# Insulating the crawl spaces and basement with Batt insulation



## drewdin (Apr 28, 2014)

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


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## nealtw (Apr 28, 2014)

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.


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## beachguy005 (Apr 28, 2014)

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.


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## drewdin (Apr 29, 2014)

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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## nealtw (Apr 29, 2014)

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.


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## beachguy005 (Apr 29, 2014)

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?


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## drewdin (Apr 30, 2014)

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.


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## nealtw (Apr 30, 2014)

Perhaps you could build a cover for the boiler. Might have code requirments


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## drewdin (May 1, 2014)

nealtw said:


> Perhaps you could build a cover for the boiler. Might have code requirments




Didn't pass the wife's code requirements....


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## Perry525 (May 23, 2014)

drewdin said:


> 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.


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## nunyabiz1 (Oct 30, 2014)

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


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## drewdin (Oct 31, 2014)

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


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## nunyabiz1 (Oct 31, 2014)

If you feel you must insulate he joist I would use spray foam, better insulating, better sound proofing and it wont trap moisture.


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## drewdin (Nov 3, 2014)

Spray foam is pretty expensive, is it worth it?


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## nealtw (Nov 3, 2014)

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.


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## nunyabiz1 (Nov 3, 2014)

drewdin said:


> 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]


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## nealtw (Nov 3, 2014)

They actually make a caulk for goiing around ridged foam. I think the stuff in the can spay is open cell?


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## nunyabiz1 (Nov 4, 2014)

nealtw said:


> 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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## nunyabiz1 (Nov 4, 2014)

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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## drewdin (Nov 10, 2014)

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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## nunyabiz1 (Nov 10, 2014)

drewdin said:


> 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!




Thanks.

I assume that you do not have your HVAC unit in the crawlspace? You got a 'Boiler"?  not exactly sure how that works but I assume it heats water and runs it through a piping system and radiators through the house? Maybe there is a way to add a radiator in the crawlspace for winter?
BTW it would seem that boiler noise would be sort of impossible to abate because the noise will just go through all that piping and water, but I don't know never been in a house with a boiler.

If you did then you would be much better off NOT putting the batting in the floor joist, just insulate the walls.
The reason the old owner had his insulation fall out is because he did not put down a vapor barrier on the ground, thus the insulation became soaking wet and falls down like a horror movie.
The batting is held in place with just a straight piece of wire called Wire Insulation Stays that you bend and stick in between the joist with the bend going up.
But if the batting gets wet it doesn't matter what you do its going to fall out in chunks of wet moldy mess.
Plus the R19 turns into about R1 once wet.
Its also a mouse and varment haven.

You probably would have been better off spending the money you spent on the floor joist insulation just adding it to the wall insulation to get higher R-value foil covered polyiso rigid foam board.
But whatever you do, make sure that the Polyethylene sheeting you put on the ground is sealed everywhere so that you have less humidity up under there, if not then your batting insulation will be crap within 2 years.

Also you might wish to get a Radon test done just for the hell of it if you haven't already.
I just ordered two from our local State Radon Program so was only $10.68 for two test.
You can find them here IF your state has any.
If not then they are still only about $15 each and if you are in either Worcester, Middlesex or Essex counties then chances are good that you might have high radon levels.

http://www.epa.gov/radon/states/massachusetts.html

I am in a "Orange" zone so odds are pretty good ours might be high also, I will find out in a few weeks.

Good luck.


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## drewdin (Nov 10, 2014)

I have a oil hot water and heater, forced hot water with baseboard. The pipes do run through the crawl spaces, three total. two 10'x10' and one in the middle thats 8'x8'.

Right now I insulated the rim joists, i do plan on insulating the walls with closed cell foil faced foam board. Thats my project this weekend.

the three crawl spaces only have the old window openings as access's but they do not have any openings to each other. There humid and stinky. I have read that since they all have access to the basement but do not have any way for air to circulate, thats why its humid and stinks.

I drilled a few 4" holes between the spaces and i planned on putting some computer fans to circulate the air between them.

Any other suggestions? thanks!


