Perlite vs. ESP insulation over concrete

[yanmars]

Considering putting 2x6 joists over a 7 inch thick concrete slab. Over that 3/4 plywood and 3/4 inch T&G hardwood flooring. Anyone have any experience with loose fill Perlite as insulation over the concrete and between the joists? Compare this to loose fill EPS or a combo of rigid EPS and Perlite on top. Cost/insulation value differences or other pros/cons?
Thickness needed in Ohio temps etc. Thanks

 

[PILOON]

Firstly you'd want to isolate the joists from the concrete as they'll draw humidity and rot.
There exists products, a foam like board, that are designed for concrete slab floors.
One I know of kind of looks like a glorified bubble wrap, only fairly dense.

 

[user.69169]

Perlite Insulation

 

[chim]

Regardless of the insulation used, it sounds like you're building a nice cozy place for bugs and little critters. I'd seek advice from a pest control company as to what you might be able to put in the space before you close it up to make it undesirable habitation for them.

Of course ten years from now there will be a report that whatever you use against the little intruders is poisoning you.

 

[yanmars]

The building is at the top of a hill so all drainage is away from the building. When built put a ThouroghGlaze type sealant on it. Plan to reseal with a new product and then put down heavy plastic or Goodyear heavy rubber roofing under the joists. I think that will address the issue but any of the plastics I have seen have deteriorated after about 50 years. Here walking on the floors could cause enough movement that could wear through?

 

[fasttruck860]

If the goal is to simply supply a substrate for hardwood flooring you can achieve that in a much simpler way. Before you pour the slab install xps or eps insulation and a capillary break, such as a heavy mil poly or a name brand product. Tape the joints thoroughly install rebar/mesh and pour the slab. You should pay attention to thermal breaks at the frost walls. After the concrete cures you could either use another vapor barrier such as a roll on waterproofing and then install the plywood directly to the slab via drilling and screwing.

The other way would be similar but 2x sleepers installed directly to concrete, plywood, then flooring. The 2x6 seems excessive unless the slab is already poured.

 

[yanmars]

The slab was poured about twenty five years ago.

 

[dlctcg]

You state you are "Considering putting 2x6 joists over a 7 inch thick concrete slab. Over that 3/4 plywood and 3/4 inch T&G hardwood flooring."
What is this space being used for?
How are you climate controlling the space?

It would be easier to help with a solution if we had more detail on the intended use & buildout of the space.

I will be upfront & say as a contractor I don't have much experience with Perlite except as as a concrete block insulation filler.... (& it's use in soilless potting mixes). So your application intrigues me & I hope to hear from someone with better knowledge on the subject.

I due know Perlite insulation materials do not support combustion, are resistant to mold, rot, and rodents so I would not rule them out; I personally do not have enough experience with it to advise on it use in this application. We use Roxul (rockwool) insulation & closed cell spray foam for may of our projects; so I hope someone with more Perlite experience steps in.... (I love to learn)

From a quick search Perlite has an approx. R-value of 2.7 per inch.... the Closed cell foam we use yields a R-value of 6.5 to 7 per inch & provides a air tight vapor barrier.

Either way my first step would be sealing the existing 25yr old slab & for that I would look at using Sanitred (or similar product), we have been using Sanitred for 18+ yrs with no failures (if prepped & applied properly) bonus it is a radon barrier also.

Then if this is going to be living space I might consider installing hydronic radiant floor heating below the flooring (we are in New England) but should work equally as well in Ohio. If I was doing that I probably would look at Closed Cell Spray Foam as my first choice.... Again a lot has to do with the intended use of the space &the rest of the construction practices to the structure.

I really hope there is someone with Perlite real world experience that can give you better info....

 

[fasttruck860]

Lol that changes things. I've never used perlite in this application.

I second dlctcg's questions since it would help a lot in considering usage. Is this an existing three season and the 2x6 would flush out with the current floor?

 

[yanmars]

The plan is to have it livable. That would mean adding plumbing, electricity and heat and cooling.
I was concerned enough about the big hunk of flooring concrete getting cold without insulation and the county inspector is worried about frost heave so he wants it insulated or perimeter insulation. That is more difficult to do so considering the interior insulation. At this time it is an open space on the bottom of 26x36 and similar on the top floor but with the gambrel roof somewhat less floor space up there.
Would like to have a restroom etc. up there also.
As no provision was made 25 years ago now I will have to cut through the concrete and rebar and mesh to get plumbing etc. in and out.
For all you good readers. Another question. The building has a 3 course high split face block sitting on top of the slab. On top of the blocks sits in effect a 6 inch high wood bottom plate the wall studs sit on. I would like to insulate inside the block. It will be difficult to drill through the 6 inch plate as there are 16 penny nails in it vertically and horizontally. Had thought of putting perlite in the block cavities.
Another thought was drilling into the mortar between the block and spray in closed foam insulation. Unsure how small of hole the can get their applicator in and if I put it in the top block will it flow all the way down to the bottom.
Also do not want something that will expand so much it will blow out the block or mortar.
I am not photo or computer literate but if it would help I could see if my wife could add some photos of the building as is if that would give some guidance.
There are a lot of good minds and experience on this site and I welcome the ideas, suggestions and concerns.
My brother who was in the building trades all his life thinks I would be better off just bring in a modular and use what I have as a garage. What I have is in the best view and location however so I hope I can work with what I have. Thanks again all.