# Insulation between floors (Should i insulate?)



## overanalyze (Dec 28, 2010)

Jaws said:


> In my opinion it is reduced by at least 75% just putting bats between the floors. I can tell a noticeable difference when my guys are walking on a second floor of a remodel where they did not insulate between the floors, in comparison to when they walk on the second floor of a home we built and insulated between the floors. We also use inch and an eighth plywood and floor trusses, so that may be a big part of it as well
> 
> Sent from my SM-N920V using Tapatalk


I would argue your subfloor thickness (mass) and the 5/8" (more mass) does way more than the fiberglass does. You even said it is different for your new home vs a remodel. Here are some STC ratings from different wall assemblies. Only a 4 point gain when you add fiberglass to the standard wall assembly. 

https://www.certainteed.com/resources/Guide for Residential Sound Control.pdf

John look into standalone ERV systems or add on setups for your HVAC systems. You can get the air exchanges you need without drawing in the hot air into the conditioned spaces.


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## ScipioAfricanus (Sep 13, 2008)

Are you all aware that both the spaces the OP is talking about are conditioned.
As far as I know, they are not separately conditioned either.

I think that there are better techniques to quiet the floor between the two than to waste money on insulation. Others have already mentioned the techniques.

Andy.


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## SLSTech (Sep 13, 2008)

In short insulating between floors in your condo does nothing except help control sound but the rim joists need to be sealed & insulated. If this is between 2 owners, then why provide them free heat / cooling not including the sound help. Now if there is a wine cellar or specially conditioned area...

As for insulation - R value is R value when it comes to thermal, the biggest issue is proper installation. As for increased air sealing it goes closed cell then open then dense packed cellulose - the rest are essentially air filters. 

Jaws I would recommend that you test with a blower door after spray foaming, it is a good QA check. I have done a few & it is a good wake up call for some on where issues come from - 1 piece I did on it http://thehtrc.com/2012/leed-habitat-targeted-air-sealing-pre-drywall-inspection using infrared & blower door


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## Stilla (Sep 23, 2017)

Jaws said:


> In climate zone 3 you are at 3 air changes per hour, which is a very tight house. I am in process of learning as much as I can about tight houses, air quality, mold control, humidity control. We definitely use dual or 5-speed air conditioning systems now to make sure the humidity is under control and we throw a duct into the attic to cool it off to keep mold from growing. There have been lots and lots of cases of poorly-built houses under these conditions, too tight and oversized air conditioning units that are not built with multi-speed air conditioning to get the humidity out.
> 
> I have always believed a house needs to breathe, nowadays I can't allow that. We had great success spray foaming all of our walls I have always believed a house needs to breathe, nowadays I can't allow that. We had great success spray foaming all of our walls with open cell spray foam and putting better than R38 blow in on the ceilings. Great success, and we were still able to put in venting in the Attic.
> 
> ...


You want to use closed sell on an exterior wall?

If I understand that right. I wouldn't. 

I would be to afraid we would trap moisture, and I don't care what house wrap you are using.

I understand you know more about this than I, as I have no idea what a climate zone 3 is.

I assume it's a dryer climate where adding a humidifier is more beneficial then installing a dehumidifier?


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## overanalyze (Dec 28, 2010)

Yes definitely a CC foam on an exterior wall. I believe at 1.5" most CC foams are impermeable and don't need a vapor barrier. In my climate zone we need 3" of CC for non vented roof assemblies. For walls I like dense pack cellulose.


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## Jaws (Dec 20, 2010)

Stilla said:


> You want to use closed sell on an exterior wall?
> 
> If I understand that right. I wouldn't.
> 
> ...


It's either closed or open and closed doenst grow mold, adds ridgity to structure and doesn't allow any air to infiltrate. They want 3 air exchanges so that is paramount. 

Time will tell on moisture there are a lot of things that are wrong with the new regs imo. 

Multi speed air conditioners have been keeping humidity down to a very low tolerance. 

Sent from my SM-N920V using Tapatalk


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## Jaws (Dec 20, 2010)

SLSTech said:


> In short insulating between floors in your condo does nothing except help control sound but the rim joists need to be sealed & insulated. If this is between 2 owners, then why provide them free heat / cooling not including the sound help. Now if there is a wine cellar or specially conditioned area...
> 
> As for insulation - R value is R value when it comes to thermal, the biggest issue is proper installation. As for increased air sealing it goes closed cell then open then dense packed cellulose - the rest are essentially air filters.
> 
> Jaws I would recommend that you test with a blower door after spray foaming, it is a good QA check. I have done a few & it is a good wake up call for some on where issues come from - 1 piece I did on it http://thehtrc.com/2012/leed-habitat-targeted-air-sealing-pre-drywall-inspection using infrared & blower door


We haven't used a whole house fan or anything that sucks any in in a long time but my point was those were the rage with green tards back in the day also. 

Sent from my SM-N920V using Tapatalk


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## Jaws (Dec 20, 2010)

overanalyze said:


> I would argue your subfloor thickness (mass) and the 5/8" (more mass) does way more than the fiberglass does. You even said it is different for your new home vs a remodel. Here are some STC ratings from different wall assemblies. Only a 4 point gain when you add fiberglass to the standard wall assembly.
> 
> https://www.certainteed.com/resources/Guide for Residential Sound Control.pdf
> 
> John look into standalone ERV systems or add on setups for your HVAC systems. You can get the air exchanges you need without drawing in the hot air into the conditioned spaces.


I meant to qoute this post when discussing whole house fan above. 

SLS I'll let you know how the door blower test goes


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