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## nunyabiz1 (Nov 11, 2014)

So you have 3 "Separate" crawl spaces?  Never heard of such a thing.

Ah, so just the "Rim joist" the little box end is all the joist part you have insulated then? Thats good, although frankly the rigid foam sealed with the spray fire foam would have done better for you I believe.
You ripped down all that manure, old batting and drywall that was seen in the one picture you posted?

It is humid and stinks because warm humid air is allowed to enter OR is created by the boiler and condense.

What did you drill through to open up the 4" holes between spaces?  What kind of wall is it? Does it even need to have these walls between the spaces?
I am having a hard time trying to picture your crawlspace and why its built that way.
I assume this is probably a really old house, like maybe 75+ years?

Best thing I can tell you without being able to see the situation is to just make sure that you use very high quality polyethylene on the ground and seal it tight to the walls and anything else to keep down the water vapor as much as 6mil can manage.
Insulate the walls as best you can, including these "windows" of which I guess is your entrance to each one.
Since you do not have any kind of air circulation under there at all that is kind of a problem.
You are in "Boston" right?

Just how humid is it in Boston?  In your area I would think it would not be nearly the same as down here in the south where the humidity is insane most of the time.
But since you have zero air circulation even IN your house because you have a boiler that just radiates heat and I guess does the same from those pipes in the crawlspace then you have kind of a strange situation.
It would be nice to get some kind of air circulation under there but in your case it would have to come from outside and if you do that then you completely defeat the reason to insulate the walls of the crawlspace because you are literally pumping in cold or hot air at exactly the wrong time, meaning pumping in cold in the winter and hot in the summer and none of it conditioned air.

Your best bet "might" be to seal everything up tight as you can, insulate best you can on the walls and then install a "Dehumidifier" in the crawlspace and open up the walls in between the 3 spaces as much as possible.
IF the 3 pipes of the boiler heat the crawl space in the winter then NOT insulating your floor joist should be fine, IF there is zero heat coming from it then you are going to get coldarse floors probably.
I would think that this boiler has GOT to put out some heat though, but also since it is heating WATER its also probably creating its own humidity.
Thus the dehumidifier may be necessary to keep the space dry.

In my crawlspace it stays between 68 to 72, period, I was under there yesterday morning and it was 32 degrees outside and was warm, toasty and dry under there because our furnace was running.


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## inspectorD (Nov 12, 2014)

nunyabiz1 said:


> I would think that this boiler has GOT to put out some heat though, but also since it is heating WATER its also probably creating its own humidity.
> Thus the dehumidifier may be necessary to keep the space dry.



great advice, let me just add this, The water boiler is a closed system and will not cause condensation issues when it is used in the winter,,, cuz there is usually no humidity in the air when the boiler is being used because there is no vapor created by the boiler.. it's all contained in copper pipes..It actually helps dries things out in the winter too much sometimes. Boston can be a humid area along the ocean in the summer, but never in the winter.
This sounds like you have water vapor from somewhere , and it needs to be controlled. The DeHumidifier that Nun suggested also needs to be sized to keep up with your space in the summer months. I'm sure there is a chart around here somewhere... good luck!


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## nunyabiz1 (Nov 12, 2014)

inspectorD said:


> great advice, let me just add this, The water boiler is a closed system and will not cause condensation issues when it is used in the winter,,, cuz there is usually no humidity in the air when the boiler is being used because there is no vapor created by the boiler.. it's all contained in copper pipes..It actually helps dries things out in the winter too much sometimes. Boston can be a humid area along the ocean in the summer, but never in the winter.
> This sounds like you have water vapor from somewhere , and it needs to be controlled. The DeHumidifier that Nun suggested also needs to be sized to keep up with your space in the summer months. I'm sure there is a chart around here somewhere... good luck!



Thats good, I had no idea about a boiler, in my 55 years I have never laid eyes on one let alone lived in a house with a boiler.  So it is totally "closed" system then at the boiler itself?
If those pipes in the crawlspace both heat and dry out the space then he should be golden at least in the winter.
Might need a dehumidifier in the summer though.

