# Blown in insulation in walls with existing fiberglass.



## Shane Collins (Feb 5, 2015)

Hi all,

Anyone have any knowledge or information about getting blown in cellulose in walls that already have fiberglass insulation?  

I know my house is under insulated but I didn't quite realize how bad.  The other day I was changing my bed sheets and they were frozen to the wall....  I had frost on the inside of my wall behind my bed.  The living room is at 70 and bedroom usually sits around 66.  Surely I shouldn't be getting ice on the inside of the walls?  I've since pulled my bed a few inches away from the wall and it doesn't seem to be happening but it's still quite cold to the touch.

I'd like to see about getting blown in cellulose in my walls but they already have fiberglass insulation.  Is it possible to put blown in cellulose on top of this? or will it not work very well?  The only other solution I can think of is to rip off the drywall and pull out the fiberglass and re do all the exterior walls?  That seems like a pretty big job and likely a last resort?

Thanks for any advice.


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## GENECOP (Feb 5, 2015)

1+1 is not equalling 2 here.....If your home has heat, and even R -11 in the walls, no way to your getting ice inside....Something else must be going on....


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## GENECOP (Feb 5, 2015)

Maybe you have siding issues....


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## Shane Collins (Feb 5, 2015)

GENECOP said:


> 1+1 is not equalling 2 here.....If your home has heat, and even R -11 in the walls, no way to your getting ice inside....Something else must be going on....



I assumed poorly insulated walls with a bed pressed against the inside, preventing the heat from getting to that wall would cause the problem.  Since I've moved the bed away from the wall by a few inches there is no longer ice on the inside of the wall, but it's pretty cold to the touch.  How could siding be an issue?  We have cedar clapboard siding, it needs painting but apart from that it's in pretty good shape.


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## GENECOP (Feb 5, 2015)

What type of heat in the bedroom?


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## Shane Collins (Feb 5, 2015)

The wood stove heats the whole house.  Our bedroom is on the ground floor, as is the wood stove.


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## GENECOP (Feb 5, 2015)

If you have fiberglass ins in the exterior walls and you still have ice inside, with a fair amount of heat getting in the bedroom, then you probably have a condensation issue, no vapor barrier, hard to say without seeing every detail, but I think your house is not breathing properly, condensation , etc...to answer your original question, if you have fiberglass, assuming 2x4 walls, r-11 or 13.....blowing in is not an option that I would consider.....


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## Shane Collins (Feb 5, 2015)

GENECOP said:


> If you have fiberglass ins in the exterior walls and you still have ice inside, with a fair amount of heat getting in the bedroom, then you probably have a condensation issue, no vapor barrier, hard to say without seeing every detail, but I think your house is not breathing properly, condensation , etc...to answer your original question, if you have fiberglass, assuming 2x4 walls, r-11 or 13.....blowing in is not an option that I would consider.....



There definitely are other issues but I'm pretty sure the wall insulation is a pretty big problem.  If you think blowing in is not an option, what would you do?


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## laynes69 (Feb 5, 2015)

Fiberglass while an insulator is not an air barrier. I would look for any areas outside on the home that may have large penetrations leading into the home, especially if it's a localized area.


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## Circus (Feb 5, 2015)

I wouldn't tear out the drywall either. Maybe you can remove the baseboard and probe the wall with a stick. Mice like to tunnel through fiberglass and it makes sense it would be on the bottom. If your lucky just stuffing fiberglass in the bottom will do the trick. Worth a try. If there's a 2x4 behind the baseboard, disregard.


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## woodgeek (Feb 6, 2015)

IF you have typical old house air leakage, then you have a lot of air coming in at the sill and rim joists (esp if mice have gnawed some large holes there in the exterior sheathing, under the siding).  Add in some pressure from the prevailing wind, and suction from your attic ventilations and this air then flows vertically up the cavity into the attic 'wind washing' and cooling the whole cavity irrespective of any insulation in there.  Voila, freezing drywall. 

This is why many folks report freezing pipes during cold windy weather, even when the indoor temps are >50°F...cold spots from windwashing.

Step 1: Pro aisealing of sills, rims and attic.  This will save a bundle on energy and prob solve your problem.  I had parts of my wood floors that were running 40°F in a much milder climate.  Airsealing fixed it.

