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post #811 of 1179 Old 09-23-2013, 08:15 AM
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This was what seemed to make sense - honestly I don't see much difference between using a wall stack and not. I just want the quietest solution - for both sound containment and air flow noise.

Any ideas? Maybe I'll need to double drywall that area.

As long as you can get the required CFM out of it, I would line the whole cavity in linacoustic. The friction rate vs metal will be higher, but for a rough-guestimate I'm thinking that lining it would be equivalent to a 6" round.

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post #812 of 1179 Old 09-23-2013, 08:23 AM
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I'm still having a little trouble visualizing your situation, but I think lining the cavity makes sense. You can also use DD+GG for the three remaining walls of the vent to help with sound isolation. If you feel it's necessary you might even add another chamber for the 8" flex you have now.

I'm guessing your return register will be going into the wall rather than into your soffit, correct?

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post #813 of 1179 Old 09-23-2013, 09:18 AM - Thread Starter
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The intent is for this return duct to be as low as possible.

Maybe I can clarify. The wall in question is the short wall parallel but offset from the door, on the left in this image - next to the window. (The supply ducts are depicted in this image, but not at their final positions - this is just to provide visual reference. )SoffitRouting1a_zpsadf2e5c9.jpg

The risers are both framed in 2x12 and very close to the wall. The wall is 2x4 staggered stud on 2x6 base, but without drywall on the outside, as yet. Of course, the inside is 7/16 OSB, followed by 2 layers 5/8 drywall and green glue.

In this picture you can see the 8" flex duct for the return running under notched 2x8 joists. The notches I cut are about 3" by 11". The hole cut in the 2x12 is much larger, of course.

RiserLandingConstruction2_zps02e1e356.jpg

The duct runs through the 2x12 riser edge and then pinches as it bends upward into the approximately 6" deep wall cavity. The wall cavity would normally be 5.5" deep, and I would just run drywall to the decking, then install the cabinet for the sink and so forth.

A couple things occur to me. I could fir out the studs some to increase that cavity size. I can use multiple layers of drywall and green glue. I don't know if I can cut through the wall at ground level, as was my original theoretical intent, due to joist positioning inside the theater - they run the other direction.
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post #814 of 1179 Old 09-23-2013, 12:12 PM
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A couple things:

  • Why do you want the return vent low?
  • I would let the joists going in the wrong direction stop the "ideal" install. It should be fairly easy to move one joist and add another if you need to make the spacing work out
  • Here's the 90 degree register booth that I used. The dimensions are pretty accurate in that the opening is 6"x12". It's cheap, and will make that turn if you decide to use the lined cavity as a duct.
  • Are you willing to fur that wall out so that the cavity is deep enough to house your duct? You'd need another 5" or so, right? If so, then you can pretty well just build a dead vent there. I would think that a full on dead vent would be your best bet at maintaining your isolation. However, if you're keeping the return very low, you're not going to have much space for the sound attenuation to happen, and you might need to look into isolating the cavity that the flex is in on the floor as well. If you move the return up towards the ceiling, you will have a more effective dead vent.
  • And a final option. You could build a short dead vent and disguise it as a cabinet under the sink. I suspect you have plans for that cabinet, though.


Before I forget, you might want to consider some of those metal protectors to keep any screws out of your drain pipe.

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post #815 of 1179 Old 09-23-2013, 12:44 PM
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...protectors to keep any screws out of your drain pipe.

"And ladies and gentlemen, Tom Logan" in 3...2...1...
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post #816 of 1179 Old 09-23-2013, 12:52 PM - Thread Starter
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I don't think I can give up 5" to the wall, and I don't think I can give up the sink cabinet.

I'll have to check on the floor joists, but let's back up a minute.

I chose to position the return at ground/riser level because I had it in my head that it should be opposite the supplies, which are in the soffits. If the airflow and temperature management inside the theater would be better served by a high return, the that's workable. I don't think I could get it into the soffit, but it could be at any height below that.

With two 6" supplies in side soffits near the screen, where would you want the return - ignoring logistics?
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post #817 of 1179 Old 09-23-2013, 01:02 PM
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"And ladies and gentlemen, Tom Logan" in 3...2...1...

HAHAHA!!!!!

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Originally Posted by HopefulFred View Post

I don't think I can give up 5" to the wall, and I don't think I can give up the sink cabinet.

I'll have to check on the floor joists, but let's back up a minute.

