Consider the natural alternative

Construction worker thermally insulating eco-wood frame house with wood fiber plates and heat-isolating natural hemp material. Finishing the walls with a white wooden board, using laser line level.

There are many benefits and possibilities for using natural ecological materials in building construction. Such materials are becoming increasingly available. However, many people are wary about using these alternative solutions when architects, builders and even official bodies tell them that it is better to use the standard synthetic and plastic materials that are currently mainstream.

Many people want to live in a healthy, thermally efficient house but find the array of options available confusing. Some assume that the place to start is to spend a lot of money on expensive technology such as solar panels, heat pumps and heat recovery systems. While these should not be ruled out, it is important to start with the fabric of the building. If a house is well insulated you can save a lot of money on heating and this is far more effective than fancy alternative technology. This applies to building a new house or renovating an existing one. Natural materials can easily be part of the fabric of a building. 

Various ecological insulations: cork, sheep wool, wood fiber, coconut fiber

The advantage of constructing and renovating buildings using natural materials is that they do not contain toxic chemicals and, in many cases, are more effective and easier to apply. Natural materials are usually vapour permeable (breathable) and thus less prone to mould and damp; they can ensure good indoor air quality and create an attractive natural feel to the house. At Rachel Bevan Architects, we are using timber, wood fibre, hemp fibre, hempcrete, sheep’s wool and many more materials which are widely available, and there are plenty of examples of their successful use. 

Despite the many benefits of natural, ecological materials, some people remain nervous about using them, preferring to stick with concrete and flammable petrochemical materials. Architects, builders, friends and relations and so on will tell them that they should stick to tried-and-tested solutions and that natural materials are too expensive and not reliable. Some excellent imported natural materials can be more expensive than they should be, as they are made in other European countries, but when we build with hempcrete, for instance, we are using hemp from Yorkshire and a lime binder from Northern Ireland or Shropshire. Some hempcrete materials are imported from France and Belgium but it is better to use local materials. We can keep the cost of houses and renovation schemes using ecological materials close to conventional products’. 


In order to understand the benefits of natural ecological materials it is necessary to look at the negative aspects of current forms of building and renovating. Using petrochemical synthetic materials such as polyurethane, poly-isocyanurate, expanded polystyrene, spray foam and many more buildings can introduce an unnecessary amount of hazardous chemicals into the building and the lives of the inhabitants. The manufacturers of these insulation materials will tell you that they are more effective, efficient and not dangerous, but doubts have been cast during the Grenfell enquiry, following the fire that killed 72 people. Sealing houses up with air-tight membranes can lead to a range of unintended consequences such as increased mould and poor air quality.

We are now able to use affordable scientific tests to check the indoor air pollutants in houses, and it is not unusual to find that these are well over the safe levels set by the World Health Organisation and other bodies. The UK Government Agency DEFRA has just issued a 142-page report on the importance of indoor air quality problems. 

Picture of fresh mix of hempcrete (hemp concrete) being cast into a cube mould.

The hempcrete cottage that we built in County Down 12 years ago has been a useful test bed. The house needs very little energy to keep warm and we have tested it for air tightness and cold bridging. Over the past year, it has been monitored by University of Ulster and so we have data showing how relative humidity stayed the same all year round, whatever the weather conditions or occupancy. People who stay in the house – as it is let as a holiday cottage – comment on the beneficial air quality and some have even gone on to build their own hempcrete houses. 

If you want to know more details about all the natural building options that are available, my book, Natural Building Techniques, (Crowood Press), explains all the different materials and techniques and also lists suppliers.


The Author

Tom Woolley is an Architect working for Rachel Bevan Architects in County Down. He was Professor of Architecture at Queens University from 1991 -2007 and has been a visiting Professor in England, Wales, Sweden and Malaysia. He was chair of the Northern Ireland Building Regulations Advisory Committee and also a member of the NI Ministerial Advisory Group for Architecture. He is chair of the UK Clean Air Steering Committee and the All Party Parliamentary Forum on Carbon Monoxide.