Double wythe CMU vs. Thermomass
After living in Europe for several years I have become a fan of concrete. I build in the Southeast and have mainly used concrete commercially and as stem/foundation/retaining walls and for slabs in residential.
I know that concrete is expensive compared to the “normal” enclosure for a home here (platform framed,2Xwall,sheathing, cementious siding). I have been following the debate on Thermal Benefits of Mass Walls and conclude that its effects are minimal if any in Zone 3, also the overuse of “effective R-value” in advertising as a reason for higher mass walls, is a non-starter with me, as it is not backed up by scientific facts.
Here is the thing about concrete, it is durable as hell. Joe L. uses CMU in his “perfect Wall” 500 year wall. I really doubt current, affordable framing stock would last so long, and this claim by Matt Risinger of 500 year wood framed structure is at odds with what BS Corp. was stating:
I think it is disingenuous to claim a persist/remote wood framed wall could last so long (BTW what is the guarantee on that house).
I was in Czechoslovakia in 1993 and met a great Czech Entrepreneur that was selling German manufactured panelized tilt-up homes (he had failed in the market with stick built homes as no one believed in their durability). One thing he said to me about 20 years ago still sticks in my mind. I asked about the porcelain roof tiles and he said they come with a 100 year guarantee (same as all the structural parts of the house) from a company in business for about 300 years. He then looked at me and asked what type of guarantees we in America give on our houses and I said frankly, i don’t know many builders that like to guarantee their structures at all. I told him once the house is sold, unless it is an ongoing large home builder concern that guarantees were not given usually. He was shocked.
This idea of durability has been in my mind ever since. I live in a part of the country with epidemic mold issues, a High decay (of wood) coefficient, now Formosan termites, carpenter bees, carpenter ants, etc.
I had decided to build my latest spec house out of the thermomass system: http://www.thermomass.com/
As the house is modern in design, I also had decided to use many of my commercial techniques on it, steel trusses, decked and poured floor.
I am sure that many of the builders on here have had to “educate” framing and finish crews about proper detailing on framing and enclosure for stick built. Most of the crews I have educated in the last 20 years have been from Mexico, Latin, and South America. One day I struck up a conversation with a framer who confided in me he had only been framing for @ 3 months and was still a rookie, but in mexico he was considered a very skilled builder. He said that if I was building the house with Concrete or CMU or stuccoing it he was not a “rookie” at those things as that is how houses in Mexico (and most of the word are constructed). I thought what a waste to educate this guy on how we stick build instead of exploiting his built-up knowledge in masonry/concrete. After that I started to ask all my trades people from other countries what building skills they were competent in, most frankly stated, “concrete, clay tile, CMU, stucco”.
I am not sure if it is true but I have been told that if you are a Cook/Chef in China and you move to the USA, you have to learn to “cook” all over as our Chinese food bears little to no resemblance to Chinese food as prepared in China. This seemed the exact parallel to the Mexican builder that must “start-over” here learning stick-built.
I am interested in a few things when building a house; cost-effective, high quality, durable, simplified structures. To that end, if i were to emulate the 500 year wall a la Joe L. I would use CMU or concrete then foam/insulation then an external elements/rain barrier (in his example brick).
I have several questions for you guys:
1. instead of the very expensive Thermomass system, could I not just build an engineered CMU interior wall, stucco/glue 3′ of XPS on the face of that wall, then, without a drain plane build another external engineered CMU wall and stucco/parge it smooth with acrylic and waterproofing additves?
2. If the external cladding in a 500 year wall is waterproofed by design, then is a drain gap necessary?
3. Do metal wall ties really cause a huge thermal energy penalty? Anyone aware of a cost effective composite wall tie?
4. this double wythe wall would have all utilities place in the internal wall during construction and be smooth stuccoed on the inside with no vapor barrier to allow drying inward, as such wouldn’t the external waterproof stucco and the xps both act as protection against external solar and or wind driven rain penetration to the structure?
Thanks for all the insights here, I am glad I found a place to ask these questions and to try to come up with more meaningful techniques.
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