# Basement insulation



## scfa99 (Oct 13, 2006)

I have a unfinished basement, kids play area, furnace and all mechanicals are down there.

I've heard a lot of people rec'd to insulate unfinished basement.  How will that help the rest of the house?  Also since heat rises if i insulate the ceiling will it be even colder down there and I'll need to worry about it getting too cold since we dont run our furnace very often?

Last question:  what do you rec'd to insulate with?  R13 in the ceiling?  What should I wrap the pipes with?  I'm located in NJ.

Thanks in advance.


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## fbelec (Oct 13, 2006)

i did what you are talking about. initially the basement was very cold i've had it in 40's one cold winter in got down to the upper 30's. anyway i finished 3/4 of the basement two rooms one big room 33 feet and one normal size (my office) up stairs was heated with a old vermont castings defiant. did a good job sometimes to good. when i finished the basement i insulated the walls and left the ceiling. no insulation in the ceiling just sheetrock. since then the basement only drops to 50 to 52 degrees with out heat and upstairs is a lot warmer i have to space out the fires in the stove unless it's real cold out then can run 24/7 or it gets to hot up there. i insulated the wall with R13
and also stuffed some in around the sill where there is a lot of drafts. we don't run the boiler unless the house gets to cold from not loading the stove or we are away. my boiler doesn't throw any heat anyway so that does nothing when it's running.

so long story short i recommend doing it. and the rooms down there will stay cleaner.
i didn't want mold so i didn't put a rug down the floor is cold but that's what i have to put up with. i did paint the floor with that rustolium garage paint/sealerthat has speckles of paint chips. it's not to bad looking it looks like a linoleum.

good luck


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## tutu_sue (Oct 13, 2006)

Hi, if you will be spending time in the basement, insulating the walls would be your best bet.  NJ has unique insulation codes and there's a free program you can download and setup for NJ codes.  Here's the link for the ResCheck software:  http://www.energycodes.gov/

Mitigate any moisture problems first.  According to the program, for uninsulated masonry block walls, it's minimun R-10 for cavity insulation (i.e. studs with fiberglass) and R-8 for continuous insulation (i.e. continuous pink foam board with furring strips).  For floors over an unheated basement, the minimum is R-17 between and ends of joists.  If using faced (kraft paper) fiberglass or the foam board, they are very highly flammable and must be covered with drywall. 

For pipe insulation, there's a brown foam closed cell inslation that has an adhesive closing which is very easy to install.  Comes in 6 foot lengths at home centers for 1/2", 3/4 and 1" pipe.

Before you do anything though, stay legal and keep your family safe by getting a permit


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## Rhone (Oct 13, 2006)

The best method, is to insulate the OUTSIDE of your foundation.  That's the process I'm in.  That option mitigates many of the humidity/moisture issues, you most likely won't need a de-humidifier in the basement anymore, it puts the foundation inside the heating envelope so it buffers against heat/cold spikes, no mold/mildew issues, very little water issues, but you have to worry about termites in certain areas.  It takes me 40 hours to insulate 12 feet of the exterior my foundation.  Tell me if you plan on insulating the outside and I'll go into the steps, but if you're like me and doing it with a shovel, it's hell... though I definetely feel the effect of the exercise on my energy and concentration.  

