Insulate block wall error

[Michael Nunez]

I am trying to model a block wall so that I can recommend adding pourable/injectable foam. When I try to add 4.0″, I get an error message that the cavity is full and automatically sets the depth to 3.5″.  Am I selecting the wrong type of block?

[Gamaliel Lodge]

The Cavity Insulation controls describe insulation added to frame wall cavities. Unless you have a wall framing described, there is no place to put the the cavity insulation. That is why you are getting that message. I can see why this is confusing.  I think we could make the interface more clear by disabling the Cavity Insulation controls, when the Framing is None.  These Cavity Insulation controls are not the proper place to model insulation poured into concrete block holes.

We do not have a direct method to model this measure, but I can give you a workaround. The options that we have in the Mass Wall control currently limited to items published in the AHSRAE HoF.  We don’t have data for a 12″ wall with insulated cores, but we can infer it from the 8″ wall.  In the 8″ wall the perlite insulation adds about R-3.1 to the total R-value.  (Note that these R-values include an adjustment for benefits of the thermal capacitance of the mass wall).  Adding insulate to the 12″ wall may improve the R-value a little more, but due to the dominance of the thermal bridging it wouldn’t be much.  I think that the R-3.1 would still be a good conservative estimate.  (If you wanted a generous estimate you could assume that the R-value doubles for the 12″ block, as it does for the 8″ block. ) Here are steps to generate an improvement that represents adding the insulation:

1. Setup the base wall
2. Click the ||Path button to open the parallel path calculator.  
3. Check that all layers are described correctly.
4. Change the Mass Wall R-value to 7.1 (adding 3.1 to the existing 4.0)
5. Record the resulting Base Assembly R-value displayed in the calculator.
6. Change the Mass Wall R back to 4.0
7. Set the Improved Cavity Insulation to None
8. Set the Improved Continuous insulation to Other (or a custom entry that you create).
9. Set the Improved Continuous depth as desired
10. Increase the Improved Continuous Insulation R-Value until the  Improve Assembly R-value reaches the number that you recorded in step 5

[Kirsten Shaw]

In going through the steps you have outlined, at step #4, are you saying that the Mass Wall values are editable by the user?

If that is correct, we are not able to make any changes to the table, only the Est. Assembly R-value below the table.

Please see the attached with the screen shot.

In addition, we are modeling an 8-inch concrete block wall, not a 12-inch.

Thanks.

[Gamaliel Lodge]

The Mass Wall R-value is editable on the main Walls interface, but not on the ||Path popup.

8″ walls are selectable with the mass wall controls on the main interface. They will be easier to do, because we already have an option for insulated cores.  You won’t have to change the Mass Wall R-value control.  You can just change the option selected in the second Mass Wall Type control, which defines thickness and core insulation.

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