Keep in mind that I am a New Englander so I equate attics to being drafty & cold. That being said the above suggestion of cleaning & vacuuming years of accumulated dust is huge. Asphalt shingles & tart paper produce lots of that black stuff and rarely do roofers clean or protect attics as they are often underused. Imagine a 100 year old house & how often it had roofs put on or when they were last cleaned & or ever inhabited. Insulation isnt too pricey. I would invest in that after cleaning. Insulate using rolled insulation while ensuring a decent electrical system exists. Many attics around my house have fixtures that are 40+ years old. A single hanging light with a string. Before the insulating I would try to get some outlets & a surge protector run somewhere. Most attics have only but 1 or 2 windows & they are not always able to open. I would want some sort of basic lock between common areas for privacy. Ideally the shared use of a bathroom elsewhere in the house would avoid those expensive renovations. Hotplates & toaster ovens with a microwave do a lot and dorm fridges are all anyone really needs. Washing dishes without plumbing can be tough but again if kitchen usage is avauilable then you are ok. I would make sure that there is at least a window or more that open & having a basic rope ladder may satisfy some sort of safety requirement. Smoke/carbon dioxide detectors will help once completed.
Depending on flooring I might lay down some woolish
underlayment then sheet the floor with plywood. I wouldnt use sheet insulation as to capture any residual heat from below floors. I would sand and then coat the
plywood floor with polyurethane or even a light stain too like in sail lofts. As seen in the picture this person took a blow torch evenly to the plywood to bring out some of the natural character 9 I would do this outside in the yard before carrying the sheets outside. Keeping with the sail loft theme I would buy cotton duck painters cloth.
9 x 12 All Purpose Canvas Cotton Drop Cloth - - Amazon.com - https://www.amazon.com/Purpose-Canvas-Cotton-Drop-Cloth/dp/B00TIXP6EU Staple it up to cover the new insulation and joists. The white color will help brighten up the space & make use of limited light. I would buy a
oil filled radiator for heat with a
small table fan if electrical system can handle it. the fan will better distribute the heat if positioned behind the radiator fins. These heaters are 1500 watts max so one needs to get creative with when & what they plug in. A microwave might require the temporal unplugging of said heater. If separation is required I would build simple walls made of found lumber that could be wrapped in painters cloth or use
rice paper divider wall sections Decorate with a few recycled denin rag
throw rugs, futon, and other space saving furnishings like these attic max storage system with some sort of
collapsible storage boxes.
depending on code requirements for it being used as a bedroom or apartment and requiring a window & closet or second egress & heating system. I would make it quickly appear as a meditation room, art studio or improved storage space. Sure it can be a homey, warm, bright & inviting space that is perfect to live in, but is it legal? Occasionally inspectors, tradesmen, firemen or insurance people may have to access the space. Be careful with trying to add electrical or cable service to such spaces as they trigger red flags. If anything connect to existing wifi, split off cable while doing a self install from below account or get dish network.