I was originally excited about this when I heard and thought there was some new innovation in insulations.  The more I read, the more data I did NOT find.  We wanted to trap a material in a steel building roof but the Low E concept just did not make any sense being trapped behind the corrugated metal.  Maybe on top, but not under.  Further more, This might "compare" with an R12 for radiant heat but come winter time, I think the performance will be sad at best. 


In a nut shell, looking to build a metal building.  We need an R40 in the ceiling.  We can get 8" unfaced bats but that puts us at R28.  We need to get the additional R value plus find a way to cover the face of the insulation and make it look decent.  Thoughts on this or additional test data or thouhts on the Low E stuff would be great.  We are in Kansas so have everything from -10F to 110F. 

Oh, I should mention that I am resistant to foam due to price.  You can get a LOT of glass for what it costs but I am still thinking. 

The only way to get R12 performance out of low-E layers is with 2 air-gaps (including additional air-barriers) on both sides. If you stacked up 6 layers with 3/4" of air between the layers, and sealed the edges to keep air currents from flowing laterally in the gaps, you might get the performance you need, but it's a LOT of detailing, and in the end, not a cheap solution at all.

Using a high solar reflectivity moderate-E "cool roof" finish (even a mop-on coating) on the exterior can a low cost way to make a measurable dent in the cooling loads, but doesn't much affect your heating season issues. See:

http://www.coolroofs.org/index.html

Sure, you can buy a lot of low-density glass for the cost of foam but without snug air-barriers on both sides will also not perform to spec, and at the temperature extremes even with air barriers it won't cut it. So with a vented air-gap between the 8" batt and the roof and no bottom side air-barrier R28 would be optimistic, to say the least. (You'd be lucky to get R10 performance out of it on a -10F or +110F day.)

If you used reclaimed rigid foam board (scavenged from commercial demolition or re-roofing) you can get EPS or iso for similar to or cheaper than batt costs in terms of $/R/square foots. You'd need to patch it up and air-seal it with modest amounts of other materials but 5" of EPS would outperform 8" batts, and 10" would meet code, as would 6" of rigid iso. If you can't find local sources, if you have a lot of R40 square footage to fill you can buy it by the truckload here and get it delivered:

http://www.insulationdepot.com/

To get the performance out of any insulation you need to avoid thermal bridging, and steel beams/trusses present quite a thermal-bridge, it's orders of magnitude more thermally conductive than timber framing. If you can't suspend it all below the trusses or beams, some amount of spray foam may be in order. A thermally broken R30 has pretty good performance compared to steel trusses penetrating R40 every few feet.

Greetings fastline,

I have an ICF building with RB insulated roof. This is a furniture store, 2 stories. 7500 sq ft total.

Roof consists of a floating corrugated Galvalum metal roof. Over the purlins is a heavy duty bubble insulation, foil, both sides.
Building equipped with 2 5 ton AC of with one is only used, mostly for humidity control, and the second under extreme heat conditions.

1st floor has ceiling fans about every 10 fee, but I don't think ever turned on.

On a 95 deg day you can touch the foil and it is room temp, about 80 degs.

I don't have specific info on winter costs but the owner is very pleased with the overall operating costs.

More info? [email protected]

Radiant cool roofing, a ventilated air gap, and a low e foil will stop an attic from exceeding the outdoor max temperature during a hot day. This will reduce the delta T the insulation below has to fight by as much as 50 degrees on a hot day. Since radiant transfer is proportional to delta T4 of the bodies where T is temperature in Kelvin it is highly dependent on a big temperature delta between the radiating bodies. It is only linearly related to the emissivity of the surfaces. Traditional asphalt shingles are good radiant absorbers and will get more than 50 degrees warmer than the cool roof material when in direct sun. Radiant barriers are good for blocking out heat from the sun but will not do much for cold weather in any case.

