly way to build, but the whole project has been a compromise between a limited budget and lofty ideals. We plan to complete the house for around IR£15,000, or £10 per sq.ft. We have always been adamant that we won't have a mortgage again, and so we build a little, work a little to save for materials, and build a little more.
By bringing a Permaculture approach to the house design, we feel that we've made the best use of the materials, and of the layout.
Siting & Layout
The house is located next to a copse of birch trees to the east. The low-impact foundations meant that we didn't have to clear mature trees from the site before construction, and the whole site already has a mature feel because of this.
We have about 3 ½ acres, and set the house in from the road by about 100m. We had to build a track across, on very soft ground, with stone laid on a mat of tree and gorse trimmings. All the bulk material deliveries have been transported across in single van/trailer loads as one delivery lorry sunk over the edge of the track and it took a whole day to get it out.
It's more energy-efficient to place the long axis of the house running east to west, with more of the space facing the sun (in our case south) side.
Living spaces are on the sun side, and less used spaces (or those with lower heating requirements) to the north. As a general rule in our climate, 50% of the glazing should be on the sun side, 25% each to east & west, and as little glazing as possible to the north.
At the heart of the house will be a heavy masonry stove and chimney, storing and radiating heat to 4 rooms that back onto it.
The main door on the north side has a glazed storm porch and an open-air integral porch. Also to the cold side is a walk-in larder for storage of fresh food.
All doorways and traffic areas in the house are placed so as not to waste too much floor space.
The main living space is a 4.5 x 7.2m kitchen/dining/living room, farmhouse style. The area above the kitchen end is a full-height cathedral ceiling, with a spiral staircase to an upstairs gallery. French doors lead into a solar sunspace on the south side, which is also full height (about 4.5m) so that we can grow tropical fruit. (I particularly want to grow bananas).
At the eastern end of the ground floor are a second reception/bedroom with a bay window, and a larger office/possible bedroom to the north. There is a small wc/shower room serving these rooms, so that the bathroom upstairs is en-suite with the main bedroom.
Upstairs, there's a galleried room with big skylight, which we call Heather's 'Quilting Studio' (or at least that's what she calls it. It looks like a music room to me.)
Then there is the main bedroom and bathroom. The bathroom for us is an important space, and so it's larger than average. A floor to ceiling dormer, glazed on all 3 sides, has French Doors out onto a small balcony, so that bathing will be semi-outside, and there'll be plenty of light for plants to grow. The shower will be a 'wet floor' arrangement.
The main bedroom is on the north-east corner of the house, with skylights facing east & west for morning and evening sun. This room needs less heating than main living areas. A step down into it from the main floor level makes it seem more cosy, and the colour scheme will be warm reds and purples.
Outside, to the north (main door) side, is a small courtyard, and my woodwork shop will run parallel to the house.
On the sun side, beside the sunspace, will be a timber-decked area with container-grown herbs and flowers, and a well-sheltered sunken garden as the main sitting-out area. The decking will jut out over a small pond. The main effect is to blur the distinctions between living room>sunspace>decking>sunken garden>small lawn>forest garden.
Construction & Materials
The house is timber-framed because timber is a renewable resource and needs less energy to process it into a building material. It's an easy, satisfying material to work, and looks and feels natural and timelessly elegant. We've heard the story of the Three Little Piggies many times from people who are dubious about timber building in Ireland's wet climate, but some of the world's oldest surviving buildings are timber, and it's the favoured material in wetter climates than this.
The main frame, rafters, joists etc. are structural graded imported softwood. We have not used any poisonous timber preservatives, relying on detailing and sound construction to keep the timber dry. Wood only rots at above 20% moisture content, and this will be achieved year-round through breathing construction and a free flow of air in the undercroft beneath the ground floor. Borax salts in the cellulose insulation will prevent rot in the in-fill wall panels, and it will be important not to seal damp air into unventilated spaces, as this causes rot. External joinery and cladding timbers are treated with organic herbal proprietary treatments.
The breathing walls mean that an internal vapour barrier is not required. Vapour barriers have been linked with health problems in conventional timber buildings. Moist warm air from inside passes through the wall, insulation and bitumen-impregnated softboard (Bitvent) sheathing, to an airspace behind the render skin, and is vented away. The breathing wall is designed so that the moisture in the air cannot reach it's dew-point and condense as it cools on the way through the wall, where it would cause damage. The insulation is also hygroscopic, and so dries out if it does become wet for any reason.
The Bitvent sheathing board is made largely from forest wastes, and the natural formaldehyde in the wood fibres keeps it together without added formaldehyde, which is carcinogenic. Forest wastes also fuel the manufacturing process. The spec says that it is strong enough to resist racking of the timber frame, but I put in sturdy diagonal braces, let into the stud panels, as it didn't feel strong enough.
