Miscellaneous Questions about Manufactured Building Systems

Dr. Nabil Taha has over 27 years of structural engineering experience. Prior to opening his own engineering firm in Oregon in 1997, he was a Professor of Engineering at Northern Montana State University and at Oregon Institute of Technology. He has structural expertise in a wide range of building systems and can answer questions related to virtually any common building method. His focus is on green design and he is always willing to trying something new. Dr. Taha is dedicated to future sustainability through innovation; he creates solutions for beautiful sustainable and safe structures by melding old and new technologies. He loves a good challenge. He is Licensed in twenty three states and can design buildings and/or consult to assist with structural permitting in these states as well as internationally. As a prior College Professor, Dr. Taha is a teacher at heart. He loves to share his knowledge and offers educational seminars and trainings for the do-it-yourselfers and professionals alike. Dr. Taha's goal is to continue to grow and provide knowledge and services for those trying to make their dream project a reality. No project is too big or too small. For information about Dr. Nabil Taha and his engineering firm see www.structure1.com

Questions and Answers

Q: I'm from Russia and Laminated Veneer Lumber ( LVL) is a new product here. Nobody knows how to figure out how much material you need exactly. Where can I find information about how to evaluate LVL and where can I replace other materials, like metal?

A: LVL is Laminated Veneer lumber. It is produced by several companies around the world. Since it is engineered lumber, its quality is way better and stronger than the natural lumber/wood. One of the companies that produce it is Boise Engineered Wood Products, www.bc.com This site has tons of information including load tables for joists, rafters and beams.

Q: We are in the design phase of an addition on our 50 year old brick Cape Cod house. Are there countertop materials we should consider that are earth-friendly? I'm planning to use Corian countertops, but your website made me wonder if there is a re-cycled material available that I should consider. Ideally, something easy to clean, attractive, not wildly expensive, that holds up well. It doesn't have to be "natural" material (I know granite is natural, but it's too cold to the touch for me).

A: (Leon) When Corian first came out, I received factory training on its installation. Corian is beautiful when installed, but it's expensive and requires a factory-trained installer. Another (similar) product is SwanStone by the Swan Corporation, which also requires installation by a professional. Their price could be one-third or one-half less than Corian according to Swan Corporation. However, complications of installation and your choice of edging design can affect this price.

The new trend is exposed aggregate. It's earth-friendly because it's the sum of "minerals and natural substance." If you wish, you can add designs and patterns into the concrete surface. This product is very dense; if you occasionally drop glasses, cups, plates, etc., be prepared to replace them because they will surely break!

Installed, the product is either 1.5" or 2" thick. Some companies offer up to 24 colors. Sample colors can range from $25 to $50 with custom colors running $75 and up. Prices can be around $65 to $125 per sq. ft., which includes a beveled edge for 1.5". These prices, of course, depend on the contractor. There will be extra charges for an under-mount sink cutout, drainboards, edge details, patterns, backsplashes, and a concrete single-basin sink. Installation of the countertop can run between $40 and $50 per hour, per person.

Countertops are either pre-cast or built on site. They also can develop hairline cracks, the result of natural shrinkage of the concrete. These cracks tend to be non-structural. However, these imperfections are the appeal and character that customers are looking for—the aged appearance that naturally occurs is preferred over Corian or plastic laminate countertops. Of course, is all based on personal taste.

A third option would be to install glass tiles made from recycled windshields. TerraGreen Ceramics created their product using a sophisticated system called "glass fusion." This process combines recycled glass and minerals to create an entirely new ceramics material with a distinctive look and feel. The body of the tile contains over 55 to 58 percent waste glass, e.g., windows, mirrors, and post-consumer glass (bottles, jars, container glass). The remaining tile body is composed of select nonmetallic minerals, such as special clays, feldspar, sand, and silica. The manufacturing process is designed to have zero negative impact on the environment while providing a non-toxic environment for employees and the surrounding community.

Because of the handwork involved during different phases of the manufacturing process, these tiles exhibit their own personality in the sense of color, texture, and shape—no two tiles are exactly alike. This is even more noticeable in the TerraClassic line due to the hand-rubbing technique applied to the surface of each individual tile before firing. They make a great product for countertop applications. Field tiles run about $7 to $16 sq. ft., depending on color. Bull-nose and outside corners run about $5 each. The only way to really appreciate the beauty of these tiles is to see and handle them yourself. This product not only helps our environment but it gives you some unique handmade tiles with real character.

Good luck with your remodeling project! You've got your work cut out for you as you research earth-friendly countertops. Contact the manufacturers and ask for samples of their products so you can get a feel for the product.

Q: Are their good kitchen solutions for handling re-cycling & composting before weekly recycling pickup, and when we walk back to the compost pile with scraps? The kitchen waste ideas I'm looking for are to: hold the bottles, cans, plastics that we recycle into a big blue bin that is picked up by the county weekly. Currently, we set them next to the kitchen trash till we go out the back door and walk out on the porch to toss things in. Not a huge inconvenience, but I'm hoping for a solution that will keep the kitchen floor from being the interim collection point. house kitchen scraps in doors for a week before dumping into the compost pile. Currently we use old plastic 1-gal. ice cream tubs that sits on the counter uncovered. Sometimes several of them sit on the porch railing (at least they are out of the house) till we walk out to the compost pile - esp in winter when we both leave and come home from work in the dark.