2 layers of plastic with a sealed 3/4 inch air gap will deliver R-2. This can be built up to achieve higher levels similar to a 5 pain window which is capable of delivering up to an R-20 in the best windows now. This does include a noble gas fill for windows. I know of a building where sheets of plastic were alternated with ¾” furring strips 3 layers on the inside and outside of the 2x4 studs. Dry wall internal and siding external and it seemed to function reasonably well. On the other hand ½ inch of double bubble wrap will never exceed R-3 in actual performance. Though that is 1/3 less energy flow than nothing. It will make a big difference compared to nothing. But it will not compare to an inch of iso or urethane foam at R-7.

Brian

Greetings,

QUOTE>Radiant barriers are good for blocking out heat from the sun but will not do much for cold weather in any case.

WRONG, WRONG, WRONG

Better go back to basic RB technology.

RBs are used in the Arctic. Navy Seals first used them in 1964 in the Arctic when they replaced the FG in the walls which kept turning to ice bars and required constant replacement.
RB sheets are also used as survival devices for mountain climbers.
A RB house will usually save 30%+ in winter energy costs compared to other materials.

With a Delta T of 85 degs a RB will emit about 2 btu/hr/sq ft and I don't think the RB cares wether it's winter or summer.

You are confused in your arguments. Radiant transfer is dependent on surface temperature not bulk temperature. As you move through the wall there is a temperature gradient from inside to outside. This gradient is dependent on conduction, thermal capacity, thermal bridging, convection, of all the materials and how they interact. If you have say 2 inches of iso or urethane foam (R-14) it will stop all radiant and convective transfer, and over 93 percent of conduction. This means that if the surface temperature of the wall is close to the external temperature on the outside of the wall. The temperature of the inside of the wall is close to the temperature of the inside of the wall. This by definition means that if the wall is insulated and air sealed the effect of radiation is minimal because the delta T of the external surface to the outside environment is minimal in a cooling mode.

If a radiant sealed material is used in a survival situation it improves your situation by stopping radiant and convective elements. In a situation where you do not have a significant insulation layer this will make a big difference. It can be accomplished with a 3 mill thick sheet. It is the biggest bang for the buck and only weighs a few ounces of additional weight; it is light enough to carry.

The sun is thousands of degrees. Almost all of its transfer through space is radiant. No atmosphere in space for conduction and or convection. The radiant effect is dispersed by the atmospheres filtering of the energy. This energy after absorption is reemitted at an energy related to the temperature of the materials that absorbed the energy. Direct sun absorption through a thin atmosphere has the biggest possible affective delta T. Cold temperature radiant energy is determined by the temperature of the masses around us and is not dominated by the suns temperature. This delta T is always much lower.

A Delta T of 85 degrees F for radiant transfer never exists in a cold situation on earth for an extended period of time if the house is properly insulated and sealed. The skin temperature of the home never goes below the outside air temperature from a cold stand point. In the sun an asphalt roof can increase in temperature by more than 100 degrees F. This shows that the maximum radiant effect of the sun is 100 times greater than the maximum cooling effect of a cold climate radiant energy.

These are the simple facts. I have spent decades studying thermodynamics as an engineer. The physics of radiant transfer simply do not allow the cold situation to be anywhere close to the direct solar absorption case.
I hope I have explained this adequately. Note that anecdotal observations have no place in physics calculations unless they lead to experimentation and data driven corroboration. Show me the data, if you think I am wrong. Do not be anecdotal.

Brian

Brian- He'll never show you the data 9that we both know doesn't exist), but it might be interesting to see him try, eh? He keeps dragging out the that low-density fiberglass straw man and environments that none of us live in (like arctic/antarctic cold or outer space) as his prima facie for the superiority of the product.

In his world air never leaks or convects, and the RB is suspended in space- never makes conductive content...

And when that fails he drags out his ceramic bead paint additives that don't appreciably change the reflectivity or emissivity of the paints. (I prefer magic-mouse-milk addtives myself, but they're wicked expensive.)

Greetings,

QUOTE> A Delta T of 85 degrees F for radiant transfer never exists in a cold situation on earth for an extended period of time if the house is properly insulated and sealed.

That's correct. The 85 Degs was a mistake made at 2 am in the morning, I should have caught it, but didn't. It should have read 35 degs.

QUOTE>The only way to get R12 performance out of low-E layers is with 2 air-gaps (including additional air-barriers) on both sides.

