Insulating the crawl spaces and basement with Batt insulation

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drewdin

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I am going to be Insulating the crawl spaces and basement with Batt insulation, my question is that since I'm using batt insulation how can I prevent it from falling down or getting insulation on everything over time?

Should i put 1/4 blue foam board under it or do something similar? If you want pics let me know but i don't have insulation up yet.

Thanks
 
No, the floor sheeting is a vapour barrier so you want free air flow below the insulation, cut 1 1/2" slats out of 1/4" plywood or if you might have critters you might put up a wire mesh.
 
A house I used to own had a 3 foot crawl space that was 24'x40' and when they did the insulation they stapled string in a criss cross pattern. A lot of work.

Now you can buy pre-cut pieces of wire that are made for you slide up between the joists to hold it in place, or use wood strapping which is cheap.
http://www.homedepot.com/p/Simpson-Strong-Tie-16-in-OC-Insulation-Supports-100-Pack-IS16-R100/100375163

I've also seen where people have added tyvek stapled to the underside of the joists.


The foam board may need to be covered for fire rating.
 
Hi Guys,

My goal is to insulate the crawl spaces and my basement for sound and temperature. That is why i was thinking about putting the blue foam board over the insulation after its up, but i don't want to make something else bad by making the floor sound proof.

So I should not use the blue foam board and just put the insulation in the rafters?

I am just worried that little pieces of insulation would fall over time so I wanted to cover it with something if possible.

The previous owner put blue foam board on the rafters and i removed it, Here is a pic of one of the offending areas i want to insulate. I already put 6mil poly covering the walls and floor.

Thanks

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Part of the problem you are seeing with insulation falling out in bits, is the fact that he installed bits and peices.
Some of the mistakes people make, is not reading the instructions.
Often you find that the small areas people just stuff in scraps. They should be carefully cut 1" to wide for the space
Joists that are 16" on center have a gap of 141/2 and the insulation for that are a little bigger, but if you measure those gaps, they can be all over the place and there should be a bag of wider insulation for fitting the wider gaps. If done right you will have very little fall out.
 
Typically the blue board is covered with siding but I don't know if it has to be covered. One side of it is covered with aluminum which should face the heated space, or up in your case.
But given that you're installing insulation, of what R value I don't know, adding more rigid insulation may not have any value.
You don't typically lose a lot of heat through the floor. There's probably no sound reducing value to the rigid foam and given it's a crawl space is noise even a real issue?
 
I have removed all insulation from the crawl space, no pink or blue foam board. I plan on doing it right and wanted to see what the best way is. The sound is only an issue as my boiler is very loud, i can hear it kick on when I'm in the room above and it resonates. I plan on at the very least insulating the floor joists, the blue foam was an overkill attempt at sound dampening, unless the effects are useless.
 
I am going to be Insulating the crawl spaces and basement with Batt insulation, my question is that since I'm using batt insulation how can I prevent it from falling down or getting insulation on everything over time?

Should i put 1/4 blue foam board under it or do something similar? If you want pics let me know but i don't have insulation up yet.

Thanks

The first Law of Thermodynamics is: heat always moves from hot to cold.

I assume that you really want to keep the heat inside your living space?

Presumably the crawl space is cold and not used for living?

So the heat moves from your living space, into the floor by radiation and conduction then into the joists and then the cold air inside the crawl space, the crawl space walls and floor.

To get the best result, keep the heat in your living space, the insulation must be above the floor. That means sheets of closed cell insulation, like polystyrene, laid on the existing floor with a fully floating floor on top.

Placing insulation below the floor, is an almost complete waste of money and time, as wood is not a good insulation, and your expensive heat is quickly passed into the joists, cold outside air, crawl space walls and ground.
 
If what I am seeing in that picture is like everything else in the crawl space then you need to get rid of that dry wall that is doing nothing but trapping moist air.

You need to pull all that down, strip it all to bare wood joist.
Lay down a 12 Mil Poly vapor barrier on the ground sealed to the walls, then put up Polyiso Foam Board on the walls leaving about a 3" gap between foam and joist band for Termite Inspection gap which is required in many states.
The Polyiso foam board should be at least R 10 which usually means close to 2" thick.
The blue foam you are talking about I think is maybe R5 at best.

