I am sensitive to indoor air quality and the Hilton, like most big hotels, does not have rooms with windows that can be opened, forcing one to breath recirculated air with formaldehyde and other gasses emitted from furniture, carpets, etc.
I note that the Townepalce Suites, which does have rooms with windows that open, is less one mile walking distance from the entry gate at NIST.  Granted, in bad weather the walk might not be so pleasant (e.g. splashing of slush from the highway if it’s snowy), but I prefer to stay there.