Eco-friendly insulators with a high R-value

Hello everyone!

In the summer of this year I want to insulate my house, but before that I want to be sure that I choose the right material. I am in particular interested in materials with a high R-value, which are eco-friendly as well. Any recommendations? A friend of mine recommended the polyester fiber, which is recycled from plastic bags, packaging or plastic bottles. If anyone has used it I would be interested to know more about it.

Thanks in advance

Insulation is one area in which there are lots of good options available. There's recycled denim batts, hemp batts, wool batts, loose and dense packed cellulose. All of these are good options, and choice would largely be based on cost and availability and whichever one you like. Performance-wise, most of these products are in the identical R-4 per inch range.

There are also site-made natural insulations like straw/clay or hempcrete. More intensive on the labour side, and both require drying time, but very low impact. They are in the R-2 or R-3 per inch range, depending on how densely packed they are.

I agree about the natural batts and cellulose. Focus on airsealing which is usually more cost-effective than adding insulation. This is especially true in the attic which is probably the first place to focus efforts.

I disagree with the R values given for straw/clay and hempcrete. I would bet most of these mixes average between .75 and 1.5 per inch... pretty lousy.

Be aware of the powerful effects of thermal bridging. The framing in most homes represents a 25% drop in R values because one is only insulating the cavities between them. A much better insulation strategy for walls is to add continuous sheets of insulation to the outside of the framing or structural members. This usually only makes sense when re-siding.

I typically argue that almost ALL insulation is eco-friendly because it does such a good job of lowering one's main source of a home's environmental footprints: heating and cooling. The damage from these on-going monthly energy and environmental costs usually vastly eclipse the damage from "less environmentally friendly" forms of insulation.

Have to reiterate air-sealing here. Many insulation resources are wasted by ignoring how airtight the structure is. If possible, do a blower door test prior to weatherization and then measure again after. Most home performance contractors will use a blower door during the air-sealing stage to see their results and better find the sources of leakage and waste. This is probably the most cost-effective strategy to reducing energy and environmental costs, increasing comfort and decreasing the risk of mold, rot and structural decay.

@ Brian Knight

Hi Brian,

Sorry this reads so challenging but I am writing really quick today and have much on the proverbial plate. I am concerned with many of these modern concepts in insulating architecture and there actual viability over time as you and I routinely discuss. Again I bring it up here just as a constant reminder that most of these current trends have no applicability in traditional, natural or historical conservation/restoration design for the "thermal envelope" of architecture.

Focus on airsealing which is usually more cost-effective than adding insulation.

Could we start calling this "draft sealing" as that is more applicable and conduce to good natural building modalities.

I disagree with the R values given for straw/clay and hempcrete. I would bet most of these mixes average between .75 and 1.5 per inch... pretty lousy.

For sake of clear disclosure and clarification, why do you not believe in the projected R values, (cite research etc,) and how many of these fully natural builds have you facilitated and tested?

The framing in most homes represents a 25% drop in R values because one is only insulating the cavities between them. A much better insulation strategy for walls is to add continuous sheets of insulation to the outside of the framing or structural members. This usually only makes sense when re-siding.

GREAT POINT!!!

This makes great sense in every form of architecture (where possible as it is often not possible or applicable in heritage conservation/restoration of vintage masonry architecture) whether re-siding or designing and building a new natural and traditional structure.

I typically argue that almost ALL insulation is eco-friendly because it does such a good job of lowering one's main source of a home's environmental footprints: heating and cooling. The damage from these on-going monthly energy and environmental costs usually vastly eclipse the damage from "less environmentally friendly" forms of insulation.

There is nothing "eco-friendly" for "pink insulation" or many of the spun glass forms. I would add, that many of the thermal wall designs are going to present with issues in the next century based on empirical observation during renovations, inspections, and razings.

Have to reiterate air-sealing here. Many insulation resources are wasted by ignoring how airtight the structure is...This is probably the most cost-effective strategy to reducing energy and environmental costs, increasing comfort and decreasing the risk of mold, rot and structural decay.