RB don't have "R" factors. Is this too complicated to understand?

QUOTE> This shows that the maximum radiant effect of the sun is 100 times greater than the maximum cooling effect of a cold climate radiant energy.

Cold climate RE. GEE I missed that one. Could you tell me what engineering source describes that?
Marks Mech Eng Hand book doesn't differentiate, It just says alum absorbs .03 of RE.

QUOTE>These are the simple facts. I have spent decades studying thermodynamics as an engineer. The physics of radiant transfer simply do not allow the cold situation to be anywhere close to the direct solar absorption case.
I hope I have explained this adequately.

No it doesn't. We are not talking about direct solar gain except for additives and special paints. We are talking about interior insulation applications. In this application the RB doesn't care if it's summer or winter which involves long wave length energy not short wave as in in solar gain. RB are not quite as effective against short wave as long wave. Your engineering explanation seems to have missed that small bit of info.

The problem I have with engineers is that they have to, by nature of their training, rely almost solely on book info. How many RB homes are you familiar with? My guess, ZIP. My experience, in field, 30 yrs. Sorry, I'll take my 30 years, in field, experience over your, sitting on your bu-- book experience. Please excuse my sarcasm.

QUOTE>Brian- He'll never show you the data 9that we both know doesn't exist), but it might be interesting to see him try, eh? He keeps dragging out the that low-density fiberglass straw man and environments that none of us live in (like arctic/antarctic cold or outer space) as his prima facie for the superiority of the product.

In his world air never leaks or convects, and the RB is suspended in space- never makes conductive content...

And when that fails he drags out his ceramic bead paint additives that don't appreciably change the reflectivity or emissivity of the paints. (I prefer magic-mouse-milk addtives myself, but they're wicked expensive.)

I offered to supply some info. Even published my e-m address. You ignored it. You could also go to the manufacturers for info. Did you? NO. So if you don't follow up then you can say it doesn't exist. Clever, clever.
I asked for your back ground and " in field" insulation experience. Again ignored. I don't think you have any practical experience. I think you're an arm chair expert (?).

You accused me of insulting you. I can't insult you. You do it to yourself.

QUOTE>RBs are used in the Arctic. Navy Seals first used them in 1964 in the Arctic when they replaced the FG in the walls which kept turning to ice bars and required constant replacement.

Used title "Navy Seals", should have been Navy C Bs. Damn 2 am pox.

Now as far as using the Arctic, that is a severe situation which tells us that RBs will have satisfactory performance in our area down south of the Arctic. Besides, you don't think bulk insulation freezes up in the lower 48. Hmmm, seems you have no in field experience.

You have never challenged the 2 btu/hr/sq ft number I refer to. You can't and we both know it. So what sys did you propose that would equal or surpass that? Hello, I'm listening.

You use basically the same tactics the bulk insulation manufacturers and US Gov use to discredit RB.
My, my does that mean ...............?

As far as suspension and conductivity, that's right. But, then you don't any thing about RB except what you dredge up from the internet or other or you what think you know. Shame, shame.

You are lost again in your anecdotal beliefs and experience. If you can not calculate the performance, you can not optimize the value porposition for the client. You can only have a feeling that will guide your guesses as a design that will work.

