# Does this ceiling need more insulation before I finish it?



## diytrying (Mar 3, 2014)

I'm starting the process of finishing my basement, and I'm no handyman but the existing insulation looks a bit sparse and well-worn.

Before finishing the ceiling (which I would like to have can-lights) should I add some more insulation? The basement will be regularly used as an office so I want it to be comfortable and quiet, without the heat escaping in the winter.

Thank you in advance for any insight!


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## joecaption (Nov 30, 2011)

Only reason any insulation is needed now that's it's being finished is for sound deadening.
It's going to be even less noisey once the 5/8 sheetrock goes up.


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## diytrying (Mar 3, 2014)

joecaption said:


> Only reason any insulation is needed now that's it's being finished is for sound deadening.
> It's going to be even less noisey once the 5/8 sheetrock goes up.


I see! Thank you very much for your answer. In that case, I will probably hold off on spending a few hundred dollars on insulation if it is not needed.


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## Ocelaris (Oct 9, 2012)

Before you put up the sheet rock, look to the rim joist at the edges of the house, you would be better off sealing the edges of the house to keep any leaks out. Basically the insulation directly below the floor isn't going to do any good except transmit the cold air leaking in from the sides of the house. 

http://www.familyhandyman.com/basement/insulate-basement-rim-joists/view-all


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## Windows on Wash (Aug 30, 2011)

+1

Seal up the rim joist prior to sheet rocking it out.


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## diytrying (Mar 3, 2014)

Ocelaris said:


> Before you put up the sheet rock, look to the rim joist at the edges of the house, you would be better off sealing the edges of the house to keep any leaks out. Basically the insulation directly below the floor isn't going to do any good except transmit the cold air leaking in from the sides of the house.
> 
> http://www.familyhandyman.com/basement/insulate-basement-rim-joists/view-all


I wish I could "Thanks!" you twice! This is a great tutorial and we actually had a ton of spiders before a home energy audit where they sprayed expanding foam around the perimeter of the basement. It seems the spider problem is taken care of but I will definitely take your advice and seal off the rim joists. The basement is very cold and I want to make sure it's comfortable when I'm using it as a work space.


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## diytrying (Mar 3, 2014)

Windows on Wash said:


> +1
> 
> Seal up the rim joist prior to sheet rocking it out.


Thank you for weighing in! I took a look at that tutorial link and it does seem like a great idea, with good results at a low cost in money and time.


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## Gary in WA (Mar 11, 2009)

No need to go off-site from here; use our forum links (found at bottom of page or use "search" box at top page) for the answers; eg. http://www.diychatroom.com/f103/rim-joist-insulation-options-159580/

http://www.diychatroom.com/f103/how-insulate-rim-joists-simply-190336/

Gary


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## Ocelaris (Oct 9, 2012)

Thanks Gary, didn't mean to point people off site, in as much as I need a quick visual for people to get what rim joist insulation meant. I will sometimes check visuals from other sites but always come back here for solutions and real world experience.

I tried doing this to a few bays and the biggest problem I have is that my spray foam gun doesn't work very well "aiming up" i.e. it shoots air instead of foam, so I have a hard time filling the edges around the foam.


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## diytrying (Mar 3, 2014)

I am just now getting around to insulating the rim joints. I have read the tutorials linked in this thread but have a quick question for any of you insulation experts:

Currently, there is some fiberglass insulation on the inside of the rim joist. I take it that my best course of action is to:

Remove the fiberglass insulation, caulk the openings behind it, and put it back
Cut 2" insulation (preferably the kind with the foil on it) to size and place it on top of the fiberglass insulation
Caulk the remaining openings

However, based on Gary's post in another thread I don't know if this will lead to condensation issues. Should I remove the fiberglass insulation entirely? I do plan on installing drywall, finishing this basement, and using it as a living space regularly.

Any expert advice would be much appreciated!


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## Ocelaris (Oct 9, 2012)

If you're making a complete seal of the rim joist, i.e. like this thread:

http://www.diychatroom.com/f103/how-insulate-rim-joists-simply-190336/

The foam keeps the cold and hot separated so there isn't an issue with the condensation. I'm not sure what you mean fiberglass on the inside of the rim joist, do you mean up against the floor and happens to run into the rim joist? I would pull that back, totally air seal the rim joist and put the fiberglass insulation back.

The idea is to just not let any air from one side of the rim joist touch the other side... I'm about to embark on a similar project, and basically I use the foam as an air seal, and will be covering any wood on the cold side to keep it from getting through to the house. I'm not sure what benefit foil does after >1" of foam whether it's polyisocyanate or Expanded Polystyrene... I thought hit would be a vapor barrier as well as long as it's sealed. 

The impression I got with fiberglass insulation is that it's fine as long as you air seal, but should never be relied on to stop air infiltration. So I would remove it as your purpose of sealing the rim joist is 90% for air sealing purposes, and fiberglass doesn't seal air very well.


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## diytrying (Mar 3, 2014)

Ocelaris, thanks for your advice! I think what I will do based on what you suggested and what I've read since my post is:

1. Remove the fiberglass stuffed in the rim joist presently
2. Caulk anywhere on the rim joist that air could move through
3. Cut a piece of 2" foiled rigid foam board insulation to size
4. Construction adhesive the rigid foam board into the rim joist
5. Caulk anywhere on the rigid foam board that air could move through
6. Put the fiberglass back over the rigid foam board
7. Proceed with framing and drywall

This way, the foam is between the warm interior / cold exterior and foil side in should prevent condensation (if the insulation itself doesn't). Also, the fiberglass is in an enclosed space (between the airtight rigid foam board and the drywall) which I understand is how it is supposed to work best.

I'm starting this little project within the next week as I wait for my permit to go through - I'll let you know how it goes! Thank you


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