Insulation Question

Wayco Wayne_2

very old house. Judging by the holes at the top of the outside siding shown in pictures from before the vinyl siding was put on I'm guessing blown in cellulose. What is the R value of blown in cellulose per inch. How much does it settle and how would I take that into consideration??? Thanks for any input. WW

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Constantin

Many materials can be blown...

For example, fiberglass has also been known to be blown in. But I think you're right, cellulose is the the most likely suspect. In theory, it's R-value is close to fiberglass, i.e. 3.7/inch. In practice, due to settling, the actual R-value of a wall may be lower due to thermal short-circuiting.

I believe it was Jerry that observed that a 5% void in the wall coverage of insulation would result in a net 50% decrease of the insulative qualities of the wall. Modern, dense-pack applications of cellulose in walls are much more likely not to settle due to the glues, binders, and greater initial density. However, the only way to really know is to open up a wall and have a look.

The ACCA way to determine the actual Wall-R-value is to see how much the cellulose has settled and then to enter the wall values into HVAC-calc as 90% with insulation, and 10% without (or whatever the mix may be), i.e. as two walls with the same orientation.

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You may want

to calc it with and without the "assumed" r value and see how wide a spread you get.

The only way I know of the see how well that insulation was retro fitted is with and infared camers. That will show exactly where there is or isn't insulation

hot rod

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