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Basement insulation

Jack_smith | Posted in Energy Efficiency and Durability on

Hi, i know there are a million questions like this, i read through a whole bunch but i’m scared i learnt just enough to get me into trouble.
I am on a very tight budget to renovate part of my below 3/4 grade basement. the walls are painted block and the floor is VCT tiles with a drop of framing which i will be removing. The basement doesn’t feel damp but i would like to make it nice and tight and put a small one bedroom apartment down there. The space i want to work in is approximately 350 square feet. and there is another 100 sq ft of space that houses the boiler, water tanks, and some storage, i don’t want to do anything in that space. if it wont impact what i’m doing in the apartment. the 350 sq ft space, the sewer lines run alongside the walls, so when framing, my frame will be 5-6″ inches from the lower part of the walls and about halfway up a foot from the walls. we plan on putting in a small bathroom with a tub on an injector pump and mini splits as the heat and cooling source. how do i go about insulating this? i cant do rigid foam since nothing is really straight and useful. should i use closed cell for the walls, just fill up this huge cavity and the rim joists where it meets the walls? i want to use Roxul in the ceiling to mitigate the sound through upstairs.
what about the floors? poly sheeting and maybe LVT? what if i use ceramic? can i use the Ditra mat as the vapor barrier? the windows need to be replaced and sealed properly which will help, all will be drywalled and i want to use Denseglass for the bottom foot and PVC moldings. is there a way to insulate this from the rest of the basement which has the utility room? maybe insulate the walls in between and put in and exterior door at the apartment entrance? there will be a below grade hallway and a set of steps leading to the apartment from an above grade back door.

thank you for your time. i’m sorry if i was all over the place with this

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  1. GBA Editor
    Martin Holladay | | #1

    This article will answer almost all of your questions: How to Insulate a Basement Wall.

    If you don't want to use rigid foam insulation, you'll be using closed-cell spray polyurethane foam. You don't need to fill up the stud bays completely; you'll probably install 2 or 3 inches of spray foam (just enough to satisfy your local building code; amounts vary by climate).

    The article also gives advice on insulating basement floors.

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