A: (Leon) If you are trying to keep the countertop and kitchen floor clear of clutter and the room free of odor, then consider incorporating an enclosed but independent porch off the kitchen where you could house both the recyclables and the waste for the compost. It's not clear from your question whether or not your county requires recycled waste to be separated. In our area it's OK to keep plastic, aluminum, and glass together, which we do in a brown paper grocery bag placed in the blue bin. That leaves the other side of the bin free for newspaper and other paper products. Cardboard is cut, bundled, and tied and left next to the blue bin. If your county requires complete separation, then it would be a good idea to contact them for the proper requirements and container.

As a suggestion, you could construct dividers out of 1/4" plywood and place them in the blue bin. They'd be easy to make. Cut your main divider (normally the longest way) the depth of the bin) and then cut short cross members (as many as needed). Once you decide how many compartments you need, mark their positions on the main divider and cut slots one-half the way up and 1/4" wide. On the cross members, cut dead center, one-half the way up and 1/4" wide. Now you can place the cross members over the main divider, open cut to open cut, and push them flush into place. Then pick up the whole unit and place it in the blue bin. You could also build the same dividers from heavy-duty cardboard to hold down the weight.

For the kitchen waste, I would build a small compartmented unit that could hold up to three large containers with lids, perhaps something similar to the plastic containers that hold bulk pickles or mayonnaise. You could also make a carrying case for each independent container to make it easier to transport out to the compost pile. The entire unit should have a lid and sit on a shelf that is at a comfortable height. Also, it should be placed in an area that is out of the path of direct sunlight or heat, otherwise, this area will need some type of ventilation, like an exterior wall exhaust fan, to remove any odors created by the heat.

Of course, you could purchase compost containers off the web or country living type catalogues to make your life a little simpler. These containers can be used directly on the countertop because the activated charcoal filter in the lid eliminates the odor of food scraps. Available in 6 quarts and 2 gallons, these containers are green and they cost under $15 for the small size and under $20 for the larger. A replacement filter 3-pack is $5.95. They also have a handle to make it easier to transport to the compost pile.

Now it's up to you to figure out what system is most user-friendly for you!

Q: I am looking for information concerning a building technique I saw on the news. It is based on a Mexican method of using cinder blocks, and then sprayed over. Are you familiar? If so can you point me the a direction where I could find out more?

A: (Kelly) I'm not sure about the specific technique that are referring to, but there are a variety of ways of building with cinder blocks. What you saw might have been the use of a surface-bonding cement. This can be used with dry stacking the blocks (without mortar) and then covering the exposed surface with a compound that has strong fibers (such as fiberglass) that will create a skin on the surface that holds the whole assembly together. This kind of cement could conceivably be sprayed. Check with your local building supplier for this kind of material and follow the directions on the can.

Q: I'm considering having a concrete patio poured - approx. 20x20. On two sides, I would like to build a wall - approx. 2.5 ft. high - using pressure treated wood, tar-paper, then wire mesh -- to finally apply veneer stone, capped off with Lime stone. How should I secure wood framing to top of concrete??

A: (Leon) Samuel, unless you can tie the walls in at the corner, I would not secure the wood framing to the surface of the patio. However, even with pressure-treated material tied in at the corner, I would still raise the wall so the bottom plate does not sit directly on the concrete patio. This will prevent the plate from contacting water. You can use Simpson's Post Base (EPB44T) for a 2x4 wall construction or anchor plate bolts and Simpson's Standoff Post Base (ABA Series) for 4x4, 4x6, or 6x6 wall construction. Both the EPB44T and ABA are placed into the wet concrete.

If the walls are not tied together, then I recommend that you place them in the ground as you would with a concrete foundation following the building codes in your area. However, between the cost of the materials and the drainage required to build treated foundations, it may be more economical just to pour concrete walls. You can also visit Leon's Web site at www.asktooltalk.com for previous questions, home repair tips and general remodeling information.

Q: Hi I’m a laborer but want to get further in the building trade. I have bought a course from the Internet on general building. Do you have answers to a question in the form of an essay I’m stuck on? The question asks me to describe the different types of building and construction methods available today. Could you please give me some advice?

A: (Leon) Lee, the information you seek is all over the web. Start your search with the following key words and try using www.dogpile.com as your search engine: Building Green, Sustainable Building, Sustainable Design, Straw Bale Houses, Earth Homes, Building homes with steel, Building homes with natural materials, Building homes with nontoxic materials,, Building homes with logs, Log homes, Timber framing, Building with concrete, Concrete home, Building with alternative materials, Homes built using alternative materials, Homes built using ICF, Homes built using wall blocks.