1. I have been designing, building, engineering, and contracting zero energy self-heated homes since the late seventies.
2. I have used RBs effectively for that entire time.
3. The most effective RB is as an external surface where the sun shines on the surface.
4. Next best use is as an internal surface in the air gap below a non-radiant roof, because it will heat up to 100 F above external temperature. This delivers a delta T of up to 100. This is not possible in a cold weather application. Radiant barriers work base on a delta T to the 4th power. This by definition shows that cold weather value is much lower because of this lower delta T. If you have a radiant roof these provide little bennefit.
5. 2 layers of plastic with a 3/4 inch air gap will deliver an R-2 performance. That is a 50% reduction in energy transfer. A 30% gain over zero is not impressive, that is only an effective R-1.5
6. I use actual dynamic FEA modeling tools which emulate the real world accurately, my designs work maintaining temperature, self-heated, no overheating and no uncomfortable drafts.
7. R factors, U factors, are often misunderstood but have to be understood to design optimized structures.
8. 2 separated insulative barriers with an isolation gap always perform better.
9. I have used RB paints both industrially and in a home. They work slightly better than white paint. They do provide a reasonable RB. Hot industrial applications these work well.
10. My 30 plus years of experience, technical and practical experience, engineering understanding, and record of successful built designed and tested buildings is what I would trust.
11. How many buildings have you calculated the total energy use for based of climatic based optimized design that delivered accurate real world results that matched?
12. Relying of an attitude backed by anecdotal experience will not deliver the best combination of results. Can you tell me exactly what the utility life time costs of changing one of the hundreds of variables in the buildings built up design will deliver? I can. If you cannot then you cannot optimize the design of the building delivering the optimum value to your client. Typically those that rely on anecdotal experience have to build to overkill to make up for the lack of knowing how the building will perform.
13. Can you deliver a self-heated house for the same cost as a custom home? I do.
Brian

Greetings,

Thank you for your response. It nice to know what the qualifications and experience a person has when imputing on this site.

QUOTE> You are lost again in your anecdotal beliefs and experience.

ANS: Anecdotal experiences trumps anecdotal beliefs when they are repeated over and over with the same results.

That being said. As I have said I have over 30 yrs experience exclusively with RB both new construction and correcting other contractors mistakes. No, I do not set and calculate heat gain and losses. How much better can you get then 2 btu/sq ft/hr. My biggest concern is the window and door placement and the resulting effects.

By the way, how many bulk insulation contractors do these computer calculations?

As I see it one of the biggest problems in the construction of new buildings is the over reliance on insulation and the complete disregard of condensation and resulting dramatic increase in energy flow.

QUOTE> 3. The most effective RB is as an external surface where the sun shines on the surface.
Ans: agreed, BUT, how many buildings do you see wrapped in alum foil?

QUOTE> 4. Next best use is as an internal surface in the air gap below a non-radiant roof, because it will heat up to 100 F above external temperature. This delivers a delta T of up to 100. This is not possible in a cold weather application. Radiant barriers work base on a delta T to the 4th power. This by definition shows that cold weather value is much lower because of this lower delta T. If you have a radiant roof these provide little benefit.

ANS: No the next best place is immediately above the ceiling drywall. Two layers in between the cords and one attached to the bottom of the cord with furring strips across the cords and then dry wall.

One other thing. It has been my experience and that of a couple of my customers, including a ME that the attic air temp on a 95 deg day, no shade, dark roof is 10 degs over ambient. How do you explain that. Over the years I've gotten two different explanations.

QUOTE> 5. 2 layers of plastic with a 3/4 inch air gap will deliver an R-2 performance. That is a 50% reduction in energy transfer. A 30% gain over zero is not impressive, that is only an effective R-1.5

What is this thing with plastic formed air gaps.

ANS: We're talking about RB and the amount of energy they reflect. I don't see any one on this forum asking how many layers of plastic sheet do I need.

QUOTE> 6. I use actual dynamic FEA modeling tools which emulate the real world accurately, my designs work maintaining temperature, self-heated, no overheating and no uncomfortable drafts.

Ans: My homes do the same and I don't need to spend time on a computer.

QUOTE> 7. R factors, U factors, are often misunderstood but have to be understood to design optimized structures.

ANS: They certainly are and that confusion has been propagated by the insulation industry and the US Gov. ( God bless the USA; Inc )

QUOTE> 8. 2 separated insulative barriers with an isolation gap always perform better.

Ans: And that is what multilayer foil is.

QUOTE> 13. Can you deliver a self-heated house for the same cost as a custom home? I do.

ANS: Yes. and cooling too. How ever custom has not been defined. The problem with RB, or rather, builders, is the over heating in winter. They just don't seem to understand that you need far less solar orientated glazing than with a bulk insulated house.

Cooling. RB insulated homes generally do not exceed 81 degs on a 95 + drg day, no shade, black roof.
Now this is ranch style. 2 story you do not have the basement cooling effect so the temp can be 1-2 degs higher. How much does your client have to spend to get the same results?

