First, I live in SE Michigan and live in a 2 year old house.
I am planning on building 2x4 framing my for poured basement walls above an existing subfloor build using Delta-FL and 5/8 osb sheeting. You can see the Delta product here if you've never heard of it:
http://www.deltams.com/deltafl/index.html
Anyhow, I have a 1/4 to 1/2 inch gap between the floor and the outside walls for ventilation and am curious about using a moisture barrier between the framing and the concrete. I'm planning on leaving an inch or so between the studs and the wall.
Should I attach a moisture barrier to the concrete wall (at ground level) to around the bottom of the wall or can I staple the plastic to the backside of the stud wall (not all the way to the top) before putting it in place? My goals are to keep the fiberglass batting away from the concrete as well as keep a continous gap from the edge of the floor to the cieling. More or less my basement will become a "box within a box" with an air gap surrounding the floor and walls.
Does that make sense???
Thanks!

 

zark,

This is an excerpt of one of my prior posts, you can read through the posting for what you feel is appropriate;

The reason to keep the wood out from the walls is the moisture that could damage them. Using larger insulation like R-19 would touch the walls. I have stated before that if a homeowner did put thicker insulation in, and the wall was only 1" from the masonry surface, I recommended hanging a vapor barrier between the back of the wall and masonry surface. This doesn't allow for the insulation to touch the wall and air movement is not restricted but at least you won't create damage to the insulation or wood. If you do want to increase the R value, move the wall out further or use the R-13 and then apply a rigid insulation over the studs (warm side) then drywall (not paneling) *Code advises a 15 minute fire rated material over any rigid insulation - 1/2" Drywall* You can then put paneling over this if desired to met code.

Kraft faced insulation is fine to use in the above scenario. No need for the poly and you can do everything easily. You may find this easier and I would do this versus unfaced and vapor barrier because I don't like to play with it any more than I have to.

Let me add one other thing, rigid insulation used on a concrete/masonry surface is fine. Considerations to make in using this is;

1. If you are just using 1 1/2" rigid and furring strips - A. You need W/T strips to protect the wood. B. The strips can be adhesively applied but they must be solid - mechanical anchors may have to be used to insure that if shelving is installed it will hold. C. Any electrical boxes will have to be shallow - sometimes makes it hard to wire. D. You must use a fire retardant material over this as per Code.

(Most books, articles about rigid and furring strips fail to say anything about the use of W/T and this will get destroyed and be a good source for mold/mildew with the slightest hint of moisture)

2. Alternative which does add cost is to apply full rigid sheets to the concrete/masonry walls, adhesively applied, then place frame wall against the rigid, then insulate between studs and cover with drywall. The rigid does then act as a vapor barrier. Do not tape/seal the seams. This allows it to breath and dry up any condensation that may form.

Check out the other postings within this subject.

Hope this helps!

 

you might want to look in to radiant barrier insulation foil/bubble/foil do a search on it it has some real advantages , you could probably either glue it right to the concrete wall or staple it to the back 1/3 of the studs,it will act as a vapor/radon barrier and would not need to worry about fiberglass insulation /moisture problems. like the delta flooring it is an innovative product worth looking into- i used both in my basement let me know if you have any questions john

 

For insulating the basement walls, does a radiant barrier make more sense than typical fiberglass bats or even rigid foam? I've looked at the foil sandwich products (like Reflectix) that John Wer mentions but I'm confused as to whether the heat lost through a basement wall is mostly radiant (as it would be above grade) or conductive? I like the fact that the foil sandwich works also as a vapor barrier, but is it really as cost effective?

 

JoelS,

You'll have to make a couple of calls and determine the cost difference to justify if you need it. I have my own opinions on this but you evaluate the link which does very well at explaining the use and where to use it.

http://www.we-intl.com/rfoil_faq.html#rvalue

Hope this helps and let us know what you think!

 

JoelS,

I just thought I'd followup with this information on the Bubble Foil product so you get a better understanding on it's use and cost;

The product used within a basement is running approx $.30 per square foot. This is for the eFoil - Double Foil - considered the economy but most used. ***IT CANNOT TOUCH THE MASONRY/CONCRETE WALLS*** This is even if you applied DryLok to the walls. It can however touch the walls if a 6 mil poly vapor barrier is hung to keep any moisture from trouching it. Warranty is 15 years.

R-value is R-14 in a basement but above grade it is reduce to about R-10. It may be used alone or in conjunction with bat

The other product - rFoil is approx. $.38 square foot and is considered their premium foil. Thicker aluminum and plstic bubble. ***IT CANNOT TOUCH THE MASONRY/CONCRETE WALLS*** Warranty is 25 years.

Prices above are for rolls that are 4' x 125' ong (500 SF)

They do make eFoil in 16", staple tab application that runs $.41 per square foot. It is not available in the rFoil application. Sold in similar rolls. This product is not considered a vapor barrier unless all seam are taped.

When you compare the cost of unfaced insulation then use a 6 mill vapor, you are paying approximately $.12 more per SF for the economy foil. $.20 more per SF for the premium foil.

If you have questions talk to Erick Deckers at

WE International, Inc.
PO Box 97
Syracuse, Indiana 46567 USA
Tel: (574) 457-3066
Fax: (574) 457-8807
Email: weexport@we-intl.com

Hope this helps!

 

Doug, thanks for the info. I had visited the rFoil website, but had no idea of the pricing. If I understand your calculations, I'm looking at approx. $0.18/ ft2 for fiberglass and poly. I can get staple-tab Reflectix locally on sale for $0.27/ft2. It's not the better quality stuff, but if is fine to use by itself (I think it is, but I got to check local code), then I may go that route. Would you recommend these foil/bubble/foil products for use by themselves, or only in conjunction with additional bat or rigid. By the way, per Erick at rFoil, they do sell a staple tab product too for $0.41/ft2.

 

JoelS,

I know about the staple product but that get's up there in cost. The Reflectix is similar in cost for the 4' roll product but it climbs when you get into the 2' wide product, like $.50 per SF. I was not able to get a 16" price as this is not used that much, at least around here.

As discussed with a couple of insulating contractors and with Erik, the use of this in a lower level has few advantages versus above grade applications. This is in relationship to R-value, radiant issues within a basement wall. Insulation quality within a basement is R-6.4. The other issue is that the eFoil and rFoil R-Values are determined by other means of testing - Thermal Heat Camera - which doesn't really give you true R value reading.

I would strongly urge the use of it above grade, under crawl spaces, under radiant heat sources where the R value increases significantly and would really keep energy costs down.

I would recommend the use of only the eFoil or rFoil product since it is at a higher R value alone. The Reflectix would not be my choice for lower level applications and if you did, I would urge the use of more insulation. Bear in mind that both products have great advantages but the application for lower level seems to be better suited to eFoil and rFoil. Both have to be away from the block wall though to attain the performance they deliver, which isn't much. The R-values that I mentioned before were for above grade applications, which I should have mentioned. In fact Reflectix has a higher R-value rating for the exterior sidewalls!

In conclusion, I would not use either products within a lower level and since I talked to reflectix as well, it was suggested that it not be used as it's performance is limited...remember "Radiant Barrier" and there is nothing there to radiate except "cold".

This has been an education on its own but I feel better knowing more about there use in lower levels. If a home was a split level, I would definitely use either above grade within the lower level. Reflectix does however outperform the eFoil and rFoil in above grade applications.

Hope this helps!