Carpets are hugely popular in the UK, but can cause problems. They provide an ideal home for dust mites, which can trigger allergies such as asthma (some carpets are treated with pesticides to try and prevent this). The mix of materials makes them difficult to recycle, and if incinerated they give off toxic dioxins and furans.
Carpets with the least impact are made of wool, with hessian backing and felt underlay - but these may still have involved toxic chemicals in manufacture.
For an eco-friendly floor, consider sustainable timber (look for the FSC logo) or a solid floor with ceramic or cork tiles.
Ceramic tiles, stone or slate are good at absorbing the sun's heat during the day and releasing it at night, so could be useful as part of a 'passive solar design'(for example in a conservatory).
Engineered wood flooring is made up of layers at right angles - similar to plywood. Less glue is needed than with chipboard or MDF, so the impact is lower.
Do note that laminated wood (thin layers of timber) is different to 'laminate flooring' - which is plastic finished with a photograph of wood grain. Besides the higher impact in manufacturing, these tend to fade and scratch, and so need regular replacement - whereas a good timber floor should last for the life of the home.
Bamboo is a quick growing plant and as long as (as with any wood) new plants are grown to replace those harvested, it is a sustainable material. However, transport impacts will of course be much higher than with more local timber. It is often treated with preservatives - check before buying.
For added comfort, use rugs or mats made from natural fibres such as paper fibre, Rattan (palm), Seagrass (grown in Chinese paddy fields), Sisal (from the agave plant of Brazil and East Africa), Coir (coconut husk fibre), Hemp or Jute (herbaceous annual from Bangladesh and India). Although mostly imported, these natural materials can be sustainably produced.
Cork is harvested from the bark of the Mediterranean cork oak without killing the tree so is a sustainable, renewable source. Without support, cork forests will be cut down, which will have a big impact on wildlife and biodiversity. However, some cork products are pre-finished with a polyurethane or PVC coating - look for unsealed cork products. There are oil based treatments for cork flooring such as Osmo Polyx-Oil which increase the floor wear and make it stain resistant and easy to clean.
Illegal child labour is widespread in the production of hand-knotted rugs from India, Pakistan and Nepal. Many are victims of bonded or forced child labour - a modern form of slavery. If a rug or carpet displays the 'Goodweave' (formerly 'Rugmark') logo you can be sure that illegal child labour was not used, and that adult weavers were paid at least the country's minimum wage.
The manufacture of PVC (i.e. for vinyl flooring) causes lots of environmental problems, including the release of asbestos and mercury. High levels of dioxins and other organochlorines are found around PVC plants - these pollutants have been linked with cancer, immune system damage and hormone disruption.
An eco-friendly alternative is linoleum - made from vegetable linseed and natural resin spread onto hessian or jute fabric and treated with water-based acrylic 'dispersion' paint. Linoneum is made from natural materials and is resistant to fats and oils, sound-absorbent, anti-static, light resistant, and has very low flammability and a natural anti-bacterial effect.
Details of suppliers of FSC-accredited timber (including cork & bamboo) should be available through the FSC themselves, and you may also be able to find further suppliers & installers of natural flooring and other building materials through the Sustainable Building Association. Please see the links below.
If you have trouble finding the materials mentioned, do contact me.