Brian, as usual for us, I have to follow up and challenge the use of the term "airtight" and note that the more of these structures I get to forensically examine, the less impressed I am with these "theoretical airtight systems." They are not as functional as the product industry manufactures are claiming, heavily dependent on "technology based" air circulation and exchange, and overall will not endure the centuries of use traditional architecture enjoys. Most will require very invasive intervention strategies to stay functional and/or complete razing within 1 or 2 generations of use to stay current. All of this is costly and unnecessary. For what degree of permeability there is designed into many of these designs few are functioning as intended, and moisture buildup in the thermal envelope is rampant, contributing to way more mold, rot and structural decay than I have ever seen in traditional and full natural build systems.

I am seeing some of the "foam encapsulation" modalities of merit if "cold wall-coll roof" venting is employed on the exterior, and "internal air drafting" between the frame work (usually timber frames) and wall decorative render-finishes are facilitated.


Regards,

j

Great points as usual Jay. I dont know of any third party testing for those walls and that's the problem. Both straw clay and hempcrete have more thermal mass properties than insulation in my opinion. If the hempcrete sellers are claiming 2.5 per inch they need to have those results tested and presented by a third party which they dont. Straw clay is pretty similar to adobe in my opinion and I doubt there would be a doubling in R value by adding more straw.

http://web.ornl.gov/sci/roofs+walls/AWT/Ref/TechHome.htm

Please point me in the direction of the difference of "airsealing" and "draftproofing"? I dont want to change my terminology here if there is no difference. Air tight homes can also be vapor permeable.

I didnt bring up the "pink" form of insulation but since you did, I disagree depending on the details. Heating and cooling is the biggest source of our homes and buildings environmental footprints. The merits of using foam is certainly debatable but I dont think its fair to say that a product that reduces decades of dirty energy use into the future does nothing to help. In my opinion, the environmental damage of foam manufacturing is nothing compared to the dirty energy and environmental damage that it prevents.

My point was that exterior insulative sheathing is a far more powerful R measurement than cavity R value. If you dont want to use foam, use mineral wool which also has a high embodied energy cost, perhaps more than foam?

I disagree that using foam or making building assemblies that can only dry to one direction somehow inherently dooms them to failure or are any less durable than vintage or traditional forms or architecture. It depends on the details. I dont think its wise to continue to build structures that depend on millions of BTUs per year to stay comfortable which describes much of the vintage and vernacular building stock. I dont think ignoring outdoor air exchange or radon mitigation is inherently more healthy than more modern forms of construction that include them.

Thanks for all the information! Any thoughts on polyester fiber insulation?

Lots of thoughts on fiberglass which is what I think you mean. As my dead horse should reveal, Its stated R values depends on stopping airleaks. Fiberglass batts are the toughest insulation choice to make this dream a reality. Not only does it not contribute to stopping air leaks through cavities, even when the cavity is sealed on 6 sides, it will tend to form stronger convective loops in the cavity as air flows through it great. The biggest problem with batts is they are VERY difficult to install correctly. Filling all voids and stopping air movement is why it almost always performs less than advertised.

Blown fiberglass is almost always preferable to batts but comes with the price increase. It should perform about the same as cellulose and cost the same too for most areas. Some people claim that FG is less prone to mold than cellulose while some claim the moisture buffering characteristics of cellulose is for the better.

There is a regional difference as PNW areas are more popular for FG while cellulose is more popular in New England.

Styrofoam, urethanefoam, etc. Closed cell is idea. If you reused material then it is greener than green - very eco-friendly. I saved up about $20,000 worth of foam insulation, packing peanuts, etc over a long period of time and then used that in building our butcher shop as part of the insulation. This cut our cost of construction and reused something. Reuse is best, better than recycling.

Next best is puffed rock. Mix with cement to make a very strong, long lasting foam insulation. Floats. Insect proof. Cover with a hard coat. Rodent proof.

The biggest thing I think all the options can fail to adress is both location and your location's effect on dew point. If you are in an area where snow stays on the ground for extended periods of time or it is just generally well below freezing you need to understand how dew point effects the structure. This more than anything else will effect mold, moisture buildup etc. if you are in the southern US then most of the arguments over specific system are certainly different.

I personally dispise batt and poly as an insulation system, I instal it all the time per architect specs and I always tell them it's failings and they never care to listen. Whatever material you choose for the batts the system sucks. Again if you live in socal then the whole arguent becomes largely moot.

