My old summerhouse has been over runned by massive spiders and i'm curious...?

my old summerhouse is now the home off some very big and vicious spiders so it's best to stay out off it (if you know what's good for you) anyways the other day i 'braved it' and went in an' i curiously noticed these white balls hanging from the ceiling an' i'm 95% certain it is something's habitat or home but i know spiders live in webbs an' they definitley wasn't there last year (when i last 'braved it') so what are they?