# Blown insulation to exterior walls - good or bad?



## dishe (Apr 30, 2013)

As part of a home energy audit, I received a grant to blow insulation to the attic and walls of my 1969 home. 

I'm aware of how messy blown cellulose insulation is for the attic, but I'm OK with that- I made sure to do any electric work I was pushing off (overhead fixtures) before they scheduled to come. But now I'm having second thoughts about the walls. 

First of all, they will be cutting holes in the walls every 16" or so to blow, and I'm not crazy about having to go around repainting everything if I don't have to. But a bigger concern is that after googling the concept a bit, I'm finding some horror stories of folks who blew insulation into old homes, only to find the cellulose absorbed moisture from natural humidity inside the home. Over time, the stuff would clump together and sink to the bottom of the cavity, causing damage to plaster walls in 100yr old homes, and possibly growing mold. 

Now, I don't know if this applies. I believe my home does not have any plaster walls, and therefore perhaps the horror stories don't apply to me? I know many people in my neighborhood have homes similar to mine, have had this done in the last few years and say they love it. I'm not sure what the long term effects will be. 

Opinions?


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## Windows on Wash (Aug 30, 2011)

What is the exterior cladding of the home?

If the wall is dense packed properly, it shouldn't be an issue in most cases but you are correct to consider your options here carefully.

Changing the was a home dries out can have disastrous consequences if you aren't careful.


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## dishe (Apr 30, 2013)

I'm not 100% sure, but I believe the exterior are asbestos (or maybe just wood) shingles. Apparently its whatever they build all the houses here with in the late 60's, it hasn't been updated at all.

I'd like to add that they are here this week working on my home, and the grant covers it 100%, so it would be of no cost to me. I'm adding this because I see some people saying it isn't worth doing because you don't recoup the cost quickly enough compared to just doing the roof/attic, where most of the heat loss occurs. This would be a free service, but only if I tell them I want it in the next couple of days. Otherwise I lose it.


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## Windows on Wash (Aug 30, 2011)

If it is wood shingles, I would do it from the exterior. 

You need to know what the exterior sheathing and vapor control layers consist of.


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## dishe (Apr 30, 2013)

Windows on Wash said:


> If it is wood shingles, I would do it from the exterior.
> 
> You need to know what the exterior sheathing and vapor control layers consist of.


I don't think that's an option with these guys. They cut holes in the interior walls and blow it in, spackle it up and leave it for me to repaint.

Its pretty much an all-or-nothing deal. I either want it, or I tell them no.

Do I want it?


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## Windows on Wash (Aug 30, 2011)

Can't say without know what the exterior cladding, sheathing, and possible vapor permeance levels are.


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## dishe (Apr 30, 2013)

Well, I'd like to think that these guys, being government contracted professionals, know what they are doing. Reality might be somewhat different, but I don't have any particular reason not to trust that they looked into what my house is made of before starting the work. 

I started looking into this because they handed me a paper to sign that I give them permission to cut holes in my interior walls and blow stuff in. Then I found this website which totally freaked me out about it:
http://bobyapp.com/blog/2009/06/myths-about-insulating-old-house-walls

But it sounds like that guy is talking about a different kind of house than mine (he's referencing plaster walls from 100+ year old structures), and may or may not be somewhat sensationalizing the problem. For a moment there I started picturing some sort of conspiracy that I'll regret getting later (something similar to the way they used to encourage asbestos inside the house until the public became aware of the dangers). This is apparently standard procedure for houses just like mine all over the county, so maybe I'm just being an alarmist?


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## jimn (Nov 13, 2010)

I am not an expert but I do have a house built in 1960. The house is a cape style with a full rear dormer, 2x4 framing, cedar shake siding, drywall and hot water baseboard heat. I have replaced all the windows with energy efficient windows. Prior owner(s) did all the insulation . Fiberglass in the attic and blown in cellulose in the walls. I beg to differ with the site you linked about the cost savings. I heat with oil and all the houses in this neighbor hood were built at the same time in the same way. My neighbor whose house was 250 sq ft bigger than my 1600 sq ft house used over twice as much oil as I did. Same antique boiler by the way. The new owner insulated and cut the oil consumption 30%. 

How is my cellulose holding up? I have had the house for 20 years and it was insulated some time before that. Quite well . I have to open walls to repair renovate. We did a complete bathroom gut. If there is anywhere that moisture would be a issue. The bathroom . No sign of mild, damp or anything else in wall. I have opened other exterior walls to install through the wall AC etc and no sign of any water issues. One winter we had some serious ice dam damage. By the time the contractor was able to repair , what insulation might have been wet was bone dry with no sign of mold. 

All that being said , it would probably not be smart to use a humidifier in a house with vapor barrier. I also use bathroom and kitchen exhaust fans extensively


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## Windows on Wash (Aug 30, 2011)

dishe said:


> Well, I'd like to think that these guys, being government contracted professionals, know what they are doing.


