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Old 07-01-2009, 01:37 PM   #1
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Insulating walls of old house


Hi, I live in central PA in a 50 year old house. The walls in this house has no insulation at all. I'm planning to cut a hole (one on top and one on bottom in between studs) and blow in fliberglass or cellulose. My biggest question is - should I be worried about any moisture problem?
Thank you all.

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Old 07-01-2009, 07:11 PM   #2
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Insulating walls of old house


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Hi, I live in central PA in a 50 year old house. The walls in this house has no insulation at all. I'm planning to cut a hole (one on top and one on bottom in between studs) and blow in fliberglass or cellulose. My biggest question is - should I be worried about any moisture problem?
Thank you all.
Cellulose has been blown into thousands of homes in this manner.
I had this done in my home by a contractor. He drilled a 1" hole at the top of the stud cavity and another at the 4" level just under the 'firestop'.
Then inserted the nozzle and filled it up.
It makes a hell of a mess. Fortunately, the house was unoccupied at the time.

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Old 07-01-2009, 10:24 PM   #3
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Insulating walls of old house


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Cellulose has been blown into thousands of homes in this manner.
4" level just under the 'firestop'.

What is a firestop and where is it? How much should the 2nd hole be above the floor level? Thank you
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Old 07-01-2009, 10:37 PM   #4
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Insulating walls of old house


In order to blow cellulose into a wall, you need a high capacity blower capable of generating about 3psi pressure. This is not something that Home Depot rents, in fact when I was looking to do this for my house, I could not locate any place that would rent a professional blower. So I hired a contractor, and truth be told, the price is not a lot higher than it would have cost me to do it myself, and I reduce the chance of me falling off a ladder and killing myself. You need to check out the cost of having a contractor do the job before you commit to doing it yourself, it may be more trouble than it is worth to save a few bucks.

But as for moisture, I checked a lot of sources, and the majority seem to agree that no moisture barrier is required, you just fill the cavity full and cover the holes with the siding.
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Old 07-01-2009, 10:49 PM   #5
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Insulating walls of old house


Celluose was blown into my house about 15 years ago. For some reason it settled after a few years and became ineffective.
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Old 07-02-2009, 07:00 AM   #6
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You need to check out the cost of having a contractor do the job before you commit to doing it yourself, it may be more trouble than it is worth to save a few bucks.

But as for moisture, I checked a lot of sources, and the majority seem to agree that no moisture barrier is required, you just fill the cavity full and cover the holes with the siding.
Last year, I took a quote from a contractor to do the whole house (he said doing it from inside the house, not outside) for $1550. He would cut only one hole in the top, fill the cavity and patch the hole. I'm not planning on using the contractor as he did NOT do a nice job insulating the attic (for $1500 - blown in certainteed fiberglass). My house is about 1900 sq feet and I don't forsee more than $500 for a DIY work. Plus, I can do it slowly one room at a time and do it right.

Now, after your response, I feel more comfortable about NOT using any vapour barrier. I also understand that I may have to redo half the job again after 2/3 years because of settling. I'll just go ahead and blow the insulation. I know you found trouble renting a blower - I can buy a blower if it is less than $200 - does anyone suggest a simple blower to use on this job?
Thanks again.
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Old 07-02-2009, 10:28 AM   #7
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Insulating walls of old house


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What is a firestop and where is it? How much should the 2nd hole be above the floor level? Thank you
Its a piece of 2X4 that is installed horizontally between two wall studs, generally half way up the wall. Thus preventing fire from traveling through the wall cavity.
It has another purpose and that is hold the studs in position and keep them from twisting as they dry out.

I paid $1100 to have my house insulated and its smaller than yours. So the price that you were quoted seems quite reasonable to me.
I'm a dried in the wool DIYer, but there are two jobs I leave to the pro's. One is roofing and the other is blowing insulation.
The blower that my contractor used was a large machine occupying about 9 s/f of floor space and was about 4 feet tall. Took 2 men to bring it in the house.

To buy a machine like this must have cost a thousand or more.
Your plan to do a room at a time, could eat up any savings that you would have, by rental fee's and transporting the blower back and forth to the rental people.
In my case, I closed up and finished the holes in the wall, so I was able to get a reduction in the price for the labor.
All this activity can be quite messy and if you do your own cleanup it could save you more.

Last edited by Wildie; 07-02-2009 at 10:31 AM.
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Old 07-02-2009, 10:49 AM   #8
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Insulating walls of old house


My contractor blew the cellulose in from outside the house. He cuts two 1 inch diameter holes per bay, and uses a flexible tube to fill in each bay. The blower he used is a 240 volt, high capacity machine, looks like a shop vac on steroids, probably cost 2 to 3 thousand dollars. Also includes a controller at the point of filling, so a single person can operate the machine.

The key to avoiding settling is to achieve about 120 percent of normal density of the cellulose. If you achieve less than 100 percent, the cellulose will settle over time, leaving a void at the top of each bay. This obviously diminishes the insulation value tremendously. In order to get 120 percent normal density, you need a high pressure blower, as I previously noted. This means at least 2.5 psi, maybe 3 psi.

The typical blower rented by Home Depot produces somewhere around 1 psi, which is fine if you are blowing loose insulation into the attic, where settlement is not a problem. However, the typical rental blower cannot achieve the required density in vertical (wall) applications, so settlement occurs over time, and you lose insulation.

The key to doing this job yourself is to determine if you can rent a high pressure blower. Purchasing such a unit seems way too expensive for a one off job. As I said, I could not find any place that would rent me one in eastern Massachusetts, not to say you can't find one where you are. Good luck with the project.
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Old 07-02-2009, 12:04 PM   #9
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Insulating walls of old house


One of the DIY shows had a demonstration with clear plexi-glass showing how blowing the insulation filled the voids. They were quite clear that a low power blower will be very ineffective in filling the void enough
You will be going back & doing the job again in a few years with a low power blower. Negating any possible savings

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