To insulate the inside, don't put fiberglass directly against the foundation wall.  You risk having the humid basement air work it's way out in winter and the moisture will condense on your basement wall and fiberglass insulation causing mold/mildew issues, or in summer water whicking through the foundation will condense on it causing the same.  Use a layer of XPS, at least 1" thick if not 2", that's extruded polystyrene directly against the foundation wall.  It's a type of readily available foam board, that never degrades by water or in wet environments, water itself can't penetrate it, mold doesn't like it, but allows water vapor to pass in/out and it will move the condensation point inside the middle of it, or behind it instead where it won't matter.  Use a wire brush and clean the foundation walls.  Then use a big caulking gun and tubes of PL and adhere the XPS to the foundation.  I spread the PL in a big pattern around the edges of each piece of insulation, you want to prevent air leaks, and then put dotted lines in the middle.  Push it and hold it tight to the foundation wall, you want to make sure it's tight.  Leave 1/4" space between each sheet (it normally comes in 4x8).  Once it dries and holding, use expanding foam (polyurethane not latex) between each seam and follow the directions on how much to fill each gap, after it dries cut off excess.  The foam cans are usually one time use, so if you want to take a break stop after you run out of a can.  That should ensure an air tight and insulated wall.  Caulk the tops & bottom of each sheet to stop air flow.  Now, you should have no moisture problems (unless it comes up through the floor).  You can do any number of things at this point, but it must be covered with drywall.  You can now place 2x4 stud wall over it, fill the space between with fiberglass batts, and cover that with drywall and you've now got some serious insulation, or if you're happy with the amount of XPS insulation you added you can get furring strips placed every 16" and cover that with drywall.  However, the studs or furring placed over the XPS must be attached to the foundation with mechanical means, it's against building code to only have it attached by adhesive.  In a fire or high heat situation, the adhesive can become soft and fail, and everything come tumbling down exposing the highly flammable parts if never mechanically fastened.  As a tip, you'll probably be using tapcons to do it.  If you've never used them, they only go in about 1" and then they lock up, trying to get them in over an inch you'll normally snap them instead.  It's better to pick a tapcon that will only go in 3/4" than attempt to get one in over 1".  If you have water issues on the floor, keep the drywall 1/2" off so it doesn't wick it up, or use cement board on the lower portions.  Also, use pressure treated wood on the bottom for the stud walls if going that route.  

As for the sill plates/rim joist area, caulk any seams in the area to prevent air leaks and the best method is with tubes of silicone that come in tooth paste tubes.  It's nearly impossible to get a caulking gun in there, and the spray foam has to be applied upside down making it difficult as well, but the tubes of caulk are easy.  Caulk the top where your rim joist meets the floor, caulk the bottom where your rim joist and sill plate meet, and if you can caulk where your sill plate meets the foundation.  Then, once again use XPS foam.  Many people use fiberglass batts, but it doesn't stop air movement, they normally settle slightly and pull away from the rim joist and leave gaps making them nearly useless.  I haven't seen a house with the rim joist/sill plate area insulated with fiberglass only that hadn't become almost useless in a year.  With the XPS, make it as tight up/down as you can and leave a small gap on each side.  After putting it in place, caulk the top & bottom of them, and use a bead of the spray foam on the sides.  The stuff is VERY easy to cut on a table saw, but wear eye protection and a breathing mask.  If you run across any pipes in that area, it's very important you don't insulate over them.  I normally take the couple pieces of XPS for the bay (I put 4" thickness in), cut in half to get behind the pipe, and then I caulk it normally along with the seam in the middle afterward.  Leave the pipes exposed to the basement air.  

The floor, the proper method is to cover it with 6 mil plastic, with XPS once again on top of that, with furring strips spaced every 16", and 1/2" plywood on top.  That's a lot of space you loose off the height of your basement, and honestly unless you have moisture issues in the floor I don't see it as a priority.

Oh, by the way there's a federal tax credit of 10% on insulating the envelope, this is part of it and up to $500.  Also, if in a financial crunch, insulating only the top half of your basement is about 70% of your heat loss from it.   However, it's usually financially not much more to just do the whole route.  Don't bother insulating the floor above if you did the walls.


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## elkimmeg (Oct 14, 2006)

Step one solve the miosture problem.  I coat the walls with drylock   2 coates I also use thompson water seal for the floor smell like hell but gets the job done. Next is to address the sill leakage Any stud wall leave atleast one " air space behind it any any fibetglass insulation the fiber glass insulation side tabs to be fully stapled and streched out in front of the studs the paper facing should be tight no sags some even go so far as duct tape mid bats seams.  PT bottom sill is required by code and if using sheer rock 1/2 to 3/4" space from concrete contact.


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## wg_bent (Oct 15, 2006)

SCFA said:
			
		

> I have a unfinished basement, kids play area, furnace and all mechanicals are down there.
> 
> I've heard a lot of people rec'd to insulate unfinished basement.  How will that help the rest of the house?  Also since heat rises if i insulate the ceiling will it be even colder down there and I'll need to worry about it getting too cold since we dont run our furnace very often?
> 
> ...



I just did this exact renovation.  Previous walls...cinderblock...furring strips (that rotted), 6mil plastic..sheetrock.

New walls...

Drylock, 2" insulpink, 2x4 wall with non-faced R13 bats, sheetrock.  ( got this regiment from the building sciences foundation AND the university of Minn.

My house is staying MUCH warmer.  

Do it EXACTLY the way I did...and you'll be very happy.  

If you have questions PLEASE PM me or add to this thread.  I'll be happy to help and advise.