As far as "traditional" building practices I haven't seen one old structure in my area of the world that did not require a massive energy dump to keep warm or a lot of ongoing maintenance to keep vertical. I think we have options, technology and knowledge available to us now that allows us to build much better then in the past. That doesn't mean that we typically do but it's available. I'm not against old world systems being used in modern construction but I don't believe our ancestors held any more special knowledge about building than we do. It's all relative.

(sorry this is a long one)


I am going to try and make a "Insulation" page here at Permies for folks to go to so I don't keep repeating myself. Then folks can start a "thread chat" like this one to ask additional questions.

@ Brian Knight

Please point me in the direction of the difference of "air sealing" and "draft-proofing"? I don't want to change my terminology here if there is no difference. Air tight homes can also be vapor permeable.

Just a semantics issue that relates to the culture of "air tight" architecture vs natural/traditional permeable/breathable culture in architecture.

I didn't bring up the "pink" form of insulation but since you did, I disagree depending on the details.

I was speaking of "spun glass" which I will get to at the end of this post.

My point was that exterior insulative sheathing is a far more powerful R measurement than cavity R value. If you dont want to use foam, use mineral wool which also has a high embodied energy cost, perhaps more than foam?

Read the last line of my last post, you confused my meaning as for modern insulation I like many of the "foam" applications and they are getting better with products like "aircrete" and the related soybean base urethane.


Pros and Con of spun glass (pink insulation) insulation

I guess this is where folks have to make there choice and live with it. Pink spun glass was developed by Owens Corning for the government during-just before WWII, and it worked great for the original purpose, which was insulating refrigerator units in the Desert from getting hot-a very dry environment. Additionally, spun glass (pink insulation) looses R factor the colder it gets, (kinda defeats the purpose IMO) and has a "cult following" by the construction and manufacturing industry that is based on very shaky research that does not hold up to real world testing or life expectancy for the product and materials around it. Real world research performed by the Department of Energy at Oak Ridge National Laboratories clearly indicates that as outside temperatures get colder, the R-value of fiber glass insulation decreases. Using a full scale climate simulator, ORNL tested loose-fill fiberglass attic insulation rated at R-19 at a variety of temperatures. When outside temperatures dipped to -8°F, the R-19 insulation performed at R-9.2. Additionally, infrared imaging revealed convective currents inside the fiberglass insulation and warm air from inside the house would rise through the insulation, losing heat by coming in contact with the cold attic temperatures, and drop back through the insulation, forming a convective loop of constant energy loss. The challenges with this product continue. We haven't even gotten to the fact that it looses all insulative value exponentially, as well, when ambient humidity rises, so at 30% there is no R factor left. Have we look at the added fact it is a perfect medium for growing black molds when water condenses in the colder climate applications or when humidity is above 80% as you find in the South?

Fiberglass insulation should not be used for cathedral ceiling applications as moisture issues will take place because of the conductive nature of fiberglass, as pointed out, spun glass fibers insulate using the air pockets that the spun glass creates. The problem is that the glass conducts energy (hot or cold) changing the temperature of the air pockets created by the fiberglass material and drastically effecting the R-Value of the product.


I will close with these thoughts, at this stage in construction, renovation and restoration, I can safely say I have seen more failures with this system than successes. Why choose a system that is less than 80+ years old, (younger for the plastic house wraps by DuPont) over traditional systems that have centuries behind them. A modified system of the two can work if the correct materials are used, and those materials work in concert with one another.

It doesn't take much research, especially with the internet to find the real truth about fiberglass insulation. If you want to look for yourself, type in "Problems with fiberglass insulation."

Regards,

jay

Brian, et al,

here is a site that has 3rd party (US, Canada, or Eu) checks to R values.

http://energy.gov/energysaver/articles/insulation-materials

Thanks Jay for the more thorough explanation of FG, most of which I agree with. Iam not familiar with that ORNL study but I think most researchers find fiberglass R value actually increases in cold weather. This would probably represent a near perfect installation which is much easier in the lab.

Dense pack FG performs much better than batts and loose fill and is specified in many high performance projects. I think loose fill FG is a great choice for increasing attic insulation as long as the ceiling plane is air-sealed first but I would prefer cellulose if available.

