"I need to insulate under my raised home in New Orleans. My initial choice was spray foam insulation, but after speaking to plumbers, electricians and termite treaters, I've ruled that out. This leaves regular bat insulation or styrofoam insulation sheets. I'm really leaning towards the styrofoam sheets. The decision now is to cut each sheet to fit between the joists or to lay the sheets over the joists. Any opinions?" If the electrician & plumber do their jobs corretly there shouldn't be issues with foam. Granted you would serve yourself & them well by taking pictures..electrical, plumbing & (crossing my fingers that you will say that your ductwork & heating system are not under your home!!) ductwork, supply boxes & plenums. I know in a perfect world..but still make sure that these guys are licensed, bonded & insured...lots of fly by night contractors preying on our hurricane destroyed areas. That said... I have both options & opinions.. First understand that what keeps batt insulation from performing to it's optimun is the air flow across or through it. Air robs insulation of its insulating value. So keeping it in a sealed area...such as with in the joist bay with a foam sheathing board nailed to the underside of the joist is the only way to go that route. I can't remember how high y'all have to raise your homes, but around here 3' to 4' is the height. (and you get $$ off your homeowners insurance if you raise it higher) So assuming your home is raised enough for a workable height this is what I would do. First take pics before you start any work..then once each step is completed. These are for future refrence. Go under your home & seal all the holes you see that enter into your living space. Plumbers, bless their hearts, cut a 4"x4" hole for a 2" pipe, and the holes cut for bath drains...don't get me started. Seal large holes with metal flashing caulk around the opening & further out..depending on how large your flashing piece needs to be. This will be your air seal. Screw the flashing in place & caulk around the pipe where it penetrates the flashing. Some holes will require less drastic sealing & for these I recommend caulk. Caulk will expand & contract with the movement of the building materials. Great stuff will overfill these holes, and after a few years the great stuff will break down & pull away from the wood. If the gap/hole is larger than 1/4" it is too large for caulk alone. This is where backer rods come in use. Backer rod is a round tube of foam sort of like pipe insulation. It comes in a few sizes 1/4" & 1/2" is what I use. If the gap is larger than this....use the flashing. If you find it too hard to use flashing...use some foam board & button cap nails to close the larger holes. And caulk it. Use a caulk with a long life..don't want to do this again & some areas will not be this acessable again. Once these areas are sealed. Then you insulate. Use an unfaced batt insulation..the unfaced can be ordered if not in stock, but there is a whole issue about vapor barriers that make the unfaced a must. Cut the insulation & fit it well around all the pipes & wires. Depending on the size of your floor joists upsize the insulation. If your joists are 2x6 don't use R-19..use R-25. If the insulation does not keep in contact with the floor condensation will occur & cause a world of trouble. There are friction fit insulation batts..but hard to find but the store where you purchase your unfaced batts will have wires to fit between joists to hold the batts in place. Once you have an area of insulation installed then come with the foam boards. Use the termite resistant ones... (and Thanks for the link MightyAnvil...I'll be buying some of this myself!! Great info, I didn't know it existed!!) I'd stay with the dow product & get tongue & groove and install this under the joists. I tape the seams with a tyvek tape..or similar product. The surfaces have to be clean & dry or tape will not adhere, And I caulk the pieces that are around the exterior of the home. This may be overkill...but I like to have secondary lines of defense. Mainly I want to stop ALL air infiltration that will keep the insulation from performing. sierraeast's idea of washers & screws is a good one. I would do these @ areas where plumbing would need to be accessed..under sinks, toilets, tub/showers & washing machine. I would also make it clear to anyone that they are to leave the foam barrier intact once they finish with it. You make a hole...it becomes your hole...fix it. (you may want to have the termite foam board info for them or even keep some for them to use) Foam insulation...well I'm not a big fan of it..mostly based on install issues, overselling & sales bs..but I do recommend it quite often as an under floor install. I've never had problems with electricians plumbers are anyone who knew their trade. Usually lack of dealing with a 'new' product is what causes people to not be happy to have to deal with it. But 2" under your floor would take care of the air sealing of most of the holes. More than that & gravity will take its toll within a few years. You would still have to catch some of the larger areas like under tubs. And if your home is ballon framed (wall cavaties open from crawlspace to attic pretty common in many New Orleans homes) these areas would need to be sealed ...again...foam board & button cap nails would be sufficient the spray foam over this would close the cracks. I've even used window screen for balloon walls cut, staple in place & let them foam away. Whichever route you choose, take the time to document, seal document again & insulate. Best of luck to you. And if you are on Decatur...visit Central Gro & have one for me!!

