MASS-AIR-MASS Question

Hi guys! I have a question about the AIR between my 2 layers... HOLLOW BRICK WALL (Rendered on both sides) AIR (10 cm) WOOD FRAME (filled with fiberglass)+2 layer of gypsum... Can i achieve better insolation if I fill the air space between my two layers with 13 kg/m3 wool? Or should I leave the air space empty? I can buy that stuff for a low price, but i don´t know if it can help me...

Fill it. The insulation will increase the TL and reduce the mam resonace frequency. Andre {edit} put a "c" in "reduce."

Julian, I'm not sure we're communicating just yet; WHICH two layers are you talking about? Maybe a sketch to show what you mean? The way I read your question, you might be talking about putting insulation between the two ADDED layers of wallboard, or between the wallboard and the bricks, or even INSIDE the bricks - which is it? Steve

Thanks Steve. Re-reading the original post, it is ambiguous. Unambiguously; Andre

Sorry guys, you´re right... the right question is: Can i achieve better insolation if I fill the air space between my two WALLS with 13 kg/m3 wool? Or should I leave the air space empty? The outer wall is the brick wall, then i have the air gap, and then the wood frame (filled with 50 kg/m3)... I think that Andre understood that way in his first reply... F air gap B R air gap R A air gap I M air gap C E air gap Ks (that´s a simple idea of my two "masses" and the air gap) The air gap is where i´m wondering to put some extra wool.

Julian, What you're describing is a 5 leaf system, the hollow brick creates (effectively) 2 leafs - the 2 existing outer layers create 3 and 4 - the innner frame and drywall will be leaf 5. One of the issues is that systems other than 2 leafs are not good isolation systems. Another issue is that I have no way of determining exactly what your final system will end up giving you. Is there any way that you can fill the hollow brick? Grout or sand would work fine to turn it into a single leafm also - is it possible for you to lose the outer leaves? It would help if you could explain the construction of those outleafs as well. Rod

Descriptions still aren't "cutting it" here; for example, the phrase "WOOD FRAME (filled with fiberglass)+2 layer of gypsum..." can mean either a single stud frame with a single layer of gypsum each side, filled with insulation in between the two layers, OR it can mean "single stud frame, two layers of gypsum on the SAME side of the frame, with insulation between the studs - can you put up a SKETCH showing the location of EACH part of your ENTIRE wall SYSTEM, roughly to scale? Thanks... Steve

Post a drawing. That will clear up the ambiguity on your design(s). Graphivally; Adnre

Okey... This is the idea... like you can see, i was meaning single stud frame, two layers of gypsum on the SAME side of the frame, with insulation between the studs... I can´t use regular bricks (no hollow), because i´m building in the terrace of my new house, and the architech said that i should use hollow bricks, because i don´t wanna overload my terrace... so filling them is not a choice neither... Do you see something wrong with this plan?

Great drawings. Thanks. Yes filling the gap with inulation will help, as per my first post in this thread. Good Luck! Andre

How about the hollow bricks? Am i creating a 3 leafs system by using the rendered hollowbricks? I´m a little concerned now...

Yes, you are; a standard, hollow brick/block wall works the same as a stud frame with panels on both sides; so your construction in the drawing would be a triple leaf wall, unless the blocks get filled with sand or concrete. Also, your drawing appears to have included some sort of floated floor; is this what you intend, and can you give more details on that? Steve

We try and help as much as possible. Your original question was if filling the space will help sound isolation. We answered that. Yes you have a triple leaf system. It would be better to fill the hollows in the blocks. As Steve wrote, what is the story witht eh floatingfloor system? If not done (designed and built) properly, a floating floor will BE WORSE than the original floor for music isoaltion. Andre

Thanks Guys! The floating floor is based on John´s design on SAE site... I don´t know how many neoprene pads i will use, i´m working on that right now... (check out the picture) I was afraid at first thinking that the hollow bricks could create a triple leaf system... the thing is, i can´t fill them (i can´t put much weight on my terrace)... so, what can i do to improve the insolation of the system? How about NOT rendering the inner side of the wall..?