If you want the heat to stay down there, you should insulate with 6" in the ceiling.

Where so you live?  I'm in NY so VERY cold days occasonaly.  I do agree the best is to insulate the outside, but if you can't swing that, what I did is next.


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## velvetfoot (Oct 16, 2006)

I am also think of doing my basement in a similar way.  Currently I have insulation in the ceiling.  Thing is I put all my junk in the basement.  I have various immoveble things next to the wall, like drain pipes, oil storage tank, and breaker box.  I sort of have the radon in check now, so as soon as the town reassessment is over, maybe I'll make a move, lol.  

I was of doing it without the stud wall somehow, just the 2" of foam.  Perhaps affix the foam to the concrete with furring strips and then put the drywall over that.  I think it would be a little harder to do the electric but use less wood.  The fiberglass gives it considerably more insulation at minimal cost.

Do you have a mechanical room?  Would you insulate the walls of that?

My basement currently has outlets that are considerably higher off the floor than in the rest of the house.  Is this per some code or something?  Like if the basement gets a foot of water in in?

I read that insulating on the outside could be a problem if you lived in an area with termites.


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## precaud (Aug 1, 2007)

Rhonemas said:
			
		

> The best method, is to insulate the OUTSIDE of your foundation.  That's the process I'm in.  <snip>  It takes me 40 hours to insulate 12 feet of the exterior my foundation.  Tell me if you plan on insulating the outside and I'll go into the steps, but if you're like me and doing it with a shovel, it's hell...



Rhonemas, I'd love to hear how you did this. I'm considering doing some of mine, especially on the south side where I want to do some passive solar (can't do the whole foundation perimeter due to irregular shapes, poured patio, etc.) and it looks like it will have to be a hand digging job. 40 hours for 12 feet - ouch!


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## Rhone (Aug 1, 2007)

Hmm.. after writing this I'm not certain it makes sense.  Just make sure you're up the task, here we have cement I have no idea how this method will work where you are.  In particular, the affects of doing such around windows and corners.  

I used
4' x 8' XPS insulation (I went 2")
Sheets of galvanized wire lath (they're something like 2 1/2' x 8')
corners of galvanized wire lath
Boxes & Boxes of 3/16 both 2 1/4" AND 2 3/4" (You want phillips flat head) tapcons
Boxes & Boxes of 1" stainless fender washers (make sure the opening isn't so large the above tapcons can "slip" through)
Lots of PL300 adhesive
Wire Brush
A mining pick
Many cans of expanding polyurethane foam
Mortar and lots of it
Tons of masonry bits for 3/16" tapcons (Boxes of 100 usually come with them, make sure as they're often stolen.  They easily warped, broke, or died that's why extras are great).  

Dig out the foundation (don't dig under the footer), hose it off, let it dry, wire brush it, and cut the XPS with a circular skill saw with the blade on backwards.  XPS will destroy the blade (it melts & sticks to it) so, use a junk blade.  

To put up the insulation, it has to be installed one piece of XPS at a time.  Use the PL300 adhesive, and squirt it out so you make a complete square around the edges of each piece and put it on thick so it reaches uneven valleys, followed by squirting some in the middle & edges.  
Push it against the wall, hold it for a minute.  Then, drill a hole every 2 feet and use a 2 1/4" tapcon w/washer.  You want to make sure the tapcon & washer sucks deep enough into the insulation to make none of it protrude.  Repeat for each piece, but make sure there's a 1/2" gap around each piece of XPS.  Once you're done doing a stretch, take the expanding polyurethane and spray it in that 1/2" gap.  It's the best way I found to seal between each piece and make it water/air tight plus adheres.  Cut the excess foam off with a razor once dry.  

Now for the fun stuff.  Put on any corner pieces of lath first (corners, windows, and doors), and put the normal wire lath over it.  There needs to be around a 2" overlap, I held it temporarily with nails pushed into the insulation and then used a hammer drill and fastened it with washers & the long tapcons.  It needs to be done every 1' or less.  You want to try to make it as smooth as possible. Once you have it all finished, time to cement!  I recommend you attempt to do it all in one day, as doing half now and half in a few days left me a visible seam.  It requires 2 coats, the first you fill in all the holes & gaps of the wire lath trying to make it somewhat smooth.  Let it dry for an hour or two, and use a plastic comb to roughen the surface to prepare it for the finish coat.  Let it dry slowly for 24 hours (you may need to wet it).  Then, I appled my second coat of mortar trying to make it as smooth as possible.  Not being a mason, it wasn't very smooth.  We used a brush, and gave it a brush affect to help disguise it's unevenness.  It certainly does not look as good as original, and the uneven surface showed pretty bad even with the brushing.  I wish I'd brushed it vertically instead of horizontal to.  Windows, we put & bent white aluminum to "extend" them.  We also cemented the entire depth of the wall to avoid termites being able to penetrate into the insulation.


