I had a quick question re: the blow on/in insulation that Ive seen a lot of folks recomend. As I start to look at my insulation options, I was wondering if anyone can tell me what the R factor is on the blow in stuff...
I thinbk you are refering to Spray On not blown......Blown is a loose material where the foam is a "Solid"
About Spray Foam in a nutshell!
How it works
Most spray-on insulation is made of polyurethane foam – the same kind of insulation appliance manufacturers have used in refrigerators and water heaters for years.
The two part preheated liquid polyurethane is pumped through pressurized spray nozzles – as it lands on the surface of your attic or side walls, it expands to form a continuous & bonded insulating barrier. Do-it-self-kit is cold spray method....equal softer & lesser expanded foam per application.
Pro
Unlike traditional insulating materials like fiberglass or cellulose, spray foam insulation can seal and fill all the tiny cracks and seams you might not even see. The seamless material virtually eliminates energy-wasting air filtration. Other word with loose or open air cells passage such as foam board's gaps, fiberglass or cellulose will allow warmed moist air (breathing) to flow thorough to condense onto inter cooler surface of outer metal skin. Which transpire into wet fiberglass mast.
In addition, polyurethane has the highest R-value for any given thickness compared to other insulation products. There is other foam such as Icynene® has no harm full emission gases but only during drying period.
R-Value Chart:
http://www.icynene.com/assets/Products/InsulationComparisonChart.pdf
Polyurethane harden enough quickly to wall cover it but gets harder still in a few weeks when all chemical reaction is done.
Foam insulation also helps control moisture condensation, it won't shrink or settle, and it's fire- and insect-resistant.
Con
Spray foam insulation is not a practical do-it-yourself project – you'll need to hire an experience contractor in applying this new technology. Do-it-yourselfer is sure to over apply to cause wastes....too thick & uneven. And after you finish it you end up paying close to expert's installation price. Remember hot-bond is better than warm or cool to bond and it expand more per application.
It's also a messy process, must be apply to inter wall before wall interior skin installed. And using foam insulation in sidewalls may cause difficulties or delays if electrical and plumbing is not already installed.
Cost
The initial cost of using spray foam insulation runs about three times more than traditional materials. Due to large investment of preheater & high pressure pump equipments and two experience technicians (one to watch equipment to be within operating specification and other to apply). But keep in mind that the increase in R-value and air sealing will lower your fuel waste about a third. Plus less "hollowing" noise over fiberglass while traveling.
FWIW
Sojourn for Christ, Jerry
The spray foam we had applied back in 2000 has an R rating of R-7 per inch. We had 2 inches applied in walls and ceiling, then added another 3" in the ceiling after we ran all our wiring conduit and AC ductwork. As was mentioned, the spray foam also completely seals the walls and prevents condensation from forming. The biggest downside is the cost. Jack