Home>Discussions>INSULATION & HVAC>blown-in cellulose insulation - good or bad?
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AmyPierce
blown-in cellulose insulation - good or bad?

Newbie here in need of the best advice possible. I've qualified for a federally funded weatherization program administered by my N.C. county. They are soon to start work on my hundred year old Mill Village cottage (990 sq. ft.) that has no insulation. Among many other improvements they will make, the program will include blown in cellulose insulation.I need advice about this from trusted professionals as soon as possible, as the entire project should be starting within the next week or ten days. I've read at bobyapp.com that this insulation technique isn't good; that it gets damp and falls to the bottom, attracting termites etc. Please share what you can so that I will know how to proceed with this insulation decision. Many thanks!

keith3267
Re: blown-in cellulose insulation - good or bad?

Cellulose is treated with a sodium borate solution as a fire retardant. The sodium borates make the cellulose very rot resistant and very undesirable to termites. But it can get wet if there is not a vapor barrier applied to the inside of the exterior wall.

In the winter, moisture laden warm air migrates into the wall cavity where the moisture will condense when it hit the cooler surfaces. To prevent this you need to keep the moisture from getting through the wall.

You can tear out all the interior wall material, probably lath and plaster and put in a vapor barrier, then new sheet rock etc. but that gets expensive. The cheapest way to do this is apply a vapor retardant paint and seal around any wall penetrations such as electrical outlet and light switch boxes. You can buy a foam material that goes under the outlet plate of switch plate. Just remove the screw or screws, remove the plate, put in the foam insulator and replace the plate and screw(s).

If any work is done tot he outside of the house, make sure they don't make it tighter than the inside surface of the exterior walls. The insulation has to breath to the outside to stay dry.

AmyPierce
Re: blown-in cellulose insulation - good or bad?

Dear Keith. Thank you for writing.

This doesn't sound like good news, since they plan to remove an exterior clapboard for each section then blow in the insulation. No vapor barrier, as I understand it. I don't have money to apply to the project (nor is that required), so based on what you've said, it sounds as if I should refuse the insulation within the wall cavities and just say yes to the crawl space and the attic.

AmyPierce
Re: blown-in cellulose insulation - good or bad?

Keith, did you mean to apply the vapor retardant paint on the interior walls? For some reason, I was thinking you meant within the wall cavity. Thanks for replying.

keith3267
Re: blown-in cellulose insulation - good or bad?

No, its just like painting the room, but you use a special primer that makes a vapor barrier.

http://www.sherwin-williams.com/painting-contractors/products/catalog/moisture-vapor-barrier/

http://www.kwalpaint.com/Catalog/Product/Interior-Latex-Vapor-Barrier-PrimerSealer.aspx

Here are a couple of options. Google for "vapor barrier primer" for more information. There are even more sophisticated (expensive) options such as membranes and such. You can also use a vinyl wallpaper as it makes a good vapor barrier. Just make sure to seal around thoses switches and outlets.

AmyPierce
Re: blown-in cellulose insulation - good or bad?

Thanks so much!

nauko
Re: blown-in cellulose insulation - good or bad?

We investigated this process here in Seattle last year when we had an energy audit done through a city program. We decided not to do the blown in insulation, but did airsealing and other insulation work. My understanding is that if it is done properly and it is dense packed cellulose insulation you should not develop a moisture problem, but the key is making sure that it is blown in properly and that they are measuring all the wall cavities to make sure that it is packed in tight. With an old house there are going to be fire blocks and stuff so it could be hard to make sure it gets everywhere. Lots of siding coming off,etc. They should have an infrared/thermal camera so you can see when they are done that they got everything. You are in a fairly warm area so I wonder what the cost savings would be for doing it. I would imagine just airsealing would be far more benificial. You should get the attic insulated. Before you start any work, if you haven't had a proper energy audit done, that would be my first choice so you know what really needs to be done and how beneficial the work would be.

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