And what is green building anyway?
According to the World Green Building Council (WGBC), there are a number of features which can make a building ‘green’, including:
- Efficient use of water, energy and other resources
- Use of renewable energy, such as solar energy
- Pollution and waste reduction measures and the enabling of re-use and recycling
- Good indoor environmental air quality
- Use of materials that are non-toxic, ethical and sustainable
- Consideration of the environment in design, construction and operation
- Consideration of the quality of life of occupants in design, construction and operation
- A design that enables adaptation to a changing environment
Admittedly, I designed and built my hemp tiny house without ever having heard of the World Green Building Council and its list of features.
I had, however, read several books on ecological building design. My starting point was The Whole House book by Cindy Harris and Pat Borer (now out of print, but worth picking up a used copy). I was also a keen reader of the French eco building magazine La Maison Ecologique. It wasn’t all theory though. At a local eco-centre I took practical courses on building with lime and earth. Later I worked with a French eco-builder for about six months on renovation and new build housing projects.
So, how does my hemp tiny house stack up? Is it really green?
1. Efficient use of water, energy and other resources
Water
In order to help save water I chose to use a compost toilet rather than a normal flushing toilet. This alone would reduce water consumption by about 20%.
Rainwater harvesting for washing and possibly even drinking was considered but rejected as being too expensive and complicated. Besides, I needed a good supply of water in order to build the tiny house (for the hempcrete insulation and concrete foundations). So I got the water authority to put a mains water connection on the site.
I would probably store rainwater for watering the garden, if I lived in the tiny house full time.
Energy
Using hempcrete to insulate the floor, walls and ceiling was my way of finding a good compromise between insulation and thermal inertia. Hempcrete may not be the absolute best insulator per cm of wall thickness but it does have some thermal mass which helps smooth out the daily fluctuations in temperature. It’s also good for getting into the nooks and crannies of the structure and so reducing draughts. Combined with the wooden external cladding I thought the tiny house would be quite energy efficient, from a heating point of view.
Other resources
I decided on a two ring kitchen hob for cooking which uses a small, refillable gas bottle. As a fossil fuel, this isn’t very green. However, I also plan to use scavenged wood to cook and heat water outdoors as much as possible. It may also be possible to cook on a wood burning stove in winter months.
Petrol (gasoline) is another fossil fuel resource that I use, specifically for the small generator. This was mainly to provide electricity for the power tools involved in building the house. I wouldn’t expect to use it very often in future, perhaps to charge batteries, run tools or maybe a washing machine. Weekly consumption would not be very high.
All in all, I think the hemp tiny house will use resources efficiently, at least in comparison to a conventional home.
2. Use of renewable energy
Electrical energy
My tiny house was conceived from the outset to have a minimal electrical system running from a solar panel. The photo opposite shows the actual panel I used being tested prior to installation on the roof. I also decided to use an inverter and conventional 240v sockets. A small fridge would be the largest power consumer. Otherwise I only need enough spare power for some lights and to charge a phone or laptop.
Heating and hot water from wood
Another source of renewable energy that I plan to make use of is wood. Besides the few trees in my garden, there are many woodland walks nearby and it would be easy to scavenge a bundle of fallen sticks in the course of a daily walk. Should this prove impractical I could buy local firewood or purchase a small piece of woodland for the purpose of harvesting wood for fuel.
With this wood, I plan to heat both the tiny house living space and hot water for washing.
For space heating I’d like a wood burning fire of some type. At the moment I’m inclined towards a highly efficient rocket stove/mass heater, although it may not be practical to build one small enough to work properly. Failing that, I’ll plump for a normal wood burning stove, perhaps from a recycled gas bottle.
For the moment though I am using a small paraffin heater, shown below.
Again, this isn’t ideal from an ecological viewpoint (fossil fuel) but it is at least quite cheap (50 Euros), simple and efficient. Heat output is up to 2.2kw and, as it uses a wick, doesn’t need electricity to run. It can also be used to heat a pot of food or boil a kettle of water. I bought mine from a French company who deal in marine products (people apparently use them in boats!). Paraffin heaters are fairly common in France and most supermarkets sell 20 litre bottles during the colder months.
In order to generate hot water for washing, I plan to build an experimental wood fired water heater. This would be installed outside, but nearby, the tiny house. Cold mains pressure water would be piped to the heater and hot water leaving the heater would be piped back to the house.
The heater consists of a steel hot water reservoir that is heated by burning wood in a firebox below it. Inside the hot water reservoir is a copper coil that acts as a heat exchanger. Cold water flows through the coil picking up heat on its way back to the house’s hot water system. As the system is outside it can use a cheap single skin flue and provide hot water in the summer without causing overheating inside the house. Hopefully a small firing of 20 or 30 minutes using scavenged wood will provide enough hot water for one or two showers.
To conclude – most of the energy used by the tiny house will come from renewable sources. Solar energy for electricity and wood for heating and hot water. A comparatively small amount of energy from non-renewable sources (bottled gas and petrol) will be used for cooking and occasionally running a generator.
3. Pollution and waster reduction, re-use and recycling
Wood, hemp, lime and terracotta tiles are the main materials used in the construction of the tiny house. I think these are relatively good in terms of the pollution caused by their manufacture and use. The lime and terracotta requires firing in a kiln which needs a fair amount of energy (possibly from non-renewable sources). The hemp and timber would have relatively low energy needs for processing. All materials had to be delivered to site, unfortunately using fossil fuels and causing some pollution. I did, however, try to buy locally where possible.
The tiny house used very little cement (which requires more energy than lime to produce). Had I built my walls from concrete blocks, I’m sure the ’embodied energy’ and likely pollution would have been higher.