This is just a starting point and you will have your work cut out for you as you review the wealth of information that will come up on the search engine. To speed the process, my book, Build Smarter with Alternative Materials, will be very helpful to learn more about the industry. Many of the methods you are asking about, including man-hours and manufacturers contacts, are listed in the book.

Q: I am searching out a method to bind recycled styrofoam. The goal is pre-cast wall units that I can then insert within a post&beam frame. The thickness of the wall panels would be at least 6", and be contained with a 1"x6" frame. Mortar is an option but the more you use the heavier and less insulative the panels! Any thoughts?

A: (Kelly)You may have heard of Rastra Blocks. They are insulated concrete forms that use recycled styrofoam. I believe that they use some form of Portland cement (and maybe other ingredients) to do this, but this could be a model for experimenting.

Q: We are about to start building a steel frame house on steel stumps. We were wondering if there is a formula or table as to how far apart the metal stumps should be. Building codes are different in Australia of course but just a general math based table would be a great starting point. Is it better to use heavier metal spaced further apart or lighter stumps placed closer?

A: (Leon) This question is outside my expertise. However, I did find a couple of sites that pertain to the Australian market that could help the reader: australiatrade.com.au, australiatrade.com.au .

Q: I am doing a school project, and I am trying to find out which is the best recipe for making cement. I am trying to find out which one would also be strongest. Please could I have your expert advice!!! The recipes are: A: 3 teaspoons of sand, cement and gravel. B: 5 teaspoons of sand, 2 of cement, and 2 of gravel. C: 2 teaspoons of sand, 5 of cement, and 2 of gravel. and finally...D: 2 teaspoons of sand, 2 of cement, and 5 of gravel.

A: (Kelly)Usually, the more Portland cement in the mix, the stronger the concrete will be, so C is likely to be the strongest. However that rich of a mix is way over-kill, and I would say that A would give you the best all-round mix that would be plenty strong.

Q & A: We are an Indian company, wishing to get into the business of manufacturing building materials of the two following choices:
1) Aerated Lightweight Concrete based on an Australian company technology. The specialty being no need of autoclaving hence saving on energy cost.
2) Expanded Polystyrene and wire netting 3D panel system applied with shotcreting on both faces based on an Austrian company technology.
We shall be highly grateful receiving your direct opinion regarding the preference of one against other. Which technology according to you shall enable a cheaper product?

A: (Kelly) I am afraid that I can't give you a definitive answer to your question, since their are so many factors involved, many of them having to do with the availability and cost of materials in your locality. From a green or sustainable point of view, it may be a toss-up in terms of energy consumption in the production of the material...but this would take some very careful analysis to know for sure. As manufactured systems, both products that you mention have their benefits, in that they render fairly well-insulated enclosures that perform well in the real world. I suggest that you study the potential market place for these products in India to see which would be more readily accepted by the workforce and the eventual home or building owners.

1) Aerated Light Concrete is a highly insulating and completely fire proof material. Whereas EPS apart from being highly processed material, it is very toxic if it burns, it could potentially outgass. Fire as a situation, we believe, nobody would like to take chance, and particularly when equally good alternative is available as far as building insulation is concerned in Aerated Light Concrete.

(Kelly) I also was of the same opinion about the toxic effect of EPS if it burns, and had mentioned this on one of my web pages. Then I got a response to this from someone who works in the industry, claiming that tests have proven that EPS is no more toxic than wood smoke if it burns, and in fact does not combust very easily when encased in wood paneling or certainly in cement. I did some independent research on this question, and it appears that he is correct about this.

2) With Aerated Light Concrete, the finished items from the factory supply, in the form of Masonry Blocks, Pre -cast Panels, it appears to us, the site construction jobs little easier for the builder. Whereas in shotcreting operation the builder requires a great deal of specialized equipment- Compressor to run the shotcreting machine, the cement mixer and to keep it fed with materials, besides concern on operator health (need of mask to keep breathing), number of tools for 3D Panels erection and special tools for many spots wire binding etc. For good operation of shotcreting nozzle, we are informed that the mix. should be more rich in cement, hence we believe relatively more cement consumption. Your comment please.

I agree with your assessment here.

3) Over all speed of construction, it appears, 3D Panels and shotcreting system scores a little over Aerated Light Concrete.

I expect that this is true. I have seen several AAC projects being built, and the work goes fairly slowly because of the precision involved. The larger panels would go much faster than the smaller blocks. In fact I talked to one contractor who put up a large commercial building with the panels in about two days!

Given your valued comments on above broad points only would suffice our purpose for the time being.

Given the above considerations, I would lean toward the AAC, especially if you can manufacture the product without the Autoclaving phase.

1) If EPS does not combust (and it burns no more toxic than wood burns) being encased in cement duly reinforced with well designed galvanized steel wires net in a 3D panel, don't you feel it is a better designed composite material and possibly better in strength to weight ratio compared to Aerated LightWeight Concrete whose exposed surfaces with cellular structure more susceptible to water/moisture absorption specially where heavy rains may take place?