We were fortunate that both our heating and AC are in the crawlspace so heating, cooling, conditioning the air was as simple as cutting a single hole in the plenum and installing a self closing flapper vent.


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## slownsteady (Nov 12, 2014)

Don't forget that you need combustion air for the boiler. Don't seal it so tight that you can't keep it lit.


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## nunyabiz1 (Nov 13, 2014)

slownsteady said:


> Don't forget that you need combustion air for the boiler. Don't seal it so tight that you can't keep it lit.



Yep, forgot about that, our crawlspace is HUGE so way more than enough combustible air for our furnace, plus I do have one small opening where the dryer vent exits to allow for some air both in or out which ever it needs.


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## nealtw (Nov 13, 2014)

nunyabiz1 said:


> Yep, forgot about that, our crawlspace is HUGE so way more than enough combustible air for our furnace, plus I do have one small opening where the dryer vent exits to allow for some air both in or out which ever it needs.



Your combustion air should have it's own vent and duct to close to the furnace and it should not be close to the dryer vent as it will pull that moisture that you don't want.


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## nunyabiz1 (Nov 13, 2014)

nealtw said:


> Your combustion air should have it's own vent and duct to close to the furnace and it should not be close to the dryer vent as it will pull that moisture that you don't want.




Yeah the outgoing vent for the furnace goes through the wall and is sealed tight.
The dryer vent is at least 20 feet away and about 10 feet above where the Furnace gets its combustible air  from.
 It gets that air from the crawlspace not from a incoming vent from outside.
But our crawlspace is unusually large, it is approx 9360 Cubic Feet of air and our Furnace which is a 93,000BTUh 92AFLUE which requires 4650 cubic feet of combustible air.
So basically it has almost exactly double what it needs.

So it meets the "Unconfined Space" requirement with no problem.
The other is the "Unusually tight construction" that is somewhat iffy because it IS sealed tight as a drum, all the crawlspace vents sealed tight, every tiny orifice where plumbing or electrical or ducts go up through the floor are all sealed with spray fire foam, 12Mil Polyethylene on the ground and 2+ feet up the walls plus 2" thick Polyiso foam insulation tightly sealed to the walls.

All except for ONE opening that is at the top of the about 10 foot high wall in the back corner where the dryer vent exits, (that is about 4"x9" with the dryer vent taking up much of that space) plus about 4 inches below that opening was one of the small size about 12"x6" or whatever that small size crawlspace vent size is, on that one small vent I do have a "Removable" piece of 2" thick rigid foam insulation that I can if needed remove in the winter to allow more Combustible air to enter if needed.

That I would think would negate that "Unusually tight construction" which is everywhere else, I mean if air starts to be used and a negative pressure starts then it should just pull the needed air in through that opening around the dryer vent. Although that should never happen because when the furnace is running it is blowing air INTO the crawlspace in order to heat and condition it, so I do not think its even possible to have negative pressure if anything it might be slightly positive.

Also in the winter we pretty much keep our house in the mid 60s, both my wife and I prefer the house quite cool.
Our furnace hardly ever runs until it gets in the 20s outside.

I know technically we probably "should" go ahead and install a incoming air vent, but I do not think it is really necessary with such a large cubic foot space that does have some air able to come in.

What do you think?


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## nealtw (Nov 13, 2014)

One of the problems with a sealed crawlspace is the chance that if ever you get enough to start mold growth or even rust on metal objects is that oxigen can be used up, so in the dead of winter, if the furnace quits leave the door open for a few before you charge in there.
Keep in mind that when a new house is built they are very tight these days, a fresh air vent is installed to a centrel hallway to allow air to be replaced as it is being used up by people, plants, and exhaust fans. 

Your crawlspace sounds more like a well sealed and insulated basement.
On the other side, you have done a great job of firestopping the house from the crawspace.


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## drewdin (Nov 14, 2014)

Im going to post a drawing or picture of the three crawl spaces so you guys can see what I'm working with. I purchased the 2" polyiso foil face board this AM so my project for Saturday is ready.

