I'm the guy who is fixing my home theater for air leaks from a missing rim joist and I want to improve acoustics now that all the wall board is down.
My first post is here explaining the situation. In this post I had only removed the wall board on the ceiling and part of one wall adjacent to my southern neighbor.
Link
http://www.avsforum.com/avs-vb/showthread.php?t=1325679
I've now demolished all the old wall board and the non-load bearing walls and have a few questions for this forum. Ted White, Ben Shafer, and BIGmouthinDC have been very helpful. I did hire an acoustic engineer as Mr. Shafer suggested. The acoustic engineer who provided advice was Henning Associates located in Rockville Maryland and his advice was very helpful. Also I've read all the background materials you all suggested and I'm now ready to go forward with the rebuild.
Now that all the wall board is down the problem and solutions I think are much clearer.
My situation: I live in a large townhouse that was advertised as sound proof; you can't hear your neighbors. This works pretty well except when very loud passages of music or video is played my neighbor on the south side can hear me.
My goals are:
1) Fix bad air leaks that keep one corner of the home theater and the kitchen above it that gets very cold in the winter. The builder left out the sealing rim joist when he put in the sister beams for the second level outside deck. He just stuffed fiberglass insulation in and its like having an open window in the floor/ceiling joist bays above the home theater. The temperature in these joist bays will get to freezing when in the 20's outside.
2) Improve the sound isolation with my neighbor.
Improving sound isolation within my house is not practical as the lower level home theater room is connected to the second and third level by an open stair well and elevator shaft. Besides its just my wife and I in the house now and we watch media together (the kids have fled the nest).
The situation is fairly complicated so I've got a couple of sketches to define the situation and some questions about how to finish this with the goals above in mind.
The post is fairly long to describe the current design, what I think is wrong about it and my proposed solutions. I think the situation is interesting from an acoustic point of view so I hope those who are interested will read through it and comment.
The home theater/entertainment room is on the lowest level of the townhouse. It is not a basement as it is integrally connected to the upper levels via decor and an open stair well and elevator shaft. Each level is 45 feet by 25 feet. The house is four levels. Each level is supported by the outside walls and two internal steel I beams 15 feet apart. The side walls between neighbors is non load bearing and they float. The home theater is 30 feet by 25 feet and is under two of these steel beams and an outside wall. The project here is to correct sound isolation in the first 15 by 25 foot bay. The next project will be to tear down the wall board in the second bay and dampen the wall board (the other 25 x 15 in the room). The current construction is very interesting. In one way I'm very impressed what the builder did to stop sound transmission from house to neighboring house but they missed some very important acoustics issues. The structure is massive and very effective but for a single item they over looked. The literature you all sent me to read says sound isolation needs to have decoupling, absorption, mass, and damping. And you admonish to not forget flanking sound. This I think is where the builder blew it. Perhaps they would have done better if they had access to this forum. And fortunately I think these problems can be fixed.
Below is a sketch of the south wall on my house and the north wall of my neighbors.
These houses were advertised as you can't hear your neighbor". We would have stayed in our single family home if this were a normal town house with neighbor noise. And as I indicated in my earlier post it works pretty well except when my home theater gear is going at full tilt. My southern neighbor can just barely hear it. As it can be seen my house is supported on the sides adjacent to my neighbor's house with 45 foot long engineered wood beams. These beams are fully live and dead load rated for a 22 foot span and the span between the lally columns is 15 feet, so no load bearing framing is needed under these beams. See the picture below.
The concrete wall does not support the framing on either house. If my neighbor's house and the concrete wall were torn down with my internal wall down as you see it, the house would be open to the outside.
Notice that the sound isolation design includes a 2.5 thick gypsum board wall that goes all the way up 3 stories above the concrete wall. This same structure can be seen in my attic at the top. It is not structurally in contact with either house wall. It is supported by a steel ribbing and does connect with the framing in each house with thin metal strips periodically at the floor joists between levels and it sits on the concrete wall. The concrete wall supports only this massive gypsum structure. It's over kill for a fire break and is intended to stop sound transmission. The joists support structure is not shown but the house is held up with two 6 x 12 steel I beams 15 feet apart with three steel lally columns for each level. The outside walls are normal studded framing with 2 x 6 studs. Each level is 45 feet by 25 feet. The inside wall adjacent to neighbors are not load bearing. All this looks good. The problem comes at the ends of the walls and the cause is flanking sound. See the picture below.
