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Is their any advantage to have an R-value over R-40? Post New Topic | Post Reply

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John Shockney Posted: Dec 22, 2010 09:48 AM	Is their any advantage to have an R-value over R-40? I had a customer ask for R-60 and I thought I would ask everyone what they would tell their customer. Thanks Airpro
steven argus Posted: Dec 22, 2010 02:38 PM	"No Problem! We are happy to spray as much foam as you like." Seriously, when I have a customer ask for higher R values I give them the price, but I also include an option for the code minimum. I also politely explain about "the point of deminished return"
John Shockney Posted: Dec 22, 2010 04:24 PM	Yes from a business standpoint more is always better and we do need to meet code minimums. But where is the point of diminishing return at R-10, R-20, R-40, or R-60?????? Thanks Airpro
jeff henderson Posted: Dec 22, 2010 05:50 PM	'Diminishing returns' is pretty much anything after R-1. You only capture half the Watts or BTU's with each additional R that you add on, as compared to the previous layer. (not sure I said that clearly enough? First R traps "x" amount of BTU's, second R traps 1/2X, third R traps 1/4X, etc...so if the first R trapped, say 1000BTU, then the 60th R traps a MINISCULE amount more....still more mind you, but not as dramatic as the first R...gonna stop now as I sense myself rambling) A heat loss calculation correlated to a Return on Investment calculation is pretty dramatic for foam. The ROI plummets rapidly, to say the least. On the other hand, it would be really nice to heat a house with just body heat, so R60 would be great. Some of the builders in my town go to R70 in the attic, but that is all cellulose - no one has deep enough pockets for that much foam, sadly (for me).
steven argus Posted: Dec 22, 2010 06:01 PM	I believe mason stated in an old post, (Mason, please corret me if I'm wrong) 4 inches of closed cell is all that is needed. Any amount beyond that is the point of deminished return. However, this does not meet code and we have to make Mr. Inspector happy. I like to tell customers, " I can spray 4 inches and tell you it is 7 inches and you would never no the difference." And I truly do believe that. Also, make sure the customer is aware that "R" values are very misleeding.
mason Posted: Dec 23, 2010 12:48 PM	In mixed climates or hot climates more than 4 inches of closed cell foam will not provide greater energy efficiency but in colder climates, I would go up to 5 or even 6 inches if you are consistently in below zero temperatures in the winter. But you do have to meet codes so be sure the code official approves your recommendation. Roger Morrison wrote a great paper of Diminishing Returns of Insulation. Happy to send a copy, email me at masonknowles@aol.com
Posted: Jan 01, 2011 07:48 PM	I realize that this is only anecdotal; however, I live in South Louisiana and my seafood processing plants are also in South Louisiana. I would often take Metal Corrugated building, insulate the floor with Polyurethane Sheets(4"), then cement the floor. We would apply 3 - 3 1/2" (21-25R Value) of closed Cell on the walls, 5-5 1/2" (35-38.5 R Value) of closed cell on the ceiling. Cover the walls with Densdeck, then FRP and put 30 hp refrigeration units into them to act as blast freezers to freeze 15,000 pounds each in less than 12 hours. I could get these blast rooms down to 30 Below 0 in less than 2 hours and not have one bit of condensation on the exterior Corrugate walls that was exposed to 90+ Degree Temperatures. That tells me that 3 1/2" of closed cell on the walls and 5 1/2" on the Ceiling is more than adequate to get a 1000 sq. ft room down to 30 Below 0 and maintain that temperature without heat loss. Now, I love to sell foam as much as the next guy, but I have to tell you that I laugh whenever someone tells me that they need an R Value of 60. So, In my opinion, architects and LEED Designeers can put all the requirements that they want code to be. However, there comes a certain point where you are just wasting material and money. There is a reason why Pre-fab metal freezer sip panels are only 3" to 5" thick. There is reason why cold storages rarely have walls with insulation thicker than 6 inches (even at -60 below zero). Take it for what it is worth
Gerry Wagoner Posted: Jan 05, 2011 05:54 PM	Tell the customer that you love to sell foam, but they don't need that much. They will appreciate your honesty. have fun, g
JohnPeters Posted: Jan 05, 2011 10:01 PM	From a physics stand point, the movement of BTU's from a heating system through building assemblies is well understood. After all, what is R-value? R-value is the measure of thermal resistance. The name of the efficiency game is to keep the BTU's coming from your radiator or duct register from leaving a building. On paper, it is very clear cut to see a correlation between uping R-value and conserving BTU loss. These calculations are why we always get architects and building science geeks recommending R-60 for walls and R-80 for roofs. Most every competent foam insulator knows anything over 4 to 5" of CC is a waste. We know because we see it in the field as previous posts have eluded. This leaves me to believe one of 3 things. 1.) We're (foamers) wrong in our assessment as to what the diminishing return point is...Maybe it is 8". 2.) The math for calculating BTU loss is wrong...unlikely 3.) Foam insulates better than ASTM tests reveal.