Hi illinigirl, The standard insulation used under basement floors is rigid insulation (XPS -- extruded polystrene). It comes in 2 inch thick often blue pieces of styrofoam. Dow manufacturers it among others. It is not spray foam. We used it in our build -- we are in southern Canada. The labour to lay the rigid insulation sheets was not high. The guys had to dig away a bit more gravel so the basement ceiling level was not compromised. They used the red tuck tape to attach the sheets to each other. This allowed the concrete flat workers to pour the floor with wheel barrow loads. I am not sure yet what a difference it will make as we are partway through our build. We have hydronic in-floor heat that was just turned on for the basement level. The floor is wonderfully warm (mostly due to the in-floor coils). We were required by code to place the rigid insulation because of our planned in-floor heat. Otherwise, I understand, the heat from the coils would not just heat upwards and instead would have been wasted heating underground? We did place the rigid insulation around the perimeter of our our unheated garage. I will go and step on the parts of the garage floor that have the insulation vs the parts that don't to see if I can detect a big difference and report back. Our architect spec'd for this rigid insulation under the basement slab. At the time, we had not planned for the in-floor heat. In other words, he felt it was a good practice even without in floor. The rigid insulation sheets are not cheap. We paid $25.00 a sheet (each one is 2 feet by 8 feet). We are in Canada where everything seems pricier. You can calculate the area needing coverage and see how much your builder is charging for labour vs material to help you decide if the price is reasonable. Don't forget the tack tape is also not cheap. Best of luck. Carol

It does sound like there might be a problem with the concrete portion of the room but we would also like to know as much detail as possible on how hvac is laid out. I hate chasing rabbits all over then be told one was hidden beneat a bucket from the start. It appears you arn't looking to jump right on this so I'll only get you started with seeing what can be done and how much effect it will have. The nuts and bolts of remediation can come later,depending how much your enthusiasm wanes after stareing down the barrels of realality. Use quick reading digital thermometer to read A outdoor ambent, B air temp in inclosed space beneath floor C soil temp beneath floor at 2" 6" and 12" below grade (test near center of room and midways between columns,not next to columns nor block walls.) Repeat soil test within 2 inches of 2 or 3 columns near center of room and 2 or 3 locations 2 inches from inside of block wall. Record and average readings for each test set. You can't use a pos device nor curupt readings with breath,body heat,lights and such. The differentials can be much smaller than you are acustomed to in daily life but are meaningful non the less. Try doing this after 3 or more days ( longer the better) of fairly consistant sun.wind,precipt and temps ( day night flux is inevetable as long as there isn't changing weather patterns.) A good thermometer isn't expensive and can be used for many different things for years to come. I try to keep secret the device I used for steak last yesterday was used last week on a boiler system. After you assemble and chart your data, you should have an aah haa moment.

Vermiculite doesn't always have asbestos in it, and, if you're just gently rolling new insulation down over it, you're not going to disturb it enough to worry about if it does. I'd simply suggest that you get yourself a respirator with the screw-in canisters that are specific for asbestos, and wear this when you do the work, and keep the attic access closed so that any dust you raise goes out the attic venting, rather than into the house. A decent repirator will cost you maybe $35 at Home Depot or an industrial safety supply store. There's not an issue in general with modern wiring being covered with insulation. However, it sounds to me like you've got some wires that are capped off or taped that aren't in boxes, and that's a code violation, so you need to take care of that first. You also want to leave several inches of clear space around any recessed lighting fixture so the insulation doesn't start a fire from heat buildup.