It is actually curious: making your home more sustainable is being strongly encouraged from all sides, by banks with affordable mortgages and by the cabinet with substantial subsidies. But with one of the most important measures, the durability of the materials used is not such an issue. For the insulation of walls, roofs and facades, the industrial products glass and rock wool, together with polystyrene foam, PIR and PUR, have been favorites for years – and are suitable for receiving subsidies.
Environmental consultancy Milieu Centraal gives glass and rock wool an ‘average’ environmental score. They are mineral products made from glass shards and volcanic rock, respectively, that are easily recyclable. But the production process is CO2-intensive and does have a major environmental impact. This became publicly known when angry farmers blocked the location of rockwool manufacturer Rockwool in Roermond. It was at the top of the list of largest ammonia emitters in the Netherlands. PIR and PUR (polyurethane) are oil-based plastics.
Is there also an alternative?
In recent years, more and more natural, so-called ‘bio-based’ insulation materials have become available. From flax, wood fibres, cellulose (waste paper), sheep’s wool, straw to hemp, metisse (recycled cotton), miscanthus (elephant grass) and bulrush. They are already being used sparsely in new construction, but you can also use them to insulate your roof on the inside or build a secondary wall with insulation in the living room.
‘Natural insulation materials store CO2 and therefore have negative emissions’, says Jan Willem of the Group of the Gideonsbende, a ‘movement’ that wants to switch construction to natural materials – the materials transition. ‘Just by insulating the current Dutch housing stock with CO2-intensive materials we would about the 1.5 degree warming shoot away. Natural materials can help reduce CO2-to solve the problem of the construction world made of steel, brick and concrete.’ In addition, says Van de Groep, they offer a new perspective for agriculture plagued by the nitrogen crisis: let farmers grow extensive crops such as sunflower crown or sorghum, instead of maize for animal feed.
But do these materials also insulate as well?
The insulation values of most natural materials are somewhat less than those of common insulation materials. This means that you get a slightly thicker structure, compared to glass and rock wool, it is about centimeters. Natural materials are more pleasant to use than easily irritating glass and rock wool. In addition, they are ‘vapour-open’, they breathe more than the mineral insulation materials due to the continuous action of moisture in the stuff.
Are there also disadvantages?
Milieu Centraal advises against sheep’s wool, because sheep produce a lot of greenhouse gas and ammonia escapes from their manure. Some natural materials are also less resistant to moisture than traditional ones. They are therefore not suitable for cavity walls. ‘Everything revolves around a correct and professional application method,’ says Van de Groep. ‘If you do that right, there’s no difference with the mineral solutions.’
Can you already go to the construction market?
Although they notice that the interest in natural insulation is increasing, the large hardware stores are still trying to get out of the tree. According to purchaser Sebastiaan Vreekamp of Intergamma, the company behind Gamma and Karwei, this is not due to the quality of the materials, but to the packaging.
‘We did a research one and a half years ago and it turned out that the natural materials were not packaged in a consumer-friendly manner. It doesn’t sell well.’ His hardware stores do sell flax insulation boards, but only online. ‘We don’t put them in the store because of the price difference.’ Although that difference has now decreased considerably, he admits, because industrial materials have to contend with the high energy prices.
And beyond?
There are specialized online construction markets, such as Groenebouwmaterialen, Eco-bouwmaterialen and Ekoplus, where the knowledge about natural insulation is also collected. ‘People are becoming more aware of what they put in their homes,’ says Michiel Kalkman of Groenebouwmaterialen.nl, which supplies builders and private individuals. ‘And in terms of price, natural materials are becoming really interesting at the moment.’ He disputes that natural materials are packaged less conveniently. ‘Rolls of insulation are in bags and sheet material is packed separately.’
And what about financially?
You will earn back in a few years with the current gas prices. Count on one to six years, depending on the type of insulation (floor, roof, facade, cavity wall). Even if natural materials turn out to be more expensive, the payback period is still clear.
You can get a 15 percent subsidy for one insulation measure, and 30 percent for two measures. Then you must have this carried out by a recognized company. If you are not going to work yourself, it is important to have a good conversation with the contractor or handyman (m/f) about his or her choice of materials. Because the average contractor is neither trained nor used to erect a wall filled with elephant grass.