jimcoler I have over 10 years of experience specifying and installing open and closed cell spray foam. I've sold my business but I'm still selling for the new owners and consulting on large and custom specific jobs. I've expanded my knowledge into t Posted: Jan 07, 2011 07:21 AM	The 4th reason is as follows: 4: The measure of thermal resistance is being measured wrong and only measures conductive heat transfer. What about the convective, and radiant heat transfer and a thermal mass??? Jim
John Shockney Posted: Jan 07, 2011 02:46 PM	First of all let me say that I started this thread knowing the most of the math and physics behind R-values and the point of diminishing return for any insulation but didn’t want to come out sounding like a know it all. I did want to start a good discussion to help everyone and get good info out to everyone. And everyone has brought up a lot of good points and one of the first business rules that I follow is the GOLDEN RULE: THE ONE WITH THE GOLD MAKES THE RULES OR THE CUSTOMER IS ALWAYS RIGHT. So I will spray whatever the customer wants as long as it will solve the customer’s problem and not bite me later. But about the math and R-value the reason the industry came up with R-values instead of using the correct method of using U-value is the consumer always thinks more is better and they will even buy an inferior product sometimes because it costs more so it must be better you can see this in every market from clothes, shoes, food, and the list goes on… So lets look at U-value: All insulation testing gives us a U-value that is converted into R-value U-value is equal to the HEAT in BTUs divided by HOURS divided by SQUARE FEET divided by DEGREE F OF TEMPERATURE DIFFERENTIAL that will go though a given material or as a math equation U=BTU/HR/SQ FT/F The lower the U-value the better!! If you have a wall that is 10x10ft and has a U-value of 0.077 and a inside temp of 70 with an outside temp of 20 you would lose 385btu per hour through that wall this is assuming that the whole wall system performs at U-0.077 and has no excessive thermo bridging from the framing. Now if you convert U-0.077 to R-value (R=1/U) you get R-13 (12.987) If you go to: R-40 = U-0.025 or 125btu per hour (in the above example) R-50 = U-0.020 or 100btu per hour (in the above example) R-60 = U-0.016 or 80btu per hour (in the above example) If you graph this info you can see that after you reach an R-40 the drop in heat transfer is minimal as more insulation is added. As I see it the biggest reason that code asks for more insulation than R-40 is that the testing for insulation is faulty and doesn’t represent real world temps. It is my understanding that when testing R-value with a warm plate at 70deg that cold plate temps are never set below 50 degrees due to condensation on the cold plate if the temp goes below 45 and when steps are taken to prevent condensation with cold plate temps at 20deg or less an R-19 fiberglass batt tests at around R-10. If this info is correct (and everything I have read supports it) you would need R-80 of fiberglass to achieve what R-40 in spray foam will give you because it doesn’t lose R-value when tested at cold plate temps as low as –20. Sorry for being so long winded I hope this info is helpful Airpro
jimcoler I have over 10 years of experience specifying and installing open and closed cell spray foam. I've sold my business but I'm still selling for the new owners and consulting on large and custom specific jobs. I've expanded my knowledge into t Posted: Jan 08, 2011 03:42 PM	U-value???? Your stil measuring conductive heat transfer!!! You even said it yourself, "...that will go though a given material..." How does heat transfer through a material? By conductive heat transfer! What about Convective heat trasfer, Radiant Heat transfer or Thermal Mass?? These are all overlook by even the U-value measurement. The U-value measurement came from the UK as a European unit of measure along with the BTU (Bristish Thermal Unit). As I recall, the R-value came from a Penn State Professor who was trying to decide how to measure thermal conductivity and used 1" of pine as a benchmark at R-1! That's how we got the R-value measurement and it just happens to be the inverse of the U-value. I don't know which one came first but I tend to agree to your claim about marketing. The customer does want more for their money and the more you can state your R-value is the better it sounds! But how much is enough??? Some studies from Roger Morrison wrote an article back in 2006 which outlined that the first 1" of CC/ 1.91" of OC foam blocked 91.3% of heat transfered to it. 2" of CC/ 3.5" of OC block over 95% of heat transfer. So, it comes back to your questions? How much is enough? Is R-40 enough? Is R-40 too much? I think so! Is r-value the proper way to measure thermal transfer when it only measures conductive heat transfer?? Based on real life practical experience and seeing the melting patterns happen with R-40+ of Filter-glass in the attic, but only 3-3.5" of open cell foam in the attic holds off more melting. I know because that's what's in my attic. I did a couple of areas as a test at only 3-.5" thick and it seems fine! No moisture buildup, and it seems to work great. Now, there is a bit more melting in these areas, but it's less than there was before with R-40 cellulose!!! Jim