About 4 years ago a tornado knocked out elect for 6.5 days. Our ranch SIPS style upgraded with RB never exceeded 80 degs with o/s temps at 95+ degs, no shade, dark roof.

QUOTE> 9. I have used RB paints both industrially and in a home. They work slightly better than white paint. They do provide a reasonable RB. Hot industrial applications these work well

When other methods are not available or the customer is money limited, then these products can provide a substantial relief in comfort and money. I think we get carried away with the optimine and forget the little guy. This is the problem with DOE and these state programs. How many states give you rebates for passive svs? They want to promote industry and see product sold, tax revenue you know. This is of no benefit to the average person.

OK, enough. I have other things to do.

Over 80 is not a comfortable temperature. Homes I have built run 68 degrees in the summer and 74 degrees in the winter without utilitiy costs using natural systems. If the home cools below 60 or greater than 80 is never acceptable. You really do not get it.

Good luck.

Brian

Greetings,

Yes I get it. Home owners who want to incorporate Trombe walls and water tubes or similar sys can get the same results. I'm not challenging your results. I'm saying that you can do so using a different approach.

Define your natural sys. please.

You're catering to a group of people who can afford high tech solutions, right?

I'm talking about joe six pack who should be able to get either the same results or very close to that on their budget.

Try looking at econodome.com and ck their turn key building costs. Incorporating the RB and some passive heat/cooling sys is a big step in the right direction to getting material management and housing costs way down while getting a superior structure.

The radiant barrier design he is talking about is only claiming an R-20 wall rating. The buildup is external sheeting, air gap, structural sheeting, ventilated air gap, radiant barrier, air gap, radiant barrier, air gap, radiant barrier, air gap, internal drywall. This is not hard to believe, though no data is provided. I believe that this could compete with standard construction but has no place in a discussion of self-heated, net-zero, or passive house alternatives. This design could be improved markedly by addressing the thermal bridging in the buildup by replacing the inner and outer most spacers with foam spacers and foam caps on the inside and outside of the 2 by members. This addition could bump the performance up to about R-30 for little additional cost.

As I stated earlier a buildup of 5 plastic sheets internal and external sheeting with 6 air gaps delivers about the same performance. The spacers were alternating foam and 1 by stock.

Moving the performance of the system up to an R-50 to r-100 is a matter of layers. Using radiant barrier on the inner most and outermost layers would be worth the extra costs for additional performance gains. Using a cool roof radiant siding or roofing would also be advisable.

Issues with this approach include lots of detailing for airtightness, space for bugs to set up shop, minimal sound deadening, no thermal mass and no thermal moderation. These issues can be overcome with additional measures.

Trombe walls, water tubes, Geodesics are so 70s and old school solar, been there, done that in the 70s. Have you ever tried to sell, insure, appraise, and finance a Geodesic. I have and no thanks for the hassels. I build attractive homes people want to live in that function and do not cost more than a typical custom home. They also have a good resale value. 90% more energy efficient than a standard to code building. I use natural, local materials as possible. I recycle materials. I source surplus materials. I shop for the best deals. I use novel methods as well. I do not limit what I can do.

I do not think you get it because your comments indicate otherwise.

I cater to people who want homes that function. I provide a carbon neutral, green, sustainable, high quality home that is self heated and cooled by design. Nothing complex, or high tech, simply smart design and usage of materials taking advantage of the natural properties there of.

Solar, thermal mass, sealed, HRVs, earth tubes, natural convection, designed in circulation, air filtering, RB where appropriate, super insulated when needed, climate specific, site and flora dependent to meet the desires and life style of the client and future dwellers.

Brian

Greetings,

you know Brian, I'm thinking we're in two different universes. That's ok, more fun.

