When thinking about green building materials there are three basic elements to consider. The first is how much ecological damage is done while constructing and transporting the materials.
The second is the energy efficiency and ecological effect of the materials once the building has been constructed.
The third is how durable they are as there’s no use making the greenest home around if you have to waste more energy re-constructing it every five years.
Where Does Cost Come in?
Many will notice that cost was not mentioned above, although it will be a serious issue for many renovators.
There’s no doubt that many ‘green’ building options are more expensive than concrete, plastic and brick, either because they need more manual labour or because they are niche products, and economies of scale make them more expensive until they are popular.
For a green renovation it makes sense to look at all the options and decide what you want to try and use, and then look at the cost afterwards to decide whether it’s worthwhile, making sure you take a long term view.
If you’re renovating a property that you intend to live in, then you might well invest more in a sustainable home if it means you’ll have low or non-existent energy bills for the next five decades.
If you’re renovating to sell on for a profit, you’ll only make that investment if you think the market will pay more for a bill-free home.
Currently the evidence is not there to support that, although there already signs that ‘green-ness’ may give a property the edge in the market as housing prices cool down (at least outside London and the South-East).
Building with Straw
Straw bales probably represent the far-out end of the ecological building market. Building is fast and cheap because of their size and availability, although they need to be treated to make them fireproof and then rendered or covered inside and out to protect against pests.
They can also usually be found locally so transportation is cheap and eco-friendly and they are superb insulators.
Structural Insulated Panels
There’s a been a lot of interest shown recently in the United Kingdom in using Structurally Insulated Panels (SIPs) for residential building for housing, although they have been used in the USA and Europe for some decades.
They are constructed from boards made from wood particles, usually known as Sterling boards in the UK, bonded together by resin and glue to give properties similar to plywood.
Two of these boards are then used to sandwich a layer of insulating material, usually a form of polystyrene.
SIPs’ green credentials come from the building process and their insulating properties. The panels are manufactured in factories and are then delivered to the site where they can be used for floors, walls and roofs, and a house can usually be erected in a couple of days.
SIPs make a house very airtight so attention has to be paid to ventilation, but this makes them perfect for heat recovery systems which take stale air out of the building, remove the heat from it and use it to heat the fresh air coming in.
However, the use of polystyrene causes some people jitters although straw can be used to achieve a higher level of environmental friendliness.
Up on the roof, thatch is considered green for it’s insulation properties and credentials as a renewable source, as well as being traditional and good-looking.
The downside is that at the moment most reed has to be imported from Eastern Europe where it is still an economically viable crop, which makes for high transport overheads.
Wooden shingles and shakes are making a comeback with a variety of different woods being used, but the most environmentally friendly roof is to put some of the garden on it.
After putting down a series of material layers designed to keep water and roots out of the roof structure, a layer of earth and lightweight but porous hardcore is laid on top. Then plants chosen for their low growing height and ease of maintenance can be planted.
As well as being an excellent insulating layer, these roofs retain rainwater, slowing down it’s journey to the water table and reducing evaporation, both of which help to reduce flooding.
They also provide an attractive area for wildlife to flourish unmolested. It’s now possible to buy already impregnated mats of plants in a membrane (similar to turf rolls) that can simply be unrolled onto the roof once the earth layer is in place.
Commitment Versus Cost
These are just a few of the environmentally friendly options, there are many more, for example rammed earth or cob walls, and timber-framed construction, all of which reduce the detrimental impact of building to some extent or another.
It is for you to decide how far you want to go down the eco-friendly route and choose the right balance between commitment and cost.