I have been told by Hebel execs that in the colder European countries it is common for Styrofoam to be added to the exterior Hebel walls to increase insulation. And I have also been told that Hebel requires a special type of stucco or plaster that allows the wall to breathe. My question is then how does an insulated Hebel wall breathe with Styrofoam attached to the exterior side?

"One inch of EPS has a permeance of 2.0 to 5.8 perms, making it a semi-permeable material"

Alton, Ivan Burgand at Sider Oxydro in Ga. is the North American AAC finish expert, and a very helpful fellow. www.sider-oxydro.com. Sider is a German company. The comforting thing about AAC is that isn't new technology. Has 80 years of history in Europe, in fact.

AAC might be the best thing ever, but the amount of misleading information is only exceeded by those selling radiant barriers. Exterior walls painted black, not comparing equal R value and infiltration values, ignoring other thermal mass (like a slab), extensive use of "equivalent R values", picking and choosing data, etc. Hebel is one of them.

I believe the walls were painted black to emphasize the point that heat on the outside doesn't make it through to the inside. (Or, rather, that AAC's eight hour thermal lag buffers inside temperatures, as heat on the outside wall ebbs and flows with daily ambient temperature swings.)

The Oak Ridge National Laborator'y developed DMBS multipliers to calculate equivalent R values:
www.ornl.gov/sci/roofs+walls/research/detailed_papers/thermal/dynamic.html

Oh. That's right. You don't believe ORNL either.

Perhaps you can explain how a slab on grade could exhibit DBMS: (i.e. buffer heat on a 24-hour basis.)

Styrofoam is a Dow company trademark used for their XPS (not EPS) products. Typical XPS sheathing products (not just Dow's) are ~1.2-1.5 US perms at 1" thickness. That's still semi-permeable, but much less permeable than most EPS products.

Most stucco other cement/plaster based siding products work better with a rainscreen-type ventilation gap between the stucco and the rest of the wall. EPS is lower perm than most of these products, and would inhibit (but not entirely block) drying toward the interior of the building, but it's generally better to purge that moisture to the outdoor air rather than into the building. Also if the exterior finish coat too low-perm and has no vent cavity it can create high moisture conditions in AAC and interior finish materials.

AAC has worked fine in Europe, where they have much lower average dew points than the eastern or southern US, and relatively mild winter temps, but it's SO vapor permeable that without other materials in the stackup I suspect high latent-loads for the AC would be a real downside in some locations. An inch of EPS or XPS on the exterior would be a significant improvement from both a thermal and moisture-control point of view. In Canadian-cool climates I can imagine spalling issues occuring in AAC from interior vapor drives without at least some exterior R factor (&/or interior side vapor retarder) too, but haven't been able to find much information about it's extreme-cold hygric performance/longevity. Hebel documentation calls for sub-0.1 perm (US) interior side vapor retarders in cold climates, as well as increasing the thickness/R-value of the wall to guarantee interior wall surface temps are always above the dew point (mayhaps a recognition that R10 doesn't really cut it in Whitehorse Yukon? :-) ).

http://www.hebelaustralia.com.au/downloads/uploaded/Appendix%20A-H_5e00_ca47.pdf

The ORNL study that ToddM mentions is the same that I linked before. The DBMS values would not apply to an AAC wall without some type of insulating sheathing. Every single wall in the study includes a form of insulation. Also, it seems the DBMS value is derived from concrete with a density of 140lb/ft3. An interior slab would meet this criteria and even the gypsum board that they use has a higher density 50lb/ft3) than most AAC(40 I think). Putting insulating sheathing ON EXTERIOR of AAC makes this debate more interesting but I dont think that AAC deserves the same DBMS as regular concrete.

Hard to get your head around it, I know, but AAC is mass AND insulation. I set a propane radiant heater in a four-sided AAC closet last Dec to keep my plumbing from freezing. On an 8 inch block, the inside face was 85; the outside, 20. Better, it has a higher specific heat (0.25) than concrete (0.20) so it is a better heat store than concrete in a passive solar house, albeit at one fifth the weight.

But DBMS is not about storage, and it works in the absense of insulation. (Remember those adobe houses?) It's about thermal lag. Delay it long enough and the inside surface will stay comfortable even as the outside surface cycles with the daily high and low. As long as those extremes bracket the desired indoor temp, mass is working for you. Because every climate has SOME days like that, an equivalent R value recognizing DBMS is the proper comparison for mass vs light.