I have not done sufficient detailed study of the properties of these materials over time to give you a definitive answer to this, but from the standpoint of simple observation, I would say that this is not necessarily so. The large AAC panels that I have seen actually also have steel reinforcement built into them, so the strength might be similar. I have seen demonstrations of AAC in wicking water, and it doesn't really pass much through; I believe it is closed cell in structure. I do like the EPS panel technology for this reason: it puts isolated thermal mass on the inside of the building where it can function to moderate temperatures.

2) In panels made out of Aerated Light Concrete there shall be more joints in erecting a building, whereas in case of EPS-wire net 3D Panels with shotcreting makes a building totally monolithic and joint less, hence we believe much better life in case of heavy rain prone areas. Besides, we believe erection and joining of the panels in case of Aerated Lightweight Concrete, is a more skilled art than 3D Panels with shotcreting?

You are right about the number of joints and the monolithic nature of a shotcrete system, but the way the joints are sealed makes for extremely tight construction, and a bonded coating could be applied later that would totally seal the joints. Regarding the skill involved, I think it is a toss-up; as you mentioned earlier the shotcrete technology itself is full of industrial complication.

3) In making the Panels or blocks in the factory for Aerated Light weight Concrete or in-situ applications at site there is regular need of forming material either of plywood, steel or both. Whereas in case of EPS-wire net 3D Panels with shotcreting there is no need of any forming material. Don't you think that the latter process saves a lot of plywood, steel or both and thereby save the environment as well as cost?

The work with AAC that I have seen employs no forming materials at all, although this is likely necessary at the factory, as it would be with foam panels.

Q: I have the problem of cracks between the concrete ceiling and masonry wall and several corners, that may be caused due to ceiling concrete expansion and also masonry foundation subside (bad foundation) .The width of the cracks are 1 to 3 mm with the depth that go completely through the other side of the wall. Please give advice HOW TO REPAIR?

A: (Kelly) Cracks in masonry buildings is very common, and usually not of concern structurally. Inadequate foundations can be a problem, and this is difficult to repair once the building is finished. I recently cosmetically repaired some cracks in concrete walls using a commercial product for filling voids in walls before repainting. Such material can be purchased, or you might try using plaster of Paris or even wheat paste to do this.

Q: Please give your recommendations re building a wine cave in an excavated area 35X11X150 ft. Present considerations are pre-constructed concrete vs. shotcrete.The frost line is 17 inches and some recommend 34 inch cover with soil.

A: (Kelly) Sounds like you are planning to bury this, which is a good idea to maintain an even, cool temperature. Whether to use shotcrete or concrete depends on the design I would say. Straight, vertical walls are easy to form and pour. Curved shapes such vaults and domes are easier to do with shotcrete...

Q: Do you think that hempcrete could replace OSB in SIP's? I guess the major question would be, does hempcrete have tensile strength? It seems like it may (if the crete bonds with the fibers) with all of those very strong fibers. I have read that the compressive strength of hempcrete is as good as that of standard concrete, but is 1/7 the weight. Also, Do you know of any specific examples of anyone making structural fiberboard out of hemp?

A: (Kelly) I somehow doubt that hemp mixed with Portland cement would have enough tensile strength to work as a skin for SIP's, but if it were pressed into panels with some other binder, like is done with wheat straw or rye grass...then it might make a superior product. I have not been able to find anyone doing this yet; if you find out more, let me know.

Q: I had a 2-story house constructed less than a year ago made of rebar and cement blocks, I now have numerous cracks on the walls. Do you have any idea why this is happening?

A: (Kelly) Usually such cracks in masonry buildings are the result of uneven settling of the foundation, and indicate that the original foundation is inadequate in some regard. You might consult a local structural engineer for advice.

Q: Here are some of the newest and latest materials I have read about. What do you think of them? Please evaluate them by looking at their links and let me know. There is grancrete http://www.grancrete.net And gigacrete and stuccomax http://www.gigacrete.com/faq.html I think they sound great but what do you think?

A (Kelly): I have this info about grancrete listed at #grancrete  and I have looked at the gigacrete site. Both of these products are interesting, but seem somewhat unproven and are speculative concepts. My general take on such industrial products is that while they may provide very useful materials for building and do so in a fairly "green" way, they are still highly industrial, with a significant quotient of embodied energy in them. There are many other, more natural building techniques that I would give a higher mark for sustainability.

Q: I have a one story house in front of the beach in Greece, with hot summers and cold winters with very high humidity. All the beach front houses like mine experience the same problem more or less: The exterior and interior stucco (over brick or concrete) is getting wet and falls out over time due to the humidity from the ocean and the water levels below. Is there a material you would suggest that can prevent this problem? If stucco is an answer, should it be mixed with appropriate materials and in what proportions?

A (Kelly): This sounds like a difficult problem to deal with. Even if you somehow render the stucco waterproof, there is always the potential that moisture can get behind it and weaken the bonding with the materials supporting it. Obviously, a stucco netting would help keep small pieces from breaking off. And it might be that a more water-proof stucco that uses a high ratio of Portland cement or has liquid latex added might help. It might take some experimenting over time to find the best solution. Maybe just leaving the brickwork exposed would be even better.