My house protrudes out behind my neighbor's house by about 2 feet. You can see the inside of the brick siding with the wall down. My neighbors inside wall is about 1 ½ inch beyond the other side of the concrete wall. The concrete supports only the gypsum board between the houses. The air gap between the outside wall sheathing on both houses has free air flow. Not only does this leak cold air but sound flanks the gypsum board and can go all the up to the top and the sound vibration impinges on inside walls that do not have any insulation at all. It may seem strange to see brick siding from the inside of the house, but this is in concert with the sound decoupling design. The non load bearing wall (now removed) was normally insulated, but the insulation was terminated about 1 foot inside of the concrete wall and in concert with the decoupling it was not sealed to the concrete to stop sound or air flow (thus cold air and flanking sound). So air flow goes freely between houses, as does sound around the massive gypsum and concrete wall. The air gap between the brick and my house walls acts like a chimney and cold air tumbles down to the bottom and directly to the inside of the now removed inside wall un-insulated wall board.
I have solutions but have some questions and would appreciate your opinions.
The solutions:
1) First the A/C air ducts in the ceiling that provide air to both the home theater and upper floor were replaced with acoustic rated flex ducts and lengthened to be as long as possible.
2) The ceiling joist bays will be stuffed with fiberglass insulation.
3) On the gypsum wall, the joint between the concrete and the gypsum will be sealed with SilenSeal. It already looks sealed but just in case.
4) On the air gap between the brick and concrete, this air gap will be stuffed with fiberglass insulation but a 2 inch indention will be left for spray in closed cell foam to seal air flow. The plan is get closed cell foam in the gap between the brick and concrete but not touch the neighbor's house or internal framing on my house. I know that you all advise that fiberglass better absorbs sound but stopping the air leaking is important here.
5) On the air gap between the gypsum wall and brick, I plan to use the same flanking sound solution as above, fiberglass and then foam in the air gap between the gypsum and brick.
6) Next I'm not sure; I plan on using the same solution in the air gap between the double 2 x 12 internal support beams. Here I'll be compromising the decoupling by connecting the support beams internal to my house to the massive sound isolation gypsum wall with foam not just fiberglass. I worry that only stuffing fiberglass into this gap will not adequately stop air leaks. Thus fiberglass sealed with foam.
7) On the 2 x 12 double beams; there is room for a wood jack stud above the concrete wall to connect the floating beam to the mass of the concrete. I would install a sill plate on the concrete then a top plate to the beams and jack the beam slightly to bring the load down on the concrete connecting the floating beam to the concrete to stop its vibration. The stud can be separate from the gypsum wall by ¼ inch or so and I can put green glue and or Silenseal between them. I'm not sure about this step. It would mass anchor the floating internal beam but perhaps put sound into the massive concrete wall (comments?).
See a picture in next post for locations of proposed jack studs
In any case the jack stud would be fitted to bear down on the concrete wall by jacking the beam 1/16 of an inch or so and putting the stud in and then letting the load down on the stud. The idea would be to freeze the beams from vibrating by sound.
8) I plan on also using fiberglass then foam to cut off air flow and sound at the end of the steel I beam and lally column which are also isolated from the concrete wall and gypsum sound wall, on the left in the picture above.
9) The new normally studded walls next to the concrete wall will be isolated from the ceiling support beams and anchored to the floor and concrete wall, with ¼ gap between the new wall and the ceiling joists and end walls. They will be fully insulated in the usual way.
I think this catches all the flanking sound. Beyond this the walls will get decoupled double 5/8 gypsum board with green glue and SilenSeal underneath the crown molding, base board and at corner joints.