I consciously tried to reduce the amount of plastics, such as PVC, that I used (Greenpeace have called PVC the most damaging of all plastics). So my windows and doors are made from wood instead.
Other ways I tried to reduce building material pollution was by using un-treated timber (most of which was not kiln dried either) and by avoiding synthetic, petrochemical based paints and varnishes.
Some compromises were made though. For reasons of time and conveniences, I bought some kitchen cabinets from a DIY store. These were made from chipboard and have some kind of ‘plasticky’ coating. Likewise PVC waste pipe was used. I also bought a 2nd hand sofa bed which has a PVC covering. In defense of that purchase, the damage had been done 30 years ago when the item was made. At least by buying an old sofa I wasn’t causing any additional pollution.
Compared to the ideal situation of using wood, earth and stone sourced from the actual building site (impossible in my case), my tiny house probably caused a fair amount of pollution. However, I’m sure that this was less than that caused by more conventional materials such as concrete and plastics.
As for re-use and recycling, I think the hemp tiny house scores fairly well too. Were the house to be demolished, the structural timbers, roof tiles and wooden floor could be re-used. I’m not quite so sure what would be done with the hempcrete. It’s much easier to break up than normal concrete, so could potentially be crushed and mixed with more lime to make new hempcrete. Failing that, as it is non-toxic, it could be buried or left to degrade without any risk to the environment.
4. Good indoor environmental air quality
The air quality inside the tiny house should be excellent for the following reasons.
A lime and hemp plaster was used to finish the inside surfaces of the walls and this in turn was coated with a white limewash (lime diluted in water). So there were no modern, synthetic paints with their VOCs (volatile organic compounds) that could have added to indoor pollution.
The ceiling consists of limewashed timber planks (again no paints) whereas the chestnut floor was treated with linseed oil rather than polyurethane varnish.
Meanwhile, the vintage PVC sofa, while not ideal, probably stopped off-gassing several decades ago!
Besides the lack of pollutants, the indoor air quality is helped by the ability of lime and hemp to regulate interior humidity. It does this by absorbing water vapour when relative humidity is high (perhaps after cooking or taking a shower) and releasing it when relative humidity drops.
Lastly, the hempcrete walls have a good thermal mass and so can store heat. This means that the house can be frequently ventilated by opening windows and doors while maintaining comfort (due to the heat being slowly released by the walls).
5. Use of non toxic, ethical and sustainable materials
It should be clear enough by now that the tiny house uses mainly non-toxic materials. But are they ethical and sustainable?
I admit that I never really considered this in detail when designing the tiny house, I just assumed that they were.
By all accounts, industrial hemp is not an environmentally damaging plant to grow. Ethically, I’d suggest it was a responsible use of land to make a very useful product.
Wood is a potentially ethical and sustainable material. The structural timber I used was douglas fir and it was supplied by a local sawmill. I assumed it would sourced from sustainably managed European forests, but I didn’t ask. Likewise, the chestnut floor came from another local sawmill and I assume the timber was locally sourced. In both cases I should perhaps have made sure where the timber came from.
For the roof, I didn’t have much choice in the materials used as the local planning rules dictated I use terracotta tiles. The tiles I chose were an inexpensive Spanish brand stocked by the local builders. Perhaps, in the interests of ethics and sustainability, I should have bought some from the nearest French manufacturer. Regardless of that, they are certainly non-toxic and long lasting. I don’t know how sustainable terracotta tiles are. I don’t think they can be recycled but, at worst, they will eventually become harmless dust!
6. Consideration of the environment in design, construction and operation
Again, I think I’ve shown that the tiny house was designed to be kind on the environment regarding it’s construction methods, at least in comparison to modern, conventional buildings.
It’s also designed to blend in visually with the local environment. Firstly, it is very small and certainly not a huge eyesore. Secondly, the vertical exterior weatherboarding, left to age naturally, is similar to that used on the old tobacco drying barns that are still to be found in the local area.
A black mark against the project is the fact that I need to travel about 1000 miles from Scotland to get to the tiny house in France. Obviously this has an environmental impact. In future this could be lessened by using public transport (train or bus) or even travelling by bicycle if I had the time and fitness! Should I decide to move to France full time, I would make a trip back to Scotland at least once per year, so the environmental impact remains. From another point of view, this is no different from anyone taking a yearly foreign holiday and doesn’t really relate to how green the tiny house is. It could even be argued that the environmental impact of any foreign trips I make is offset by the swapping a normal house for an eco-friendly tiny house.
7. Consideration of the quality of life of occupants in design, construction and operation
As the designer and constructor of the tiny house, I have obviously given careful consideration to the quality of life that I will have as the occupant! This is very different to a commercial property developer who is unlikely to live in one of his/her buildings.
I’m satisfied that the quality of life in my tiny house will be very high, according to my own criteria.
That means that the tiny house will be comfortable, with a good thermal performance. It will also be healthy (good indoor air quality) and economic to heat.
By virtue of it’s low build and maintenance costs, it will give me a sense of security. That is to say, I will be able to live in my own place and not be dependent on a landlord.
8. A design that enables adaptation to a changing environment
To be honest, I’m not sure exactly how much the local environment of my tiny house will change in my lifetime.
Should it be necessary, the tiny house can be easily modified thanks to it’s construction method. It would not be difficult to add an extra room, porch, or whatever (just screw the new bits to the existing wooden frame).
More generally, the tiny house is well placed to adapt to changes in the global environment. It will hardly be affected by rises in the costs of electricity or fossil fuels, for example.
It could also be argued that the ‘low tech’, low cost and simple lifestyle afforded by the tiny house will be increasingly sought after by those who are weary of an increasingly busy, precarious or unsatisfying ‘normal’ lifestyle.