Q: Do you know where I can find engineering details (in depth) on arched steel buildings.....the manufacturers are very tight lipped on this.....I live in Florida and erect steel buildings...and must have 'details" on their wind loads , etc.

A: (Leonard Jones) You're pretty much correct.  The manufacturers of arched steel buildings - and other prefab steel buildings as well - are pretty tight-lipped about the engineering details of their buildings.  I have dealt with a few of them in the past.  They regard all their information as highly proprietary.   The best way to deal with them, in my experience anyway, is to get together all the necessary design information...  Wind load, snow load (Ha! - YOU don't have to worry about that one, but I'm here in Colorado and I do...), soil conditions, etc. and then go to them for a proposal...  Make it clear that you are soliciting proposals from several manufacturers.  This will usually make them a little more reasonable.   If you need stamped drawings, etc., most of the manufacturers or their distributors have local Professional Engineers on retainer to check and stamp the building plans.

C: The reason for my interest is that I am an erector of these buildings, and as you may know, Florida is in the maximum wind zone area. I am curious to know what the possibility is for designing an arch building that will withstand the worst case scenario. 14 gauge is as thick as it gets for most prefab arch companies. Could 12 gauge or 10 gauge (or lower) be the trick that surpasses the maximum wind? There has got to be an engineering company that can verify the possibility. I am looking for a "niche" here in the wind belt; there is so much sub-standard construction here. You may not of heard about the insurance companies not wanting to insure against wind problems (they will win....they don't insure against flood now); so the homeowner is stuck between the bank and the insurer. Building owners here must become "self insured" or lose all. If we have another "Katrina" in this area, many will lose it all...(the Fed won't help em). So I guess people must build for the most possible hurricane winds.

R: (Leonard Jones) I'm afraid I have some bad news for you.  It is theoretically possible to design a building for the worst-case scenario, but in practical terms it is impossible.

The reason for this is that no one actually knows what the worst-case scenario is.  All we know is what has happened in the past, and we can look back into the records to find out.  But no one knows whether the historical record contains the real worst case - or not.  On this account, engineers have developed a statistical model, called the 100-year model, for use in such situations.  On this basis, things like the "100-year Flood" and the "100-year Wind" have been conceived.  These are the worst cases that are likely to occur during any 100-year period.  In some cases, models have also been developed for the 25-year and/or 50-year intervals.  In each instance, the shorter the interval, the less severe the likely weather incident. 

The problem is that the 100-year storm or wind is by no means the worst that could happen.  Hurricane Katrina is a good example.  It has been said that this storm exceeded the 100-year expected storm by a significant amount.  Perhaps Katrina was a 1000-year storm...  We don't really know for sure; there's just not enough data...

So engineers are left with only a couple of alternatives:

1)  Design a building (or other structure) to withstand a 100-year (or other interval) storm, advise the owner/insurer of the limitations, and document the heck out of them.  In this case, if the weather exceeds a 100-year interval and the building fails, the engineer is off the hook.  There are issues of proof, etc., but that's basically the situation...  Insurance companies are usually willing to insure a building that's designed to such standards because they utilize the same kind of statistical modeling to calculate their risks and set their premiums, and they are comfortable with the concept. 

2)  Grossly over-design the building to such an extent that it will withstand the worst possible situation that could possibly be conceived.  In this case, it is extremely unlikely that the building will ever fail.  But, the cost of designing and building such a structure will also be extreme.  The average building owner is very unlikely to be willing to pay these costs.  Moreover, such a building will be - almost by definition - out of the ordinary, and insurance companies don't like out of the ordinary things.  They prefer standard things of proven performance...  And there is some engineering risk in going "beyond the ordinary." So that's about how it is... Wish I had better new for you...

Q: Would you kindly review this manuscript entitled "Development of Straw-Cement Composite Sustainable Building Material for Low-Cost Housing in Egypt"?

A: (Kelly) First of all, I applaud anyone who is seeking sustainable solutions for building technologies, as these are essential for our continuing health and success as a species. The aspects of the concept presented for manufacturing building blocks from rice straw and cement that I would consider sustainable are:

