Styrofoam insulation in basement

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  #1  
Old 12-08-07, 06:46 PM
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Styrofoam insulation in basement

The one contractor that I was talking to was telling me he would recommend putting styrofoam insulation rather then BAT because of the moisture and mold issues... He said the styrofoam is moisture resistant and would put a sheat before the wall studs against the concreate block and then more once the walls are studded.

Any thoughts on using styrofoam insulation rather then regular BAT or the basement walls
 
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  #2  
Old 12-09-07, 05:05 AM
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Ther correct name for the stuff is EPS(espanded polystyrene) and is better than bat type insulation because it does not soak up water and mold is not an issue. Owens-Corning(pink) and othere make is with indents for furring strips, so it goes directly on the wall and the furring strips(2'OC) both anchor it to the wall(with tapcons) and provide nailers for drywall. I have used it a number of times and it seems to work well for our climate. 2" thinck boards are about R9, if I recall right.
 
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Old 12-09-07, 06:07 AM
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Bat insulation will not cause moisture/mold problems. Bat will be fine. Bat Will not grow mold. That being said I go poly because of the higher R value.
 
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Old 12-09-07, 05:41 PM
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Ok, now I am REALY confused... Ok, if I go to Lowes or home depots website, what do I look up? espanded polystyrene?

The contractor said if the BAT got moisture from condenstation or got wet, then mold could grow and it can be ruined. That is when he mentioned about styrofoam insulation.

He mentioned about attaching to the concreate block first, then frame and then add more once the walls/frames are up. Is that the right/best way to do it? What is the price of this stuff? Is it more then regular BAT?
 
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Old 12-09-07, 06:08 PM
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Fiberglass does not suport mold growth. But once it has gotten wet is very hard to dry out. So it will keep sheetrock etc wet. But if you have that much water chances are you will have to replace sheetrock no matter what type of insulation.
Their are a lot of ways to do it. I have furing stips then a 3/4 stiren then another furring strip. His way is fine but if its under ground like my basement his way is over kill.
 
  #6  
Old 12-09-07, 06:13 PM
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Originally Posted by airman.1994 View Post
Fiberglass does not suport mold growth. But once it has gotten wet is very hard to dry out. So it will keep sheetrock etc wet. But if you have that much water chances are you will have to replace sheetrock no matter what type of insulation.
Their are a lot of ways to do it. I have furing stips then a 3/4 stiren then another furring strip. His way is fine but if its under ground like my basement his way is over kill.
Thanks Airman..

Yes, it is underground... My brother in law mentioned about being an inch away from the concreate block in case of moisture. The contractor mentioned about putting the styrofoam insulation against the block first, and so forth. I have no water issues in the basement. I am going to be dryloking it first so that should help. It is all the Just in case scenerios.

What is the owens corning one called?
 
  #7  
Old 12-09-07, 07:10 PM
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Styrofoam insulation in basement

Fiberglass. by itself does not absorb moisture or suport mold growth. BUT - the dust and dirt in it do support mold and the fiberglass does hold moisture. Because of the structure, it does not dry out unless you take it out, so you might as well throw it away.

When you go to buy your foam, look for EXTRUDED foam (XPS) that is usually tinted pink, blue or yellow depending on the manufacture. Do not use EXPANDED foam (EPS) since that is lighter, has lower insulating values and if only good for coffe cups and cheap coolers that fall apart.

If is too short to tear out everything if you get moisture in fiberglass and have to tear out all your work.
 
  #8  
Old 12-09-07, 08:45 PM
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Originally Posted by Concretemasonry View Post
Fiberglass. by itself does not absorb moisture or suport mold growth. BUT - the dust and dirt in it do support mold and the fiberglass does hold moisture. Because of the structure, it does not dry out unless you take it out, so you might as well throw it away.

When you go to buy your foam, look for EXTRUDED foam (XPS) that is usually tinted pink, blue or yellow depending on the manufacture. Do not use EXPANDED foam (EPS) since that is lighter, has lower insulating values and if only good for coffe cups and cheap coolers that fall apart.

If is too short to tear out everything if you get moisture in fiberglass and have to tear out all your work.

Hi Concreate,

THANKS again for your input...

Do you agree about putting a piece against the concreate block and then attach the studs/frame to that and then add more in between?

What do you recommend?
 