BTW, my walls are distant second to those windows in a HEED list of energy drains on an average January night. Sorry. I don't want to live in a windowless box. You wouldn't either if you had my views.

AAC is both mass and insulation sure, but it's ~1/4 the mass of an ICF of similar dimensions- to be in any way equivalent it would need a specific heat ~4x that of concrete, not 1.25x.

Even if you were comparing a 6" concrete wall to an 8" AAC wall, the mass of the AAC wall is only a third, and would need 3x the specific heat to be able to claim rough equivalence to 6" of concrete clad with 2.5" of EPS.

Even 3.5 dense-packed cellulose in 2x6 framing has a measurable dynamic benefit due to it's thermal mass, but it's not marketed that way- it's an ~ R14 wall, give or take, even though an argument could be made that it performs to "R16-equivalant" in some climates.

It IS difficult to think of a material as insulation AND mass! With AAC an R value per inch of 1.25(at most)not including the mortar penalty its not that great of an insulator. With Thermal Mass, I dont think Specific Heat is as important as Heat Capacity. 4" of regular concrete has almost 2x the Heat Capacity of 8" AAC.

it is a better heat store than concrete

A good example of misleading hype.

Yep- total hype. The "...albeit at one fifth the weight" counts. (I thought it was more like 1/4 the density than 1/5, but, OK.) The relevant heat storage capacity is the mass times the specific heat that, so in no way is it "...a better heat better heat store than concrete in a passive solar house", if it's an 80% reduction in mass, with only a 25% increase in specific heat, and it's not fully within the insulation envelope.

A 2" non-structural slab will have the same thermal storage capacity per square foot of 8" of AAC, but far more passive solar heat storage capacity per square foot than 8" AAC, since it's fully inside the thermal envelope- stored where it counts (indoors) rather than in a progressively lossy wall. The outer couple of inches of the AAC can't be counted as ANY passive storage during any heating-dominated weather conditions, and the middle 4" doesn't count for much. The inner couple of inches counts though. A real concrete slab (of a structural thickness) fully inside of the conditioned space has many times the thermal storage of AAC walls and moderates the interior temps much better.

I understand that some have found that interior passive mass can outperform exterior mass - if you go along with the assumptions and inconveniences involved - temp swings, opening windows, sweaty surfaces, humidity, solar gain, effect on setbacks, etc. On the other hand, exterior or middle mass (ICF) seems like it has most of the advantages without most of the disadvantages. Any thoughts?

Phoenix is not a good example. summer temps are more like 80-105 vs 60-100. Sedona would have a better climate. You are right mass would work well when the go above and below the comfort range on a daily basis. Another time mass might work favorably is if you can get realy cheap off peak rates. Then you could drop the temps and then allow the mass to keep it warm or cool.

I agree, off peak rates create a big savings potential. But I think that a water storage tank is a better way to make use of it.

Off peak rates are beneficial for the consumer and the community and most electricity providers offer them. I agree with Jon that water is better, DHW being the most cost effective. Matching Thermal Mass with Off peak rates however, usually requires a greater level of cost and complexity, especially for homes that need AC.

Phoenix is one of the few cities that Thermal Mass might have a favorable ROI according to the ORNL study above. Sedona might work better in the summer but certainly not the Winter. Climate change however, might be changing this. Its another reason that designing exterior walls with Thermal Mass only and not insulation is risky even in these climates that have wide diurnal swings that remain consistent throughout the year(very rare for most US climates). Climate change will mean more extreme temperatures on both ends of the scale and insulation is much better suited to this than Thermal Mass.

As for the "hype" comments I agree but think most "equivalent R value" claims are closer to misleading advertising, something that the FTC should enforce more.

Jon, the ORNL study of the Thermal Mass advantages of ICFs show very little benefit. ICFs have some great advantages but reduced energy use from its Thermal Mass is not one of them. In my opinion, pre-cast concrete panels are usually a better alternative to ICFs.

Greetings,

QUOTE:As for the "hype" comments I agree but think most "equivalent R value" claims are closer to misleading advertising, something that the FTC should enforce more.