  • One component (the straw) is a surplus renewable material that when utilized will take it out of the waste stream and avoid possible air pollution from burning it.
  • The straw is free, which lowers the cost of the production
  • The straw-cement blocks can be produced locally by relatively unskilled labor, again lowering costs
  • The resultant blocks provide better insulation values than conventional concrete blocks.
On the other hand these blocks call for a substantial component of Portland cement which is known to be a major contributor of CO2 greenhouse gas into the atmosphere. This cement (along with the straw) must be transported to the building site, which also contributes to effective pollution. And the cost of Portland cement is significant ( I suspect much more than the $1.50 per bag estimated in the paper). If you compare this proposed technology with the vernacular use of straw-reinforced mud (adobe) bricks that have been used since 4,000 years B.C. (according to this paper), then the newer technology does not appear to be as sustainable. Hassan Fathy has clearly demonstrated the appropriate use of mud bricks in Egypt, especially for low-cost housing. Consider these aspects of mud bricks:
  • Every component (clay, sand, water, straw) is potentially free
  • Every component has little embodied energy
  • These materials are potentially available on site, or locally
  • These building blocks can be used in load-bearing walls, or for other compressive purposes (which the straw-cement blocks cannot)
  • The mud bricks provide nearly as much thermal resistance as the straw-cement blocks (R-1 per inch)...neither of which is very impressive, especially in a hot climate, but at least the mud blocks provide better thermal mass, so under certain circumstances they will perform better thermally.
  • Mud bricks can be "stabilized" with a relatively small amount of Portland cement (or asphalt emulsion) for use in circumstances where a greater degree of durability is required.
  • Mud bricks can be produced with relatively unskilled labor.

In conclusion, if sustainability is to be the criteria for choosing one technology of the other, I ask why introduce a new cement-based product when the older vernacular material (mud bricks) is superior in almost every respect?

Q: Could you please share with me the benefits and even the down side of using cinder blocks for building a house: (I am considering using a textured version that resembles stone so as to not paint the outside and a colored clay on the inside without paint to allow for breathing of the walls)

A: On the positive side, you have already pointed out that the textured blocks need no further treatment on the outside to provide a durable finish. Also such block homes can be rather easily and quickly assembled, as far as the walls go.

On the negative side, such a as wall system provides NO insulation, which is essential in any climate that gets very hot or very cold during the year. The hollow blocks might be slightly insulating, but a large portion of these cavities get filled with concrete, so you will be constantly bleeding energy from the house. Also, these blocks are an industrial product that uses a lot of cement to manufacture and energy to transport, so they are not very sustainable in that regard.

Q: The cement floor in my garage is turning to powder. Any way to stop it...or lay new cement?

A: (Kelly) It sounds like the concrete floor was not well made in the first place. If it is just the surface that t is powdering, then you might be able to stop it by coating the floor with a concrete sealer (something like Thompson's Water Seal might work). If the concrete is decomposing beyond the surface, then you might need to pour a new layer over the old. If you do this, I recommend using fiber reinforced concrete to keep it from cracking. Light-weight concrete would not be a very good choice for a floor in my opinion.

C: (Matthew G.) I have a patented product of lightweight cement called new-crete. I was reading your website and it was saying that lightweight cement is not as strong as regular cement. New-crete is designed to form millions of air bubbles when cured. This makes new-crete 50% lighter and stronger than regular cement and 35% lighter and stronger than lightweight cement. It is also 30%-40% cheaper than regular cement. It has an R-20 insulation value with a 9-inch thick wall. A .5mm saturation point for water. It is nontoxic and not corrosive and it floats. We do need about $200.000 to build a proto-type house and get it CSA (Canadian Standards Association) approved. After it is approved we can start selling homes. If you are interested in using new-crete we can build one of your greenhomes out of it and get that CSA approved. We can build the entire house from top to bottom using new-crete. (foundation, flooring walls, drywall, doors, cabinets, window frames, roof and shingles.) I believe we must start using other building materials instead of trees before they are all gone. If interested you can contact me at InfiniteEarthDesignATyahoo.ca

Q: I was interested in the concrete homes made with fly ash but wonder if the ingredient is safe or if its too toxic to live in? Does it require any other form of insulation with it?

A: Fly ash is used really only as an additive to standard Portland cement to make it more durable and use less of the cement. Once it is bound in the concrete, there would be no toxic emission. The fly ash will not make the concrete more insulating, so you would need some other form of insulation to make the home comfortable.

Q: I would like a house that breathes here in Florida, so that means less wood or anything that rots or gets moldy. I was wondering if filling concrete block with dirt or sand would give R-value without having to use regular insulation? I know its strange to say but most houses I have lived in I can't breathe well; they feel stale. I need to open the windows, but that isn't practical. The garage is actually my favorite place in the house; its not very good for insulation value, but I can breathe in there.

A: (Kelly) I'm afraid that your idea of filling concrete blocks with soil or sand would not really improve the insulation value of the wall. Like concrete, both of these materials are more thermal mass than insulation. Even if you filled the voids with something more insulating, like rice hulls, the concrete block wall would still not be particularly insulating, because of all the thermal bridges that happen where the concrete goes solidly through the wall. For breathability, concrete blocks would not be a good choice either...If you want a well-insulated and breathable wall, then I suggest that look toward other methods, such as strawbale, earthbag, or cordwood construction.

C: Just read a report on Insuladd that takes it down quite a few notches. Thought you might want to know. http://www.energyideas.org/documents/Factsheets/PTR/Insuladd.pdf

R: (Kelly) Thanks for letting me know about this. I read the report and found it very interesting and informative, and obviously the product is not all it is cracked up to be. I had done some informal tests with Insuladd a couple of years ago and was impressed with it at the time, but have not followed up over time...