mason Posted: Jan 09, 2011 07:05 AM	Having been a player in the codes arena, I can say without too much reservation that the reason for increasing R values in the codes is based on a couple of major factors 1. The fiberglass industry recognizes that they require additional insulation to meet energy conservation efforts and want to increase the total volume of fiberglass sold in the market place. 2. They also see that by increasing R values that competitive insulation such as sprayfoam costs significantly more than equal R values of fiberglass 2. They are supported by many influential folks feel that it is too difficult to calculate the real energy efficiency of other types of insulation such as sprayfoam or other energy saving designs. 3. Many folks in our industry support increased R values because they feel that they can sell more foam of all types (EPS,XPS, Polyiso, etc) by increasing the code required R values. I don't mind the fiberglass folks having to use more insulation if they do not take care of thermal bridging, air infiltration, convention currents, etc. But the sprayfoam industry should be able to use performance testing that is currently available to demonstrate greater insulation efficiency. It is well known in our industry that I fought the increase of R values in the code in lieu of better thermal performance metrics. Sometimes succesfully sometimes not. For example, there was a strong attempt to require R 60 in attics that was beaten back. But, expect to see the proposal again for the next series of code changes.
Circle-D Posted: Jan 09, 2011 07:50 PM	Mason, Where are he foam manufacturers while this battle rages? I had quite an extensive converstion the other day with an ICC guy at a building code seminar I was invited to. He did not want to hear about the superior performance of foam. He did not want to hear about proven test results from independent testing organizations like Oak Ridge. He said all he wanted was "R" value. Very adamantly "What is the tested R value. That is what the code official must go by" No decisions based on their "interpritation" They say these new codes are to "protect the homeowner" How much protection are they getting when they are forced into using filterglass because the extra foam is so costly? We know (as foamers)that R-35 of CC is plenty, but the codes are still required to install R-49 or greater. That extra couple of inches accounts for a 40% price increase with little to no performance increase. How come the foam companies(Bayer,Demilac,Lapolla,etc.) aren't throwing a fit to get a standardized rating on a performance basis. Foam is beginning to gain market share as we are all aware (especially the filterglsss companies). I can see it going the other way, losing share again as the price increases for the homeowner. We (SPFA, somebody) needs to get the foam companies to get involved. Just my 2 cents.
jimcoler I have over 10 years of experience specifying and installing open and closed cell spray foam. I've sold my business but I'm still selling for the new owners and consulting on large and custom specific jobs. I've expanded my knowledge into t Posted: Jan 09, 2011 09:56 PM	Mason, I have to somewhat disagree with you. I see the fiberglass industry as just trying to hold on to their market share when they've ben down by 40-60% in sales in the past 1-2 years and foam has been steady to up 10% over the last 1-2 years. So, to put it bluntly, we're kicking the pants off them!! The real issues is that Insulation is measure by R-value and R-value only! That's all they want to hear and see! The filterglass companies just want to throw more of the nasty stuff into the problem. They aren't interested in fixing it right when it doesn't involve their stuff! WHy would you just try to fix something that allows air to pass through it by putting more in? So, maybe it wil filter it more, before it condenses on the glass fibers or on the back of the OSB!! Again, the real issue is the way insulation is measured and the fiberglass companies don't want anything to do with measuring it right when it says their stuff blows - literally! I agree that we need a unified front and measurement system which will come up against the fiberglass R-value measurement system. SO, how do we fight against these guys who have lots of money, write the rules and significantly influence the codes? SO, there are really three issues: 1. the R-value measurement - measuring conductive heat transfer and not taking convective, radiant heat transfer or thermal mass into consideration. 2. the codes which are largely and unfairly influenced by the fiberglass companies. 3. The fiberglass companies which have lots of money and lawyers to fight whatever approach we take. So, where do we go from here? How do we come up with a new measurement system and upset the apple cart being pushed by the fiberglass industry? I'm open for any input and looking any help here!!! Jim
mason Posted: Jan 11, 2011 04:44 PM	Jim, I think you will see by my past efforts, research, articles, presentations etc that I agree with you on this specific issue. There are many suppliers that support our efforts to make the code bodies recognize better performance measurements and metrics that identify and quantify factors that affect the thermal performance of wall and roof assemblies. We have gained some market share but fiberglass is still king. I will continue to support and work to help make it a more level playing field. There have been some significant progress as evidenced by fiberglass distributors getting into the foam business in order to make their fiberglass systems more efficient. I have been fighting this battle for more than 35 years. We are getting closer every year.
