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As I understand it...

One of the problems with old-style balloon construction of walls was that since there was a continuous space between studs which ran the full height of the house, a housefire could be exacerbated by these spaces acting as chimneys to draw more air into the flames. The usual fix would be to install blocking to divide these spaces into a set of shorter ones, closed off from each other, stopping that updraft.

In the absence of blocking, would blown-in rockwool insulation retard airflow enough to have some of the same effect?

(I'm honestly not sure if my place is unblocked balloon or not; it's of an age where it isn't completely impossible.)

keshlam
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  • Interesting idea and relevant to me. I've just installed wood blocking in a small area (impacted by an addition) of 1890s balloon-framed exterior walls. Will be putting rockwool below and, likely above, too. – FreeMan Feb 08 '23 at 13:54

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Any insulation will slow down air convection so would be better than none.

Even the wood based insulation is fire-retardant and is easy to use, it’s what we used as our first time build and the professional carpenter adopted that insulation as it was easier to work for his staff - not itchy so just dust masks. Same thermal performance as well.

Did try burning the waste wood insulation but did not work well - good for our worries about safety of a wood framed and wood insulated building with wood slats outside.

Solar Mike
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  • Cellulose insulation is actually quite effective at stopping fire. It's better at blocking air movement than fiberglass, and is indeed well-treated against burning. https://www.advanced-fiber.com/wp-content/uploads/2020/12/Cellulose-and-Fire-Resistance-12-20.pdf The internet being what it is, there are, of course, thinly veiled misinformation sites put up by the competition if you like that sort of thing. – Ecnerwal Feb 08 '23 at 16:38
  • the cellulose is treated but if it gets wet the treatment can be lost. also doesn't perform if it is wet - probably bigger problems if inside your walls is getting wet. rock wool is a better product but it is itchy. – Fresh Codemonger Feb 08 '23 at 17:40