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paul rogers Posted: Jan 09, 2011 06:28 PM	thermal efficiency per inch of open cell What is the thermal efficiency of open cell foam? closed cell: 78% thermal efficiency 1" for heat loss 1" 78% closed cell 2" 88% closed cell 3" 92% closed cell I am not finding any info on open cell thermal efficiency. Thanks
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 09:08 PM	The 2006 SPFA conference had a presentation by Roger Morrison who presented that 1" of CC/ 1.91" of OC foam blocks 91.3% of heat transfer. It also shows that 2" CC/ 3.5" OC blocks over 95% of theThere was a chart and graph attached to the presentation that broke it down into the % of heat blocked. I heat transfered to it. I can't say it's perfect, but it's better than nothing. I'll look for it and I'd be happy to send it to you when I find the presentaion article. Jim
Bill Clark Posted: Jan 19, 2011 04:40 PM	Razor Back - Remember that while these % of heat blocked numbers look good, they do not take into account "thermal saturation" over time. Such thin amounts of spray foam will become heat saturated over time and then allow significantly more heat to flow through them. Spray Foam, regardless of OC or CC, needs to be thick enough to stop the flow of heat during the daily heat cycle... If you have a "Dare to Compare" box for home show purposes, set it up and let it run for hours, somewhere after 5-6 hours, depending on the ambient temperature, you will start to get a much greater transfer of heat through the spray foam. Spray Foam does a great job don't take this wrong, BUT you have to install enough foam to do the job correctly. On a related note, whenever possible cover all the roof framing when spraying unvented attic assemblies, the wood rafters will conduct a lot of heat into the attic assembly, if you only spray the roof deck with foam.
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 19, 2011 08:38 PM	California Spray Foam, If you mean a hot box as a "Dare to Compare box", many of these have an inherent problem. You see the heat from the fiberglass and cellulose on the sides transfers through to the foam in the middle. There is little to no insulation on some of the versions I've seen. There are some out there which are designed much better and work more accurately. I haven't seen the heat satuation point that your talking about but I've also modified my hot box with Low-E insulation between the foam section and the fiberglass/cellulose. Since insulating between these sections, the temperature in the foma section seems to be performing much better. I also agree that spraying over the rafters is a MUST!! We see the rafters in many houses that we've insulated only the cavity. We don't see the ones where we've covered over the rafters. So, just goes to show that it makes a difference! Jim
SPFer Posted: Jan 19, 2011 11:32 PM	Jim, I understand how you can see the rafters when you don't cover them with foam, and not see them when you do. What I don't understand is how this tells you anything about thermal performance?
mason Posted: Jan 20, 2011 12:50 PM	The efficiency of any insulation systems can vary significantly depending on climate, type and design of assembly, indoor and outdoor temperatures and humidity, occupant behavior, HVAC systems, air infiltration, thermal bridging, convective currents and more. While at SPFA we conducted testing of wall assemblies trying to take into account many of these factors in closed cell, open cell foam compared to fiberglass and polyiso insulated wall assemblies. Both sprayfoam assemblies performed very well. In fact, even with air infiltration taking into consideration, the foam assemblies performed close to or even above their labeled R value. You can obtain these reports from SPFA. Ask for the ATI wall performance test reports. I also have them in my files.
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 24, 2011 09:49 PM	You can see where the rafters are when you don't spray them because the heat transfers through the rafters to the roof deck. When you spray over the rafters, then you don't see the roof rafters, even with 1" of open cell! Remember, wood is R-1/inch, so a 2x6 rafter is only about an R-6 as compared to the insulation next to it which is an R-23! Now, if you cover the rafters, then you get an R-10 to R-14. It's still not perfect, but it's much better than an R-6 over 10-15% of your roof!
SPFer Posted: Jan 25, 2011 06:56 AM	Oh... you mean see them from the outside of the roof. I thought you were talking about just being able to see the rafters from the inside. That makes more sense.
