How to insulate a room "inside" a basement


2 story house with crawlspace located in Portland, Oregon.
Crawlspace is a "conditioned" crawlspace.
Since the crawlspace is "conditioned", this means that there are no vents to the outside, the crawlspace walls (part cripple wall and part concrete foundation wall) have an insulation and vapor barrier system installed, vapor barrier system applied over the ground of the crawlspace, and there is a heating system that keeps the crawlspace area around 55 degrees.
Crawlspace has been converted to a "basement". I think it is not necessary to explain this in order to get an accurate answer to my question below.
A "room" has been built "inside" the basement. This room has its own walls that are not part of the crawlspace walls and has a ceiling that is not part of the crawlspace ceiling (house floor).
Question:
With the research I have done so far coupled with the fact I like to do more than the minimum, I am thinking that I want to insulate the 2x4 walls and ceiling of the room "inside" the crawlspace with fiberglass insulation, then wrap the inside of the room with polyethylene, and then install drywall.
Comments????
Jess Keyword = jessjoemama
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Jess wrote:

Hidden soundproof room with no direct outside egress under the house. Got it. How is air in the room exchanged? Is your insurance company aware of it?
As to what to finish it with- it is still a basement/crawlspace. Fiberglass and drywall will suck up any eventual floods or even basement dampness from furnace going offline for a week while you are out of town. Check borg or google for insulation and wall systems designed for below-grade use.
--
aem sends...

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And if the rest of this mysterious crawspace is "conditoned", why the need to insulate the new mysterious room within it? The rooms inside my living space are not insulated from each other.
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