# rigid foam insulation



## Bob Mariani (Dec 1, 2008)

tape the joints and seal the edges and gaps with spray foam. extruded polystyrene (XPS) is the correct insulation to use.


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## ccarlisle (Jul 2, 2008)

I think it matters a great deal where you are because most of us in the same zone are more familiar with our own building codes that the other codes...Look, I personally think they are equivalent, the blue being Dow's STYROFOAM board and the pink being Owens Corning's and I think there is a good reason they're different colours...differentiation.

At one time, Dow and Corning had a closer relationship than they do now. After the Dow Corning 'silicone' public relation nightmare, Dow distanced itself from the "Corning" name and presumably agreed to a deal that would allow Dow's technology to find an amiable "competitor". Enter Owens glass and hence Owens Corning. I'm probably way off the mark but I used to work for Dow Corning silicones (back in the day) when the breast implant scare came about. True or false, eveyone tried to disown Dow Corning without trashing their name. So Corning was sacrificed and the other divisions let to prosper.

So, I imagine it's "I'll make a pink one, you make a blue one" and we'll sell at the same price". But one will have deals on one week, the other the next...but the technology is the same, the marketing may be too, so it's six of one, half a dozen of the other, as they say.


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## ctkeebler (Nov 8, 2009)

They are both XPS, the owens corning is available at the big orange store, the dow is at a local lumber yard. I try to support the local guy, but at 5.00 more per sheet and needing 20 sheets, that a big difference.

What type of glue do I use to attach the boards to the cement foundation and do I have to use other mechanical means?

Also if I frame the wall outside of the rigid foam insulation and they put up sheet rock, do I have to fill that void, between the foam insulation and the sheetrock?

Thanks

Tom


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## fubar79 (Nov 5, 2009)

From what I've read, no you don't have to fill the void. But you can fill it with another insulation to bring up the R value since the rigid is usually rated 1"=R5. Just depends what R value you want, and how much $$$ you want to spend.


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## dave11 (Mar 16, 2009)

I might be remembering this wrong, but I believe it used to be said that the blue board acts as at least a partial vapor barrier. The pink stuff was reported to be vapor permeable. This would make a difference if moisture is an issue. The blue board also has a radiant insulating layer, which also can be useful.


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## ctkeebler (Nov 8, 2009)

dave11 said:


> I might be remembering this wrong, but I believe it used to be said that the blue board acts as at least a partial vapor barrier. The pink stuff was reported to be vapor permeable. This would make a difference if moisture is an issue. The blue board also has a radiant insulating layer, which also can be useful.



Dave,

I am not sure, but I copied this from the owens site" High-performance FOAMULAR 250 works to: Retard the transmission of water vapor
and moisture in masonry walls, helping prevent structural damage

I just have to make sure it does not come into contact with the hot water pipes that run in cavity between the sill plate the the concrete foundation. 

Does anybody know how far away from hot water pipes. I understand it cannot come into contact, but is there a recommended or common sense distance. 

"FOAMULAR insulation is ideal for all buildings under normal temperature
conditions, but should not be used in contact with chimneys, heater vents,
steam pipes or other surfaces where temperatures exceed 150 °F. It is not
recommended for applications where sustained temperatures exceed 165 °F.

Thanks


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## dave11 (Mar 16, 2009)

ctkeebler said:


> Dave,
> 
> I am not sure, but I copied this from the owens site" High-performance FOAMULAR 250 works to: Retard the transmission of water vapor
> and moisture in masonry walls, helping prevent structural damage
> ...


Yes, I think Foamular is a vapor retarder, but I also think the blue stuff is a vapor barrier, which is different. In other words, pink will slow down moisture but allow to pass, whereas blue will stop it altogether. This would be an issue if you were installing in areas where moisture needs to pass through, or where a vapor barrier was not allowed or recommended.


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## Bob Mariani (Dec 1, 2008)

in a basement you will want the water to move both in and out. No vapor barrier. Do not fill the void. This is used as an airspace to allow the wall to dry if it ever encounters a wet condition. Use kraft faced batt insulation in the stud wall. Residential heat pipes and water pipes do not get hot enough to harm this insulation. If you are concerned with it, then cut around the pipes and use fire retardant spray foam to seal these areas.