We got 1" of snow today, not that bad but its expected to be 10 degrees next week and keep getting colder. Winter has begun!


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## nunyabiz1 (Nov 14, 2014)

drewdin said:


> Im going to post a drawing or picture of the three crawl spaces so you guys can see what I'm working with. I purchased the 2" polyiso foil face board this AM so my project for Saturday is ready.
> 
> We got 1" of snow today, not that bad but its expected to be 10 degrees next week and keep getting colder. Winter has begun!




Cool.
What are the walls of your crawlspace made of that you are installing the rigid foam insulation on?
If it is cinder blocks, bricks, stone etc then you should use Tapcons with large stainless fender washers.
you will need a hammer drill to drill those holes as a regular drill is utterly worthless drilling masonry, will take about 10+ minutes per hole and by the time you done the hole is useless because it is so wallowed out.
Hammer drill takes about 2-3 seconds and hole is perfect.

Also what I did was to liberally spread Boric Acid powder and Diatomaceous Earth all over the walls as much as I could to stick into every little crack in order to kill, deter whatever bug might decide to try to take up residence behind those boards.
Then put a bead of fire foam about an inch or two inside the outer edge of the top and both left and right sides leaving the bottom open then put the board on and screw in the Tapcons to hold it tight then the foam expands  to usually past the edge and seals top and sides tight. I go around the top with an extra bead of fire foam after all of them are in place.
Also not sure about Boston but here in my area code requirement is you must leave a 3" gap at the top between the insulation and the joist band for termite inspection, also leave about 3" or so gap at the bottom plus I used quality foil tape to seal all exposed foam edges and the seams between boards. 
I leave the bottom open, not sealed with spray foam just in case any moisture gets behind there it will be not be trapped will just drip out the bottom and under the polyethylene.


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## drewdin (Nov 16, 2014)

Thanks for the suggestions, I followed them to a T.

The crawl spaces have cinderblock walls, I did make one mistake buring the process, hopefully its not a big deal. Since its dark in the crawl space and I only had a head light on, when i put the foam board up i had it reversed in two sections before i realized it was backwards. I had the metal foil facing the cinderblock and the plastic facing the inside of the space. It was too late to reverse them as they were glued and screwed.

I hope this isn't a big mistake, but one i realized after i had it done. How big of a deal do you think this is?

Thanks


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## nunyabiz1 (Nov 17, 2014)

drewdin said:


> Thanks for the suggestions, I followed them to a T.
> 
> The crawl spaces have cinderblock walls, I did make one mistake buring the process, hopefully its not a big deal. Since its dark in the crawl space and I only had a head light on, when i put the foam board up i had it reversed in two sections before i realized it was backwards. I had the metal foil facing the cinderblock and the plastic facing the inside of the space. It was too late to reverse them as they were glued and screwed.
> 
> ...



Well it certainly isn't optimal, but really shouldn't make any real difference.
The only difference it would make would be code wise to an observant home inspector and that would only be IF your crawlspace is considered "conditioned" (which yours is NOT unless I am mistaken) which would mean it would need a 15 minute Thermal Barrier and that is IF the Polyiso insulation you bought has a 15 min thermal barrier on the foil side.
A few do have the thermal barrier, most do not.

The particular insulation I bought was the Rmax TSX8500 which does have at least a 15 minute thermal barrier on one side.
Not sure what is available now but 1 year ago there were only 2 such foam insulation sheets that passed the ASTM C 1289 requirements and those were Dow Thermax and Rmax TSX8500.
Here is a memo to building inspectors from the fire marshall in Maine which is probably pretty much the same in most states.
Stating that these two materials met the 15 minute thermal barrier.

http://www.mboia.org/documents/2013/Rigidfoamletter.pdf

If your crawlspace does not need a thermal barrier by code then shouldn't really make any difference I would assume.


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## nealtw (Nov 17, 2014)

If that's a problem just add a couple sheets overtop of those two. Maybe


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## drewdin (Nov 18, 2014)

its 35 bucks for a 4x8 sheet, that's the only problem of covering it up a second time. I have noticed a big difference in the past few days, temp wise


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