If I make sure to purchase very high PSI blocks and use a lot of rebar is it really necessary to fill the cores of the blocks? It seems to me that the heat transfer would be much less with an air chamber in the walls. If the air provides natural and free insulation it seems illogical to fill this cavity if the blocks themselves are very strong. Also, If the blocks are strong and the walls are constructed very well is it really necessary to cover the blocks with mortar? Why not just pay to have the blocks laid really good and then just paint them directly?
You've got several good points there doromaner...may I make one more suggestion? If blocks were strong and much rebar used, the blocks were left hollow but laid and positioned correctly, hence, mortar unnecessary, blocks were left bare, So, If grey is an acceptable color for you, then why even paint it at all? And then, its color and looks would match most of the rest of the dwellings here.
EMMEDUE If you are looking for insulation you might try this new technique of building. They are building a number of high rises in Cebu with this type of construction. It is a bit more costly but very much stronger than hollow block construction. We are scheduled to look at some of the buildings under construction early next month. We have already toured a manufacturing plant that makes the styrofoam panels with the wire on either side. It is quite simple, not necessarily easy, to do this type construction. However it may be impossible to find locals that are trained in this area.
I have built 3 houses and a huge 2 story building in Cebu. I make the blocks strong, paint the rebar with red lead and make sure the workers fill the blocks full of cement with no air chamber. In my opinion as a builder that is the only to go here.
So, you are saying just to stack the blocks without any connection other than the rebar? Have you ever seen this done? Is in not necessary to coat the exterior of the blocks with some type of water barrier even if it is just a clear coat?
First Earth tremor and the building will fold, like a run of domino's, using no ties or concrete. Locals, do they use external water-proof on their blocks? doubt it! Not a good idea to leave bare blocks to the elements.
I have also read that you can use Styrofoam pellets instead of sand when mixing the concrete that fills the hollow blocks. That would provide a good insulator. However, I have not seen it done here.
Because the best cement you can get here is far lower in quality standards than in first world countries I would have to do some serious testing before I would attempt to use styro pellets instead of clean river sand. I would also think that sourcing the pellets would be difficult and my guess would be much more expensive. I Helped a friend who hated noise soundproof his bedroom, what we did was use double 6 inch blocks with 1 inch styro sheets and 1 inch air gap sandwiched between. He hated the karaoke outside so much we also filled in all the windows and installed a big split type air conditioner. Now he is a happy camper. I realize this thread was for insulation not sound proofing, but this applies for both. Good luck on your project. Ron