If your HVAC is in the crawlspace then cut a hole in the plenum and install a vent to "condition" the space.
That way it stays bone dry and the insulation is on the walls where it is supposed to be, all your wood joist stay dry and mildew free.

Any vents should be sealed
 
I'm actually doing this project soon, the crawl spaces are off of the basement, the boiler kicks on and its wicked loud. When I'm in the room above the crawl space i can hear the boiler loud.

Not only do i want to keep the heat in the room above, i want to block the boiler noise from working its way up.

I want to insulate the walls and the floor joists if its worth it.

Thanks
 
If you feel you must insulate he joist I would use spray foam, better insulating, better sound proofing and it wont trap moisture.
 
Spray foam is pretty expensive, is it worth it?
 
It does stay put and does not take on moisture, closed cell. We have had a lot of discussion here on different threads. Do your research.
 
Spray foam is pretty expensive, is it worth it?

It is ridiculously expensive, in fact I think its a full blown scam because the actual chemicals used to make the foam simply can not be that expensive to manufacture and obviously actually applying it is far easier and quicker than any other form of insulation.

The manufacturer's simply charge as much as the market could possibly bear.
Even the DIY spray foam systems are actually MORE expensive than having a contractor do it.

Is it "worth it" probably not.

Is it the best? Yes

You can get close to spray foam by buying polyiso rigid foam board and cutting it to size to fit and then spray foaming that into place.
That is a poor mans spray foam but labor intensive.

It is what I did around by entire band joist.

[ame]https://www.youtube.com/watch?v=i1guAwzyEOQ[/ame]
 
They actually make a caulk for goiing around ridged foam. I think the stuff in the can spay is open cell?
 
They actually make a caulk for goiing around ridged foam. I think the stuff in the can spay is open cell?

I only use the "Great Stuff FireBlock Foam" it is both closed cell, water resistant, has very good adhesion holds the rigid foam VERY tightly, good insulation and is fire resistant to boot.
Also one 16oz can does the same job of 20+ tubes of caulk.
Make certain that you use some kind of glove when you use this foam, if you get it on your skin it is THERE until it wears off days later, nothing takes it off.

http://building.dow.com/na/en/products/sealants/fireblock.htm

I spray foamed ALL of my polyiso insulation around the top and both sides behind it at least an inch or two, left the bottom unsealed just in case any moisture gets behind the insulation its not trapped and can just drip to the ground under the polyethylene.
I left a 1/4" gap in between the foam sheets and filled it with the fireblock foam to make a tight seal, since the edges are bare foam the adhesion is rock solid and virtually forms one solid sheet, then I trim the excess off flush and then tape over it with high quality aluminum tape Nashua Cold Weather.
So it is literally like one solid sheet of 2" thick R13 foam around all the perimeter walls.
I used the fireblock foam to also seal every point where plumbing pipes, electrical wires, HVAC ducts and floor registers go through the floor, plus on the thin metal registers I completely covered them in about 2" of fireblock foam so no metal is exposed. They should really make these registers double walled polypropylene with insulation in between, pretty stupid to make them out of thin galvanized metal that sweats like crazy.
I also covered the cement block and brick walls with boric acid powder prior to installing the foam boards that should keep any possible bug problems at bay at least for a few years.

It is so dry under there now I don't think there is much chance of any termites, especially since even when it was a rain forest cave hot and humid and dripping wet we never had termites for the 20 years we have lived here which is surprising since many of our neighbors have had termites and we certainly had prime conditions for them before the encapsulation.

Top pic is what one corner looked like when I started, after repointing and then covering with 3 coats of the Portland Sunny Dry waterproofing, one end of the French Drain is seen and you can tell the soil is soaking wet and insulation in the joist is worthless wet manure.
Bottom is what that same corner looked like after encapsulation.

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Few more pics of various parts during and after.

In earlier ones you can see how soaking wet the soil is, I let it dry out after I closed all the vents and opened up a HVAC vent to condition dry out the air before I put down the Polyethylene.
You can see how steep the incline is also which made it a bit tricky to cut the foam boards to fit and also to lay down the Polyethylene especially by myself.

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Nice job with the insulation, I put unfaced batts in the floor joists and now im going to put 2" closed cell foil faced foam board on the walls using the fire block suggestion above. Only half done but crawling on the floor in 2 feet of space is my favorite!
 

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