Insulating floor over crawlspace

[Cdshakes]

I live in small cape cod in NJ, basically the first floor is 4 main rooms (plus bathroom) over a crawlspace basement.  The basement height is enough you can squat or sit up down there (not true "crawl")
I feel like the floors are always cold here-- i've uncovered and refinished the original red-oak floors, so there's no carpet on the first floor.
I was thinking about insulating between the floor joists down in the crawl space to see if this helps.  I am going to use Rockwool--i know it's more expensive, but just seems like a better product.  I will not be throwing gobs of money at this at once- but rather piece-meal it over time.
Do you think it would be more effective to start with the perimeter of the whole house (just doing 4 feet in across the front and back)
or to complete one whole room at a time?
My feet are always cold, unless i'm wearing slippers or shoes-- so i'm hoping to do something that will help alleviate this.

Colin

[Turner52]

Your absolute best option in my opinion would be to have it foamed by a professional company. Yes very pricey but in the long run would probably pay for itself. Just my 2 cents worth.

[Cooler]

I would have thought to insulate the joists, but this long discussion (an advertisement) suggests that it not the best way to go.  They suggest insulating the perimeter of the crawl space with closed foam panels.  The ground would not need to be insulated and once the walls were insulated the floor would not require insulation.

They discourage fiberglass (and I assume rockwool) because they will hold moisture and promote mold growth.

https://www.basementsystems.ca/crawl-spa...rison.html

Of course they are selling a service so it might make sense to seek out other sources of information, but much of what they say makes sense to me.

However, I have a crawl space under my garage and it is vented.  So I am not sure that insulating the walls would have much purpose if the vents let in outside air anyway.

[Cub_Cadet_GT]

I live in small cape cod in NJ, basically the first floor is 4 main rooms (plus bathroom) over a crawlspace basement.  The basement height is enough you can squat or sit up down there (not true "crawl")
I feel like the floors are always cold here-- i've uncovered and refinished the original red-oak floors, so there's no carpet on the first floor.
I was thinking about insulating between the floor joists down in the crawl space to see if this helps.  I am going to use Rockwool--i know it's more expensive, but just seems like a better product.  I will not be throwing gobs of money at this at once- but rather piece-meal it over time.
Do you think it would be more effective to start with the perimeter of the whole house (just doing 4 feet in across the front and back)
or to complete one whole room at a time?
My feet are always cold, unless i'm wearing slippers or shoes-- so i'm hoping to do something that will help alleviate this.

Colin

Around here (VA) every house that has a crawlspace has insulated joists. I have never seen one that is not.

[Robert Adams]

A crawlspace is a short basement and is to be treaded as such. The ideal solution is to encapsulate the crawlspace by sheet foam on the exterior walls and a plastic liner similar to a pool liner that is sealed to the exterior wall and the piers and then you may still require a dehumidifier. Often you can get away with a small residental dehumidifier but it will run allot until the humidity is brought back down to a reasonable amount then it will maintain as needed.

           This is how it's supposed to be done. https://crawlspaceninja.com/crawl-space-encapsulation/  

              https://www.buildingscience.com/document...her-or-out

              I don't know what those guys charge but their work is far better than what I have ever seen here and it is done correctly.

[Snipe Hunter]

There should be insulation between the floor joists. And vertically between the joists at the rim joist. Not sure what the floor of the crawl space is?? Dirt? Concrete? If dirt, it should be completely covered with 6mil plastic sheet and up the walls.

Careful with rock wool as it's much heavier than fiberglass and tends to hold moisture and dry out slower than fiberglass and can fall out much easier. Just make sure you use more hangers. Remember, paper side up.

BTW, Rock Wool is really best suited for sound deadening and won't give you much/if any more insulation value. Might not be "money well spent"..

[Cdshakes]

There should be insulation between the floor joists. And vertically between the joists at the rim joist. Not sure what the floor of the crawl space is?? Dirt? Concrete? If dirt, it should be completely covered with 6mil plastic sheet and up the walls.

Careful with rock wool as it's much heavier than fiberglass and tends to hold moisture and dry out slower than fiberglass and can fall out much easier. Just make sure you use more hangers. Remember, paper side up.

BTW, Rock Wool is really best suited for sound deadening and won't give you much/if any more insulation value. Might not be "money well spent"..

I've done a bit of research on rockwool-- they have a sound deadening version-- "safe and sound"-- it is for sound deadening and fire safety, not much R value.
However, their comfort batt product is slightly higher R value than fiberglass (not by much), but it's much more rigid, so strapping isn't 100% necessary, but the other part is the fact if it gets wet, it dries out and doesn't compress, or lose R value like fiberglass.  It also won't grow mold/mildew like Fiberglass will.

The walls of the foundation are basic cinder block from the 50s, and the floor is rough concrete.  

Colin

[Snipe Hunter]

I've done a bit of research on rockwool-- they have a sound deadening version-- "safe and sound"-- it is for sound deadening and fire safety, not much R value.
However, their comfort batt product is slightly higher R value than fiberglass (not by much), but it's much more rigid, so strapping isn't 100% necessary, but the other part is the fact if it gets wet, it dries out and doesn't compress, or lose R value like fiberglass.  It also won't grow mold/mildew like Fiberglass will.

The walls of the foundation are basic cinder block from the 50s, and the floor is rough concrete.  

Colin

Mold can grow anywhere and on any surface where there's moisture and food. Food can be something as simple as dust. That's why it grows on vinyl window sashes. It's eating dust. Kiln dried lumber is about 8% moisture content out of the oven and can be 19% before it's sold. In a crawl space it can easily be well above that and so is the insulation. Mold will easily grow above 20% MC. That's why the plastic vapor barrier is so important in a crawl space.

[Robert Adams]

I've done a bit of research on rockwool-- they have a sound deadening version-- "safe and sound"-- it is for sound deadening and fire safety, not much R value.
However, their comfort batt product is slightly higher R value than fiberglass (not by much), but it's much more rigid, so strapping isn't 100% necessary, but the other part is the fact if it gets wet, it dries out and doesn't compress, or lose R value like fiberglass.  It also won't grow mold/mildew like Fiberglass will.

The walls of the foundation are basic cinder block from the 50s, and the floor is rough concrete.  

Colin

         The safe and sound is nothing special it is just thinner. It is made for interior sound deadening as when you want to stop sound you do not want the insulation contacting the drywall as that contact transmits sound. 

          If you encapsulate the crawlspace you DO NOT put insulation in the floor joists. Not sure why so few people know how to do crawlspaces correctly. Those links I posted above will tell you everything you want to know about what to do with a crawlspace. Yours sounds like an easy crawlspace to encapsulate. Plastic over the floor and up the walls, foam on the walls and seal all penetrations to the outside.

             All the science is right here. https://www.buildingscience.com/document...rawlspaces

[crokett™]

This must be location dependent. Here, you either insulated between the joists, or you insulate the foundation perimeter and line the floor with plastic, but you don't do both. My county at least prefers that the foundation perimeter is lined rather than insulation in the crawl space. Also, cold floors IMO the insulation won't do much. Heat rises. You're not losing a ton of heat through the floor. A much more effective solution is to figure out how to heat your floors. I've no idea what kind of flooring you have and if there are any products that could go in the crawlspace between joists. In-floor heat is usually done on top of the subfloor and under the flooring.