The insulation is Warmcell, made from shredded recycled newspaper treated with borax to fireproof it and deter insects and rodents. 100mm of Warmcell is equivalent to 150mm of fibreglass, and so 50% less timber was used in the walls for the equivalent insulation value.
The breathing roof is formed by using a microporous plastic membrane (Tyvek) instead of conventional felt. This allow moist air through from the inside, but is impervious to water getting in from outside if rain breaches the roof tiles.
The roof tiles are interlocking concrete, slate-style tiles. Concrete is not a sustainable product, but natural slate has it's problems and would be too expensive. The roof slope, at 45o, is too steep for a turf roof. Thatch would have been too expensive. To cut down on lead on the roof, we have used GRP valley liners.
Externally, the upper floor gables are clad in vertical 'board & batt' timber on battens and counterbattens to promote air-flow between cladding and sheathing.
On the ground floor, external walls will be a lime render (for flexibility), again with an air gap to vent away moisture. The usual option for render substrate in single-skin timber houses is expanded metal lath, but we were worried about disruption to natural magnetic fields by sheathing the house in metal mesh, and so have decided to use sawn timber laths to carry the render coat.
The whole house sits on 20 concrete pads, 450x450mm. Because our land is very soft, we had to sit each pad on a concrete pile that sits on the underlying rock 1-2m below the surface. All these holes were dug by hand to save site disruption. The ground under the house in the 450mm crawlspace/undercroft is covered in polythene to slow down moist air rising from the ground, and topped with gravel. We'll need to close off this undercroft with chicken wire before the floor is laid, as it is a big cat litter tray at the moment.
The advantages of pad foundations are : low-cost, with major savings in concrete; small footprint when the house reaches the end of it's useful life; the pads can't be undermined by trees and so the site didn't need to be cleared of trees up to 1m from the house in fact the bathroom and bedroom feel a bit like a large tree-house; less surface area in contact with the ground means it's easier to prevent rising damp.
The main disadvantage of a timber house like this is that, although it is well insulated and quick to warm up, it doesn't store heat, and so temperature fluctuations can be uncomfortable. This is because of a lack of 'thermal mass', and also means the house can overheat in summer. To counteract this, a heavy masonry 'Russian' stove is situated at the heart of the house, to store heat and release it gradually.
Construction of the sunspace is an improvement on the conventional conservatory. A tiled, insulated roof is preferred to glazing, because it shades the space from high summer sun when overheating is more a problem than underheating, and also helps to retain heat generated by low winter sun shining through the glazed walls. The floor of the sunspace is mass concrete, insulated and damp-proofed, to store warmth during the day for release at night. The floor will have a dark finish so as not to reflect heat away. Venting options will allow pre-heated and freshly scented sunspace air into the main house, or in summer cool air will be drawn through the house from the north.
Originally, we wanted to build a totally 'off-grid' house. We've lived with wind & solar (photovoltaic) power for 4 years in our temporary timber home. However, due to the limitations that this has created, and the fact that a more complete renewable system would be well out of our price range, we've decided to hook up to the mains electricity. By being able to use computers, a freezer, washing machine, power tools, we can use our time more usefully (and enjoyably this life shouldn't be a drudge). We're fortunate that Ireland has no nuclear power, and our nearest power station is hydro, so we managed to convince ourselves that this was a sensible u-turn, on balance. Next time, when we're so far from civilisation that we don't have the option...
So, the wind generator and PV panels will be a back-up for when our rural mains supply goes down.
The house has other solar features. The sunspace, orientation and layout are designed for solar heat gains. Double glazing and integral draught-stripping of doors and windows are a cheap but effective way to make the most of these passive gains.
Solar water heating panels on the roof will pre-heat water and save fuel in the masonry stove, which will drive a back-boiler. In summer, even in Ireland's climate, most of the hot water required will be provided by the sun.
Most of the fuel for the masonry stove and oven will eventually be from bio-mass willows we've planted on our land.
Food and vegetable wastes are either composted or fed to our various animals.
We have a dry composting toilet which recycles nutrient for use around our forest garden. We have a successful business designing reed bed systems , and a reed bed will treat all wastewater from the house.
We re-use before we recycle, and most of our refuse consists of the plastic, non-recyclable packaging that we can't easily avoid.
The project has been enjoyable so far, and the most frustrating aspect has been having to take time off to earn the money to keep building it.
Since we started building, we've been approached by other people who want similar houses, and are also agents for a company importing pre-fabricated timber houses into Europe.
I'm happy to talk about any aspect of green building on the alt.permaculture newsgroup, and if anyone wants to discuss having a similar house designed or built, they can email@example.com or check out our website.