I would appreciate all your comments critiques and advice on this before I start rebuilding.
Thanks Keith
My first post is here explaining the situation. In this post I had only removed the wall board on the ceiling and part of one wall adjacent to my southern neighbor.
Link
http://www.avsforum.com/avs-vb/showthread.php?t=1325679
I've now demolished all the old wall board and the non-load bearing walls and have a few questions for this forum. Ted White, Ben Shafer, and BIGmouthinDC have been very helpful. I did hire an acoustic engineer as Mr. Shafer suggested. The acoustic engineer who provided advice was Henning Associates located in Rockville Maryland and his advice was very helpful. Also I've read all the background materials you all suggested and I'm now ready to go forward with the rebuild.
Now that all the wall board is down the problem and solutions I think are much clearer.
My situation: I live in a large townhouse that was advertised as sound proof; you can't hear your neighbors. This works pretty well except when very loud passages of music or video is played my neighbor on the south side can hear me.
My goals are:
1) Fix bad air leaks that keep one corner of the home theater and the kitchen above it that gets very cold in the winter. The builder left out the sealing rim joist when he put in the sister beams for the second level outside deck. He just stuffed fiberglass insulation in and its like having an open window in the floor/ceiling joist bays above the home theater. The temperature in these joist bays will get to freezing when in the 20's outside.
2) Improve the sound isolation with my neighbor.
Improving sound isolation within my house is not practical as the lower level home theater room is connected to the second and third level by an open stair well and elevator shaft. Besides its just my wife and I in the house now and we watch media together (the kids have fled the nest).
The situation is fairly complicated so I've got a couple of sketches to define the situation and some questions about how to finish this with the goals above in mind.
The post is fairly long to describe the current design, what I think is wrong about it and my proposed solutions. I think the situation is interesting from an acoustic point of view so I hope those who are interested will read through it and comment.
The home theater/entertainment room is on the lowest level of the townhouse. It is not a basement as it is integrally connected to the upper levels via decor and an open stair well and elevator shaft. Each level is 45 feet by 25 feet. The house is four levels. Each level is supported by the outside walls and two internal steel I beams 15 feet apart. The side walls between neighbors is non load bearing and they float. The home theater is 30 feet by 25 feet and is under two of these steel beams and an outside wall. The project here is to correct sound isolation in the first 15 by 25 foot bay. The next project will be to tear down the wall board in the second bay and dampen the wall board (the other 25 x 15 in the room). The current construction is very interesting. In one way I'm very impressed what the builder did to stop sound transmission from house to neighboring house but they missed some very important acoustics issues. The structure is massive and very effective but for a single item they over looked. The literature you all sent me to read says sound isolation needs to have decoupling, absorption, mass, and damping. And you admonish to not forget flanking sound. This I think is where the builder blew it. Perhaps they would have done better if they had access to this forum. And fortunately I think these problems can be fixed.
Below is a sketch of the south wall on my house and the north wall of my neighbors.
These houses were advertised as you can't hear your neighbor". We would have stayed in our single family home if this were a normal town house with neighbor noise. And as I indicated in my earlier post it works pretty well except when my home theater gear is going at full tilt. My southern neighbor can just barely hear it. As it can be seen my house is supported on the sides adjacent to my neighbor's house with 45 foot long engineered wood beams. These beams are fully live and dead load rated for a 22 foot span and the span between the lally columns is 15 feet, so no load bearing framing is needed under these beams. See the picture below.
The concrete wall does not support the framing on either house. If my neighbor's house and the concrete wall were torn down with my internal wall down as you see it, the house would be open to the outside.
Notice that the sound isolation design includes a 2.5 thick gypsum board wall that goes all the way up 3 stories above the concrete wall. This same structure can be seen in my attic at the top. It is not structurally in contact with either house wall. It is supported by a steel ribbing and does connect with the framing in each house with thin metal strips periodically at the floor joists between levels and it sits on the concrete wall. The concrete wall supports only this massive gypsum structure. It's over kill for a fire break and is intended to stop sound transmission. The joists support structure is not shown but the house is held up with two 6 x 12 steel I beams 15 feet apart with three steel lally columns for each level. The outside walls are normal studded framing with 2 x 6 studs. Each level is 45 feet by 25 feet. The inside wall adjacent to neighbors are not load bearing. All this looks good. The problem comes at the ends of the walls and the cause is flanking sound. See the picture below.
