Ytong is a long established company , they pass all the necessary tests to get accreditation . Relatives of mine build a house back in the early 70s with blocks of that material. But then there were also reports in the middle of the 90s that some Ytong blocks contained asbestos . It was discovered by concerned parents which had it got tested or discovered test results made for the German health and safety authorities, I cant remember who was first, how it came out. The large blocks had been used for sculpturing in schools.
First the company denied it but then their own tests revealed the same results. It was an unwanted impurity and as far as I understood it was only in the large blocks and most likely had been rectified since then.
To ask me (thanks for considering my opinion) what I think are the right materials for an eco-house would need an explanation first: what is an eco-house?
Are the demands of the occupant more important than the impact of the structure/construction on the global environment?
Living in a small flat in a well designed city centre (infrastructure!) in a multi storey apartment designed to use as little energy as possible during construction and habitation would be the least damaging way for the global environment, for global social structures. But only if one has a job there as well, a reason to live there.
Importing materials from around the globe to build an energy consuming home in a place far away from the everyday demands would be the opposite. Buildings like that are getting architectural prices. And that is how we build nowadays.
An expensive method of building –I’m talking of money- has to answer the question how much “grey energy” is invested, how much destruction is caused earning to pay the total sum. And when we look at “Ms./Mr. Average” here in Ireland how inefficient they use resources to make a living, an income, at the waste of resources to produce the wanted wealth, then there is no simple answer to the question how an eco home should be made.
For every penny spend/earned on reproduceable products exactly the same amount of energy- translated in terms of money- has to be spend. And it’s the demand for energy that is causing havoc to civilisation .
So building cheap is a must for those concerned about mans future. The less we spend in terms of money the less we have to earn- the less our impact is. Or as they say in the lonely planet books: take nothing but pictures and leave nothing but footprints.
But I think that isn’t exactly what you had in mind when asking me how to construct an eco- home? Now, soft boards come in various forms, shapes and are made from various material. Hemp, straw, sisal, coir, reed, timber, cellulose etc… First you should check what are the manufacturers saying, what references they have to show, what the engineer says and so on. Then you should check what man power it needs, not only physical but also intellectual. Are the workers able to handle the new material, are they used to it, must they be trained? Are they adaptable to the new methods? What would the training cost in work hours, lost material, delayed finishing time?
Soft boards are prune to take up water, to rot if exposed to water for a longer period, loosing their original physical structure. So strict workmanship quality control is necessary, a crack in the vapour barrier, bad taping, a forgotten nail sticking out and destroying the vapour barrier can have expensive consequences. Esp. if used for load bearing stabilising purposes. They are commonly used to build timber frame home walls and roofs where the boards not only hold the insulation but the entire structure in shape. It’s worth to employ real carpenters, not only some staff that had seen a saw and hammer before.
When using soft boards for structural purposes it is also very important that tongue and groove fit exactly, that glue is used to combine them might be necessary as well. Check what vapour barrier is necessary, the “Lambda value “ must decrease towards the outside of the building.
My post is getting very long, so good luck and my excuses to the moderators using up all that space.