I chose to position the return at ground/riser level because I had it in my head that it should be opposite the supplies, which are in the soffits. If the airflow and temperature management inside the theater would be better served by a high return, the that's workable. I don't think I could get it into the soffit, but it could be at any height below that.

With two 6" supplies in side soffits near the screen, where would you want the return - ignoring logistics?

My understanding is you want the returns high in the back to pull off the hot air rather than pulling out the cooler air at the floor. Since your supplies are at the front, you should get good mixing throughout the room, and since we're rarely concerned about heating this space, you want to focus on getting the hottest air out as quickly as possible. I'll see if I can dig up the Erskine post on this.

Here you go sir
Quote:
........You'll want two supplies (typically in the front of the room, high mounted) and two returns (high mounted) in the back of the room. You do not want air flow directly on any seating location......

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post #818 of 1179 Old 09-23-2013, 03:29 PM
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Yes, supplies and returns are both high in a cooling arrangement. When the cool air dumps on the floor, the hot air rises in the rear.

8" oval duct will fit in a 3-1/2" stud cavity (same circular area as an 8" round, it measures 10" wide)

Alternatively, just use the stud cavity as a plenum and place a return grill at the top of the wall.

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post #819 of 1179 Old 09-23-2013, 08:21 PM - Thread Starter
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Originally Posted by Mr.Tim View Post

Alternatively, just use the stud cavity as a plenum and place a return grill at the top of the wall.
This sounds like the easiest choice, and was what my father-in-law was recommending. I was/am concerned that this offers low sound isolation, but I suppose there's not too much to be done about that.

I suppose the question is should I build a sheet metal duct in the wall, or line the cavity with duct liner?
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post #820 of 1179 Old 09-24-2013, 03:20 AM
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This sounds like the easiest choice, and was what my father-in-law was recommending. I was/am concerned that this offers low sound isolation, but I suppose there's not too much to be done about that.

I suppose the question is should I build a sheet metal duct in the wall, or line the cavity with duct liner?

Just line it.. after making sure you've caulked all the joints.

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post #821 of 1179 Old 09-25-2013, 06:28 PM - Thread Starter
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Strike one locating duct liner. The place I went, http://www.shookandfletcher.com/index.html, had lots of products, and was open to the public. The nice lady at the counter, as well as the guy packing orders in the back, had never heard of Linacoustic RC (or any other variety). She made a call and found that for her to source it, she'd pay retail and have to mark it up form there. Her source was wittichen supply. I know that J_P_A had no success in dealing with them directly from his neck of the woods, so I'm not too optimistic about them selling to me - plus they're not as conveniently located. On the up side, she said that they were about (in the next two weeks) to start carrying Knauf. So I asked her to see if she could get a couple rolls of their equivalent, Sonic XP, added to the initial stock order. I actually like the idea of the Knauf stuff a little better, because of the ECOSE technology (binder is renewable, and does not contain formaldehyde or phenol). She's got my contact information... :crosses fingers:
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post #822 of 1179 Old 09-26-2013, 06:48 AM
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If Shook & Fletcher can't get what you need, try General Insulation (Atlanta tel. (770) 662-5622). They quoted me $172 for a 100' roll of either Certainteed Acoustablanket Black or Knauf Sonic XP. I used them for all of my rigid panel boards (unfaced Knauf and faced Certainteed) and should have used them for my ductliner. They offered the best prices I could find in the Houston area (by far).

I wound up paying about the same for a roll of JM Ductliner through another supplier in what turned out to be a bait and switch. Had I known it was going to be the same price as GI, I would have used GI for the Knauf Sonic XP.
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post #823 of 1179 Old 09-26-2013, 07:04 AM - Thread Starter
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Thanks Spaceman! That's one hot tip!
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post #824 of 1179 Old 09-26-2013, 07:29 AM
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I actually called the Wittichen supply in Columbus and they were willing to work with me directly. Interestingly enough, they also carried Linacoustic, which the local Wittichen did not. If you run out of other options, it would at least be worth a call to Wittichen to see if they're willing to work with you. Just make it clear you need a FULL roll of Linacoustic. I think they get a little nervous that a regular old Joe off the street will want about 10' and try to bring the rest back.