John Shockney Posted: Jan 25, 2011 01:24 PM	I have seen and heard of this term “thermal efficiency” several times now but it doesn’t give us in the HVAC business anything that we need to know to size heating or air conditioning equipment. When using Manuel J (and I didn’t have a computer program when I learned how to figure this) you are trying to calculate the total heat loss or heat gain for a given structure. This means that you have to add up all the square footages of the different building materials (walls, doors, windows, ceilings, and floors) multiply those by the U-factor of each taking into account any thermo bridging from framing. This info is then multiplied by the temp difference based on the hottest or coldest average days for that location be it Indy or Yuma, AZ. By adding all this info along with the heat given off by people, lights, computers,… how many times (and how big) the doors open we can then figure the total heat loss or heat gain in BTUs per hour and size equipment correctly. So what we really need to know is what is the actual U-Value (or R-value) for the wall at a given condition most manual J calculations have been based of fiberglass’s poor performance at colder temps or high temp differences giving us the only option to over size equipment to make up for the added heat loss or heat gain. I have seen test data that shows fiberglass loosing over 50% of its R-value when outside temps drop below 30deg (70deg inside) due to convection air currents forming inside the insulation this makes an R-19 batt only performing at R-10 where even open cell will hold its R-value so R-19 of foam is still R-19 when the temp drops. I tell my customers that spray foam will perform like twice as much fiberglass and most testing will support that but not when comparing foam to cellulose. And I have tried to get GCs to build super insulated walls to cut down on the thermo bridging but most won’t even consider it. Just try to get them to build a 2x4 wall 24 on center with closed cell or a 5.5inch stager stud wall using 2x4s 12inches on center with foam and both are stronger and better insulated than any normal framing done today. Just look at ICFs and SIPs they both out perform “normal” framing. Also look at a refrigerator little to no thermo bridging in their design only some around the door, due to the use of foam and point out to your customers how long has it been since fiberglass was used to insulate them (1960) or even water heaters. If fiberglass is so great why isn’t still being used in those products!! Enough rambling on I just think that we should use good science and testing in our comparison of different insulations and wall designs and right now it is still R-value this is a good measurement of the heat transfer through the material but the testing should be done at real world temps not with a hot plate at 70 and cold plate at 50 where most testing is done, Thanks 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 26, 2011 09:42 PM	I couldn't agree with you more about Manual J and the lock us in on using R-value! Except that Cellulose doesn't perform as it states either!!! Air still passes through cellulose. How do I know, I have it in my house and I use an IR camera to see the air leaks all over the place. I also went above and beyond to try and seal the house up tight from the outside with tubes and tubes of caulk. No great luck though! My walls and ceiling still leak cold air from outside. Yes, my house is energy star rated and passes all the necessary guidelines. As a matter of fact, it was one of the highest rated homes ever rated at the time at under 900 CFM 50 for a 3300 sqft house. So, cellulose does pretty good, but not as good as stated or as good as foam! The other point I have with what you said is that fiberglass only performs at 50% of it's stated R-value. That's true when you take into effect one of the factors that degrades it, but when you take them all into effect (which is what you have in real life), you get only 1/4-1/3 of the stated R-Value. You also don't account for the condesnation which can occur in the filterglass! Then once it gets wet, it starts breaking down into formeldyde gas and fiber mush. So, what do we use when we enter in data into a program when the data it's asking for is flawed? You give it flawed data, knowing it's flawed in your favor. BUt then the question is, how much do we fudge the data? Now, I think we're getting somewhere! Let's start talking about a real measurement of heat transfer with Conductive, Convective, Radiant Heat Transfer with a thermal mass! When they ask us for this measurement in all of these Manual J or other programs, then I think we can truly model a house. Until then, we put garbage in and expect gold out?? I don't think so, Garbage In - Garbage Out! Jim
Posted: Jan 27, 2011 03:43 AM	uh jim only data i enter is wall components and temp and humitidy in and out.. calculates dewpoint in the wall cavity,,hard to fup,,flawed??how
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 27, 2011 09:51 PM	...wall components...??? What are you describing as your wall components? They have an associated R-value to them don't they? That's the "Garbage In- Garbage Out" thought process! When all you put in is Garbage, how can you expect anything that smells any better to come out?