Dan Beecher Posted: Jan 11, 2011 09:21 PM	As I read these threads and sit by quietly, I now would like to throw my 2 cents in. There are a lot of dedicated, long time , educated members of this industry in here. You wouldn't be posting if you didn't care. I myself have been in the industry for 18 years. I live in a very cold climate (ND). I started working for a contractor that has now been foaming for 33 years. A lot of our sales come from word of mouth. Be it commercial, new home construction , or agriculture, interior or roofing, once someone has experienced a building with foam they are sold for life and they aren't afraid to tell their friends. I've never had anyone say it was a waste of money. We all know the R value is a myth and if we sit down with the customer can show them how. I ask my customers all the time for their heating and cooling bills, most have no problem doing that. Use them as your biggest tool. Know what you are talking about, do the research. Most of our customers are like us, give me the facts in a straight forward approach. Show them that you can heat a 4000 sq/ft home in ND for $175 a month with nat gas and off peak elec, that means something to them. Show them what geo therm will cost upfront and what spray foam will cost up front. If they really want to get into the science have the ability to do that. We can dazzle them with the blower doors and and all the science but if in my experience if we show them real world results that means a lot more to guys like me. I guess you can call me a northern redneck. Ha. So many of the new guys know how to pull that trigger but have no idea on the science behind the testing and efficiency of spray foam. Unfortunately, that goes for a lot of the foam salesmen as well. Quiz the crap out of them, if they don't know the science behind the brand they are selling, move on to someone else. They might be a rep for a "national " brand but if they haven't been through the proper training they are part of the problem too. Take you code official out to lunch!! It's amazing if you sit down one on one with them in a neutral site and a free lunch how they can accept and understand our data. I have never had an official deny me to "only" put 5" of CC in a cathedral ceiling. We have to realize it is not going to happen overnight as we would all like to see, but look at the strides we have made in the last ten years alone. The filterglass guys are scared, and by the reaction of them all getting in the foam biz tells me a lot of where this industry is going. I had to hide my laughter from an Owens C salesman who told me they would not get into the foam business as all of their competitors were because of all the health effects of spray foam insulation. I calmly swallowed and said good for you! Most of us are doing a good job and are being a good steward of our industry. I think our biggest hurdle now is to get all the new mom n pop foamers either up to compliant with the ways things SHOULD be done or get them out of the industry. These low ball, yea we can do that companies will take this industry down just as it did when the roof foam fiasco of the 70's and 80's. Thanks for letting me vent guys.