Walls - you may have hit on something; if you render the OUTSIDE of the blocks but not the INSIDE, this will lessen (but not FIX) the bad effects of multi-leaf; if you then maximize the air gap between blocks and your inside gypsum, that will also help; if you can add another layer to the gypsum it will help even more. Floor - can you describe the existing floor - thickness, material, layer by layer, support, etc? You're making me VERY NERVOUS mentioning weight limits and floated floors in the same breath... Steve

I just take this pictures... The first one is the floor i´m planning to float... a tipical terrace floor in Argentina... (the thing is that the floor is a little angled, so, i also want to float the floor to correct it) Te second picture is where the new window will be put... bigger and wider! ;) On the last one you can see where the new wall will be constructed... Te room showned is the control room, so the new wall will make the recording room... What do you think? See any problems? Thanks!

Depends; are those tiles that are the terrace floor resting ON THE GROUND, or on concrete, or are they on an elevated floor? How thick are the tiles? Your architect said not too heavy on the walls; this tells me that there may be a problem with too much weight on the REST of the terrace floor, so I need more info to be sure... Steve

Steve... i don´t know if i used wrong the term "terrace"... That´s the second floor of my house... i mean, above the GROUND it´s the whole house, and above the house you have this terrace... By now, i can´t really tell you how thick are the tiles.. i´ll try to figure it out... So, you can say that under that floor, you have my sisters bedroom ceiling... The architect told me that´s not a good idea to overload the terrace floor, because this may cause the ceiling that is under start to crack. So she suggested to use hollow bricks, but didn´t said that anything about the floating floor... Her advice was to try to reduce as much as i can the weight of my new construction to avoid typical overload problems... So, yes, the idea of not put much weight is for all the construction, no just the walls...

BTW, Congrats on your 4K post!!!! You´re tha MAN! :D

BTW, Congrats on your 4K post!!!! You´re tha MAN! Wow, this just PROVES I need to get out more... :? Besides, probably a few hundred of those were just "fluff", so they don't count... :lol: Just as I suspected on where your studio will be; now, can you (or your architect) do some sort of sketch showing the various layers between your sister's ceiling and your studio area's floor, including thickness and shape of framing, spacing between frame members, type/thickness of floor materials, etc? Also, is gypsum wallboard available in your area and if so, how expensive? I think your architect is trying to save your sister's life here; I'd recommend you listen carefully... Steve

I´ll try to post the sketch this afternoon... stay tuned... And, yes, gypsum is available here, and it´s not expensive... in fact, i´m planning to use 2 layers of gypsum as my inner mass... Why you asked me that? By gypsum wallboard i mean this... http://www.eco-alum.com.ar/botones_vert ... rlock2.JPG (check the drawing i posted in this thread to see where i´m planning to put the gypsum)

I asked you that because gypsum is a good mass layer anywhere except outer surfaces, and can allow lighter WEIGHT partitions with as good isolation, if the extra space that would have been taken up with hollow blocks is instead left as air/insulation space - remember, it's mass-air-mass, so the more "air" between the better. This can compensate for lack of mass somewhat, keeping your construction lighter but still good for isolation... Steve

So, do you think that this it´s the best possible layout ? I will only render the wall on the outside, and create a 20 cm air gap... (i can´t make it bigger, my room is not that big) The gypsum boards are 15mm thick. By now i´ll only use 2 layers, ´cause i don´t have all the money, but if i really need it (after seeing what happens with 2 layers) i would put the 3rd one. Any other suggestion? THAnKS!

What I'm talking about is to NOT use the hollow blocks (or are they already in place??) but instead use something lighter WEIGHT 8) that would eliminate the extra "leaf" of the hollow blocks, and at the same time INCREASE the air gap to compensate for the loss of mass - something like a stud frame with about 30mm of MDF plus a layer of weather proof siding outside, these mounted on a normal wood stud frame; then your inner frame with gypsum, and fill between frames with insulation. This would save weight, get rid of the third leaf, and give better low frequency isolation while keeping mids and highs as good as your drawing would do... Steve

I like the idea! ;) By using that system i can achieve a 300 mm air gap! The thing is, high density fiberglass is a little expensive here... so, do you think that i can use 50kg/m3 wool on the inner frame, and a 13kg/m3 on the outer... It´s critical on this kind of design?