Folks considering "hemp" for insulation should be aware of the difference between hempcrete and "hemp insulation" which Ive never actually seen but sounds promising.

I didn't have a lot of time yesterday to explain poly as an air/vapour barrier yesterday.

The reason I don't like poly is because in final application it is only 100% positive or not. So in the "ideal" installation poly is a perfect seal and your house will not breath, which if you have a mechanical HRV type setup can be ok. However I've never seen an application where the poly doesn't fail on some level. Screw/nail holes, failure of the sealant or tape etc allows air from the inside to penetrate in a specific area and you get frost buildup etc all in one area. This will cause mold and rot within the wall system.

People often think that sealing positively with a product like poly is worth more than insulation but that theory only works when you don't have enough insulation. Look at systems like the arctic wall, outsulation with foam etc they all work well when there is a high R-value in play. You ideally want your building envelope to be able to handle humidity and in order to do that you need to move the dew point outside your framing system in into some type of closed insulator later.

Brian Knight wrote:I think most researchers find fiberglass R value actually increases in cold weather.

That is the opposite of what I've read and observed. Open celled (e.g., fiberglass, peanuts, etc) insulation gets worse in colder weather due to convection effects as the force the thermals gets stronger.

For better efficiency look to closed cell.

For perfect efficiency: vacuum.

Four factors:
Convection
Conduction
Reflection
Thermal Mass

The fourth one is rarely mentioned but I have found it to be very significant.

Yes mass is significant but unless your using a thick dense pack or something like straw bale I think you need to address mass as a separate element of your building system. You can't replace insulator value with mass. That mass can only flywheel the energy so long before it starts requiring a significant energy input to keep going.

Ive always wondered why or how FG R value could increase in cold weather with the convective airflow problems it has. I did more research but couldnt find a clear answer. Chris Shumacher with BSC seems to have made the discovery but cant find any published papers on it. This link has the relevant graph that I saw in several places.

http://www.energyvanguard.com/blog-building-science-HERS-BPI/bid/59419/Big-News-The-R-Value-of-Insulation-Is-Not-a-Constant

I also saw snippets of the study that Jay was talking about and it seems the test was based on 6" of attic loose fill. Thats a pathetic amount of attic insulation that doesnt meet code minimum anywhere in the country. I also believe that the study found reduced R value in all loose fill products including cellulose. Its probably a common situation and problem that building to code and above should solve. I couldnt track down this study but know its by J.D. Ned Nisson, “Attic Insulation Problems in Cold Climates,” Energy Design Update, March 1992, 42-43. Iam curious how they seperated air leaks and thermal bridging from their conclusions. I think the hot box testing done by BSC is more accurate than the conclusions and research from this one by the ORNL.

Of the many reasons to NOT use fiberglass, I dont think reduced R value in cold temps is one of them.

Brian Knight wrote:Ive always wondered why or how FG R value could increase in cold weather with the convective airflow problems it has..

Hi Brian, et al.

I am planing on a comprehensive expose' and profile on insulation to be written here on Permies over the next 6 month to year. I am contacting several major universities "Building Science Departments," that I have been in contact with over the past few decades to assist in vetting the information. What I can share with folks now is this; of all the industries involved in architecture, directly or indirectly, the three most "corrupt," "misinform-misrepresented," and simply hard to get a good honest answer (I worked in two of them,) is:

1. The "rising damp" industry in the UK (and its satellites) and few other European locations.

2. The pest control industry.

3. The insulation industry.

I consider myself a "nobody," but because I write profusely and often I attract attention to the point that even I got a letter, about 15 years ago threatening lawsuit for libel, "cease and desist order" if I continued to write about a certain application and modality the way I was. This insulation industry is "sideways," most of the time, and even the "experts," often do not agree with each other about applications, methods, and types of insulation (just look at how Brian and I banter back and forth sometimes... ) As I have written about earlier, "pink" (or spun glass) was developed to keep things cool in desert environments (not warm in cold ones) and all of the original testing was done in laboratory settings, not "real world" applications. Simply put, don't ever consider using this type of insulation in any of its forms, and warn others about it. It simply is bad system...period.

I would also back up what Brian said about "loose fill anything," it just is not worth the effort or expense. 100mm (4") of dense pack cellulose is better that 200mm (8") of its loose fill form, just as an example.