  #9  
Old 12-10-07, 05:27 AM
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There has been a ton of debate about this and I think the jury is still out on the verdict...however, for someone who works in the energy conservation field, I feel the XPS applied directly to the concrete wall is the best way to go. I am in the process of finishing my basement now. Here is what I am doing:

Step#1 - 1" XPS Foamular 250 insulation glued to ALL concrete wall surfaces within the finished area using caulk made specifically for foam boards. I am also installing XPS on the top of the foundation to cap the wall and make sure the walls are 100% covered.

Step#2 - Tape all of the seams using Ventura red tape. You can get this stuff from efi dot org. Although the XPS is tongue and groove its not a prefect seal. For large gaps, and you will likely have some...I used regular caulk then taped.

Step#3 - Frame the walls. Since you have already covered the walls you don't need to keep a gap between the XPS and framing other than for leveling.

I am an energy engineer so my approach is a little overboard though your goal is to prevent warm air from condensing on the cool concrete surfaces. For this reason I am making sure the entire surface is covered and sealed. My local code office is requiring R-13 in the basement so I will use R-11 bat in the framed space to add to the R-5 XPS on the walls. Since I have eliminated the potential for condensation there should be no issues with the bat getting wet other than a flood in the basement.....My code office also wanted the walls sealed with Drylok or something similar but I easily got them to agree to the XPS. I'm not so sure about using that stuff as you should always try to prevent moisture from the outside and not the inside. The drylok will only mask the problem temporarily. I have a friend that used it and it started peeling a few years later...
 
  #10  
Old 12-10-07, 07:17 AM
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Basements, Attics and Crawl Spaces > Styrofoam insulation in basement

I would use Thoroseal rather than Drylok for this application.

Drylok is a paint-type coating, While Thoroseal is a cement-based material that is more compatible with the concrete walls and actually becomes part of the concrete if it is applied to a previously dampened surface as recommended.

Thoroseal is messy to apply and is not as easy to find since it is really a commercial/industrial product that is used in residential.
 
  #11  
Old 12-10-07, 10:50 AM
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Originally Posted by jbrscot View Post
There has been a ton of debate about this and I think the jury is still out on the verdict...however, for someone who works in the energy conservation field, I feel the XPS applied directly to the concrete wall is the best way to go. I am in the process of finishing my basement now. Here is what I am doing:

Step#1 - 1" XPS Foamular 250 insulation glued to ALL concrete wall surfaces within the finished area using caulk made specifically for foam boards. I am also installing XPS on the top of the foundation to cap the wall and make sure the walls are 100% covered.

Step#2 - Tape all of the seams using Ventura red tape. You can get this stuff from efi dot org. Although the XPS is tongue and groove its not a prefect seal. For large gaps, and you will likely have some...I used regular caulk then taped.

Step#3 - Frame the walls. Since you have already covered the walls you don't need to keep a gap between the XPS and framing other than for leveling.

I am an energy engineer so my approach is a little overboard though your goal is to prevent warm air from condensing on the cool concrete surfaces. For this reason I am making sure the entire surface is covered and sealed. My local code office is requiring R-13 in the basement so I will use R-11 bat in the framed space to add to the R-5 XPS on the walls. Since I have eliminated the potential for condensation there should be no issues with the bat getting wet other than a flood in the basement.....My code office also wanted the walls sealed with Drylok or something similar but I easily got them to agree to the XPS. I'm not so sure about using that stuff as you should always try to prevent moisture from the outside and not the inside. The drylok will only mask the problem temporarily. I have a friend that used it and it started peeling a few years later...
Thank you VERY much for your suggestion!!!!

I was going to put the Drylok Extreme on the block first and then have the contractor put that XPS on the concreate block. He will then stud it out and then put more of that XPS but can you put BAT insulation in instead since the XPS will be on the block along with the drylok extreme?
 
  #12  
Old 12-10-07, 11:29 AM
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Styrofoam insulation in basement

If you already have XPS, why in the world do you think you need more insulation in a basement wall? Even in the very cold climates it is hard to justify the insulation because the temperature differential (20 degrees max) between the soil and the interior is so much less than what you are accustomed to above grade (70 to 90 degrees differential).

One more thing to think about as a reality check - most basements are not 100% insulated. Do you insulate the interior basement walls when they separate the finished areas from the unfinished? This is not done because the basement is actually a semi-conditioned space (because it is below grade) and is not unconditioned like an above grade uninsulated space.

Have you ever considered the floor? It is the same temperature as the lower part of your walls and may have more area that your exterior walls.
 
