# Cost Efficient Construction Options



## Guest (May 24, 2008)

I am in the early planning stages for a home addition that will include a home theater/family room. I have already learned so much from this forum that a couple of weeks ago I didn't even know what questions to ask. So this the first of probably many posts. 

What would be the most cost effective methods for constructing a home theater aimed at improving acoustics? I'm not necessarily focused on sound proofing to prevent sound from the theater disturbing others in other parts of the house but understand they are probably related. I am trying to prioritize and spend my money where it will make the most difference in terms of affecting sound quality in the room. Due to space considerations I have omitted the room within a room option. 

In terms of cost efficiency, how would you rank these design options?

1) Staggered studs 
2) Double drywall
3) R 13 Insulation or another size of insulation or mineral wool insulation
4) RSIC sound clips (not sure how they even work)
5) Green Glue
6) Other framing, insulation options etc.

Thanks for any suggestions.


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## Guest (May 24, 2008)

all the things you listed are aimed towards sound proofing and not so much acoustics. when considering acoustics, definitely plan ahead for the dimensions of the room. proper insulation will keep the walls from resonating


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## bpape (Sep 14, 2006)

Agreed. Everything you've mentioned is geared toward isolation though they will impact ambient noise level in the room and some can change bass response.

Insulation filling wall and ceiling cavities is just an absolute must no matter what else you do. If you don't, it can be a definite detriment to the sound quality as all your walls will ring like drums.

Double drywall and Green Glue go together. You don't do one without the other. Double drywalled walls will have a lower resonant frequency but also be less efficient at absorbing the little that they already do. Translation - better isloation, better dynamics, more powerful bass, even more increased importance of sufficient proper broadband bass control.

DC-04 clips around the perimeter at the top can negate the need for staggeredstuds on some walls and also eliminate the need for RSIC-1's on the walls - still need on the ceiling.

Bryan


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## MatrixDweller (Jul 24, 2007)

Using RISC clips on a ceiling when using double drywall can be risky and often times the benefits of the clips can get negated by accidentally driving a screw into a joist. Why I say risky is that ceiling failures can occur (ouch) especially during a fire. Two layers of drywall is a lot of weight.

Cost effective approach to soundproofing.


Use 5/8 drywall (double layer if you can afford it).
Use green glue on the face of all studs and joists and in between layers
Stagger studs on long walls (3ft wide walls etc don't get much benefit)
Stuff all cavities with Roxul Safe n Sound
Isolate the bottom and top plates of walls from the floor/ceiling
Use solid core doors and weather stripping and door sealing
Minimize any holes in the ceiling and walls.
Use track lights instead of recessed lights
Use sealed I/C rated recessed lighting if going that route
Use molded vapor barrier and TUC tape to seal receptacle boxes even on inside walls
Never have receptacles back to back on the same wall

Build baffling into HVAC and/or use duct wrap and liner
Wrap any water and drain pipes


Acoustics is a whole different ball game. Figure out the ideal room dimensions that work with your space before you do anything.


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## bpape (Sep 14, 2006)

Actually, if you use the right length screws into hat channel and RSIC-1 clips, it's basically impossible to short the system by driving a screw into a joist. 

Not sure how RSIC and hat is any more prone to failure in a fire than plain joists are with double drywall. Also, Audio Alloy (Green Glue manufacturer) does not recommend Green Glue on joist/stud faces behind drywall as an effective isolation technique. It's designed to work between 2 massive layers.

Bryan


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## MatrixDweller (Jul 24, 2007)

True the RISC clips makes it harder to mess things up because the hat channel hangs down a little bit further. The benefits are negated if you have any holes in ceiling (ie: Recessed cans or even standard electrical boxes). I would feel really uneasy having two layers of drywall on a ceiling using RISC clips.

To answer the question on how RISC clips work: You attach the clips to the joists or studs then attach the hat channel to the clips so that the channel runs perpendicular to the studs/joists. The drywall then gets screwed to the hat channel. It makes it so that the drywall is isolated from the joists. It's the next best thing to using a double wall or false ceiling (room within a room).

RISC clips can give soundproofing close to that of a double wall if done on both sides and is probably equal to double drywall and green glue on 2x4 construction. RISC clips can get expensive though at $8+ for larger quantities (the hat channel is relatively cheap). So on an 10x8' wall using 16" on centre studs you would need 6 clips for every stud and the wall would have about 8 studs. So at $8 a pop that would be over $380 (double if doing both sides of the wall) for just the clips (add $30-$60 more for the hat channel). Staggered stud would only cost about $50 more because of the need for 2x6's for the top and bottom and ends and few extra 2x4's. A double wall using 2x4's would double the cost of lumber which might only add $40 to the price tag of the wall. Of course you loose inches of room space progressively from RISC, staggered to double wall.

The thing you really have to ask yourself is how much soundproofing is really necessary. And then there's the floor above it. Footfalls or dropped utensils on linoleum are hard to get rid of. Half the equation is treating the floor surface above. 

You're not really concerned about soundproofing as much so just do staggered or normal studs and stuff everything with roxul to stop resonance and soundproof slightly to soundproof the theater from the rest of the house (not the other way around). The benefits _you _are after would be seen more in the room dimensions and acoustical treatments. Use the room mode calculators at the top of the "Home Theater Design and Construction" section. Build your room to an ideal shape and then spend the money you save, by not doing fancy soundproofing techniques, on room treatments.


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## MatrixDweller (Jul 24, 2007)

bpape said:


> Not sure how RSIC and hat is any more prone to failure in a fire than plain joists are with double drywall.


You have far fewer screws holding the entire assembly onto the joists. Fire ratings actually go down by 25% using resilient channel and 5/8" firecode drywall as opposed to just studs and 5/8. I would assume similar for RISC clips. 

2 layers of 5/8 drywall is a lot of weight to hold up there on the clips.


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## bpape (Sep 14, 2006)

Don't confuse resilient channel with RSIC and hat channel - 2 very very different things. I would never ever encourage using resilient channel. RSIC-1 and rolled edge hat channel is rated up to 2 layers of 5/8" drywall for 24" spacing and 3 layers of 5/8" for 16" spacing. You can run just as many screws into the hat channel as you can straight into a joist. The only place you stay away from is where the clip grabs it every 24".

Also, just for general info, RSIC can be had a whole lot cheaper than $8. I personally sell RSIC-1 for less than $5 ea. Also if one does DC-04 clips around the perimeter, you can do staggered stud on the walls and get better iso for way less money. Then you only need RSIC-1 and hat on the ceiling. DC-04's are a a bit over $5 ea but you only need 1 every 2' around the perimeter of the wall. 

There are lots of ways to skin the cat. It all depends on what you have more of to play with. If you have lots of space, then double walls are great - though you still need DC-04 on the wall top and RSIC/hat on just the ceiling. Add double drywall and GG to that and you have basically the best you can get without getting silly about it. 

Bryan


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