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Old 10-16-2017, 10:32 AM   #1
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Ceiling Insulation

Has anyone used the injected spray foam insulation? Drilling a few small holes into the ceiling and injecting the insulation seems to good to be true. What am I missing? I really like the idea of not messing with removing the inner skin of the ceiling. Structural integrity and all that. Any feedback is welcome.
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Old 10-16-2017, 12:08 PM   #2
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Has anyone used the injected spray foam insulation? Drilling a few small holes into the ceiling and injecting the insulation seems to good to be true. What am I missing? I really like the idea of not messing with removing the inner skin of the ceiling. Structural integrity and all that. Any feedback is welcome.
You are missing the fact that the space is filled with elderly batt insulation which has to be removed.
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Old 10-16-2017, 01:08 PM   #3
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You are missing the fact that the space is filled with elderly batt insulation which has to be removed.
Over the past couple years I have given this some thought and have a couple questions.

1. If there are no leaks in the roof and the old insulation is dry, why would it need to be removed?

2. If the old insulation were left in place, would the force of the expanding foam be sufficient to compress it, or would the foam mix with the old insulation? Where would be the harm?

3. If it were necessary to remove the old insulation, why not cut in an access hole and install a cover panel when done. This could be done by cutting a 10 X 10 in. square hole between sets of ribs in the ceiling, and pulling the old insulation out using a straightened metal coat hanger having a hook bent into one end. Try to plan your acce4ss holes in places where they wouldn't be to obvious. These 10" access holes would also allow more room for the spray nozzle tube to ensure a fuller more complete coverage. Cover the 10X10 hole with a piece of 11 X 11 in. material metal or plastic ... then paint the ceiling.

4. I am curious if there might be commercial businesses who could do this for you.


It the ceiling panels do lend a bit of structural support you won't disturb anything by cutting in a couple access holes. This could be a time and material saver, at least you wouldn't have to remove the entire ceiling.

Make sure that you use a closed cell foam and NOT open cell foam like great stuff. I see Hilte has a good product and a couple different length foam guns.
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Old 10-16-2017, 03:25 PM   #4
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I would think the expanding foam would compress the old insulation down to almost nothing. I think an experiment in a small clear box is in order. I bet I could drill a few small holes and be good.
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Old 10-16-2017, 03:29 PM   #5
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I would think the expanding foam would compress the old insulation down to almost nothing. I think an experiment in a small clear box is in order. I bet I could drill a few small holes and be good.
In theory, yes. In practice, no. Foam needs to be trimmed after spray, if it was confined in a space, you could turn a Blue Bird into a Crown. Poof !
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Old 10-16-2017, 04:17 PM   #6
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In theory, yes. In practice, no. Foam needs to be trimmed after spray, if it was confined in a space, you could turn a Blue Bird into a Crown. Poof !
Injecting into a void is a real thing, but it's a skilled operation. In theory there is no real reason why this couldn't be done, but if too much catalyst is added the thin ceiling could end up bulging down.

It's an attractive idea, if it worked.
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Old 10-16-2017, 04:22 PM   #7
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Over the past couple years I have given this some thought and have a couple questions.

1. If there are no leaks in the roof and the old insulation is dry, why would it need to be removed?

2. If the old insulation were left in place, would the force of the expanding foam be sufficient to compress it, or would the foam mix with the old insulation? Where would be the harm?

3. If it were necessary to remove the old insulation, why not cut in an access hole and install a cover panel when done. This could be done by cutting a 10 X 10 in. square hole between sets of ribs in the ceiling, and pulling the old insulation out using a straightened metal coat hanger having a hook bent into one end. Try to plan your acce4ss holes in places where they wouldn't be to obvious. These 10" access holes would also allow more room for the spray nozzle tube to ensure a fuller more complete coverage. Cover the 10X10 hole with a piece of 11 X 11 in. material metal or plastic ... then paint the ceiling.

4. I am curious if there might be commercial businesses who could do this for you.

It the ceiling panels do lend a bit of structural support you won't disturb anything by cutting in a couple access holes. This could be a time and material saver, at least you wouldn't have to remove the entire ceiling.

Make sure that you use a closed cell foam and NOT open cell foam like great stuff. I see Hilte has a good product and a couple different length foam guns.
1. You can't judge the condition of the old batts, without seeing them.

2. Probably, and probably little harm if the batt is still in place and uniform. Likelihood of the foam pooling would be high as it needs to flow.

3. Would be possible

4. All I can suggest is that you find an expert in foam injection, and ask them if it is possible, and at what cost.

Let us know because it's an interesting idea.
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Old 10-16-2017, 04:44 PM   #8
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In theory, yes. In practice, no. Foam needs to be trimmed after spray, if it was confined in a space, you could turn a Blue Bird into a Crown. Poof !
Poof? What does this "poof" mean?

Poof as in mixing closed cell foam with old insulation batts there is a possibility of a fire? Or something worse?

Also, why would expanding foam need trimming after being injected into a closed space?
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Old 10-16-2017, 04:49 PM   #9
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Poof? What does this "poof" mean?

Poof as in mixing closed cell foam with old insulation batts there is a possibility of a fire? Or something worse?

Also, why would expanding foam need trimming after being injected into a closed space?
He means that the roof and ceiling could bulge out.
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Old 10-16-2017, 04:54 PM   #10
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Also, why would expanding foam need trimming after being injected into a closed space?
It wouldn't need trimming if you knew exactly how much to use. I think the point being made is that the idea is technically possible, but your typical DIY foam insulation user doesn't have the expertise to gauge the exact empty space and know how much uncured foam to inject. This would be particularly difficult with an unknown quantity of batting already in place. If too much was used, it could wind up pushing against the sheet metal and deforming sections of the ceiling.
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