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post #825 of 1179 Old 09-26-2013, 07:54 AM - Thread Starter
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I haven't run the numbers, but I bet I need 2 rolls. Two large supply boots, one large return, plus I was figuring on using it for the screen wall, but if I go with 2" there, I may find cheaper options.
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post #826 of 1179 Old 09-26-2013, 10:15 AM
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Most of the recommendations I've seen are for a 1" layer + poly + 1" layer. Are you planning for two 2" layers? Or just one 2" layer with no poly?

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post #827 of 1179 Old 09-26-2013, 10:25 AM - Thread Starter
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I was expecting/hoping to hang 1" and measure, but having plastic and another inch on hand.
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post #828 of 1179 Old 09-30-2013, 08:21 AM - Thread Starter
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Can I run 3.5mm stereo over Cat5e over 20 feet? (Today is LV cable day - Hooray!)
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post #829 of 1179 Old 09-30-2013, 09:19 AM
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Can I run 3.5mm stereo over Cat5e over 20 feet? (Today is LV cable day - Hooray!)

Won't be a problem. But when doing non-standard things like this (assuming you are directly connecting the ends) I would test the cable with a quick guerilla setup before permanently installing.

You could also use Leviton Quick ports and a 3.5mm to stereo RCA adapter to get a more polished look since female 3.5mm ports aren't available until you get into the commercial lines which are significantly more expensive:
Here's a link to the Leviton solution: http://www.datacomtools.com/store/40830BWE.html

If you are a true install ninja you can take a Leviton Quickport blank like THIS and drill an appropriately sized hole for a 3.5mm solder jack with front facing locknut like THIS to make your own Quickport jack with 3.5mm input. I've gone this route a couple dozen times, primarily for stealth installs of IR emitters, but that's just my OCD shining through. smile.gif

So you have to ask yourself....do I feel like a Ninja? So, do you.....punk? tongue.gif
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post #830 of 1179 Old 09-30-2013, 09:29 AM - Thread Starter
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I feel like a pirate. And I'll take Pirates over Ninjas, any day!
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post #831 of 1179 Old 09-30-2013, 10:02 AM
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post #832 of 1179 Old 09-30-2013, 06:15 PM - Thread Starter
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I'm working in the theater all week, so I'm getting a lot done - electrical, low voltage, stage framing, etc. I've had a few details come up that I wasn't sure about, and I need to get some feedback before I close in the soffits and riser with provisions included. I ordered step lights from Amazon. I went with the 7W incadescents that BIG has recommended before. The product description says that for only $10, they include both the vertical and horizontal louvered face plates. I'll paint them to blend in with the carpet - probably black. 4 lamps at 7W each should make the GE happy, so I hope I'm good there without adding the resisters or extra lights that we discussed a few months ago.

The more complicated issue needs some feedback, but it is in the wheelhouse of a few of you - so let's see those chops you guys have! smile.gif

I'm ducting exhaust for a projector hush box. There is room for a small flex duct to empty into the top of the equipment closet, or even out the face of it into the adjacent space at the bottom of the stairwell. Here's the general layout I'm considering:


That box is modeled at 30" square, by 11" tall. I think that should give me the height I need to allow the projector to be ceiling mounted and still allow the hush box to fit around it. I used dimensions from a JVC DLA-X55, Sony VPL-HW50ES, and a Panasonic PT-AE8000 and just took the largest of each of them for each dimension. Any of them should fit I think, as long as the height is okay - the tallest is only 7", and I think a low profile ceiling mount shouldn't need more than 4" more. But if anyone disagrees, please say.

I'll connect a 4" flex duct to the back, inside a soffit extension, and route it through the wall, where it will meet a small fan. A 100mm computer case fan is basically the same size as 4" duct, so I think I can work out a reasonable connection for them. This fan is very quiet and very cheap, and moves up to 36 CFM with 60mA of 12V power. Unless I'm wrong, that means I can power it directly from the 12V trigger of a projector - the JVCs and Panasonics are both listed at 100mA 12V trigger.

So two main questions: 1) am I reading the electrical specs right and setting this up to actually do what I want it to do? and 2) does this have a chance of drawing in enough room air and exhausting it at a rate that will keep a projector cool?
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post #833 of 1179 Old 09-30-2013, 07:28 PM
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36 CFM is the amount of air moved in free space by the 12v fan. Adding the ductwork and forcing the fan to create a negative pressure through filter media would challenge the fan's ability to move that much CFM. I just don't think the fan would have the electric version of "torque" to compensate for the things fighting it.