  #13  
Old 12-10-07, 12:23 PM
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I was hoping to get away with only installing 1" XPS on the walls but my code official is requiring R-13 so I have to follow their rules....Like Concretemasonry says there really isn't much need for it since it is underground. My basement temp only varies a few degrees year round with no heat or cooling added. I'm going to use R-11 bat in the framed walls as this will be quicker and cheaper than cutting XPS to fit and the condensation/mold issue should be resolved with the XPS applied directly to the walls.

dcanesdbs, one critical step I left out that I did was to insulate and seal my rim/band joists. The builder had previously insulated the basement ceiling and the rim/band joists with fiberglass. (I'll leave this in the ceiling for sound attenuation) However the insulation at the rim/band joists was barley an inch long and it was not air sealed. I took 2" XPS and cut it to fit the opening with a little gap all around that I filled with foam gap filler in a can. This served to seal the joist area and hold the XPS in place. I'll have a very tight basement when I am done. As a side note, my builder didn't worry about framing very much....There were a ton of gaps between the sill plates and rim/band joist areas that bugs were able to get in. Over the past few weeks I have been completing the rim/band joist sealing. I found hundreds of ladybugs that found their way in and were camping out in the rim/band joist area....Another reason to make sure your basement is sealed!
 
  #14  
Old 12-10-07, 04:35 PM
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I appreciate ALL your advise and comments! Thanks guys..

So, concreate, are you saying if I put XPS on the concreate block, I won't need anymore insulation? As JB stated he is using BAT betwen the studs... I think I might do that as well. Sounds like a good idea...

Floor? Not sure.. I wanted to put carpet, but the contractor said I can have to put it directly on the concreate floor. I don't want to put a subfloor down cause I'll lose headroom.

Any suggestions on that? I want the warm eel down there I would love to mostly have carpet.
 
  #15  
Old 12-10-07, 05:34 PM
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Depends on how much R-value you want or need...I need R-13 per code but would be satisfied with the R-5 I already have with the 1" XPS.

I plan to use delta-fl on the floor and install laminate directly on top of that. I'll use area rugs over that. You can also install carpet on delta-fl but I believe you need to install OSB over it first. Other options are to create your own subfloor or use a prefab system like subflor at Lowes or Dricore from Home Depot though these are fairly expensive and don't provide a good continuous seal.
 
  #16  
Old 12-10-07, 05:58 PM
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Originally Posted by jbrscot View Post
Depends on how much R-value you want or need...I need R-13 per code but would be satisfied with the R-5 I already have with the 1" XPS.

I plan to use delta-fl on the floor and install laminate directly on top of that. I'll use area rugs over that. You can also install carpet on delta-fl but I believe you need to install OSB over it first. Other options are to create your own subfloor or use a prefab system like subflor at Lowes or Dricore from Home Depot though these are fairly expensive and don't provide a good continuous seal.
Thanks JB!

One questions, what is OSB?
 
  #17  
Old 12-10-07, 07:16 PM
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Originally Posted by dcanesdbs View Post
Thanks JB!

One questions, what is OSB?
OSB = oriented strand board, kinda like plywood but stronger
 
  #18  
Old 12-10-07, 09:45 PM
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Originally Posted by jbrscot View Post
There has been a ton of debate about this and I think the jury is still out on the verdict...however, for someone who works in the energy conservation field, I feel the XPS applied directly to the concrete wall is the best way to go. I am in the process of finishing my basement now. Here is what I am doing:

Step#1 - 1" XPS Foamular 250 insulation glued to ALL concrete wall surfaces within the finished area using caulk made specifically for foam boards. I am also installing XPS on the top of the foundation to cap the wall and make sure the walls are 100% covered.

Step#2 - Tape all of the seams using Ventura red tape. You can get this stuff from efi dot org. Although the XPS is tongue and groove its not a prefect seal. For large gaps, and you will likely have some...I used regular caulk then taped.

Step#3 - Frame the walls. Since you have already covered the walls you don't need to keep a gap between the XPS and framing other than for leveling.

I am an energy engineer so my approach is a little overboard though your goal is to prevent warm air from condensing on the cool concrete surfaces. For this reason I am making sure the entire surface is covered and sealed. My local code office is requiring R-13 in the basement so I will use R-11 bat in the framed space to add to the R-5 XPS on the walls. Since I have eliminated the potential for condensation there should be no issues with the bat getting wet other than a flood in the basement.....My code office also wanted the walls sealed with Drylok or something similar but I easily got them to agree to the XPS. I'm not so sure about using that stuff as you should always try to prevent moisture from the outside and not the inside. The drylok will only mask the problem temporarily. I have a friend that used it and it started peeling a few years later...