My house protrudes out behind my neighbor's house by about 2 feet. You can see the inside of the brick siding with the wall down. My neighbors inside wall is about 1 ½ inch beyond the other side of the concrete wall. The concrete supports only the gypsum board between the houses. The air gap between the outside wall sheathing on both houses has free air flow. Not only does this leak cold air but sound flanks the gypsum board and can go all the up to the top and the sound vibration impinges on inside walls that do not have any insulation at all. It may seem strange to see brick siding from the inside of the house, but this is in concert with the sound decoupling design. The non load bearing wall (now removed) was normally insulated, but the insulation was terminated about 1 foot inside of the concrete wall and in concert with the decoupling it was not sealed to the concrete to stop sound or air flow (thus cold air and flanking sound). So air flow goes freely between houses, as does sound around the massive gypsum and concrete wall. The air gap between the brick and my house walls acts like a chimney and cold air tumbles down to the bottom and directly to the inside of the now removed inside wall un-insulated wall board.
I have solutions but have some questions and would appreciate your opinions.
The solutions:
1) First the A/C air ducts in the ceiling that provide air to both the home theater and upper floor were replaced with acoustic rated flex ducts and lengthened to be as long as possible.
2) The ceiling joist bays will be stuffed with fiberglass insulation.
3) On the gypsum wall, the joint between the concrete and the gypsum will be sealed with SilenSeal. It already looks sealed but just in case.
4) On the air gap between the brick and concrete, this air gap will be stuffed with fiberglass insulation but a 2 inch indention will be left for spray in closed cell foam to seal air flow. The plan is get closed cell foam in the gap between the brick and concrete but not touch the neighbor's house or internal framing on my house. I know that you all advise that fiberglass better absorbs sound but stopping the air leaking is important here.
5) On the air gap between the gypsum wall and brick, I plan to use the same flanking sound solution as above, fiberglass and then foam in the air gap between the gypsum and brick.
6) Next I'm not sure; I plan on using the same solution in the air gap between the double 2 x 12 internal support beams. Here I'll be compromising the decoupling by connecting the support beams internal to my house to the massive sound isolation gypsum wall with foam not just fiberglass. I worry that only stuffing fiberglass into this gap will not adequately stop air leaks. Thus fiberglass sealed with foam.
7) On the 2 x 12 double beams; there is room for a wood jack stud above the concrete wall to connect the floating beam to the mass of the concrete. I would install a sill plate on the concrete then a top plate to the beams and jack the beam slightly to bring the load down on the concrete connecting the floating beam to the concrete to stop its vibration. The stud can be separate from the gypsum wall by ¼ inch or so and I can put green glue and or Silenseal between them. I'm not sure about this step. It would mass anchor the floating internal beam but perhaps put sound into the massive concrete wall (comments?).
See a picture in next post for locations of proposed jack studs
In any case the jack stud would be fitted to bear down on the concrete wall by jacking the beam 1/16 of an inch or so and putting the stud in and then letting the load down on the stud. The idea would be to freeze the beams from vibrating by sound.
8) I plan on also using fiberglass then foam to cut off air flow and sound at the end of the steel I beam and lally column which are also isolated from the concrete wall and gypsum sound wall, on the left in the picture above.
9) The new normally studded walls next to the concrete wall will be isolated from the ceiling support beams and anchored to the floor and concrete wall, with ¼ gap between the new wall and the ceiling joists and end walls. They will be fully insulated in the usual way.
I think this catches all the flanking sound. Beyond this the walls will get decoupled double 5/8 gypsum board with green glue and SilenSeal underneath the crown molding, base board and at corner joints.
I would appreciate all your comments critiques and advice on this before I start rebuilding.
Thanks Keith