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## ctkeebler (Nov 8, 2009)

Bob Mariani said:


> in a basement you will want the water to move both in and out. No vapor barrier. Do not fill the void. This is used as an airspace to allow the wall to dry if it ever encounters a wet condition. Use kraft faced batt insulation in the stud wall. Residential heat pipes and water pipes do not get hot enough to harm this insulation. If you are concerned with it, then cut around the pipes and use fire retardant spray foam to seal these areas.


Bob, are you saying use the Batts instead of the rigid foam? or use the pink foam as it allows the water to flow back and forth and fill the void with kraft faced insulation. 

I just want to make sure its done right. My basement was finished when I bought the house, but discovered mold behind the sheet rock and the non pressure treated sill plates all rotted.

Thanks


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## Gary in WA (Mar 11, 2009)

The blue and the pink are as *ccarlisle* said, same but different color. Both are rated at 1.1 permeability, a vapor retarder. This is what you want against the concrete wall. Neither one stops vapor as a vapor barrier. 

http://www.dow.com/PublishedLiterat...foam/pdfs/noreg/179-04454.pdf&fromPage=GetDoc

http://insulation.owenscorning.com/WorkArea/linkit.aspx?LinkIdentifier=id&ItemID=788

The unit of measurement typically used in characterizing the water vapor permeance of materials is the “perm.” Several classes of vapor retarders are further defined as follows [4]:


Class I Vapor Retarder: 0.1 perm or less
Class II Vapor Retarder: 1.0 perm or less and greater than 0.1 perm
Class III Vapor Retarder: *10 perm or less and greater than 1.0 perm*
Test Procedure for vapor retarders: ASTM E-96 Test Method A (the desiccant method or dry cup method)
 Finally, a vapor barrier is defined as:


Vapor Barrier: A Class I vapor retarder.
 Materials can be separated into four general classes based on their permeance [4]:


Vapor impermeable: 0.1 perm or less
Vapor semi-impermeable: 1.0 perm or less and greater than 0.1 perm
*Vapor semi-permeable: 10 perms or less and greater than 1.0 perm*
Vapor permeable: greater than 10 perms From: http://www.buildingscience.com/docu...rol-for-new-residential-buildings?full_view=1
 Be safe, Gary


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## dave11 (Mar 16, 2009)

Regarding the type of blue Dow product, I was assuming the original post was comparing pink and blue at the box stores, and here, the only blue board I've seen is Dow's Super Tuff-R, which has a perm rating less than 0.03, which makes it a vapor barrier.


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## Gary in WA (Mar 11, 2009)

" Both are *2 inches thick *and offer *r value of 10*." In original post. So *1" would be R-5,* the FOAMULAR 250, as in my sited reference. Not the foil and poly faced R-6.5, with the perm of .03 as you correctly stated. It can be confusing with a dozen different boards and applications from the same company: 
http://building.dow.com/na/en/products/insulation/rigidfoam.htm

http://building.dow.com/na/en/products/insulation/supertuffr.htm 



Be safe, Gary


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## Bob Mariani (Dec 1, 2008)

I am saying to use the rigid against the foundation wall. It will keep the wall warm enough not to sweat. It acts as a capillary break, not as a vapor barrier. Then the 1/2"-1" air space. Then the wall. Between the stud spacing use kraft face insulation. You need to follow code requirements for R-Value once you finish the basement. The 2" foam is not enough R-Value. So you need both.


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## ctkeebler (Nov 8, 2009)

Bob Mariani said:


> I am saying to use the rigid against the foundation wall. It will keep the wall warm enough not to sweat. It acts as a capillary break, not as a vapor barrier. Then the 1/2"-1" air space. Then the wall. Between the stud spacing use kraft face insulation. You need to follow code requirements for R-Value once you finish the basement. The 2" foam is not enough R-Value. So you need both.


Thanks for the clarification. Can I just cut the rigid into 15 inch wide pieces and put them into wall instead of using the batts? It may be more money, but I would be eliminating the possibility of mold growth correct?

The only issue I would see if trying to put the rigid where the electrical wires run. As the wires run about in the middle of the stud there would have to be alot of slack in the wire to run infront or behind the rigid foam board and Im not sure if that is even allowed.

