Insulation Question(s)

POLOMiNT

Hey all,

I've a question I could not find answered in prevous posts..

I'm in North Carolina (eastern) I've an unfinished Attic that had blowin throughout, and i plan to create a media room (with help).

The current insulation (blow in) needs to be compacted down to the rafters (2x6's) to be able to add a subfloor, this reduce the R value and made the less resiliant to sound. So I plan on placing R30 down over the blow in to make up the insulation as well as help increase density and assist reducing sound between floors.

- Question is this ok to do rather than remove the blown in?
- Does a Vapor barrier need to be inplace between two floors that are heated/cooled - couldn't find anything to say that is does.
- Behind Knee walls the insulation WILL NEED a vapor barrier facing inwards to the warm room is that correct?

Thanks for you time.

POLO

Bob Mariani

making the insulation denser will make it less effective and less sound deadening. No vapor barrier between floors. Vapor barrier is not needed a vapor retarder is. Use kraft faced insulation facing inside on the knee walls.

POLOMiNT

Thanks bob for answering.

I have to reduce the density to be able to add the subfloor to the joists, so i guess with your answer is remove the blowing and replace with fiberglass batts to botain the R-Value required.

I've also read that fiberglass batts are better than blowin as a sound suppressant due to the tighter density which goes inline with sound suppressing materials this isn't to say it's the soul soundprooing i'll be using but will help.

But the main question can I reinforce the Blow in insulation with Fiberglass over the top and then obviously subflooring etc..

cheers.

POLO

Bob Mariani

you could, just do not pack it tightly. Also look into sound attenuation batts instead.

jerryh3

Why would you put a vapor retarder between conditioned floors? While I agree compacting the insulation will hurt the thermal efficiency, I don't think it will hut the sound attenuation of it. Sound blocking material is usually very dense. The mass of the material is what helps absorb the sound enerygy.

Bob Mariani

I would not.. I said nothing in the floor only the knee walls. Maybe it was a run-on sentence. Sorry for the confusion. Answer was in general that code specifies a vapor retarder, not vapor barrier thus the faced insulation on the outside walls faced to the warm side.

jerryh3

Are you saying you are going to use the 2x6's as the floor of the new room?

jerryh3

Gotcha.

POLOMiNT

Thank you Jerry, Thank you Bob,

You both have clear this up for me, just wanted to ensure that it was ok. but behind the knee wall I did think a vapor retarder would be required so thank you both on you replies.

I look forward to posting more questions in the future.

POLO

POLOMiNT

It's a little more complex than that, these 2 x 6 run across (8-11ft) into 2 x10 on the lower load bearing walls.

So yes but they not as you would be thinking the only supports of the floors, i've had a survey done and they are load bearing for what i'm planning and should be fine .

does that make sense?

StereoJoe

Hey Polo, new to this fourm but been in Construction for 30 years and I have never liked that blown in stuff, so if it was mine I would remove it and make a pillow or bed or something with it (about all its good for).. what is your main purpose for this? Sound proff or heat/cooling retention? Be careful with the insulation between the knee walls/ceilings and roof sheeting to not hinder your air flow out the ridge vents and soffits..(**BIG PROBLEMS THERE BUDDY**)!

POLOMiNT

Hey Joe,

Thanks man, I'll take any advise, I’m learning and willing to understand as many points of views as i can so thank you..

the main purpose is turn the Attic into a living space but mainly as a media/entertainment area. I've an engineer coming out next week mainly because of a Gable Dormer that will need reinforcing as it has no header where the laminated beams come together at the ridge.

Because of the raised ceiling below the floor is set at three levels, I’ve checked and there is plenty of room for the regulation 7.5ft (9.5ft actually) living space and total space will be about 8-900ft overall.

First plan to do is insulations between floors at a minimal cost, and then have a framer bring the lower parts of the floor up to the second level maxing out the overall end part of the floor plan, then add sub flooring then a 2x6 knee wall (for extra insulation and increase the space between the front and rear sheet rock.

Obviously there alot more involved but that the general approach I have in mind

Oh and yeah i know exactly what you mean about the soffits, i do plant to add 1 ridge vent/baffle with insulation in to the soffit to reduce the sound coming in from outside but to still maintain the air flow to the ridge vent. Where the angle in the roof is I need the baffels again to transfer the moisture/air from dead space behind the knee walls to the ridge vent as well.. btu good point one i had to read over and over again..

POLO

StereoJoe

I think you should be fine with the 2X6's for the floor, POLO. Just as long as you are not planning on having some 300 lb pole dancer with 50 pals jumping and raising hell and blasting lound tunes!

POLOMiNT

lmao... i bloody well hope not as well..

thanks Joe.

POLO

jerryh3

You make that sound like a bad thing...