I am just finishing up my basement project now and used the extruded polystyrene foam board. This project took over a year!

I lived in my new home for a year to make sure the basement was dry. I didn't even put on downspout extensions because I wanted to test the exterior waterproofing agent and drainage/sump pump system. I live in NJ and we had that massive rain last May. I had basically a moat around parts of my house. This is the only time in 2 and a half years the sump pump turned on. But the basement remained dry. I have since fixed some grading issues and extended the downspouts. The sump hasn't turned on since then.

I Dryloked the walls not so much to prevent water intrusion but to act as a vapor barrier of sorts.

Next I put up 1" Foamular 250 using PL300. Taped seams with Tyvex tape. Caulked sill plate seams as you did. I also had the ladybug problem. My local code only requires "insulation" and didn't understand the foam thing but knew I was an engineer so I think they figured it was okay and they passed me.

I have 900 sq ft finished and added 5 supply ducts and one 12" return. Air moves from extremities to the return for good flow. I only have the ducts partially opened or it gets too hot down there compared to the upstairs! The R5 XPS was plenty! I did a heat loss calculation before starting the project and pretty much knew that. I have more thermal loss due to infiltration from my windows down there actually. This is from a "hand test" around the window.

Next I framed, then rock.

I have a humidity meter down there and it's currently 32% and it rained today and has been wet for the last week.

If you are going to put fiberglass in stud spaces I would recommened unfaced batts or you will be losing much of the permeability that the XPS provides.

Good luck!

Mark
 
  #19  
Old 04-15-08, 12:39 PM
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The Home Depot guy's opinion

I went to Home Depot armed with a foolproof moisture resistant basement wall design like this one to do some cost estimating, and when I mentioned my plan to do a layer of 1" EPS (not worried about going to XPS, since BuildingScience.com recommends either/or) on the concrete wall for thermal and moisture control, then frame out a stud wall and infill with mineral wool batt, the guy looked at me like I was nuts... "Why would you do that? Just throw up a stud wall with some faced fiberglass batt insulation and call it a day, its got a vapor barrier".

Any chance this is overkill? I'm in Colorado, which is pretty dry. I do have a humidifier running in the winter, so I still imagine that there is enough moisture to condense on the foundation wall. The local building department recommends a 1" air gap behind a stud wall with batt insulation. I only ask because doing it with the EPS adds quite a bit to the cost.

Also, in my case, I have a structural wood floor with another crawl space underneath the basement for swelling soils. I'm thinking of just insulating with batt along the perimeter walls in the crawl space.The fact that there is about 2' of space below the basement floor gives me comfort in terms of basement flooding and an escape for any condensation that might manage to form between the perimeter stud walls and the foundation wall.

I'm a commercial architect, which is not much better than being an engineer in terms of overdesigning things based on the science and lacking real-construction-world common sense. Any thoughts from any basement veterans? I'll probably be hiring a contractor to do some of the work, so I'm sure he'll also have his two cents to add.

We're planning on sticking around in this house for a while, and even if we weren't I wouldn't want to stick someone with a moldy basement down the road... especially given my profession. However I'm also not made of money.
 
  #20  
Old 04-15-08, 01:33 PM
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Originally Posted by woops View Post
I went to Home Depot armed with a foolproof moisture resistant basement wall design like this one to do some cost estimating, and when I mentioned my plan to do a layer of 1" EPS (not worried about going to XPS, since BuildingScience.com recommends either/or) on the concrete wall for thermal and moisture control, then frame out a stud wall and infill with mineral wool batt, the guy looked at me like I was nuts... "Why would you do that? Just throw up a stud wall with some faced fiberglass batt insulation and call it a day, its got a vapor barrier".
It's your money! Just remember that while it is drier where you are, you are not without moisture in an underground structure. You're also not in a desert. Look at the University of Minnesota research along the same topic. The consensus seems to be that more evidence supports the use of XPS against the wall than not.

As for the Home Depot guy. There was a time when associates working at HD were in the trades. That is far less the case these days. I wouldn't bet my investment on one individual's "opinion" - and that's all it is anyway. But then why would you if you are an engineer. I myself am an engineer by trade and research the hell out of something before I put my hard earned dollar to it. It's one reason why my wife thinks I take too long on projects. From following the posts of some folks here, I would trust the advice from guys like Dick (Concretemasonry). I think his and others have the straight poop on basements.
 
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