Choosing fiberglass

Hi guys... here´s my situation, and my plans to insolate my drums... I was a little confused about the statement on the temporary faq about the density of the wool is not THAT important when used inside the studs, behind the gypsum... Based on my situation, should i: A) Use 70mm 16kg/m3 wool inside the studs, 50mm 50kg/m3 between the steel frame and the wall (leaving a 120mm air gap). B) Use 50kg/m3 wool inside the studs (behind the gypsum), nothing between the wall and the frame, with an air gap of 170mm air gap. C) Use the 70mm 16kg/m3 wool inside the studs and between the frame and the wall, leaving a 140mm air gap. Saving money is important, but i think i need to keep my drums as quiet as possible, so... which would you choose? The frame is floated as on Snippers Studio... (btw, no, i can´t replace the bricks wall... i wish i could! :wink: )

For inside the walls, I'd stay with the 16 kG stuff (1 PCF) but use enough layers to fill the cavity, up to a slight compression. IF necessary, remove any paper or other backing from the batts first. The only exception to this would be the batts closest to the normally WARMER wall should keep their backing, which needs to be closest to the warmer wall. By that, I mean that if more of the year is spent HEATING the space, then the backing should go to the inside; if more of the year is spent COOLING the space (with an air conditioner) then the backing should go toward the OUTSIDE of the wall cavity... Steve Using the combination of lighter and heavier insulation could get you into a problem with some multi-leaf faults in the wall; too heavy insulation inside a wall can act acoustically like more wallboard, effectively creating another leaf ...

Cool steve... 3 more... Should i use the same wool (16 kg/m3) to fill the space between the frame and the bricks wall? (or just leave air??). With that design, the only use for high density wool is bass traps, right? Using the this low density fiberglass, how am i supposed to stop the lower frequencies..? (30mm of gypsum can take care of that?)... By slight compression you mean using 70mmx48mm wool when studs are at 40mm centers? BTW, the fiberglass i´m talking about is not rigid... check the pic of the actual product... Thaks a million... on monday i´m supposed to make the order to the store!

Steve, should we be concerned about...

• The sole plates not being pressure-treated?
• The rubber pucks under the wall frames -- are there calculations to ensure that the rubber isn't overoaded or underloaded?
• The gaps between pucks under the wall frames -- will they be sealed?

I realize these points are aside from the question you have asked, Julián... But I wanted to make sure you're not making any mistakes that you'll regret later. :roll:

Thanks sharward for the tips... Here Steve, all questions togheter... :oops: Steve, should we be concerned about... * The sole plates not being pressure-treated? * The rubber pucks under the wall frames -- are there calculations to ensure that the rubber isn't overoaded or underloaded? * The gaps between pucks under the wall frames -- will they be sealed? * Should i use the same wool (16 kg/m3) to fill the space between the frame and the bricks wall? (or just leave air??). With that design, the only use for high density wool is bass traps, right? * Using the this low density fiberglass, how am i supposed to stop the lower frequencies..? (30mm of gypsum can take care of that?)... * By slight compression you mean using 70mmx48mm wool when studs are at 40mm centers? BTW, the fiberglass i´m talking about is not rigid... check the pic of the actual product... Thaks a million... on monday i´m supposed to make the order to the store! Once again, Steve, thanks, thanks and thanks...

Julian,

* The sole plates not being pressure-treated?

Not an issue - the shoe is not in contact with the deck.

* The rubber pucks under the wall frames -- are there calculations to ensure that the rubber isn't overoaded or underloaded?

Yes there are - and you should have performed them just in order to determine the spacing of the pucks. If they are over compressed or under compressed they will fail at their job. How exactly did you calculate their spacing?

* The gaps between pucks under the wall frames -- will they be sealed?

The wall bottom must be properly caulked to finish the asembly - this should be done at the drywall itself - just search the site for "caulk"

* Should i use the same wool (16 kg/m3) to fill the space between the frame and the bricks wall? (or just leave air??). With that design, the only use for high density wool is bass traps, right?

Personally I would leave the air - tis nice for the brick to be able to breathe freely - and the extra inch or o of insulation is not giving you all that much. The high density for traps is correct.

* Using the this low density fiberglass, how am i supposed to stop the lower frequencies..? (30mm of gypsum can take care of that?)...

You stop low frequencies with mass mass and more mass - the 2 layers you show aren't bad - I would install them - but before finishing the room complete - seal everything up to perfection - and then test to see if another layer would be required.

* By slight compression you mean using 70mmx48mm wool when studs are at 40mm centers?

Nope - by slight compression he means that the insulation acts to damp the face of the drywall - thus compressed against it. You can acheive this - and still maintain that air gap at the brick if you install strapping on the back face of the studs on 12" centers - 6" below the top and 6" above the bottom plates. Then compress the insulation in the cavity and the drywall over that.

BTW, the fiberglass i´m talking about is not rigid... check the pic of the actual product...

