Using Vetiver /khus roots for cooling screens and cooling blinds/thick curtain is very very old tradition in India. One can find households using it still. In Madhya Pradesh and UttarPradesh in India so many manufacturers still make this curtains for domestic use as well as export. In fact the people applied for patent must be of Indian origin. Because for such knowledge we have local phrase in Hindi "yeh to bacha bacha janta hai" Means "each and every child knows it."
As for its references, one can find it in any Sanskrit writings including centuries old Ayurved, Charaksahinta and other literature. It has been in extensive use by East India company before independence of India 1947,tribal people hand made cooling curtains and cooling pads were used for several years in Desert coolers, as it is locally called, from wild indigenous Vetiver root. After colonial raj,independent India had this cooling curtains in all the government offices located in in Nagpur and Chandrapur in Maharashtra State. In fact 2 months of extreme summer i.e April and may every year Cetral Government of India had special budgetary provision in these district offices, for watering personnel's special allowances.