# Does Fiberglass Batts Insulation works for windows?



## Windows on Wash (Aug 30, 2011)

In most cases, no.

If sealed properly and caulked, it is okay. 

My question would be why use it if foam is better and easier to use.


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## baby327nd (Mar 14, 2011)

Windows on Wash said:


> In most cases, no.
> 
> If sealed properly and caulked, it is okay.
> 
> My question would be why use it if foam is better and easier to use.


1. Does sealed properly includes these [since I also have done that already]:

A. Using Shrink Insulator windows kit on both exterior window and indoor window like these ones:
http://www.acehardware.com/family/index.jsp?categoryId=1259828
B. Using bubble wrap on the windows as shown in this method: 
http://www.builditsolar.com/Projects/Conservation/bubblewrap.htm
C. Using weather seal tape around storm windows.

2. Which foam I should use than?


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## Windows on Wash (Aug 30, 2011)

FG would be stuffed in the cavities between the RO and the insert window or cripple cavities in the RO framing.

Most insulation discussions about FG and windows are in terms of window replacements. If you are speaking to your existing window, they you are mostly looking at just sealing up the interior surfaces against any air leakage. Stuffing the little bit of FG that you can get in there is not going to do much and will not the the improvement as compared to sealing up the envelope (i.e. caulking/sealant).

The foam you would use would be the window and door specific foams.


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## baby327nd (Mar 14, 2011)

Windows on Wash said:


> FG would be stuffed in the cavities between the RO and the insert window or cripple cavities in the RO framing.
> 
> Most insulation discussions about FG and windows are in terms of window replacements. If you are speaking to your existing window, they you are mostly looking at just sealing up the interior surfaces against any air leakage. Stuffing the little bit of FG that you can get in there is not going to do much and will not the the improvement as compared to sealing up the envelope (i.e. caulking/sealant).
> 
> The foam you would use would be the window and door specific foams.


1. It is for existing windows and a temporary solution for a rental house which I will be moving out of within a year. Also, it won't be a little bit of fiberglass but the whole RJ-30 fiberglass [at least 3 inches thick and 1 feet long depending on how long the windows are] between the windows.

2. Is this the foam sealant you are talking about:
*Great Stuff® Foam Sealant *

http://www.acehardware.com/product/index.jsp?productId=1390371&CAWELAID=109328542

3. What if instead of using fiberglass, I use many usps boxes stacked together like the one shown in link below:
Priority Mail Large Flat Rate Box 12” x 12” x 5 1/2” 
https://shop.usps.com/webapp/wcs/st...viewAll=N&rn=CategoriesDisplay&WT.ac=10001232

Will that work better than fiberglass for what I want to do?


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## Windows on Wash (Aug 30, 2011)

Define "between the windows". Do you mean between the window and the storm window or between the rough opening (i.e. stud framing)?

What are you trying to do?


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## baby327nd (Mar 14, 2011)

Windows on Wash said:


> Define "between the windows". Do you mean between the window and the storm window or between the rough opening (i.e. stud framing)?
> 
> What are you trying to do?


Thanks for replying again. I think this is the info you need in order to give the correct answer:

what I mean is between the window and the storm window. And only doing this so cold air does not come through window. [I live in Iowa and it is already 23-30F at night!]. So its not for trapping the heat of the house inside [from the heater] and doesn't matter if i will be able to see outside the window or not?


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## Windows on Wash (Aug 30, 2011)

In that application, you are going to use fiberglass, mineral wool, or some other sort of batt of insulation.

I would recommend the stretch film over the windows to get them airtight and maintain the visibility.


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## baby327nd (Mar 14, 2011)

Windows on Wash said:


> In that application, you are going to use fiberglass, mineral wool, or some other sort of batt of insulation.
> 
> I would recommend the stretch film over the windows to get them airtight and maintain the visibility.


okay. what if I also use between the windows bubble wrap [by applying on the window directly as shown here http://www.builditsolar.com/Projects/Conservation/ BubbleWrap1.jpg], usps cardboard along with fiberglass will that reduce the effectiveness of the fiberglass?

And I would also do the stretch film over widows.


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## Windows on Wash (Aug 30, 2011)

Bubble wraps do not hold any performance advantage over the fiberglass.


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## baby327nd (Mar 14, 2011)

Windows on Wash said:


> Bubble wraps do not hold any performance advantage over the fiberglass.


That is not what I mean but what I meant was does the bubble wrap hinder fiberglass ability if I put it along with fiberglass between the windows?


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## Windows on Wash (Aug 30, 2011)

No, it should not.


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## baby327nd (Mar 14, 2011)

Windows on Wash said:


> No, it should not.



Just one last question, so I hope you don't mind 

If I only have two option available which are using just bubble wrap OR usps cardboards to put between the windows [like the same method for fiberglass] , which will be better if I only do this and not do anything else for the windows?


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## JoJo-Arch (Sep 15, 2011)

Its the air inside each bubble that prevents heat conduction in bubble rap. It will also let light in but block some rays because of frefractions within the curved bubbles. It also allows more light in than cardboard. The only drawback I see is if people can get access to it. The proverbial joker will pop them all, just to make a noise and I'm not talking about young kids.

Insulation is to stop heat from a source seeking a cooler source, not the other way round. A cold source like outside snow, doesn't transfer energy in the form of cold as this cannot exist. A definition of cold is the absence of heat. In a cold state, electrons wizzing around the centre of atoms are sluggish and slow. However as energy is expended by generating heat, heat acting on the atoms cause the electrons to speed up, knocking other atoms and thus transfering heat from one to the other. That's why metals are good conductors of heat and electricity. Glass, air, plastics, glass fibre and other insulation products are poor conductors of heat. Glass can stop conduction and convection within the glass, but limited in stopping radiation. Air can stop conduction, but not readily convection or radiation. Glass fibre is a poor conductor, stops most radiation and by trapping the air within the fibres, will prevent convection and that's why its a good insulator. Also, it is fire neutral, It dosen't burn, can withstand high temperatures and gives off no smoke when heated. It is also a good fire insulation blanket to spread fire jumping across ceilings from one room to another. It is also glued to stick together like fairy floss to restrain free fibres waffting about Heat can and does transfer from a hotter souce (the inside) through the glass in the form of radiation, convection and conduction to the outside. In the application of insulation in general, all the side effects should be considered. Some plastics can be good insulators, but in a fire situation can give off deadly toxic gases when burnt. In judging what insulation to use, the ones that tick all or most boxes should be considered first, and as the cost variance is usually small, cost should not be an issue in the first analysis.


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## baby327nd (Mar 14, 2011)

can someone answer this question please:
what about bubble wrap sprayed with water and attached between the 2 windows [same space where the fiberglass was suppose to be]? That won't damage the windows right? [similar method as shown here http://www.builditsolar.com/Projects/Conservation/bubblewrap.htm ]


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