Regardless - the fact is that you don't get any real sort of gain for the extra cash you pay for this material in comparison to standard batt insulation. Sincerely, Rod

1.000.000 thanks, rod! Here´s how i decided how many rubbers pucks should i use... check it out. Mason SuperW Neoprene Pads: Recommended load per puck= 55kg. (i only can find pucks duro 40)... So, if the gypsum board has a weight of 11kg/m2, each layer of gypsum (on each wall) weights about 100kg... Since i will put 2 layers of gypsum, i have a wall of 200kg+1/4 of the weight of the ceiling (25kg). That means: (on the larger walls,3.6mtsx2.2mts): 225kg/55kg= 4 pucks to hold the wall and the ceiling. That means that i should put a pad every 0.9mts... I´m planning to use 6 pads, spaced by 0.6mts (that will make me able to put a add a 3rd layer of gypsum)... Am i doing it right? :?: So, should i start construction with this low density wool and ONLY use the 50kg/m3 for traps??? Are we talking about 2 layers of gypsum, 16kg/m3 wool between the steel studs, 10cm air and my "lovely" unfilled hollow bricks wall...??? -No 50kg/m3 wool so far- I´m a little concern about spend all that money and still no get the insolation that i need... should i attach some mass to the hollow bricks wall? I mean: bricks-gypsum or mdf as mass - air gap -inner walls with insulation... What do you think?

Julián Fernández wrote:

Since i will put 2 layers of gypsum, i have a wall of 200kg+1/4 of the weight of the ceiling (25kg).

Julian, Wrong equation there - each of the end walls will only carry wall weight - each of the long walls will carry wall weight plus 1/2 of the ceiling weight. Begin there. Also - you don't tell us the size of the ceilling members - and don't take into account the weight of the framing itself (what is the spacing on that and the ceiling frame?) Rod

You´re right... anyway, for long walls the total weight is 250kg each. 250kg / 55kg = 4.54 pads on each wall... I´m planning to use 6 pads, to be able to put a 3rd layer of gypsum (350/55=6.36 pads). The spacing on the walls is 40cm and 48cm for the ceiling. I don´t take into account the weight of the framing ´cause is almost nothing... The 70mm steel studs are very light... (and i´m putting some extra pads, so the max load weight (73kg/pad) is still far away) I´m not sure what a ceiling member is... :oops: Check the picture... And here´s the questions about fiberglass... Should i start construction with this low density wool and ONLY use the 50kg/m3 for traps??? Are we talking about 2 layers of gypsum, 16kg/m3 wool between the steel studs, 10cm air and my "lovely" unfilled hollow bricks wall...??? -No 50kg/m3 wool so far- I´m a little concern about spend all that money and still no get the insolation that i need... should i attach some mass to the hollow bricks wall? I mean: bricks-gypsum or mdf as mass - air gap -inner walls with insulation... or just put all the mass on the inner walls... What do you think? Can´t get tired of say THANKS!

Yes - those are ceiling members......... BTW - you can't discount anything - the reason for this is because if you overload these - it can actually be worse than if they didn't exist. Understand that they can amplify certain frequencies plus transmit as if they didn't exist if they become compressed too much. Rod

I found the weight of the wall with studs and two layers of gypsum -on the site of the retailer-... It says 26kg/m2. (including fiberglass) So, larger walls (3.6x2.2) 7.92m2 x 26 = 205 kg + 103 kg (half of ceiling weight) = 308 kg each wall. 308kg / 55kg (recommended load weight) = 5.6 pads. Same count for smaller walls... 2.6mtsx2.2mts= 5.72mt2 x 26kg = 148 kg / 55kg = 2.7 pads. Celing members are 2"x5". The picture is an actual pic of my room. Can you give me some (more) help with last questions in bold (about choosing wool, mainly)? Thanks!

I'd use the lighter wool inside ALL walls, and save the heavier stuff for traps/absorbers. I'd forgotten that your blocks are HOLLOW - not good. Any way you look at it, you'll end up with a 3-leaf wall. This will worsen isolation at low frequencies, and probably IMPROVE isolation at mids and highs a few dB - I think you'd be better off NOT putting a second frame up - instead, if you can "render" at least one side of your blocks with a thick mortar layer, you'll improve the performance of your block walls and save yourself some usable floor space... Steve

I already have the outer side of the wall rendered... And i can not play the drums inside the room, because it sound TOO loud. I need to stop the sound some how -and i can´t destroy the walls- What do you think? BTW, i found this: To reduce sound transmission through gypsum board walls: * space studs at 600 mm (irc.nrc-cnrc.gc.ca/pubs/ctus/1_e.html) This applys to every wall that we should make? I was thinking to space studs at 400 mm.

Yes, 600mm stud spacing helps ALL framed walls by allowing the wallboard to flex a bit - if you're into martial arts at all, it's more of a "soft" defense than a "hard" one. When you play drums, is there anyone who can move around outside the room and help find out WHERE the sound is leaking the most? or is it just EVERYWHERE? Steve

When you play drums, is there anyone who can move around outside the room and help find out WHERE the sound is leaking the most? or is it just EVERYWHERE?

EVERYWHERE is the right word... That´s why i thought of approaching it with the room inside a room idea. Is there any better way -in this particular case- to stop the sound from the drums?