C: There is residential tilt slab building system being used in Colorado and Nevada.  The wall panels are made up of a 2" layer of concrete a 2" layer of high density polystyrene form and a 4" layer of concrete on the inside.  They claim to be getting an R factor of 25. 

R: (Kelly) You see these kinds of claims all the time from manufactures of of kinds of building systems, from SIPs to ICFs to AAC, and sometimes they couch the claims with their own analysis of "the real world" and performance data, which is hard to verify. It is true that R-Values can be somewhat elusive, in that the performance of any given building systems depends on many specific parameters, such as design and climate. That being said, there is no way that a standard scientific test of this described wall arrangement will yield values that high, when major manufactures of EPS place its value at R-10 and the concrete value is negligible. Because of the high mass of the interior concrete, this wall will actually perform better than most walls with higher insulation and no mass...so, again, it all depends...

Q: I have a new Green Brick I've invented. Want to see what you think. www.aeonianbricks.com The new building material combines modern chemistry with a centuries old brick making process of compressing dirt and clay together. With a safe, environmentally friendly process, the clay is water stabilized. It will no longer expand when wet or contract when dry, ever! The clay and earth is then compressed into an interlocking shape with tremendous force. No firing is required, which saves huge amounts of energy in the manufacturing process and produces no pollution. Testing conducted by independent certified testing laboratories have shown that a wall built with these new "interlocking earth bricks" will withstand 240 mph winds with no structural damage. They are also fire, flood and termite proof. All walls in the home are made with bricks, which eliminates all wood, insulation and drywall in the home (the three main causes of mold and mildew). The side of the brick is smooth as glass, and can be sprayed to look like drywall, wall papered or textured and painted. The exterior walls are sprayed with a textured material that can take on the appearance of stucco, brick, wood planking or any look desired. The homes will save vast amounts of energy with an R-45 thermal mass and an R-20 heat resistance. To complete the home, a concrete roof system is used that has a 300 mph wind resistance and is also fire and insect proof while providing superior insulation qualities. The concrete roof system employs 12" of double density styrofoam with steel beams embedded. To this we will add the coating to the top of the roof where the concrete is sprayed and then have a 1" tile cemented to the roof made with our brick material. All this and more at no extra cost!

A: (Kelly) This is an interesting new building concept that you have come up with, with many obvious merits. Here are a few observations about how sustainable it might be considered:

1) While the main ingredients are earth, it is still a manufactured product, with all of the embodied energy that is implied by this, both during the manufacturing process and the transportation. Compared to ordinary adobe bricks (which can easily last for centuries) these bricks do not come out too favorably.

2) I question your assertion that this system will create an equivalance to R-20 insualtion. Your promotion literature says something about a coating on the blocks that provides this, but I have my doubts. Earth is primarily a thermal mass material, as I am sure you know. Earthen homes can perform quite well in certain climates, and it may be that South Carolina is one of them...but in much of the country this system will need some additional insulation to be comfortable and energy efficient I suspect.

Having said this, I do like the fact that you are seeking solutions to our environmental problem through this sort of research and development. I am sure that as you get further into this project you will discover ways to improve the system and overcome some of my objections.

C: There is only one company that I know of that advertises that their steel vaults can be buried, and that is www.americansheltertechnologies.com . They are the only one I have found which doesn't specify galvalume coating. I wrote to the manufacturer (of galvalume) and it is not OK to use underground or in direct contact with wet cement; regular old galvanized is better for that.

Q: What are your thoughts about geodesic domes? Pro's vs. con's.

A: (Kelly) I have always liked geodesic domes. They are very strong and resist earthquakes; the framework can be made with relatively short pieces of rigid materials; domes in general enclose the greatest amount of space for the least amount of material; they are fairly easy to assemble, and there are many kits available; they are interesting and fun. On the negative side, geodesic domes notoriously leak. All of those seams are difficult to seal because the different materials that are used to make the struts, panels, connectors, insulation, and waterproof membrane often have different rates of expansion and contraction in response to the weather. Also, what appears to be a very simple and regular series of equal-size components, is deceiving: the struts have several different lengths, so fabrication and assembly is more complex than it would seem.

Q: Your site mentions ThermoPlan / Ziegel Blocks. I have been trying to find a dealer or manufacturer that would carry those or similar honeycomb thermal clay blocks in the North America but could not find any, while in Europe there are plenty. Do you know of any company that carries similar products in North America?

A: (Kelly) If there are companies selling these sorts of products in the US, I am not aware of them. A quick Google search certainly did not reveal any. This is unfortunate, since I think these have many excellent qualities, and should be available. There is a wide door open here for some entrepreneur in the US. See this page for more about these.

Q: I have begun making lightweight cellular concrete blocks in a village near New Delhi, India. The process uses high volumes of fly ash (up to 80%), Portland cement, water and a vegetable oil based foaming system. I want to know if I could replace a portion of the cement with lime. Given the amount of fly-ash, the setting time is delayed and I want to accelerate it but keep the strength of the blocks. I was hoping to replace a larger portion of Portland cement with lime - hopefully making it cheaper and faster setting because when using up to 80% fly ash the setting time is long. I wouldn't want the lime to retard the set time though. If I add gypsum (Plaster of Paris) it'll set faster but I don't know how durable it'll be.

