Your welcome Lenny and thanks for thinking that Iam a guy on the internet worth asking.. This gets a little opiniony knowing squat about your situation involving many variables but.. probably not, yes and no in the same order you asked. I have no idea what level of code is enforced in your area but I highly suggest sticking to the minimum levels of energy performance called for in the International codes. IECC 2012 is about to have its 2015 update and Iam excited to find out how wrong or right I am in squawking how they arent going to raise many insulation requirements but blower door testing will see a lot of very overdue attention. This thread is long overdue, for a serious plug on reducing uncontrolled air leakage. If your home is not a certain level of airtightness, then insulation can be an enormous waste of resources. If you are concerned about reducing your exposure to toxic air then focusing on the interior materials is a waste, if youre not building tight and ventilating it right with the "home as a system" priority. Insulation is expensive compared to airsealing and less effective in terms of overall energy performance. Uncontrolled, moving air carries a lot of moisture that does serious damage when moving through building cavities and thermal enclosures. It also leads to condensation and mold, especially in poorly installed fiberglass batt wood framed wall cavities with small levels of insulative sheathing. Add in a good vapor source, moisture reservoir cladding like stucco and brick that really soaks in the rain and drives it to the interior when the sun comes up and you contribute to much job security for those in renovation. But hey, it could be fine if the masonry has a good draining and ventilating airspace and that 1/2 piece of foam is well taped foil face isocyanurate, and the wall cavities are air sealed on all six sides with a dense batt filling all voids. I suggest pricing between OC spray foam and dense pack cellulose or FG (not batt). These are the things that best achieve a completely filled wood frame cavity. If not venting the roof deck, I suggest spray foam or insulative sheathing to the exterior. More important than insulation, is your ACH50 as measured by a blower door. The level of air leakiness in most homes is unacceptable leading to massive amounts of energy loss and unhealthy indoor air conditions. The code calls for an ACH50 of 3 or lower for building climate zones 5 and 6. I think that's pathetically leaky and not at all appropriate for a home built with the current international levels of insulation in the code. Homes in all climate zones should be pushing hard for an ACH 50 of 1.5 or less. Cost effective energy efficiency, increased durability and moisture resistance, and the ability to control the cfm rate of outdoor air exchange, which is probably the best way of improving Indoor Air Quality. As for levels of insulative sheathing, cant explain it any better than Martin at GBA. Its an important detail for everything weveve talked about, cost-effective energy efficiency, increasing indoor air quality and durability of the building envelope. Minimum For 2x6 in zone 5: R7.5 and zone 6: R11.25. Even 1" Isocyanurate with a foil facing the air cavity will be slightly below code and risky as far as interior condensation. I would do my best to get 2" thickness, even if it meant falling back to 2x4 instead of 2x6. I also suggest everyone to set a goal for ACH50, inform your builder that you expect to meet it and hire a third party to do a blower door test which puts a number on the value of the integrity of your home in terms of energy efficiency, indoor air quality and healthier building science. Here is a link that might be useful: Calculating the minimum thickness of insulative sheathing

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

I tried to see about putting in a baffle at the perimeter, but I have a ranch house with low sloping roofs. So, I can't get that far to attach the baffles to the rafters. What to do? put two baffles together. overlap the baffles and tape the two baffles together. push the baffle into the soffit, attach the longer end of the baffle to the roof deck. not ideal, but I've done this in homes like yours with low roof pitches. this will maintain the air flow, and the baffle will be held in place by areas you can reach to attach to decking. you can dump insulation on an IC can. but it is the air leakage that will keep the insulation from performing. 1 IC can is equal to 1 sq ft of uninsulated space. this is due to air movement thru the insulation. IC cans can have insulation next to and over them. it is the air leakage that is a concern. if each IC can lets 25 cfm of air into the house. this air is attic air..hot in summer cold in winter. usually laden with humidity and insulation particles. it is the air sealing that is the concern, but it will also improve indoor air quality and reduce amount of particulates entering the house. if you don't seal the IC cans, it doesn't matter if you insulate them or not..it doesn't address the air leakage. insulation slows air movement..it doesn't stop it. use same method for speakers in the ceilings. both are leakage sites. "I have a brick chimney extending through the attic. The fireplace is natural gas, and rarely used. Do I need to flash the chimney or something or can I dump insulation around it. I have numerous wires, light fixtures, wall cavities, etc." seal everything before adding insulation. else it is a waste at the areas that leak into the house. best of luck.

The moisture problem on the roof deck may occur when the deck is colder than the air rising into the attic. How is a whole house dehumidifier going to solve this problem in the winter. During the winter houses in SE PA are struggling to raise their humidity level to 40%. Many are running humidifiers in the winter which will further aggravate the problem. I have looked at a lot of new houses in the NJ and PA area. I can't recall any having HVAC equipment in the attic. I have never seen a house with a spray foamed roof deck either. I am skeptical you will find an insulation contractor who has experience doing this in a new residential home. If you do find one, you know the questions to ask. See if his answers make sense.