Dan Beecher Posted: Jan 11, 2011 09:21 PM
jimcoler I have over 10 years of experience specifying and installing open and closed cell spray foam. I've sold my business but I'm still selling for the new owners and consulting on large and custom specific jobs. I've expanded my knowledge into t Posted: Jan 12, 2011 09:18 PM	I agree with your comments about 5" of CC and the true science behid foam. But what about a job I just loked at yesterday which was spray foamed because of ice damming and it still didn't work! Come to find out that the foam ranged from 1/8" to 7-8" thick and it wasn't continuous!There are a lot of voids and cavities in the foam and no air seal around the outside edges. So, what about these guys who insist on spraying clsed cell foam on the underside of the roof deck but can't spray it consistenly? Yes, I mean all of these ma & pop companies but I was one once too! SO, we need to teach them how to do it right!! I see this industry taking off very quickly and rapidly like wild fire and we need all the people who can spray to be on board! I wouldn't shun them just yet, but try to train them because they may never have had the training you have had! If once their trained and they still do this, then you can shun them! Jim
jimcoler I have over 10 years of experience specifying and installing open and closed cell spray foam. I've sold my business but I'm still selling for the new owners and consulting on large and custom specific jobs. I've expanded my knowledge into t Posted: Jan 12, 2011 10:46 PM	OK, found the document showing the effective thickness of open cell and closed cell foams from Roger Morrison back in 2006. Anyone who wants it, just email me and I'll send it to you. jim (at)coler(dot)com
jimcoler I have over 10 years of experience specifying and installing open and closed cell spray foam. I've sold my business but I'm still selling for the new owners and consulting on large and custom specific jobs. I've expanded my knowledge into t Posted: Jan 12, 2011 10:46 PM	OK, found the document showing the effective thickness of open cell and closed cell foams from Roger Morrison back in 2006. Anyone who wants it, just email me and I'll send it to you. jim (at)coler(dot)com
Posted: Jan 13, 2011 06:21 AM	in addition to showing my potential customers my previous customers elect and gas bills and foot print,,, at times i provide the fancy diagnostic studies as well,,, blower shows leakage,,show em a filterglass home as well,,real numbers,,,subjective info,,,we can do this,,they can do that,,your home will hold the heat this long,,theres this long... overall effective leakage,,(there aint none) duct leakage to outside (none in conditioned attic,,helps sell the concept,,deer) heat load,,,real number cool load,,,real number appliance load,,real number lights load,,real number lets keep it seperate so we can make informed decisions here,,, with some of the $$$ being put down for the foam packages it helps to close the deal by giving the consumer some of this information at times... and some just get glazed eyeballs and are only doing foam cause there bro-in-law said so..lol..
Dean Nash Posted: Jan 13, 2011 09:59 AM	I remember an expression used by the media in one of the presidential elections that went something like this: "its the economy stupid!" Not to imply stupidity or even ignorance here but the underlying reason behind the "foam industry" or manufacturers NOT getting behind a performance standard is their economic goals which are to sell POUNDS and the market share which according to the last study I saw, was maybe 10%. An increase in R-value means more POUNDS and using CC foam means more POUNDS so with more R-value and your using CC foam in lei of OC foam, they are selling more pounds. As a former foam salesman and an independent rep for several companies, I can attest that the first question asked by the manufacturer I was working with was "how many pounds can you sell this year?" For me, as a passionate fan of the product, this was troublesome. The first goal of the foam manufacturer is to sell pounds because they have to commit to purchasing a speculative quantity of material that will be sold each year. Unfortunately, they are forced to focus on the pound approach because of how they purchase the raw materials. As referenced by insul8 (well said btw)discussing, debating, compromising, and educating our customers along with our respective code officials should be the first step in moving our product to the forefront of the industry. I don't know if there is a way to change how the manufacturers see an R-value increase except through united stewardship of our product, whichever brand you might spray. Good thread FWIW!
jimcoler I have over 10 years of experience specifying and installing open and closed cell spray foam. I've sold my business but I'm still selling for the new owners and consulting on large and custom specific jobs. I've expanded my knowledge into t Posted: Jan 14, 2011 07:44 PM	So what does "FWIW" mean? Oh, just got it! "For What It's Worth"!!
Jesse Luetzen Posted: Aug 24, 2012 12:14 PM	Has anyone posted about the fact that foam is/or should be rated as a coefficient. The inner layers are not as effected, or as responsible for stopping themal transfer.
SprayFoamSupply.com Posted: Aug 25, 2012 09:57 AM	"The inner layers are not as effected, or as responsible for stopping themal transfer.” Do u have any test data to support that statement? Please elaborate. George
Mark Mouton Posted: Aug 27, 2012 09:09 PM	I went into the attic of a new construction house we installed spray foam on the walls and roofline. They had been living there for several months, 2500 sq ft 10/12 pitch. I had my laser thermometer. This is southeast Texas and its 3 o'clock in the afternoon on the west side roofline. Outside temp was 96 degrees. Decking temp in the un-insulated roofline of the garage was 140 degrees. I went to the semi-conditioned attic of the house and shot a 2x4 brace at about chest high in the middle of the room. It read 81 degrees. I shot a few more places and came up with the same. The thermostat was set at 71 degrees in the house and it was 71. I shot the temperature of the face of the foam(1/2 lb.open cell) and where the foam was 5" thick or more it was 81 degrees. There were a few places where the foam was about 3" thick and the face temperature was 86 degrees(not good). At some 4" places it was 82-83 degrees. This told me that 5" is bare minimum to achieve a 60 degree spread. I immediately went to my men and we made sure we spray 5" minimum. Its usually 6-7". It cost me something to go a little thicker, but almost every new phone call I get is a recomendation, so its really not costing me. I also realize the decking temperature is gonna be higher under the foam, so in reality the spread is higher. I've been an insulation contractor for over 20 years and spraying foam for over 3. I still shoot temps on the sheetrock ceiling of a home and if its hotter than the thermostat setting, then I figure attic insulation isn't sufficient. So you men up north where yall have real winters, get out your laser themometers and shoot surface temps when those blue northerners blow through. I know it isn't as smart as adding a bunch of numbers(I do that too), but it will tell you something.