You CAN blow cellulose into FG filled cavities.  Depending on the FG, it can be easy or less easy.  If the cavity is airsealed, this is unlikely to be economical in terms of energy savings.  So there is no Step 2.


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## Highbeam (Feb 8, 2015)

I too have 2x4 walls with just thin r5 batt insulation that was labeled as 1.5" thick. It has an attached vb. As we all know, even if the installer tries to succeed it is unlikely that the old school fg insulation is done well. Mine was installed in 1963. 

I haven't had ice on the wall.


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## Shane Collins (Feb 8, 2015)

You have any plans on adding more Highbeam?

Woodgeek. Good ideas there.  I have had a pipe freeze recently, luckily caught it before it burst and have sorted the problem for now.  I was planning on pulling out the fiberglass in the rim joists and getting spray foam in there.  In the next month or so I'll probably see about getting an energy audit.  Not sure how well the spray foam kits work from home depot or lowes, or if I should just hire somebody.


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## Highbeam (Feb 9, 2015)

Shane Collins said:


> You have any plans on adding more Highbeam?


 
Well I insulated the R-0 floors to R-30 and then blew in the attic to current code+. Even replaced the windows and all exterior doors. The walls are much harder to fix. As I've remodeled I've replaced the R-5 with R-13 done properly but I have no intention of removing all of the sheetrock or siding so if I do anything, it will be blown in through holes.

They say that the huge majority of heat loss is through the ceiling. Walls aren't nearly as important. I don't know, maybe some day.


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## Shane Collins (Feb 9, 2015)

I haven't actually ever been in my attic, I need to sort that out! there is no access to it and I haven't had time to sort that out.  Probably something I should see about soon.  When you say insulated the floors, do you mean the ground floor, the basement ceiling? Did you notice any big changes after that?  When you remodeled did you tear out the sheetrock to replace the insulation?


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## Highbeam (Feb 9, 2015)

Shane Collins said:


> I haven't actually ever been in my attic, I need to sort that out! there is no access to it and I haven't had time to sort that out.  Probably something I should see about soon.  When you say insulated the floors, do you mean the ground floor, the basement ceiling? Did you notice any big changes after that?  When you remodeled did you tear out the sheetrock to replace the insulation?


 
Here in the northwest we usually build houses over crawlspaces. These are low (like 3 feet tall) ventilated areas under the house within the stem walls of the foundation, have dirt floors, and the "ceiling" of the crawlspace is insulated. So under my home is a cold crawlspace and back in 1963 the codes apparently didn't require insulation of the floors. After adding insulation (I hired out that miserable job) the floor was much warmer. You could even feel the warm spot on the floor from where you had been standing. The subfloor of this old house is 1.5" thick tongue and groove boards. 

The remodeled areas where I upgraded the wall insulation involved total gutting down to the studs. New electrical, framed in old windows and doors, etc. I never removed the siding and sheathing. The sheathing are these crazy 3/4" thick boards they call "ship lap", then tar paper, with old growth thick butt cedar siding on top.

Probably the biggest change was replacing the aluminum single pane windows. Big ones. When the wind would blow the curtains would move they were so leaky. We had a few nights with frost on the inside of those windows.


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## jdp1152 (Feb 12, 2015)

Shane Collins said:


> I assumed poorly insulated walls with a bed pressed against the inside, preventing the heat from getting to that wall would cause the problem.  Since I've moved the bed away from the wall by a few inches there is no longer ice on the inside of the wall, but it's pretty cold to the touch.  How could siding be an issue?  We have cedar clapboard siding, it needs painting but apart from that it's in pretty good shape.



Rotten sheathing compromising your insulation with wind.


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## jdp1152 (Feb 12, 2015)

Highbeam said:


> Well I insulated the R-0 floors to R-30 and then blew in the attic to current code+. Even replaced the windows and all exterior doors. The walls are much harder to fix. As I've remodeled I've replaced the R-5 with R-13 done properly but I have no intention of removing all of the sheetrock or siding so if I do anything, it will be blown in through holes.
> 
> They say that the huge majority of heat loss is through the ceiling. Walls aren't nearly as important. I don't know, maybe some day.




Walls aren't as important because of windows and wood/thermal bridging.    Top is definitely the most bang for your buck, though air sealing is king.


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