QUOTE>
29 Sep 2011 08:45 PM QuoteQuote ReplyReply AlertAlert
The radiant barrier design he is talking about is only claiming an R-20 wall rating. The buildup is external sheeting, air gap, structural sheeting, ventilated air gap, radiant barrier, air gap, radiant barrier, air gap, radiant barrier, air gap, internal drywall. This is not hard to believe, though no data is provided. I believe that this could compete with standard construction but has no place in a discussion of self-heated, net-zero, or passive house alternatives. This design could be improved markedly by addressing the thermal bridging in the buildup by replacing the inner and outer most spacers with foam spacers and foam caps on the inside and outside of the 2 by members. This addition could bump the performance up to about R-30 for little additional cost

You keep applying "R" values to RBs. If I did that in trying to sell RB, the Gov. would close me down and send me to jail. RB do not have "R" values.

If you are referring to my wall construction, it is:
2x4 framing, Sheathing, Type 3 RB (two layer) 3 reflective air spaces, RB/VB interior sheet over studs, horizontal 1/2" "z' strips, dry wall
Calculations come from Marks Mech. Eng. Handbook, 13 th ed. Which shows that a 110 deg foil surface will radiate 2 btu/hr/sq ft/ hr to a 75deg floor.
Needles to say the surface foil doesn't get any where near that. So then, what is my RB "R" factor?
If I thought there would enough of an energy reduction I could install a RB on the exterior sheathing, then furring strips, and then install steel siding or other.

for FG and Cel "R" values are derived from manufacturers data with is seriously flawed and having been in the business long enough you know that. According to NBS test in 1977 heat flow was increased about 50% and 72% respectively. So if you are using Cel and using mafg. supplied data you misrepresenting the performance expectations. However you have nothing to fear from the FTC because they endorse such mis representation with bulk installations.

But you're building a different type of structure and I applaud that, even if it is an ugly sq house. Oops, fingers got out of control. But again you're using tunnel vision. Not every one wants your type of house. Some people love domes, others don't. If every thing was the same on this earth it would be a very dull place. Variations on a theme allows for spontaneity and creative expression.

You say you have used RB. My feeling is that you haven't used them to their fullest potential.

Now mass is important and I am putting forth the basic structure the AVERAGE person would want to build. After that they can do what ever they want to employ passive features. You're not going to go into a avg $200,000, housing subdivision and build the type of house you say you're building.
I've notice that on the homes where the builder installed 1.5" foam on the exterior of the basement walls, full hgt, that the concrete help stabilize the temp, whole house and reduced the energy use. Now that is passive and doesn't cost that much.

Since it isn't going to take much mass to flywheel the interior temp I believe using 6" pvc pipe installed vertically in some of the interior walls would be of great benefit.

It doesn't take much window space to heat a RB house on a zero deg day. and considering the low heat loss at night you will easily get 24 hr flywheel benefits.You can do this in sub division homes, IF the contractor wants too. Unfortunately the builders in the St Louis area don't care, anymore.

Financing and insurance is available for domes. Econodome.com has an arrangement with a national bank and insurer.

Even though you didn't mention it other posters keep bring up the Florida tests as if that was the final answer.

1 These were retrofit tests not new construction utilizing muti layer RB.
2 The RB were not installed for maximum benefits for retrofit
3 When multi layer RB are installed above the drywall it doesn't matter what color the shingle is. with a proper ridge/soffit vent sys the attic temp will only be about 11 deg above ambient.
Which reminds me, you did not provide an explanation why this is so.

So what it boils down to is that you are providing a service to the people who are attracted to your design philosophy and I get the ones who are attacked to mine, and the other poor slobs get scre---. And unfortunately, far too many.

80 years ago it was snake oil....today, it's radiant barriers...

Greetings,

If RB were not effective the gov would have put them out of business long, long ago.
On the other hand the gov has and is trying to discourage the use of RB because they cut the energy tax revenue too much.

It would seem that you're another one of those people who know all there is to know about something you know nothing about, and you're going to make sure you get your meaningless points published, right?

The universe is the same. Your perspective seems to be limited to RB. You do not listen to the posts and seem hell bent on pushing RBs no matter what. I understand how RBs work. They are wonderful with a large delta T period. This limits the optimum use of RBs. Please explain how you achieve 99% reduction in heat transfer with only RBs. The reality is that is not practical to do this. In passive house designs 99% reduction in heat transfer in the wall and ceiling portions is the goal to make up for the lower performance of windows and doors. Brian

Greetings,

QUOTE> The universe is the same. Comon now, that was suppose to be a bit of humor. Lighten up. If you have a stroke who will I spare with?