I agree,BUT, the reason you have this situation is because the Mineral wool industry controls the Insulation testing methods. In 1981 the FTC put in forth that ALL insulations would be tested IN THE INSTALLED CONDITIONS. This would have put FG and Cell out of business. The US Senate: llc cut off operating funds to the FTC for two days until they rescinded this regulation( documented). Guess who push for the rescinding of the regulation. The FTC is now controlled by industry not the people so the FG people don't have to worry about this happening again.

The RB manufacturers are force by FG backed regulations to use tests that do not reflect the actually operating conditions of aluminum and to list those results as "R" factors. RB DO NOT have "R" factors.

By the way the tests used to FG ARE NOT installed summer/winter test conditions.

I just posted on residing foam insulation/9/2/ 12:33 About Paper back FG batts that you might find interesting.

I have written a paper that shows how the whole "R" factor fiasco can be circumvented and allowing the home owner/ builder determine by dry wall temps the actual BTU gain in a building.

I had to get away for a couple days. It's hard to relax sitting amongst so much unfinished work. I see you kept banging away in my absence without inflicting any damage to the barnside looming above you. I may not have all the answers but, happily, I do have a clue. Maybe some math will help you with the diurnal dynamics of passive solar.

Let's say that insolation amounts to 20kbtu/hr through my windows on a bright Jan day. Let's say that 80 percent of it reradiates from the concrete slab in direct sunlight. So 16k btu/hr would add 0.005 degrees to 300 tons of concrete or 0.07 degrees to 60 tons of AAC. (Yes, Dana, R10 AAC is ~30 pounds per cubic foot or one fifth the density of regular concrete.) Not much of an argument for heat capacity, eh?

You'd want mass anyway to guard against 40kbtu/hr coming through the windows on a 50-degree day. More specifically you'd want AAC because it is 25 percent more effective than concrete at soaking up heat; it has a specific heat of 0.25 vs 0.20 for concrete. The "good example" I see exhibited in this thread is less one of hype than it is of prejudice and ignorance.

Yes, jonr, water storage could capture 100 percent of the heat if you have money to burn. Myself, I figure I needed walls, floor and windows anyway. If I could build them in a way that provided much of my heat, and at a lower cost than stud walls, my scots forebears would be clapping each other on the back. I understand that passive solar is not for delicate types like you.

You are entitled to believe what you want to believe about equivalent R value. My mother-in-law, bless her, thought those newfangled satellites screwed up the weather. I didn't argue that point with her either.

But spalling, Dana? Really? I can tell you've never seen AAC because all that entrained air would tell you at a glance that AAC's resistance to freeze thaw damage is orders of magnitude higher than regular concrete. While it needs to be covered, and covered by specially formulated stuccos and plasters, regular old stucco would suffice except for application issues. The blocks suck water so quickly from conventional stucco mixes that adhesion is a problem, I learned in my conversations with Ivan Burgand, U.S. head of Sider Oxydro. Sider solved that problem 40 years ago. Sider sold stucco and plaster to me for $1.13/sf including shipping from Ga. The stucco guys said it spread like butter. AAC may be new here but it isn't new technology.

Are you serious? Does the concrete in your example have a glossy white enamel painted surface? Would the re radiated direct sunlight just disappear? As Dana has repeatedly pointed out, without insulation on the exterior of your AAC you cant possible expect to get much advantage from the Thermal mass in your AAC.

There certainly is an argument for concrete having more heat capacity because it has 2x the capacity of AAC. The higher specific heat variable is not nearly enough to overcome the entire equation.

Your AAC walls(without exterior insulation) are not providing enough beneficial heat storage to make it worth the loss of R value. In fact the meager R10 walls will be the biggest source of your heat loss by far, especially if you really built your roof to R60 which from the sounds of some of the details, I doubt achieves a true R60.

AAC has an R value of 1.25 per inch...Pathetic! No scientific studies have shown Thermal Mass to be a good option for exterior walls, outside of Phoenix and Bakersfield, unless there is insulation on the exterior. Equivalent R value of 17 is a fraudulent claim. Some of your other arguments make it seem like you either work for an AAC manufacturer or are in denial because you have already chosen and installed this material for your personal home.