Regards,

j

I'm 100% with you on this J. Glass is awful in practical applications. I would typically lump poly in with that too for other reasons like I said but yes for sure glass batts are terrible with blown applications only slightly better.

Probably the worst application and a very common one for glass batts is the perimeter of basement walls. The concrete amplifies it's weaknesses and in a cold climate I would say mold is only a matter of time.

Wow, thanks guys! This thread is incredibly informative. I had never heard that loose fill decreases its insulating value in cold temperatures. We had never thought about the idea that idea that convection within loose-fill materials is a big issue in cold weather. -- Doh!

We've been building with thick earthen walls, and sometimes packing (clean) garbage into a cavity for insulation. Sometimes between joists in the roof, sometimes in a 6-inch cavity on the north wall. We have also been using earthen buildings with locally traditional roof and no insulation, with thermal results that we are satisfied with, though they could still be better. We don't have any measurements of performance. We've just done it from the assumption that some insulation is better than none, though the thick earth walls do pretty well in the first place (and are tried and true for durability in this climate). This insulation debate is REALLY food for thought!

We have also started using straw clay. Since it's really largely chopped straw with just a coating of clay as a binder, I don't think it will be thermally similar to adobe as Brian suggested. What do you think, will it be sort of like closed cell insulation? It doesn't seem to have long air passages within it but does have little pockets of air.

Keep the discussion going, guys! Please use full forms, though, so we newbies can understand. For example, does "poly" refer to the recycled polyester fiber insulation the Original Poster asked about?

Thank you!

Whoa there! Let me clarify a few things please.

I LOVE loose fill insulation. Fiberglass, Cellulose, Vermiculite, Perlite, feathers, garbage, whatever is a good fit to increase R value to use energy more efficiently is a great thing. With most homes, the best fit for loose fill is attics, because you have the perfect opportunity to pile it on thick.

I think loose fill fiberglass is one of the best things available to anybody, including those interested in permaculture, to decrease their energy and environmental costs in the right applications, mainly attics. Its cheap, readily available, fire resistant, mold resistant, and requires no specialized skill to install. There are few products available (cellulose) that are so easy to increase a home's attic insulation levels. Again, air sealing first followed by loose fill insulation in the attic is about the most cost effective and environmentally friendly things a person can do to both existing homes and new homes. This goes for hot, cold and mixed humid climates.

While I agree that there is probably a measurable decrease in R value for loose fill applications, I largely disagree with the conclusions of the ORNL study/Energy Design Update article that it's a big deal. Again, install code minimum or above "loose fill" insulation and the problems suggested in the study/article goes away.

There are 3 common ways to use fiberglass and this is how I feel they rank in terms of performance from best to worst:

1. Dense pack fiberglass; great performance for the money but takes specialized installer. Not available in all areas.
2. Loose fill fiberglass; great performance when applied thick. Very affordable, readily available and excellent DIY.
3. Fiberglass batts; poorest performer, extremely difficult to install appropriately, very affordable/available and has higher (better) R value at lower temperatures. Despite this better performance at lower temperatures, its not recommended for installation difficulty.

Again, loose fill insulation anything (mainly FG and cellulose) is an excellent product to use for new and existing homes attic insulation, just be sure to air seal first.

Rebecca, I think anything you can do to add R value to exterior walls is beneficial in almost ALL climates that require heating or cooling. So I think your garbage infill is probably a good thing. Raw chopped straw probably has a decent R value while clay has something entirely different. I was extremely generous with my R value estimate for adobe and straw/clay. The ORNL hot box measurements for the adobe bricks were close to .25. I think the amount of straw to get such a wall to 1-1.5 would make it mostly straw and very weak.

And in the inverse, I think Walters suggestion of mixing puffed rock with cement would result in something strong and good Thermal Mass but a poor performing insulation.

Poly refers to a plastic vapour and air barrier that is often run on the inside of a framed wall with batt insulation running on the outside of the poly inside the wall cavities.

@ Brian Knight

Hi Brian,

Need clarification please:

You wrote:

I think loose fill fiberglass is one of the best things available to anybody, including those interested in permaculture, to decrease their energy and environmental costs in the right applications, mainly attics. Its cheap, readily available, fire resistant, mold resistant, and requires no specialized skill to install.