Matthew Gowin Posted: Oct 31, 2014 12:47 AM	I have been lurking in the shadows a bit. I started looking into foam for my addition and was very put off by my first quotes. I was looking to do flash and batt with 1-2 inches of closed cell foam at about 1200 board feet. I was very put off by the first quote at over $2.50-$3 a board foot (I cant remember exactly but it was bad) and ready to chuck some spray foam stuff up to the same HVAC snake oil people pull. However, after that I got more reasonable quotes but got yet even a better deal by going with the sprayez fast kick kit. The price I was paying for the 3200 board foot kit made the fastkick gun almost free when you calculate the discount per case for the bulk order. I figured it out that I was paying around $.70 a board foot for foam after I purchased the compressor. The install went so well I began pricing the open cell foam price. After I did the math I figured that my open cell foam cost would be just about 10cent higher than rock wool. Since I had installed double stud cavities I figured it would fill better anyway. I originally planned to flash and batt with cellulose so I was going to build my second inner wall at 24inches on center with 2x3s and with a 3 inch gap between the inner and outer wall. When I decided to go with foam I found documentation saying the point of diminishing return for 40deg difference is around 5 to 6 inches. So, I built the inner wall flush with the outer wall. Studs still staggered so the only thermal bridging is at the top and the bottom. Technically there is something like a 12 inch overhang for the roof at the top which will be filled by foam so the only bridging at the bottom. This will give me 1-2 inches of closed cell and the rest open cell for a total of 5 to 6 inches of foam (since the last layer of open cell is not perfect at my skill level.) Bottom line I will get the perfect amount of foam. I intend just to spray 6 inches (1 - 2 inch closed and the rest open) under the roof deck. I can add foam under there later if I choose since it will not get drywall over it. However, everything I have read suggests R40 walls. Once the drywall is up I don't want to take it down for the addition. I already want to rip down all the drywall in the existing house and apply foam in the future. So, I am considering building a third inner cavity with 2x4 construction (since it is more rigid than the 2x3s) and use it as a service / electrical cavity. I would fill this cavity with regular R13 fiberglass batts or maybe in some places rockwool insulation. This would give me a code valued R40 on the external wall but stay at the cost optimal point of 5 to 6 inches of foam. If push came to shove I could staple net to the underside of the foam with a 10 inch gap and blow in fiberglass (would rather cellulose but quite frankly it would be too heavy for the trusses.) My take from this debate and research - limited experience made me come up with this conclusion. Correct me if I am wrong. -For temps within 40deg difference the point of diminishing return is at about 5 to 6 inches of foam. -For a roof deck or any surface with higher difference of 40 deg difference you are looking at a 8, 10, 12, or even more optimal depth. -Even at optimal depths thermal bridging will still suck the heat out of your structure. This problem gets worse the higher the temp difference. -Once the point of diminishing returns is reached it might be a good idea to go with traditional insulations for code minimums. For a roof 6 inches of foam backed with 6 inches of fiberglass could be nice. Finally, I also ripped out all of my floor insulation and sprayed and inch of foam on my crawl space walls and placed r30 batts against them. This led me to the following theories. -1 inch closed cell is insufficient for flash and batt. -Thermal bridging is a ****** through wood beams touching outer beams. -While the crawl space floor maintains around 60deg all winter (VA climate)long it STILL sucks the heat out of the bottom of your house due to it's huge thermal mass and temp difference being just like cold outside air. My fix would be to blow another 1 to 3 inches of closed cell foam on the outer walls and lining the coated crawl space floors with an inch of 3lb roofing foam which should alone make up for the moderate 10deg difference and allow be to crawl around under there without damaging the foam.