It looks like R-11 is the lowest R value I can buy, plus the r-10 from the foam, puts me at a the upper limits of whats recommended R-21 in the cavity and R-19 recommended. I guess its better to have more than not enough? ( I live in Connecticut if that makes a difference or helps)

Thanks

I


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## ccarlisle (Jul 2, 2008)

The addition of insulation, whether it's xps or fibreglass, doesn't alone affect the level of mould you may or may not have...are you saying you have mould? or are you just worried about its future growth.

If you already have visible mould, then lowering the relative humidty in that area will reduce it and you can do that by increasing the ventilation in the basement. Moulds love stagnant air...If you are worried about getting mould but there's no sign of any now, then the above still applies. But applying insulation layers just prevents your inside warm air from getting out and to the colder areas, say a concrete foundation wall, and must be a part of an entire overall approach. 

Same for vapour retarders and vapour barriers; what you need in _your_ situation could be quite different from your neighbours', although you are both in the same climate zone. It depends on the structure of your house and the basement walls. You can't take a piecemeal approach to conserving energy, in has to be looked at as an _assembly_ of components and changing one has an effect on the others. 

Neither xps nor fibreglass support mould growth; humidity and a source of food, do and if both of those are readily available, then mould will thrive anywhere. Mould often eat mildew too. But remove or lower the humidity level and the moisture, and the mould, go elsewhere.


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## Bob Mariani (Dec 1, 2008)

I'm in CT also. Not sure what you are attempting here. The board needs to be against the foundation wall. Then an air space. Then the stud wall. so wiring can be inside this air space. So foam or batts in the walls will work. Electrical will not come into play as an issue. But sealing the insulation in the stud wall is tough. If you go this way I use metal studs. Place one stud in place, then insert the ins. board, then the next stud against it. Much easier, much safer, straighter wall. A little better is better. Overkill will never yield a return on the cost.


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## Gary in WA (Mar 11, 2009)

"Also what type of tape do I use to seal the seams where the boards meet?" ------ If the joints are too tight for foam, use cold-climate tape or foil tape: http://www.lowes.com/lowes/lkn?action=productDetail&productId=96179-1410-T96A&lpage=none http://www.lowes.com/lowes/lkn?action=productDetail&productId=135512-56291-FT210&lpage=none
Be safe, Gary


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## ctkeebler (Nov 8, 2009)

Bob Mariani said:


> I'm in CT also. Not sure what you are attempting here. The board needs to be against the foundation wall. Then an air space. Then the stud wall. so wiring can be inside this air space. So foam or batts in the walls will work. Electrical will not come into play as an issue. But sealing the insulation in the stud wall is tough. If you go this way I use metal studs. Place one stud in place, then insert the ins. board, then the next stud against it. Much easier, much safer, straighter wall. A little better is better. Overkill will never yield a return on the cost.


Bob, it makes sense, I was thinking the air space was the space between the studs in the wall. But now I see you mean a space between the stud wall and the foam boards.

Then the wiring will actually be behind the studded wall, not through the studs are in a traditional wall where the cavity is filled with batts.


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## Bob Mariani (Dec 1, 2008)

yes now you get it.


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## ctkeebler (Nov 8, 2009)

Bob Mariani said:


> yes now you get it.



Took awhile. Thanks, but one last (hopefully) question

How do you attach the wires to the back side of the studded wall?


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## Bob Mariani (Dec 1, 2008)

with staples? Normally I staple above or below the box and that is all. Technically the rest is fished in a void in the wall space and as such it does not need to be fastened.


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## ctkeebler (Nov 8, 2009)

Bob Mariani said:


> with staples? Normally I staple above or below the box and that is all. Technically the rest is fished in a void in the wall space and as such it does not need to be fastened.



Sorry, I know you stable above or below for code, what I meant and it wasnt clear, but you covered it, I didnt know if the wire needed to be fastened in the the air space. So you basically use the air space as the holes in the studs, into the box back out into the void then back into the box like a weave?


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## Scuba_Dave (Jan 16, 2009)

You can attach the electric wire at the side of the stud towards the back
With an 8' wall by code you are supposed to have a staple in there
It would really suck to have an Inspector make an issue of that


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## Gary in WA (Mar 11, 2009)

NEC 334.30 and 334.17 Type NM (nonmetallic) cable shall be secured at intervals not
exceeding 4.5 feet and within 12 inches of each box. When a single gang box 2-1/4” x 4”
or smaller is used without a cable clamp, the cable shall be secured within 8” measured
along the sheath.
Be safe, Gary


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