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## wg_bent (Aug 2, 2007)

So now that I"m living with this renovation in the summer... it's significantly dryer down there.  The dehumidifier only needs to be emptied once every 2-3 days and in winter I was able to heat the area with only a small electric heater.  My method which is documented in the building sciences web site worked very well.  

Rhonemas is right that exterior insulation is best, but hard once the building is there.  My method seems good so far.

It's now a very usable space.  I have pics of the renovation if anyone wants me to post.


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## precaud (Aug 2, 2007)

Rhonemas said:
			
		

> Hmm.. after writing this I'm not certain it makes sense.  Just make sure you're up the task,


Thanks for the detailed reply. What an ordeal! Methinks it's more than I can tackle, with all the other things on my plate to complete before winter. Perhaps I'll post separately a description of my basement and get some input on how best to deal with it.


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## begreen (Aug 2, 2007)

My hats off to you Rhone. That is a big project. The good news is that you will see some nice benefits soon. 

If I had a really nicely finished basement and insulation meant a total tear out, then I can see insulating the exterior. Also can see it if I was sealing things up on the outside to stop leakage. But otherwise, it is so much easier to do the interior. We had the interior of the tall crawlspace done in one day. Of course, we had clean unobstructed, fresh cement walls, which made it a lot easier. BTW, you can also score the foam board on both sides with a utility knife and then snap it. We got nice clean cuts that way.


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## BrotherBart (Aug 3, 2007)

My biggest problem with the unfinished basement office has been stale air. The $18.00 screen door this year has made it a delight. I will just cook lots of wood to keep it warm in the winter. The dirt that sucks out the heat in the winter is cooling it in the summer. Can't win both ways it seems.


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## precaud (Aug 8, 2007)

BrotherBart said:
			
		

> I will just cook lots of wood to keep it warm in the winter. The dirt that sucks out the heat in the winter is cooling it in the summer.



Well BB, that is the crux of it, really. My basement keeps the house a quite comfortable 78 max in the summer, without fans or air conditioning. If I insulate it's walls, I'll lose some of that. 

So I'm back to lining one side of a central brick chimney and the installing the F602 in the basement. Problem is, both stacks in the chimney are already in use: one side (11"x11") by the steam boiler, the other (7"x7") by the water heater. Haven't decided how to deal with that yet.

The steam boiler only comes on at 3-4am on the coldest nights. It connects to the 11x11 via a 6" pipe. I _was_ considering running a 5" stainless liner up the 11x11 side for the F602, but I know many will scream about doing that.

My current thinking is to run a 3" pipe up the 11x11 side and hook the water heater to it.
Then line the 7x7 side for the basement stove.

Thoughts?


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## fbelec (Aug 8, 2007)

i'd check with the local inspector on the code but i have seen it done with the boiler and water heater on the same pipe. just upsize the pipe going into the chimney and put on a y. the problem may be in the summer the water heater may not put out enough heat to make a draft. and you'll smell used gas. and or carbon minoxide might spill in your basement.

you could install a powerventer that would run on the water heater or the boiler or both and that would free up one or two flues. this idea might be best idea. then you could hook up two stoves  








			
				precaud said:
			
		

> BrotherBart said:
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## Gibbonboy (Sep 10, 2007)

Has anyone done this with a stone foundation? My basement walls are dry-stacked fieldstone, "mostly" parged. Finding a sprayer beefy enough for Drylock would be ideal. I'd probably cover that with PE sheeting, then come in far enough to build a plumb wall, and insulate that. Other option would be to fasten 2" XPS to the walls somehow, but exposed XPS is a big fire hazard. Sheetrock is out of the question, and I don't want to buy that much Durock/Wonderboard. Any bit of insulation I add will help, as long as I don't trap moisture and get into mold issues. I have access to truckloads of XPS 1" panels, about 2'x3' in size. I would probably not be able to do the entire 3 walls (back slopes to crawlspace under garage) due to sewer lines, elec. panels, etc.


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