The move is the first big, new attraction at the Garden for several years and is part of a plan to appeal to a wider audience.
This summer, the garden has opened a new £50,000 play park – complete with zipline and trampoline – a straw bale maze, water-zorbing pool and is promising 100 days of family activities.
As well as being a big attraction, the new Butterfly House also underpins the scientific research work the Garden is doing with bees, pollen, honey, hoverflies, moths and other pollinators, says NBGW.
Head of marketing David Hardy said: "The world has woken up to the importance of bees but bees are only part of the pollination picture. As well as being a place of awe and wonder, this new attraction will help raise awareness of other pollinators. Without pollinators there is no chocolate, there is no coffee – it is that important.
Head of science Dr Natasha de Vere said: "We can all help the pollinators in our gardens. We can grow flowers that will attract different pollinating insects, from bees to hoverflies, butterflies to moths. We also have to learn to garden a little less tidily. Long grass, nettles, dandelions and brambles provide important food and habitats for our pollinators, as are hedgerows and native woodland. So, if you are going to mow the lawn, leave some areas long; let some dandelions flower and leave some nettles (in a sunny patch). Most of all: don’t use insecticides. Instead, encourage native pest control like birds, frogs and toads. Our new Butterfly House is an exciting and fun way to spread the word."
The new attraction – which is in the Tropical House, designed by US-based and Wales-born architect John Belle, in the Double Walled Garden – will feature tropical butterfly species from all over the world, including native species.