Are you doing this for comedic value? Even so, I did laugh out loud when I read this first part.


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## ThatDaveGuy (Dec 31, 2010)

Insulating the walls will help, I wouldn't lose any sleep over that site you posted, but it isn't the end all/be all of it. Air sealing/ stopping the drafts will be a huge part of being comfy in your home. If it were me I'd have the walls done, ride out the winter, and then make a determined effort to seal every possible penetration on the exterior. Having a completely tight shell around it enhance the insulation's ability to hold the heat.


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## dishe (Apr 30, 2013)

Windows on Wash said:


> Are you doing this for comedic value? Even so, I did laugh out loud when I read this first part.


LOL- glad you liked that. 

I was trying to say that I'm not DIYing this at least- this particular guy has 40 years experience. Geuss that would give him more credibility than the govt contract part!

Meanwhile, I think I'm going to do the wall insulation. I'm just really not too keen about the holes cut all over the place. He'll spackle it up, but I have to more-or-less paint the house. I've avoided painting certain rooms since we moved in because 2 of them have super-high cathedral ceilings that I'm not comfortable reaching on a ladder. Sigh.


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## Windows on Wash (Aug 30, 2011)

Yes. If he has that kind of experience you should be good.


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## HomeSealed (Jan 3, 2008)

+1 on this being a widely recognized, proven procedure. There are about a million and one circumstances that would have to exist for you to get moisture logged cellulose insulation in your sidewalls due to interior moisture. I would recommend doing it, although as WOW stated a bit earlier, it would be ideal to do from the exterior unless the house has masonry cladding or siding that could contain asbestos. Cleaner and easier for both you and the installers... My thought as to the reasoning in mandating the interior installation is to streamline the program rather than a hodge-podge of some interior and some exterior. Also there is a chance of siding damage when done from exterior. Not a high likelihood in most cases, but again in terms of streamlining the program it is probably easier to explain to people that they will have some wall patches to finish and paint as opposed to finding 40 yr old pieces of obscure aluminum siding or pathing in cedar and painting, etc.


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## Nailbags (Feb 1, 2012)

dishe said:


> As part of a home energy audit, I received a grant to blow insulation to the attic and walls of my 1969 home.
> 
> I'm aware of how messy blown cellulose insulation is for the attic, but I'm OK with that- I made sure to do any electric work I was pushing off (overhead fixtures) before they scheduled to come. But now I'm having second thoughts about the walls.
> 
> ...


blow it with fiberglass it has a density of 2.2 pounds per sq foot and will not do what that paper mache does. and those horror stories are 100% true for the cellulose.


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## dishe (Apr 30, 2013)

Nailbags said:


> blow it with fiberglass it has a density of 2.2 pounds per sq foot and will not do what that paper mache does. and those horror stories are 100% true for the cellulose.


I'm not really given an option. The installers are told what to do by the program, which I'm not paying for (so I really don't have a say). I can say no, but then they won't do it at all.


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## Windows on Wash (Aug 30, 2011)

Cellulose is fine. If both are done right, they are air barriers and should be fine when installed properly.


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## HomeSealed (Jan 3, 2008)

+1. Cellulose is most commonly used in this application and will do a good job. It is UNANIMOUSLY preferred by pretty much the entire home performance industry, whose only motivation is to use the most efficient and effective methods and materials possible. The same can't be said for the "fiberglass contingent" and the massive corporate $$$ behind it, along with a few goofballs that fall for their propaganda. If you are not sure what I'm talking about, I'm sure that Nailbags will oblige in "enlightening" you. 
Ultimately, as WoW stated, either will get the job done, cellulose will just do it cheaper and debatably more effectively.


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## msaramak28 (May 3, 2017)

Hello all,

I just purchased an old 1800's farmhouse and am contemplating the same thing as spoken here. Unfortunately i will be paying for this as im sure the grant is long gone. 

We have a 2 story 1700 sq home with wooden siding. Im sure plaster walls, there have been updates but from what i have found in my short time here, mainly just 1/4 over top. 

All the windows are very old and am at the point where i need to decide when i replace whether to go replacement or new construction. My wife wants to keep as much character as possible and with some arched windows in the front this poses issues with the choice or replacement over new build. The frames show their age. I know this is in the wrong category, but figured i would share. 

With the reading i have done it seems that some are for the blown in insulation and like others have mentioned, some are dead against it. I just want to save some money with heating. No AC we have baseboard boiler system. 

All thoughts, advice and insight is greatly appreciated. I would post picture, but i do not have enough posts, which is annoying 

Thanks,
Matt


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## Windows on Wash (Aug 30, 2011)

Matt,

Start a new thread and take a handful of pictures that you can post up. That will keep it separate and you will get more feedback to a new post with visuals.


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## msaramak28 (May 3, 2017)

Wow,

I will get some pictures for you guys and start a new thread in a day or so.

Thanks,
Matt


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