After everything I have just written, information cited, and observation I have made in the field over thirty five years, how do you stand behind this above statement?

It is not mold resistant at all and actually promotes mold growth when humidity is above 80% (much of the south). Fire resistance is relative, because it really is not fire resistant compared to an open source flame. It burns much quicker than properly treated log wall, , straw bale, light clay chip or straw,and even dense pack saw dust and even cellulose is superior to fiberglass for "real world" application in fire resistance. I left out mineral wool, which is made from recycled by product, and has better sustained R factor, is at the top of the list for fire resistance. Once again, there is little to redeem spun glass insulation in any of its permutations.

Simply put, the longer we continue to feed the "fallacy" that it is actually a real insulation, and the multi billion dollar "Dow Corning Multinational" conglomerate corporation," its lobbyists, its funded counter research, and general bad environmental practices, the worst we will have it on this planet. Fiberglass is not an appropriate or applicable insulation in any of its types when all "real" aspects of performance character is examined. It simply should be remove and discontinued as an insulation (IMO) as in real world application it fails to perform after just a few decades or of course if it gets really cold out side also.

With the deepest respect Jay, I dont agree with your assessments. Fiberglass is extremely mold and fire resistant in my opinion. I agree with the link you provided regarding R values of common products. Did you notice that the cover photo is someone installing loose fill insulation in an attic? While it doesnt come right out and say it, the R value of loose fill fiberglass is very similar to loose fill cellulose around R3.5 per inch. How can you say this is not insulation?

As for the Oak Ridge National Labs study information you mentioned, it seemed to me to be copied from a source that used it as advertising propaganda to push a product other than fiberglass. If you can show us the original version of that study, we would love to see it. Iam not sure but I think it came form this one:

http://web.ornl.gov/info/reports/1981/3445605458590.pdf

This study basically says that loose fill settles to thicknesses less than what's installed. Shocking. Its also meant as a guide to direct how much loose fill to add to compensate for the settlement. This study seems to back up my case that loose fill is the perfect product for attic ceiling applications. Its the easiest place to go thick in most homes. Just air seal the ceiling first!

I would almost always prefer cellulose to fiberglass. However, there are great fiberglass products out there and are very effective at saving energy. One of them is the BIBs method mentioned in your R value link.

If you have some secret evidence that fiberglass is not insulation, grows mold or is not fire resistant please dont withhold it from us!

I have dug into a few moldy walls in my time and they were all fiberglass filled voids. I would be willing to say that the glass itself doesn't grow mold, it is the fact that the glass holds water that is an issue. fiberglass batt insulation is like a sponge when exposed to water so it might be better to suggest that FG insulation "promotes" mold growth by holding the moisture in place. I have seen batts themselves saturated in mold where they are wet, does that mean that there is something feeding the mold growth in those areas I'm not sure but it definitely lives in the FG batts. To a lesser degree I've seen roxul products hold moisture too, I haven't seen any with mold in them but roxul is used so little that its hard to compare to FG products.

Loose fill insulations are kinda known to be inconsistent due to the inconsistency of their installation. If you have convection currents moving through batt insulation then I can't see how that wouldn't happen to a greater extent in loose fill products be they FG or cellulose. One installation I'm kinda liking in a typical wood truss system is spray foaming the cavities and then adding your loose fill cellulose, you could use a .5lb open cell foam as well to allow moisture to permeate the assembly. The foam does a good job of air sealing all the little crevasses etc so you won't have air movement through the assembly and the loose fill sits like a blanket over top. I've never actually had a chance to use this system but I know it is done and it removes the requirement to sheet the underside of the trusses with OSB and Poly. With a dense pack application you would still need to at the very least sheet the underside to support the weight and then you would want to seal all the joints to support the weight before finishing.

JC how would you address dense pack cellulose in a timberframe application?

Additionally I should mention that about 75% of the moldy Fiberglass batts I've had the pleasure of working with were used to insulate concrete basement walls. I can't say this enough, DON"T INSULATE YOUR BASEMENT WITH FIBERGLASS BATTS!!! I honestly believe that in 95% of the cases where fiberglass batts (I"m sure other batt products will have a similar result) are used in a concrete basement you will have mold growth 80% of the time you won't see it because it is brewing behind the 6mil poly where you can't see it till it is really bad.

