Rastra or Durisol? Eco-Alternatives for Construction
Let me first preface this post with the following: I’m not a construction professional. I’m just a curious homeowner seeking out the best building materials for my home. With that said, I was familiar with three options in residential construction - concrete block, wood frame or the super green alternative, rammed earth.
Turns out there are new options that combine the wonderful qualities of Portland cement with recycled post-consumer plastics (Rastra) or recycled wood fibers (Durisol).
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An informative, if not slightly amusing, video at the Rastra site shows the blocks being formed in giant looking muffin pans before being cooled and shipped to the building site. They are then assembled with the ease of a child connecting Lego blocks. I hope that assembly of a home could actually be as simple as they make it look - but having survived a few construction projects it is hard for me to swallow.
Both products claim superior resistance to pests, fire and noise and both look easy enough for trained hands to assemble (click, snap, glue and fill with concrete). The differences, of course, being the strength of the pre-assembled product, materials used in the mix and price.
I’ll examine all three of those issues next week. In the meantime, I’d like to hear from you. Have you used either of these products? Were you satisified? Do you have a question about the performance level? Quality? Any concerns you’d like me to try and clarify for you?
Image courtesy: Rastra
please take a look at ICF’s, http://www.BuildBlock.com is my favorite, it is are a green building product that can be the basis for 18+ LEED points, they also deliver an insulation performance R Value of up to 50+, which means the heat from the sun never penetrates through the exterior wall to heat up the interior wall, I stacked a 2900 sf 2 story home that only needed a single 3 ton AC unit, a stick frame house that size would require at least 6+ tons of AC. ICF’s lower your utilities 30-70% & Insurance 20-40 percent because of 4 hour fire rating & high wind proof to 250 mph !! Good Luck !
i know nothing about these, i would be curious about the long term performance, particular with regards to water/moisture. what kind of stress testing have they done with water exposure, what is the longest lived installation in a wet climate so far?
@ John
Good questions, I will be interested to find out what Susan thinks about durability, especially from water protection and structural corrosion. There is a green concrete company that addresses this issue by greening regular concrete. http://www.youtube.com/watch?v=Pg_z3CZbr-A
I am in the process of finishing up a house made with Perform Wall, The Mexican made version of Rastra. I chose it over Durisol primarily due to local availability, but also because it’s available sizes were more conducive to my design.
Technically, both Durisol and Rastra are ICFs and will provide many, if not all, the benefits Todd mentions. One significant difference, to me, is that they are built with recycled content, which is not the case with many (most?) ICFs.
Both of these products are porous and need to be coated to keep water out. Wind driven rain will wick thorough it to the interior if it isn’t sealed. I used brick on the outside and plastered the interior. While I live in a very dry climate, I would not hesitate to use Perform Wall/Rastra in a wet climate if it is properly sealed.
I found a fair amount of disparity between pieces of wall form. The two pieces that are glued together to create each wall form occasionally appear to have slid slightly before the glue set, making for forms that were not precisely square. The polyurethane foam used to assemble the walls filled gaps well, but shims were sometimes needed for precise placement. Large metal staples are required to hold the forms together while the glue cures.
There was also a degree of difference from piece to piece in the consistency of the material itself. Some being very solid with a relatively high cement content and others being softer and almost crumbly. This is really not an issue unless one is doing a lot of modification to the forms as I was while constructing a curved wall. I actually preferred the slightly crumbly consistency as it shaped easier with hand tools.
Another interior and exterior finish alternative is KEIM’s UniversalPutz Render systems for a crack-free 100% mineral plaster finish with a silicate coating to protect the plaster for decades of service. From interior self cleaning Ecosil ME to exterior Granital, Royalan and Soldalit, KEIM has a proven 130 year history for these finishes. KEIM is unique with 77-83 perms permeability yet water resistant and will not contribute to fire or smoke. These are complete mineral systems that offer another choice beyond the traditional.
I built my house in Northern California wine country using Rastra. I commonly get 100 degree days here an I never use my AC ( the house design has overhangs on the South facing walls so that contributes to shading also. I’ve just had an attic fire and the Rastra material saved me from losing the whole house. This stuff takes a couple of tricks to use properly, but in the great scheme of things it’s terrific. I don’t think it matters if it’s perfomr wall or Rastra, they are pretty much the same. The real trick is sealing the outside from wind driven rain - I’m having water problems, Howver, that’s because I used a conventional brown coat and elstomeric finish without first applying a seal coat before the brown coat. I’m now looking for a solution to cover the finish to make it completly water proof. This KEIM product looks intersting.