Insulation in Reinforced CMU Cores 1

[StructuralEd]

Is it allowed to leave cmu insulation in cores having vertical reinforcing bars?
It would seem to me that it would cause a bond breaker to the cmu shells.
Unfortunately there often surfaces a conflict with the energy conservation part of the Building Code when we try to use a single wythe exterior masonry wall.

 

[JAE]

Insulation and grouted/reinforced cores don't mix in the same cell. You have to do one or the other.

You can, of course, alternate between adjacent vertical cells (rebar in one, insulation in the next three, rebar in the next, etc.).

 

[msquared48]

Wherever there is rebar, there IS grout, and NOT insulation, as JAE said.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[StructuralEd]

That is my opinion too.
The Architects scratch their heads trying to meet the requirements of energy section of the code when insulation gets voided.

 

[JAE]

It simply shows the reality that insulated cells of CMU isn't very effective.

 

[concretemasonry]

There are some propriety polystyrene foam inserts that allowed to be used in grouted walls that are backed up by full wall tests and approved by various codes. The reason they work is because the entire masonry code concept is based on the wall strength and mot the individual dissected sections or details.

They (the foam inserts) are not frequently used because of the thermal effectiveness and superior performance of rigid XPS to isolate the masonry mass on the the side of the insulation where it will be most effective for long term comfort and economy.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[JAE]

concretemasonry - not sure what you mean: The reason they (polystyrene inserts) work is because the masonry code is based on the wall strength?

You make no sense. Sorry.

 

[msquared48]

I'm confused too.

Are you saying that this special foam is as strong as the mortar infill in shear and compression?

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[concretemasonry]

JAE -

In some of the products, the cores are partially filled, which contributes to the strength of the entire wall panel and cannot be neglected if it is justified by actual panel tests.

I do not agree with the general concept, but the test results for certain products do take advantage of the over-all conservative limits imposed by traditional old test results of lower quality products. The manufacturing process of modern units has outstripped the traditional properties and the outmoded ASTM C90 requirements since it is now impractical and not economical to make weaker units that comply with the minimum standards.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[JAE]

Are you talking about inserts like this:

http://www.cbisinc.com/korfil.html

Or like the examples I've attached:

 

[concretemasonry]

JAE -

Those are a couple of the products I was familiar with in the 1970's.

One used the very traditional CMU old-fashioned and inefficient shape that suffered from "thermal short circuiting", but did test adequately from a structural standpoint.

The other was a lighter insulating insert that was made for a unique shaped CMU meeting ASTM requirements (single aligned cores with recessed webs) that was much more thermally efficient, but the cost of different CMU molds ($10,000+ per size for each producer) did not allow it to be economically viable. The structural tests were very good, especially with a center insert grouted on both sides.

The results of the wall structural tests did show the ability of grout and insulation to produce a wall strength equivalent or superior to the "common" units made for minimum code standards. Incidentally, the CMUs used in the wall tests did exceeded ASTM minimums because minimum strength units were not available from any supplier, but the grout used was made to ASTM minimum strengths with 8" to 11" slump with strengths less than the f'm of the CMUs.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[StructuralEd]

I asked the NCMA and was told not to have insulation in grouted reinforced cores in standard blocks.

Apparently there is a different type block with a double face on one side with a separate core area for insulation, but not in the main core used for reinforcing and grouting.

 

[StructuralEd]

Correction, NECMA.

 

[concretemasonry]

The NCMA is the one with huge capacity lab and representation on all major codes and masonry associtaions. The NEMCA (New England Concrete Masonry Association)is just a small regional association that uses the nationally recognized codes and test results as they chose to interpret them.

I still do not personally like the use of compressive materials (especially EPS foam) in grouted cores, but the ultra-conservative test reports of full wall sections cannot be ignored.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.