The foaming agent is a palm oil based concentrate that is mixed in a ratio of 1:30 with water. The mixture is put in a foam generator to which an air compressor is attached. Through a perforated nozzle the foam is shot directly into a cement mixer that contains no course aggregates. The foam does not chemically react with the concrete but retains its shape while the paste hardens leaving tiny pores in the hardened concrete. See www.casthome.com for more information. Foaming agents can be made from animal proteins, chemicals or vegetable. I guess the system could work for poured earth if the setting time is similar to concrete - except you cannot have any course aggregates because they'll cause the foam bubbles to collapse. Another thing you need to watch out for is that adding foam will reduce the strength - inverse reaction to strength.

A: There should be no problem using lime (called quick lime here as it is calcined or processed by heating). It should take only a small amount(.1 to 1% by weight). Also the concrete industry here uses accelerators giving you a faster initial set. It may be worth trying.

Q: I would like to read/see/hear research or evidence of E.M.F. in steel framing buildings or houses. Can you provide and further information on this subject?

A: (Kelly) From my reading it seems that most concern about EMF radiation in buildings is associaited with elecrtical wiring. In some cases a steel structure can actually mitigate EMF exposure due to the "Faraday Cage" effect. I know that personally, I have lived in steel-framed buses and other steel enclosures for periods of time, with no noticeable negative effect, although I suspect that really sensitive people might feel something that I don't.

Q: I want to lay down a concrete walking path in my large garden. I will mix concrete with concrete mixer. I want the concrete to be able to permit rain water to travel through into the ground. What concrete mix should I use?

A: Concrete is generally not porous enough to allow water to travel through it. I suggest that you consider porous pavers that are designed for this purpose.

Is "pervious concrete" an way to enable water to travel thru it?

Yes, it does appear that this would work for you. See www.perviouspavement.org

Comment: I became interested in green home building about a year ago. I discovered that you could convert shipping containers into suitable housing. I found this to be very interesting and I looked into how to insulate & fireproof the containers. Through research and testing, I became very knowledgeable on the subject. It resulted in becoming a regional sales developer for SPI, that produces Super Therm (coating) for insulating the shipping containers, Omega Fire (coating) for fireproofing that exceeds 3 hour fire resistance, and the iStucco™ System is a mixture of high performance acrylics and ceramics specially blended for insulation, breath-ability, adhesion, toughness and texture. I noticed you recommend Super Therm on this website, and I would like to become the contact person for any questions that may arise, to help people who visit your website. I have helped with projects where the containers were used for dormitories, apartments, temporary housing, etc. in the Caribbean and Haiti. Bob Bjorkdahl (207) 710-8519 or r3bjorkATgmail.com

Response: (Kelly) The whole concept of thermally efficient paint has always intrigued me, and I did some experiments with mixing Insuladd ceramic spheres to some paint for a roof once. The performance was impressive at the time. On your site you say, "Insulation Equivalent Rating - Super Therm® reflects over 95% of radiation from the sun replacing the 6 to 8 inches of traditional insulation to block initial heat load." Obviously, this is quite good for reflecting heat. What happens when it gets cold?

I know what you're saying, because I thought I same thing; it's probably 100% more effective in a hot sunny climate, but it does act a sealant which has it's merits. In my house right now, I have a closet that is fully insulated, on the sunny side of the house and it was a constant 28 degrees and 10 to 15 degrees on the floor of the closet during the winter. I took a thermal gun and found small hole under the siding that would let outside air in, once sealed, the closet was warm again.

My overall impression is that Super Therm is particularly effective at providing a breathable sealing coat that keeps wind and moisture intrusions to a minimum, as well as provides a reflective thermal barrier. It seems to me that this would be most effective when combined with an aerated insulation product to also slow down the movement of heat transfer.

In a situation, such as with a metal container home that is painted with Super Therm, where the metal is a ready conductor of heat and cold, the performance of the paint would be compromised without some additional porous insulation, in my opinion. Obviously the metal itself does not breath, so that is not much of an issue.

Q: Can I build an adobe style home out of 12" exterior walls made of EPS foam, with interior load barring walls out of 12" EPS and the rest of the interior walls out of 6" EPS, and foundation and roof out of 12" EPS with everything being glued together?

A: EPS foam is an insulation material and not a load bearing member/wall. So, the answer is no, sorry.

Q: What natural insulation would work for a wide range of temperatures? How much insulation would I need? I would be using the insulation for a homemade pull camper with pull out sides. I would be traveling the US and doing some "boondocking" year round. I am confused about what would work well, the thickness needed and the R value needed.

A: (Kelly) For that particular application I would suggest using a good foam panel about 2 inches thick. Polyicynene generally provides the best insulation value.

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