When mold is found in a cavity insulated with fiberglass, its a problem associated with wrong location or poor building practices. I kind of agree with you Sean that basements are no place for fibgerglass. However, if the basement walls were properly damp and water proofed from the exterior, the drainage details are correct and the vapor barrier is removed from the interior then the physics change dramatically and the problems probably go away. My favorite insulation for below grade walls is closed cell foam followed by open cell foam. Havent used mineral wool yet as its tough to get and expensive. There is a lot of promising development with this material lately and will explore using it more as the price comes down and it becomes more available.

For above grade wall cavities containing mold, there are many possible explanations. The most common is that the mold is from a bulk water leak. The next most common: air leaks through the cavity. Insulation can act as a filter and will collect dust and pollen as air moves through it. The mold seen on the fiberglass is usually the result of this situation. There is also the issue of cold framing and sheathing with high indoor humidity. Keep your indoor humidity below 40% in the wintertime to avoid vapor diffusion and condensation problems. Installing exterior insulative sheathing also helps this problem in a big way by keeping framing and sheathing warmer than the dew point.

The only place I recommend loose fill is attic floors NOT cathedral ceiling cavities or wall cavites. I generally dont recommend batts for walls but if you are meticulous with air sealing and filling all possible voids then it can perform well. I think choosing thicker and wider batts to stuff into the cavity will perform better than batts "sized" for a specific cavity. Some of these issues are why spray foam has become so popular. It blocks air movement really well and is easier to install. In our area, open cell spray foam is about the same cost as dense pack cellulose. Uncontrolled air movement through and within the building envelope can cause many durability problems besides high energy and environmental costs.

Yes in the "ideal" application with perfect conditions for the batts they can perform alright. The problem is those conditions are near impossible to actually achieve and even then any failure of the interior vapour barrier down the road comprises all that effort.

It's just not a great system even with a perfect installation it is still prone to failure.

Exactly Sean, and even if what I shared about the "fallacies" of spun glass insulation where not true, these simple facts you just shared are the primary reason never to use this system. I can not even begin to relate the countless "fails" of this type of insulation I have observed over the years, or heard (read) from others that do remodeling, and/or restoration work. This delusion that we are going to have these "vapor permeable plastic members" and or vapor retarders function as intended for the life of the architecture is pointless. None of these systems are presenting that way after just a few decades nor are they easily inspectable, serviceable, and more importantly at this moment "confirmable" that they are functioning as intended.

Yea the system was pioneered not far from where I live and the guys who started doing it themselves were using double layers of poly sheeting and relied on tar paper exterior to allow the wall system to dry out.

Bottom line the system sucks, if you have the choice don't use it. This comes from someone who oversees millions of $ worth of work annually and has a lot of exposure to it.

This entire section of the conversation clearly reflects that we as humans (and builders) get into what are called "architectural habits." Yes sometimes they are just aesthetic, and follow a decorum of a culture for a period of time, while other times they are a "concept" that we seem to attach ourselves to and won't let go. It is fine to have a concept and apply it, but when there is such mounting evidence that it has no long lasting durability as a practice; then one can only conclude it has become a "habit" that is perpetuated by those that can profit from it, our habitual nature, and the naivety of the average consumer. As one of the industries (insulation) most prayed upon by "industry driven" modalities, not necessarily good practice, consumers must me vigilant.

Yea there is definitely an industry component but I think it has a lot more to do with progressional change and learning about building science. 25ysars ago the standards were different and far less than today. People didn't realize just how much insulation a wall system needs to perform and there are other factors too like batt came about as a solution designed to work with the existing wall cavities of typical construction. The remote wall systems we might promote now are really a completely new theory of wall system vs what was happening 50+ years ago.

It is all relative though, if I lived in SoCal r20 batt and poly is probably way more than enough.

You guys totally lost me. What "system" are you talking about? Ventilated attics, interior polyethelyne vapor barriers (poly), fiberglass batts, stick framing???

Sean seems to be talking about interior poly, definitely a bad idea.