The best way to design the box is to look at the maximum BTU output of each projector you are considering and find a fan with sufficient CFM to ventilate the cubic volume of the box to 85 degrees or less. I called Epson to get the maximum CFM output of their cooling fan or the BTU output. Surprisingly, they didn't know the exhaust fan's maximum CFM and gave me the BTU output which is 1218 BTUs per hour, fyi.

I'd personally look for a larger fan (or inline / impeller) that can be run at lower speeds and deal with the electrical on/off situation rather than push a small 12v to its limit. Just my 2 cents of feedback.

THIS is an inexpensive thermostatic controller for their in-line duct fans. Considering the fan would be remotely located at the end of the run and will only run as hard as needed because of the thermostatic control, it should be quiet, although I couldn't find any db specification data.

And I'm sure you know this, but the front portal should probably be square / rectangular at a minimum. Making it a small circle means that you have to be absolutely perfect in your mounting position to get the beam propagation to fit in the widest spot. Going with square or a mini 16:9 rectangle will also give you maximum up and down installation flexibility.
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post #834 of 1179 Old 09-30-2013, 09:10 PM - Thread Starter
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The best way to design the box is to look at the maximum BTU output of each projector you are considering and find a fan with sufficient BTU to ventilate the cubic volume of the box to 85 degrees or less. I called Epson to get the maximum CFM output of their cooling fan or the BTU output. Surprisingly, they didn't know the exhaust fan's maximum CFM and gave me the BTU output which is 1218 BTUs per hour, fyi.
It seems that most of the projectors use lamps of near the same power, so I'll assume the same heat output. Searching for ways to calculate the CFM required to cool the projector to 85F, I found this document (.pdf) from captiveaire which gives an equation for heat removal based on exchanging air. CFM=(BTU per Hr)/(1.08xDeltaT) I don't know where the 1.08 comes from. If we allow only 10F degrees delta, we come to more than 100CFM - a 15F degree delta requires only 75CFM (approx).

That doesn't account for frictional losses or any system static pressure. I think, based on that same document, that 0.5"WP is a reasonable guess. "Ducted Applications - .20 to .40 per 100 feet of duct (based on duct velocity of 1000 to 1800 feet per minute). Fittings .08” per fitting (elbows, register, grille, damper)" I expect to have about 15' of duct, and probably the equivalent of 4 fittings. I don't know/understand how to add that into the CFM estimate, though I feel sure that the ratings for the inline fans don't assume the static pressure I will have, so the fan will deliver less than rated.

Suncourt's 4" inline fan is rated for 65CFM in free air and puts out 52dBA noise. The 6" fan jumps to 160CFM in free air, for the same 52dBA. 6" duct will be really tough to route, but I can probably do it.

I feel like I would prefer that the fan run all the time with the projector, and not rely on a thermostat to switch it off - mostly because if it makes a noise, I don't want to hear it cycle on and off. I suppose that would mean a relay for the projector to trigger, instead of (or perhaps in addition to) the thermostat.

Suncourt says these fans are compatible with their solid state speed control, VS100, so if the flow is too noisy or the fan cycles off and on all the time, I can throttle it back with that.

That would mean a parts list like this:
I'm not sure if I'm seeing how that all can get wired up, but I think that's it.

I'm also nervous about the 52dBA noise rating. I imagine that I will also need much larger air intakes on my hush box to allow that much airflow.
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post #835 of 1179 Old 10-01-2013, 02:13 AM
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You could also look at it a different way . . . . how much CFM can those little projector exhaust fans actually move if they were at maximum output? And second, what is the total frictional resistance based on the duct length and number of elbows? Essentially you are trying to take the amount of CFM output from the projector and then add the impact of the duct work to it. That being said, I'd go with the 4" duct because you would be well within the CFM limits of the duct without the noise of air turbulence while still getting the amount of ventilation you need.

I personally like the thermostatically controlled fans with the remote temperature sensors because they will only run the inline duct fan as hard as needed to maintain a certain ambient temp. To me it just makes more sense than manually picking and subsequently tinkering with fan speeds.