Comparing Equivalent R value to your mothers distrust of satellites comes across as desperation. Other notable claims of Equivalent R Value come from manufacturers of Radiant Barrier paint and spray foam manufacturers who use it to try to be cost competitive with other insulation. I wouldnt put the AAC marketing hype in the same category as radiant barrier paint but certainly the spray foam people who routinely advise foam applications in thicknesses less than what code requires. Spray foam arguement: because its so much more airtight, it has an equivalent R value of "x" inches of other insulation. If anything, AAC should be using the airtightness argument instead of its Thermal Mass benefits which you seem to favor. Most Energy Efficiency experts would agree that the airtightess of AAC is a MUCH bigger advantage than its Thermal Mass.

If you know of a notable, independent Building Scientist who recommends AAC without exterior insulation in climates outside of Phoenix and Bakersfield, please tell us about them. Maybe their argument is more convincing.

Greetings,

QUOTE: Other notable claims of Equivalent R Value come from manufacturers of Radiant Barrier paint and spray foam manufacturers who use it to try to be cost competitive with other insulation

I addressed this before. Correct the obviously bias testing standards and you wont have use comparisons. I'm including at the end a copy of an article I wrote addressing this problem.

But First. There has been a spirited conversation about the overall eff of 8" ICF and similar wall sys. Here's one experience I had with and ICF wall sys home, basement and upper walls.

Split level. full basement, 1st floor, living rm and bedrooms to upper section over bedroom section. All vaulted ceilings, about 3M sf. Geotherm sys from pond.

Ceilings insulated with type 4 RB ( 4 reflective air spaces) and single layer across the bottom of rafters with 7/8" stl furr'g strips then dry wall. RB on exterior of ICF walls, vinyl (ugh) siding.

The only problem he has is in the summer time with heat from single , south facing window on upper story. I've repeatedly have told him to install a vented alum awning.

Pos. results. After 5 mos the utility company changed the meter because they refused to believe the house was that eff. This isn't the 1st time I've had meters changed on my homes.

The humidity level is so low the wife drys clothes in the basement.

So yes, RB on the exterior can make a substantial difference.

Many of the questions raised in the article I have asked on this forum, without response or attacks. These questions have to be addressed if you are going to have an energy eff home.

George Himmeger 224 SOUTH St TROY, IL 62294 CELL 618 698 8393 HM 618 667 4222 e-m [email protected]

Information and opinions by George Himmeger : The chart data enclosed is taken from a mechanical engineering handbook along with
opinions from thirty years field experience

EXPLORING THE LEGITIMACY OF CLAIMS OF CHARACTERISTICS, TEST PROCEDURES AND “R” RATINGS FOR THERMAL INSULATIONS USING MECHANICAL ENGINEERING HAND BOOK DATA AND FORMULA

Fiber glass FG - Radiant Barriers RB

Confusion about the performance of various insulation materials is not a recent phenomenon. Some of the confusion comes from the fact that various materials control heat energy transfer according to the specific physical properties of the materials and their assembly for use. Another problem is that large manufacturers, with government sanction, literally control the methods used to test their product and competing products. This has been an ongoing fight for over fifty years in this country. Some products, commonly used here, are not allowed in other countries because of low performance and serious health issues. The most common testing problems are:

(1) The tests do not reflect actual “installed summer / winter conditions”, which can reveal up to fifty percent difference in performance compared to “accepted tests”.
(2) Most tests favor conductivity resistance and limit the effects of radiant energy. Most homes have about 12-15% conductive surfaces, about 7% is convection and air spaces accounting for up to 80% radiant energy gain or loss.
(3) Some tests do not reveal the serious performance degradation from condensation, actually storing and increasing heat flow, and how it affects the interior humidity levels.
(4) Some tests do not reveal possible mold and other problems.
(5) Some tests, or labeling, do not reveal the health problems due to toxic chemicals. This information is classified as proprietary information and given only to the government.
(6) The tests or labels do not reveal the ratio of material to air volume This ratio can be as low as 1% mass to 99% air volume allowing radiant energy to travel through like an open door, plus air infiltration. The exception to this is radiant barriers which rely on the air space to perform efficiently. If insulation tests were performed with the best interest of the consumer at heart, there would probably be only two insulations available to the consumer.
(7) The other subject ignored by the bulk insulation manufacturers is the approximate 80% heat gain/loss in buildings through radiant heat, infrared energy. This can be expected because most bulk insulations are only about 10 – 20% efficient in rejecting radiant energy, compared to about 97% for radiant barriers.
(8) The “R” factor for bulk insulations are based on the reciprocal of a “u” factor, a conductive test ( for a material that is about 99% air spaces?). The efficiency of RBS are based on a “k” factor. You cannot obtain a “R” value from a “k” factor.
The independent, non competitive, method presented here is based on long established data of energy exchange between two surfaces, ceiling/floor, at a given Delta T” (temperature difference between two surfaces) and will tell you what amount of heat energy is radiated into and out of the home summer and winter. This method depends on no tests and incorporates the characteristics of the insulation, building materials and the effects of any climate condition. It can be performed by anyone with a thermometer. Conventional “R” factor calculations cannot tell you this, due to the problems mentioned above and that the calculations are usually for material only. With “R” factors you can calculate for one set of condidtions and then find out the calculations had no reference to what is actually going on in the structure.