Jay what specific "architectural habits" or concepts do you have such a problem with? Fiberglass? Loose fill fiberglass, fiberglass batts? Insulation? Anything made by an "industrial" company?

LOL currently we're hacking on Fiberglass batt and poly in wall systems.

In a traditional attic space loose fill is a somewhat favorable option although I'd probably shoot for cellulose over glass based on price and sustainability though.

Hmmm, I agree with Sean, we are discussing the short comings and real world issues with all forms of "spun glass" insulation in all its permutations, sorry if that was not clear to you Brian. I would further point out Brian, that where Sean lives most architects, builders and Code demand is that the vapor barrier of poly goes on the inside of the structure. That is considered "good practice," which Sean and I are both saying is "daft" and not good at all. I am further saying that plastic of any kind, inside wrap or outside wrap, is bad practice. The head of the Minnesota Building Science department (as of the 1990s) concurred and still recommends the using of building felt/paper and not these seldom permeable plastic warps such as Tyvek, I can not give an exact quote, yet his general premise is one I have followed for over thirty years: "Buildings mush be draft free not "airtight," and the walls should be as permeable as possible. This falls in line with most traditional and natural building modalites.

Jay, you know I love you man but as passionate as we are I have to challenge you on some of this stuff. Ventilated attics are the most common, resilient and proven form of roof in N america. Millions of people have insulation levels that could use major improvement. Some of the highest performing, net-zero, new homes continue to use ventilated attics with insulation at the ceiling plane. For these most common of roofs, there are two main choices for insulation: cellulose and fiberglass. Both products work well, are very affordable and are easy for homeowners to DIY. I think its unproductive and confusing to rule out any forms of a certain product when there are clearly applications that it can work well with. Ventilated roofs with insulation at ceiling plane can be used with any wall system; cob, strawbale, earthbag, earth berm, tire walls etc. Just air seal the ceiling plane first !!

Iam not familiar with what codes require in very cold climates like Sean's but I can almost guaranty that there is room to use products other than polyethelyne plastic for the interior vapor retarder. I think most building science experts would say its NOT best practice to use them. This is certainly an architectural habit that needs to die.

As for Tyvek vs. building felt/paper I think it once again depends on the application. These are not products intended for airsealing and insulation. They are Weather Resistive Barriers WRBs meant to keep bulk water out of the house. I think we should move any further discussion about them to the new thread on Vapor Permeability in Temperate climates (which includes most of US). I must point out however, that Tyvek is MUCH more vapor permeable than most building felts. Some building scientists think that Tyvek is too permeable for most applications. I think both forms of WRBs can be useful but dont recommend tyvek behind real wood as the tannins have been shown to break it down (with no rainscreen). The jury is still out on fiber cement. I should also point out that almost all building scientists recommend rainscreens behind siding and masonry, for most climates, and most commercial products made for that purpose are made of plastic. That being said, I think the best rainscreens use furring strips (some are plastic) for siding applications. Still, depending on the application, a plastic WRB or rainscreen can add years or decades of life to most cladding systems and paint jobs.

Once again we are back to "draft free" versus "air tight". The subject of air sealing definitely belongs in this thread as Insulation is a waste if you are not accounting for air leaks. Again, most of the mold people discover on fiberglass is the direct result of an air leak. In this very thread, you said the difference is just semantics. Are you back to claiming that there is a difference now? If so please explain. Thanks!

Home wrap (tyvek) is I think as much a victim of aplication as most materials. CCHRC is doing some really good research and with their arctic wall it seems to be permiating the moisture quite well. I think part of the issue with tyvek is that you have the inconsistent poly later on the inside of most walls and so the tyvek can't compensate. The arctic wall has been used to good effect on passive homes in Europe as well so again I'm not against it's use so long as it's done properly.

Overlaying home wrap on top of exterior sheethimg is kinda counter intuitive, combined with the wood in surface contact I can't see how any moisture is able to permeate out of the wall cavity. Just a thought.

I know this stuff is related, but things are going to get confusing really quickly if we dont move the tyvek, WRB and vapor permeability stuff to here; https://permies.com/t/31490/green-building/Vapor-permeability-material-suggestions-humid

I know there is much more insulation specifics to explore!

agreed, moving to: https://permies.com/t/31490/green-building/Vapor-permeability-material-suggestions-humid