The latest order comprises mobile eco12 and static eco28 units, supplied by Luton-based Easy Cabin.
Hewden national operations manager for accommodation, Steve McNulty, said: "We're currently experiencing customer demand driving high utilisation for our eco accommodation fleet, and this investment will ensure we're equipped to meet that demand.
"We made a similar investment in eco accommodation units in September 2012, and this latest order demonstrates our continued and long term commitment to this product range."
Hewden said that tis new cabins were among the most technologically advanced units on the market, with such energy-saving features as PIR-activated LED lighting, blown-air thermostatically-controlled heating, thermostatically-controlled hot water and intelligent generator charging technology.
Including excavators and dumpers, Hewden has so far this year spent more than £3m on new kit for its core fleet this year.