The common denominator for all insulations is; what is the temperature of the drywall and the floor it is radiating to? This “in situ” method incorporates all the variables because the drywall temperature determines your heating / cooling costs. You can use either Btu calculations or temperature calculations. You can see why the manufacturer of low efficiency insulation will not want to use this method. The drywall emission rate, about 90%+, is used in the following chart because that is the most commonly used material. The source of this information, and the following chart, is from an emissivity chart and formula of a mechanical engineering handbook. You may not be familiar with this source of information. It is a manual of materials charts, characteristics, formulas and numerous other factors used by engineers to manufacture most every thing you use. For many professional engineers it is the engineer’s “bible”.

THE HUMAN FACTOR The average person believes that the air temperature is the dominant factor in comfort. This might be true if it wasn’t for the energy radiating into and out of the building with its effects. It is this energy ratio between the interior surfaces and the surface of the body that ultimately determines the comfort factor and energy consumption.
For maximum energy savings you want the lowest rate of absorption and re-radiation of energy. Lower is better. The determining factors of any insulation’s performance are:
1 The rate of absorption and re-emittance ( radiating ) of energy. From the “bible” we see that wood (cellulose), and glass (fiberglass) is about 90%+ efficient in absorbing and re radiating energy. Base foam materials are about 20% efficient. Aluminum foil about .03%.
2 Other than the basic material and its construction features, moisture, either from humidity or condensations can cause substantial energy flow. Using the ratio or 5% increase per 1% of moisture by weight, data published by the National Bureau of Standards shows that fiberglass and cellulose can increase energy flow about 45 / 72% due to moisture in an uninhabited structure. Even the relative humidity can account for a dramatic increase in energy flow. Increased humidity levels in an inhabited structure can cause even more energy lose / gain along with the 1,000+ btu used to convert vapor to liquid. Since radiant barriers do not cause condensation and are superior vapor barriers, the interior humidity levels can be lower than with other insulations.
3 The low quality of installation can also be a detriment to the effectiveness of insulation.
The following chart shows Btu transfer for various ceiling temperatures. Calculations for infiltration, doors and windows are separate as they will be the same for any insulation installed. To increase the envelope efficiency even more, Insulation Specialists has developed a simple method of installing RB to reduce to about 1% the conductivity surfaces of studs and ceiling joists from the normal 12-15 % surface area. In summer you can measure the drywall temperature which can reach up to 110 degs on a 95 deg day with the lower efficiency insulations and no roof shading. If the floor temperature is 75 degs the ceiling, using temperature figures, will radiate about 99 degs/sf/hr. The 110 deg ceiling temperature is about 25 degrees hotter than a winter radiant heat system, causing the air conditioner to run continuously to try to compensate. Without the air conditioner the interior temperature could exceed 100 degs. If the RB is 110 degs it will radiate about 2-3 degs /sf/hr. In a properly designed ranch home the interior temperature, with RB, will be about 80-81 degs without air-conditioning. The humidity levels can also be lower as the RB does not cause condensation which can be forced into the home by the high temperatures in the structure as with some of the lower efficiency materials. Question; if the indoor temperature can be hotter inside than outside without the air-conditioned, how can the manufacturer claim their material is insulation?
As you use the chart keep in mind these two questions;
1 If bulk insulations are about 99% airspaces and radiant energy travels through space at about the speed of light, and the base material absorbs and re-radiates the energy at about an 80-90 percent efficiency, how can a manufacturer claim their material is an insulator? More importantly how can an “R” value be assigned to them ?
2 If the function of a RB is to reflect energy, how can an “R” factor be assigned to it? How can the government and the manufacturers of bulk insulations legitimately force the use of “R” factors in evaluating radiant barriers? More importantly, why?
3 Why has the US Senate interfered with, at least twice, the governments fair trade polices, including FTC regulations, when it comes to insulations? Regulations which would have provided for a fair playing field. Answer: Over $100,000,000,000.00 tax revenue per year due to the excessive use of energy.
Because of this and other reasons the American home owners is using up to two to three times the amount of energy to heat a cool a home than what should be used.
In summer you can determine the temperature of your ceiling drywall by taping a thermometer to the drywall surface.
This chart is based on a 75 deg floor temperature. The chart can be validated by using the emissivity data and formula from Mark’s Mechanical Engineering Handbook. FG values are for insulation between joists and include joist heat transfer. The RB value is for the joists surfaces covered with the RB and a furring strip to separate the RB from the drywall. “A” is the dry wall temperature. “B” represents the Btu’s radiated for the FG installation. “C” represents the Btu’s radiated for the RB installation. “D” the Btu difference between the FG and RB.
Although the mechanics for side walls will be slightly difference this method can be used for approximate comparisons.

