Use semi gloss for hallways because walls there are more likely to be touched, bumped or otherwise marked over time (semi gloss cleans more easily). However, use flat for a living room. Flat will help hide imperfections in the walls. If you want the same color in both the hall and living room, then no problem. Use flat in the living room, semi gloss in the hall, making the threshold the transition point.
One of the first considerations when it comes to interior house paint is the base. There are two schools of thought, each with their pros and cons. Some brands commonly sold to contractors for commercial projects are oil-based, meaning the chosen pigment is mixed with an oil derivative called alkyd. Oil-based paint provides thorough coverage, and the finished coat resists moisture well. However, oil-based paint releases a high level of volatile organic compounds (VOCs) as it dries, and it can only be removed from floors, brushes, and clothing with strong chemical paint thinners. In fact, many states have actually banned the use of oil-based paints because of their VOC levels and hazardous ingredients.
Expect to pay between $600 to $3,500 or $1.25 to $3 per square foot to coat vinyl, with prices likely increasing for the finish. It is one of the more inexpensive siding materials to have repainted, especially with recent innovations in materials. Changing the finish on your siding is not recommended unless it's completely degraded and worn away by the weather. You can save nearly half the vinyl siding installation cost of $4 per square foot by painting rather than replacing. Before adding a new coat to vinyl siding,