Julian, do you have any of the higher density insulation already? If so, you might try this http://www.johnlsayers.com/phpBB2/viewtopic.php?t=4013 It's a relatively cheap way to find out how much of your drums are coming thru the floor; if it helps, great... Steve

Great thread, i really missed it... it´s surprising that a riser can make such a difference..! The thing is, i didn´t order the wool yet, ´cause i was waiting to be sure what procedure i´m gonna use. Anyway, i need to improve the insolation far beyond "between 65-70 dB" (the result exposed by Dieter@be on the link). I have an idea, and i´m not sure if it´s crazy... let me know. If i take a driller and i make several small holes on each hollow brick, i´m virtually distroying one of the masses of the brick, right? I mean, the only mass will be the outer face of the brick (which is rendered). This way, i can start building the new gypsum room without compromising the low freqs response. What do you say?

Doubt if that would work like you want it to - more likely you'd end up with a mid-range helmholtz absorber, which would weaken the wall more at the resonant frequency. Depending on the size of the holes, that frequency could run anywhere from maybe 100 hZ up. Drilling holes in a third leaf doesn't make it "go away", because air is a stiff enough spring that it can't get out of the way fast enough to stop having an effect on close surfaces. Please refresh my memory; your sisters bedroom is below the studio? Or am I thinking of someone else? Just how much isolation DO you need for drums? Steve

Hey GOOD memory Steve! My syster is right under the studio... Anyway, i make some raw tests and she´s not the one who suffers the most the sound of my drums... the floor is 30mm concrete and somehow it stops the sound on the drumkit (at least, more than the walls). With i riser i think i´ll be able to forget about disturbing her. The way i see it is, i need as much insolation i can afford. I play about 4 hours a day, and i need to play without taking care about annoying people. We discuss a lot o possible constructions (here on the forum)... and i learn a LOT (really), the last thing left to do is choosing the right procedure and give it a try. I certanly won´t blame no one, ´cause i know the risks of working with hollow bricks, but, i can´t do anything about it... so, with your priceless help i think i can make a really decent studio. BTW, i´m NOT into heavy, so forget about a band banging at 160db (like the bands that Hugo have to take care of). I´m into jazz, fussion and latin. Anyway... What´s the best option for insolation? Should i forget about the room within a room approach? Didn´t you have a soft to predict STC of different type of constructions? I may be usefull in this case. What do you think? Thank you again, and let me say all you guys keep surprising me, with your time and dedication... God bless you.

Julián Fernández wrote:

Great thread, i really missed it... it´s surprising that a riser can make such a difference..! The thing is, i didn´t order the wool yet, ´cause i was waiting to be sure what procedure i´m gonna use. Anyway, i need to improve the insolation far beyond "between 65-70 dB" (the result exposed by Dieter@be on the link).

You have your work cut out for you big time with that requirement.

f i take a driller and i make several small holes on each hollow brick, i´m virtually distroying one of the masses of the brick, right? I mean, the only mass will be the outer face of the brick (which is rendered). This way, i can start building the new gypsum room without compromising the low freqs response. What do you say?

This would work IF you were to fill each of the cavities completely with expanding foam. Although the foam will add virtually no value to the wall from a mass point of view - it will effectively damp the multiple faces so they act as one. Rod

Finally, a good use for "Great Stuff" :wink: Thanks, Rod. Hadn't seen you around for awhile, guess your schedule's back down to "only ridiculous" ??!? Mine too... Steve

Cool idea, Rod! :idea: :idea: :idea: So, we´re back to 2 layers of gypsum, 16kg/m3 wool between the steel studs, 10cm air and my now-foam-filled-hollow bricks wall... right? What a team you make guys!!! ;)

I have a couple of doubts about how to finish the walls... From the specs sheet of my local gypsum retailer, when installing a gypsum board, you should a 15mm gap between the gypsum and the floor to avoid moisture to travel trought the floor and touch the gypsum. Since i wanna float the walls but no the floor, i do have to 2 spaces to fill (i think)-between the neoprene pads and between the gypsum and the floor-. Check the pic. So, how should i place the gypsum on my case? Touching the floor and caulking or leaving the gap and filling it with wool or some kind of rubber? This pics shows the way gypsum is installed here in Argentina. Just to be sure, can you check it to see if something missing? Caulk: I read the sticky about it, and go trought the discussion about brands... but, besides the gaps created for cables, where should i caulk a wall? As always, THANKS...

Julian, your concrete is not a ground floor so moisture shouldn't be a problem; still, the proper way to build soundproof walls works either way. Your pix of gypsum install look fine. I've done 3 sketches that will hopefully explain more. Neoprene should NOT be surrounded by any hard materials when used to float objects; this makes the neoprene MUCH harder and less compressible, so it changes the entire equation DRASTICALLY. I don't know that you're doing this, just a reminder. In order for neoprene or any typical rubber to act as a spring, it needs someplace to "squish out" or it becomes nearly as hard as a wood frame. The only place necessary to seal your walls is around the edges of the gypsum - not necessary to seal frames to wall or floor, etc. HTH... Steve

Great illustration and great explanation. 8)