QUOTE> Your perspective seems to be limited to RB. You do not listen to the posts and seem hell bent on pushing RBs no matter what.

No so. I recommend foam in some apps where RB will not fit. Gee, and the other posts are pushing what they believe. Right? I don't see you challenging them. Why?

QUOTE>I understand how RBs work. They are wonderful with a large delta T period. This limits the optimum use of RBs. Please explain how you achieve 99% reduction in heat transfer with only RBs.

I can't believe you said that.

Yes, large delta T, which means that the less efficient materials are passing more energy. Think, think.
The limits you talk about are the same for ANY material. The lower the delta T the less energy available to pass thru, or reflect, true of ANY material. For instance, why, on a FG house doe the interior temp get higher than the ambient temp? Isn't suppose to retard heat flow?

Quote>The reality is that is not practical to do this. In passive house designs 99% reduction in heat transfer in the wall and ceiling portions is the goal to make up for the lower performance of windows and doors

It's not practical? Brian, what are you smoking? So if I can make this reduction it doesn't mean anything because I didn't use the term passive?

The goal is to make as eff an envelope as you can and then attack the window and door problems. All you can do with door and windows is placement, size and number.

You said a few times that you understand how RBs work and then turn around and make these contradictory comments. You wouldn't be trying to confuse the old man, would you?

How many of these passive homes have you built over the years?

I don't know if you mentioned what kind of engineer you are. Civil or ME?

RBs work best at high delta Ts. Foams and other bulk insulation materials reduce the heat transfer through the material by a percentage based on the surface temperature of the inner and outer skins of the insulation itself. Conduction is based on a function of linear relationship to delta T of the inner and outer skin temperatures. Radiant thermal transfer is a function of delta T to the fourth power. It is also dependent on the absorption and emission characteristics, filtering of the atmosphere, cleanliness of the surfaces and several other factors.

Generally foams work equally well as temperatures change. On the other hand the performance of RBs very dramatically with Temperature. This means that a combination of the two makes more sense. This means that the value of each is application dependent. Your observation that it means one is superior in all cases is simply incorrect. Again it depends on the variables you are working with.

Another interesting fact is that RB traps isolate the insulators on both sides making them act more independently. For example if you have a vacuum in the void space in the trap then the insulation on both sides will act independently. This means that if you have R-10 on both side of an evacuated radiant trap that is equivalent to R-100 in application out of R-20 of bulk foam. Since we do not have a vacuum in the void space the effect is not as pronounce but is still significant. The convective transfer is much less than conduction this is why a ¾ inch air gap counts as R-2 in a buildup. Using a triple radiant trap with two inches of foam on the inside is superior to 4 inches of foam with no radiant barrier.

You seem to be anti-understanding of the actual performance and physics of what is going on. Anecdotal experience is great but often leads one to the wrong conclusion. Many of the things you claim are not completely correct and are filled with partial truths. This is why the reaction to your observations often are rebuked or expressed as voodoo or snake oil. If you stick to facts you will be better received by others.

I am a Materials Engineer. Specifically that is the study of materials, their properties, manufacture, modification, applications and the physics of augmenting the properties in applying those materials for optimized applications in complex systems. I have worked in the material, construction, utility and medical device industries as a consultant, engineer, contractor, builder and project manager. I have specifically worked in high temperature physics designing structures that dealt with delta Ts that exceeded 2000 degrees F. This is a place where RBs play a very important role.

I designed my first low cost self-heated and cooled passive home in 1976. It was very similar to what John Hait later called a PAHS home. I have designed high mass, double shell, super insulated, earthen heat storage, annual heat storage, and have used surface bonded foam, ICF, SIPs, shipping containers, cob, rammed earth, sand bags, logs, filled gabions, straw bales, stressed skin wooden arches, wood and metal geodesics, straw bale, tire walls, concrete post and beam, solar, thermal, solar PV, earth tubes, Biomass, rain water collection, gray brown and black water, standard construction and other systems. I have embraced alternative methods and ideas for 30 plus years. I have experience with them and can tell you the benefits of each and why I now do what I do. I think you would be hard pressed to find someone more open to trying new things. I also have enough experience that I can keep people on a successful path to a passive, self-heated, zero energy home without additional cost to construct them.

