Underlay is as important as the flooring that goes over it, providing insulation from noise and preventing heat from escaping. Modern foam backed carpets are often laid without underlay but there’s nothing to stop consumers putting underlay down as well to increase the amount of insulation.
Old-style underlay is less thermo-dynamically efficient than modern materials. Rubber underlay has been around for many years and the other traditional material used is felt often mixed with horsehair and other fibrous waste by-products.
Not much attention was paid to the insulation properties of underlay in years gone by. Its primary purpose was to prolong the life of the carpet backing, taking the brunt of day-to-day wear.
Reusing Old Underlay
However if you are committed to sustainable living there’s nothing better for the environment than reusing old materials. If you are replacing carpet and find underlay underneath then perhaps reuse would be the best option. But make sure you move it around in the room so that portions that have had the heaviest wear get put down somewhere else.
Old underlay should be cleaned before being laid back down although vacuuming it is tricky, as it’s not normally stuck down. It would be better to get it out into the open air and beat it over a washing line if the weather’s good enough. This only applies to felt, not rubber underlay, the latter can be lightly sponged down and left to dry.
New Rubber and Foam Underlay Products
Many new underlay products are made from polyurethane so they are best avoided if you are trying to put together an eco-friendly home. As well as the damage done to the environment during their manufacture they slowly give toxins off over their lifetime, although the danger to our health from these isn’t conclusively proven.
As an alternative recycled polymer underlay is are now coming onto the market. This is lightweight so easy to transport and lay in place. More commonplace is underlay made from ‘crumb’ rubber which is recycled rubber and performs like foam in use.
Sustainable Felt Style Underlay
There is a variety of felt or fibrous underlay on the market manufactured from natural or recycled products. All wool felt underlay is as about as natural as it is possible to get but there are a number of retailers who use the word ‘wool’ to refer to the felt-style rather than to indicate that it is made from wool from a sheep’s back, so be careful with product descriptions and check the small print before buying.
Be careful too about the claims for recycled material in felt-like underlay. There are many underlay products that claim ‘100% recycled fibres’ but unless you know that those fibres are you could be fooled into assuming that the fibres are natural. Unless it specifically states that the fibres are natural, rather than man-made, then they won’t be and you could be making a mistake.
Using Different Underlay Types
One point to make about underlay is that if you discount polyurethane there are largely two types, those made from felt or other fibres and those that are more rubber or sponge like. To a large extent it doesn’t really matter which one is used in which room, but there are a few exceptions.
On stairs felt underlay is usually preferred as it doesn’t degrade on the exposed front edge of each step as rubber or sponge will. The other exception is with carpets that have seams on the backing. If they are laid with sponge or rubber underlay the seams will tend to stick up and be more noticeable, because the underlay springs back into position after someone has walked on it.
Felt or other fibrous underlay materials don’t do this, so over time the seam beds down into the felt, giving a more even surface on top.