Carpet Concerns

Over the years, there has been a lot of inaccurate and, at times, ‘scaremongering’ material written about carpet – particularly on the subject of asthma and indoor air quality. We can categorically state that carpet is not a problem for, or cause of, asthma. In fact, leading scientists worldwide agree that there is no scientific evidence to support the view that the removal of carpet is beneficial to asthma sufferers.

Similarly, underfloor heating has grown in popularity in recent years – and some maintain they are not compatible with carpet. Not true!


Carpet and Asthma – The Facts

Bedding and bedrooms are the primary locations for dust mites to thrive. That is because they need a certain temperature (between 18C and 25C) and 60% – 70% humidity to live.

In carpets, the temperature and humidity are too low.

The live dust mite is NOT the issue. The problem is their faecal pellets which, when inhaled, can trigger asthma attacks in sensitised individuals.

Carpets act like a sponge and soak up most of the allergen particles. Furthermore, they do not become airborne – as they do with smooth floors – and so reduce the risk of sensitisation.

Opening the windows and letting in lots of fresh air, together with temperature and humidity control, significantly reduces dust mite populations.

Regular vacuum cleaning will remove most of the allergen from the carpet.

Leading scientists worldwide agree that there is no scientific evidence to support the view that the removal of carpet is beneficial to asthma sufferers.

Don’t just take our word for it…

In Sweden, a 77% reduction in sales of carpet led to a corresponding 300% increase in asthma in the same 15 year period.

The German Allergy and Asthma Association states: “The main reservoir of mites is in the mattresses of beds. Further habitats are textile upholstered furniture and carpet.  In the case of house dust mite sensitisation, it was formerly always recommended to remove the carpet.  The current state of research can no longer uphold this.”

Research in Germany showed that the average level of fine particles, including allergens, in the indoor atmosphere above carpeted floors was 30.4ug/m3.  Above smooth floors, the average was 62.9ug/m3.

A comprehensive study looking at carpet and its purported link to asthma and allergies by Dr M Sauerhoff covering research in the USA and around the world concludes: “Carpet does not cause asthma.  Carpet does not increase the incidence or severity of asthma or allergies, in either adults or children. Well maintained carpet is safe.”

These assertions are based on 43 research studies, reports and articles.

Indoor Air Quality

Carpet and Indoor Air Quality – The Facts

Most manufactured materials and products emit gasses from VOC’s (Volatile Organic Compounds). This does not make them dangerous. For example, the distinctive smell of the interior of a new car (often perceived as pleasant) is the result of VOC emissions.

The smell of a new carpet is the result of VOC emissions – usually from the back coating material. This will disappear in time and the more ventilation in the room, the quicker it will go.

Studies by leading research organisations in the USA and Germany have proven that carpet contributes much less to indoor pollution than many other indoor finishes and materials.

These studies showed that taking paint as being rated 100, adhesives are 72.5; wallcoverings 8.5 and carpet 0.5. In other words, carpet emits 1/200th of the VOC gasses given off by paint.

There are three major pollutants of indoor air quality:

  • Formaldehyde, which is emitted from a wide range of building products
  • Oxides of nitrogen
  • Oxides of sulphur

Research has shown that wool is particularly effective at absorbing these gases. A study in the USA showed that wool has one of the highest rates of removal of nitrogen dioxide from the atmosphere. Why? Because the three-dimensional nature of carpet with the wool fibres in the pile standing vertical from the backing presents a considerable fibre area to absorb gases.

Other studies have shown that large amounts of sulphur dioxide are also absorbed and held by wool fibres in carpets.

Carpet contributes significantly fewer emissions than other building materials, indoor furnishings and finishes.

Indeed, carpet makes a significant contribution to better indoor air quality.

Underfloor Heating

Underfloor heating is growing in popularity. Suppliers have stated that carpets must have a thermal resistance of no more than 1.5/1.7 tog. This is not the case.

In conjunction with the Underfloor Heating Manufacturers Association, the Carpet Foundation carried out a research project.

Five different carpet types and two different underlays were tested over an underfloor heating installation in a test chamber that was 4m square by 3m high. The combined laboratory tested thermal resistance of these was in the range 2.6-3.4 tog.

The results showed that:

  • None of the carpet/underlay combinations interfered with the efficient warming of the airspace in the room above.
  • The tog values of the carpet (using the test chamber as a life-size ‘tog meter’) were significantly lower than previous tests had shown.
  • The laboratory test method used, while accurate in predicting the prevention of heat loss downwards through a floor where conventional heating (i.e radiators) was used, was of no value when considering underfloor heating.

The Carpet Foundation now advises manufacturers to subtract a conservative 1 tog from the tested thermal insulation to provide a measure of the ‘real’ thermal insulation of their product when it is used over underfloor heating systems.

A ‘real’ thermal insulation figure of 2.5 tog is now considered a realistic maximum limit for carpet and underlay combined.

Carpet can be used with confidence over underfloor heating systems and will not impair their performance. We do, however, recommend that underlays with tog values of less than 1.3tog are used.