If you want a fixed amount of CFM draw, have you considered just tying the hush box vent into the main HVAC's return line with a 4" flex duct and using a baffle to mechanically set the amount of ventilation CFM you are looking for? I believe that's what this Forum's Illuminati do, but this also involves getting a fancy thermostat to turn on the HVAC fan at a minimum when the projector is on. Cheap, too.
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post #836 of 1179 Old 10-01-2013, 02:39 PM - Thread Starter
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I've pretty well committed at this point to the final arrangement of the HVAC and hush box exhaust. I went to the third and final place I was willing to consider for fittings and stuff: Grainger. What a let down. With the limited array of things they stock and the amount of counter sales they process, you would think the guys there would have some idea what parts they stock, what they are called, and what they are for - you'd be wrong.

So, not finding any plenum boots or such that would be useful, I set out to make my own. I started with the plenum I built to go in the soffit. Having decided that it wouldn't be needed (confirmed today), I cannibalized it.


I partially disassembled and reshaped it to be a rounded boot to fit in to the soffit at the top of the wall cavity (the one we looked at a few days ago, to house the 8" return. Here it is partially re-made:


Here's the hole it will fill, from the outside first, then from the inside:


It needed a little adjusting to fit in, but here it is in position. Air will enter the underside of the soffit, then descend through the wall cavity, back to the air handler. It will still need a little extra material to finish off a boot, but I will wait and do that when I fit the duct in the next step.


The open arched section on the left side of the image can accommodate (with some slight modification) a 4" round duct from the hush box. I am interested in hearing opinions, but here's the way I envision this being set up - against normal better judgement, I've take two of TMcG's ideas and blended them. The hush box vents to the air return, but I still don't want to use the 120V inline fan and the relay and everything that goes with it. I'm thinking I'll still wire up the computer fan to the 12V trigger, and place it at the hush-box end of the duct (for service access). Then I could (potentially) just run the fan and the exhaust will be able to exit the hush box back into the room, through the return HVAC grill; or if the HVAC is running (which I expect it will almost all the time) the exhaust is then further drawn into the return, aiding the flow of the fan.
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post #837 of 1179 Old 10-01-2013, 05:08 PM
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Originally Posted by HopefulFred View Post

So, not finding any plenum boots or such that would be useful, I set out to make my own. I started with the plenum I built to go in the soffit. Having decided that it wouldn't be needed (confirmed today), I cannibalized it.

HVAC-smithing at . . .


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Then I could (potentially) just run the fan and the exhaust will be able to exit the hush box back into the room, through the return HVAC grill; or if the HVAC is running (which I expect it will almost all the time) the exhaust is then further drawn into the return, aiding the flow of the fan.

If it makes you feel better, that's the same conclusion Bud (Chinadog) came to with his new Tennessee build. The hush box will dump into the return very near the opening of the return duct into the room. But he won't be using a separate 12v or 120v fan, just the natural negative pressure from the return duct to draw air through the hush box. He invested in a Crestron thermostat to work with his automation system so every time the projector turns on, the HVAC system fan switches to "on" from "auto".
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post #838 of 1179 Old 10-01-2013, 05:14 PM - Thread Starter
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Well, I feel better smile.gif Thanks a bunch for your feedback through this, TMcG!



This is funny! Ben (my helper for the week) and I had a good chuckle at my handy-work. I am actually surprised at how well it came out. I learned from an old-school red-neck. He was a machinist in the army, and I've learned a lot about hammering and bending metal watching him work.
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post #839 of 1179 Old 10-02-2013, 05:55 AM - Thread Starter
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Spaceman wins! I was waiting for my connection at Shook and Fetcher to pan out, so I haven't made a move to buy any duct liner. I followed up with them this morning, and it's still a no-go. So I called General Insulation at Spaceman's suggestion, and they have 1" Certainteed CertaPro AcoustaBlanket in stock, at only $150/roll. It's not often you speak with someone about duct liner and they have any idea what you are talking about - so when he didn't freak out when I mentioned it on the phone, I took it as as good sign. Bob has their data for comparison: "AcoustaBlanket Black 150 1.5" (38mm) 1.5pcf (24kg/m3) 0.16 0.53 0.95 1.02 1.03 1.00 0.90" which is much higher across the board than Linacoustic RC - for whatever that is worth. Hopefully one roll is enough.
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post #840 of 1179 Old 10-02-2013, 06:09 AM
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Here are the numbers for the 1" product:
AcoustaBlanket Black 150 1" 1.5pcf 0.10 0.32 0.66 0.84 0.91 0.91 0.70
vs.
Linacoustic RC 1" 0.08 0.31 0.64 0.84 0.97 1.03 0.70
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