Summer Winter
“A” “B” “C” “D” “A” “B” “C” “D” 75
150 88 5 83 75 0 0 0
140 75 4 71 70 5 .3 5
130 61 3 58 60 14 1 13
120 49 3 48 50 22 1 21
*110 37 2 35 40 31 2 29
100 26 1 25 *30 38 2 36
90 15 1 14 20 45 3 42
80 5 .3 5 10 52 3 49
75 0 0 0 0 58 3 55

The 110 deg is high lighted to represent a 95 deg day. The 30 line is highlighted to show the similarities of the summer winter conditions. Note the jump when the temperature gets down to zero degs. Because of the rapid drop off in FG efficiency as the material thickness is increased it is difficult to extrapolate the RB and FG data for “R” value comparison. Compared to the advertised “R” value for FG the RB “R” factor could exceed “R”100 value by a considerable amount, and it is impossible to have a “R” value of 100 much less 100 plus.

Myth: Dust adversely affects the RB performance. A: Dust has little or no effect on a horizontally installed RB with airspace both sides. The top surface could be painted black and the bottom surface might emit 1 or 2 extra Btus. Most ceiling installations have one or more layers, so any increase in heat flow is doubtful. There is little or no dust on vertical installations. Even with dust present the RB is superior to other materials. These comments never reveal the test material type or test method or actual performance differences.
Myth: Holes adversely affect the RB performance. A: Some RBs are manufactured with vapor escape holes. I know of no laboratory tests showing an increase in heat flow, particularly in multi layer installations. Obviously you don’t want large holes, these should be repaired.
Myth: RBs are not as efficient on up heat (winter) as summer. A: The engineering handbook does not make such a distinction. The mechanics of up heat vs down conductive heat flow are different; therefore any given material may exhibit slight differences for winter. However these comments never note that the RB is still superior to other materials.
Myth: Aluminum corrodes. A: Pure aluminum, such as the 99.9% pure foil used in RB, does not corrode under normal atmospheric conditions.
A light, invisible, oxidation does occur preventing any further oxidation. You would not want to breathe the fumes that could cause severe corrosion. Corrosion can and does occur in some unfinished alloy aluminum because of the dissimilar metals used for alloying the metal.
Myth: RB loses its insulation values over time. A: Since RBs do not corrode, the answer is self evident. I know of installations over 30 years old that work just fine.
Myth: You can’t use RB in very cold climates: A When Perry and other scientists went to the poles they use aluminum foil to insulate the structures. The Navy SEALS used multi-layer foil (mfg’d to mil spec HH I 1252) in 1964 in the Artic buildings where the mineral wool was failing. RB are used quite extensively and exclusively, in severely cold conditions, such as, cryogenics and space platforms.
Myth: RB are not very efficient in attic add-on application. If the application is not proper then this is a true statement. However, the retrofit tests so far conducted are not the most effect application method. I have found that a double layer installation directly over the existing material can reduce a/c run time 50% or more. Why test the most inefficient method?