My current preferred system is using modified earthen filled wire basket structures for walls, and super insulated roofs with radiant cool roofs and a ventilated radiant barrier trap under the roof. I can build a superior structure that is 90% more energy efficient than a standard home for a lower cost, lower embodied energy, lower labor content, low maintenance costs, longer service life, with the options to have living walls, no utilities, natural convection air exchanges and an overall superior quality of life.

This construction method allows the building of a passive home at no additional cost. Not understanding how this all works is not unusual. Most builders simply use standard materials and have not spent their entire life striving to find something better. Your observation of more efficient is not practical assumes a limited imagination and limiting your methods to those that you are familiar with. Instead of making statements that are incorrect you should ask how it can be done. The more I have learned in life has divulged the fact of just how little we actually know and understand and how much further we still have to go.

Example of something most people do not understand is that is you have a foot of earthen fill in a wall it averages the temperatures over a period of time eliminating the effect of the highs and lows of the day and week. 2 feet averages the temperatures over a month and 4 feet averages that temperature over 4 months. If you understand this you can eliminate the need for air conditioning in almost the entire USA with nothing more than dirt filled walls and a super insulated roof. This is why adobe homes work in most of the hot climates in the USA. People claim high insulation values for adobe homes. That is incorrect it is that the material is a poor conductor and has relatively high thermal capacity which is the definition of a good moderator. By the way dirt is low cost, local, green, sustainable, carbon neutral, sound deadening, and tough.

Utilization and integration of radiant barriers, thermal moderation, thermal mass, purposed insulation, micro climatic factors, proper glazing, air sealing, heat recovery ventilation, isolation layers, Merv-13 plus ventilation, No VOC materials, alternative construction materials and methods allow one to build a healthier, higher quality, longer lasting, more comfortable home at no additional cost. The issue is having the knowledge and experience to put it all together. It is not a question of whether it can be done. It is can the person you are working with put it all together, most cannot.

Brian

Greetings,

That'll teach me to ask what do you do for a living.

Before I respond to your post, are you familiar with Harold Hayes, Skytherm sys?

QUOTE> RBs work best at high delta Ts.

I believe a more accurate statement would be, The results are more dramatic at high delta T compared to other common materials.
The foil itself is .03 emissiuve regardless of the delta T. Right? As I said before as the delta T goes down the less dramatic the comparison. But it isn't always the delta T its the radiant factor. Granted the conduction factor enters in in a wall construction, but, after the energy is absorbed the energy passes thru as, conduction thru the material mass, the moisture, radiant from fiber to fiber , surface to surface, and radiant thru the air volume. With RB you eliminate most of that buzyiness.

I am confused as haw I am misstating my claims(>). Foil emits at .03 eff., fro eng hand book, Mutilayer foil properly installed does not condensate moisture. That's about it.


I'm familiar with the construction methods you out lined. How long do you think an adobe wall would last in the mid west?

Quote> Utilization and integration of radiant barriers, thermal moderation, thermal mass, purposed insulation, micro climatic factors, proper glazing, air sealing, heat recovery ventilation, isolation layers, Merv-13 plus ventilation, No VOC materials, alternative construction materials and methods allow one to build a healthier, higher quality, longer lasting, more comfortable home at no additional cost. The issue is having the knowledge and experience to put it all together. It is not a question of whether it can be done. It is can the person you are working with put it all together, most cannot.

I agree, but, how many builders are you going to get to do this, not counting the resistance from building inspectors that have no, none, nada imagination?

I do not have the time now, unlike engineers who seem to have all the time in the world to indulge in meaningless past times instead of the task in front of them, ( I speak from experience here, anecdotal as it may seem) so I shall depart for now. I have my house to side.

Kinda wish you lived next door. If nothing else you could help with the siding job.