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post #31 of 108 Old 04-15-2012, 09:52 PM
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post #32 of 108 Old 05-15-2012, 05:30 AM
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Quote:
Originally Posted by rabident View Post

Will that gap be a problem for soundproofing?

NO, as long as you use the whisper clips, hat channel, double DW and GG that you have pondered using. Fill the stud cavities with pink fluffy.

If the wall had been built on top of the concrete ledge how would the bottom portion of the wall have been attached? You would have needed to fasten whisper clips by using concrete anchors, a very tedious task compared to a deck screw into a stud.
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post #33 of 108 Old 05-15-2012, 05:54 AM
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Originally Posted by BIGmouthinDC View Post

Love that open web design.

Firemen tend to hate these trusses. They tend to burn up much quicker than conventional lumber and cause collapses. An neighbor of mine is a Captain in Fairfax and he has trusses. That was the first thing he noticed when he visited my build (I have joists that are conventional lumber).

It's going to be a beautiful build too!

Carry on...

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post #34 of 108 Old 05-15-2012, 10:06 AM
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Just a related note on open trusses. In my jurisdiction there is a fire/building code of how large (Sq ft) of a ceiling structure can be open. When you reach the limit they will want you to partition off the truss system by covering a face with drywall. This might come up in your framing inspection. Can't remember the limit.
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post #35 of 108 Old 05-15-2012, 05:25 PM
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What are those trusses' spec? live/dead load?
Are they 16" deep? And what is your span? 21' 9"
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post #36 of 108 Old 05-25-2012, 09:06 AM
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Wow, four pages back..... You've really got to start posting more pictures

I've been thinking about HVAC a lot recently, and it seems to be a popular topic here on the boards. I had forgotten just how big your room is! Those 12' walls really add to the volume. Looks like you're going to have over 7,000 c.f. once you account for risers, soffits, stages, seats, etc. etc. So you're going to need roughly 700 cfm flowing into and out of your space to get the oft-quoted 6 exchanges per hour.

Now, I don't remember how many people this theater is planned to seat, but assuming your shooting for 8, that's going to require 4,000 BTU/hour of heat removal. A rule of thumb for sizing HVAC is 400 cfm/Ton, so you can figure you need about 135 cfm of cooled air from your HVAC to keep the room cool. Another rule of thumb here is 15-17cfm per person to keep the space cool (both rules of the thumb give about the same results )

That's a pretty large discrepancy between the needed cooled air and the amount of air you need to exchange. Here's a chart I found for sizing HVAC lines, and it looks like you could get by with a single 8" supply from the HVAC. Maybe even go up to a 9" to be safe.



With all those open trusses, you could easily add some dead vents to exchange air with the other rooms in the basement. Panasonic makes a 440 cfm inline fan that's supposed to be super quiet. Here's a link if you're interested. If you go with the 9" supply, and add the 440 cfm dead vent, on paper you're at 665 cfm. Obviously the actual installation might be a little lower, but that's pretty dang close.

As far as velocity goes, again, an oft-quoted requirement is 250 fpm. If you go with the 9" supply from the HVAC, you can up the size to a 10" a couple feet before you enter your theater to slow down the air. Note, you can't run a 10" all the way and get the same result. You need a restriction to limit the flow to what you want, and then an expansion in the duct size to slow down the flow. It's still going to be too fast with the 10" duct at around 400 fpm, but you can build a register with a bar diffuser on it to slow it down the rest of the way. The other option would be to use a 12" or 14" going into the theater or hidden in the soffits which should get you right at that 250 fpm mark.

The dead vents would be similar. If you split the 8" from the inline fan into two lines before entering the theater or in your soffits, you'll have about the same flow in each as the HVAC supply.

Sorry for posting the novel here, but I've been reading a lot about this lately, and thought it might help. Feel free to tell me to stop cluttering your thread if you like

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post #37 of 108 Old 05-25-2012, 04:04 PM
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Morph1c has two in-line Panasonics in his air exchange design, bottom line is talk to him before going that route. Cooling and noise have plagued his project.
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post #38 of 108 Old 05-25-2012, 05:08 PM
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First thing first, when in doubt, I would always defer to Big. He's done this before, I've only built...... Well..... Other stuff

With that out of the way, I actually had Morph1c in mind with my previous post. There are a couple of key differences. Rabident would have a supply capable of cooling the room with all 8 occupants on its own with no aid from the dead vent. Next, the dead vent I mentioned would have 220 cfm flowing through an 8" minimum duct (split the fan duct into two) compared to more than 300 cfm that Morph1c has in a 6" duct.

Again, Big is correct that there are some potential gotcha's to keep in mind, but I think with careful planning, and utilizing previous lessons learned, it can still work. Suggestions?

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post #39 of 108 Old 05-25-2012, 07:04 PM
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Just so you know dead vents also apply to a traditional forced system. Running acoustical ducts laterally inside a soffit with soffit and walls and ceiling built with DDW and green glue helps reduce the noise that would escape a theater via a simple typical hole in the ceiling duct work. It also helps to either line such a soffit with Linacoustic or stuff gaps around the duct with loose fluffy.
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post #40 of 108 Old 05-25-2012, 07:41 PM
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Why is the conditioned air entering at the rear? The Typical recommendation is for cool air to enter at the front so that you don't have cool air blowing down the back of your neck. I guess we're conditioned to expect the cold air on our face instead of our neck. Also, if you run a supply, you should run a return back to your HVAC if you can. My earlier recommendation for the dead vents was merely to provide additional flow to meet the requirements that the HVAC doesn't meet. Can your HVAC designer meet the flow requirements for six exchanges and the 250 fpm recommendation? With the open joists, you should be able to get the HVAC line wherever you like. On top of that, with 12' ceilings you can add soffits around the perimeter to house them as well. If you do have to add a supplemental dead vent, them you will need both inlets and exhausts capable of handling the required flow.

I'd seen that 15cfm figure before, and I've been curious as to where it came from. However, if you take the 400cfm per ton (1 ton = 12000 BTU/hr) and multiply by 500 BTU per hour per person, you get 16.67 cfm per person. So I wonder if that's the source. Seems reasonable.

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post #41 of 108 Old 05-26-2012, 06:28 PM
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Quote:
Originally Posted by rabident View Post

. I have 8" lines running through 2" slits above beams for example.

You realize this is smaller than a 5 inch round line.
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post #42 of 108 Old 05-26-2012, 06:43 PM
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Quote:
Originally Posted by rabident View Post

I have 8" lines running through 2" slits above beams for example.

Dude, that's not good

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post #43 of 108 Old 05-26-2012, 07:23 PM
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Dude, now that is good! That's gonna be an awesome spot for the morning cup of joe!

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post #44 of 108 Old 05-27-2012, 05:00 AM
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I see so many pinched lines it would make me uneasy, I would get a professional opinion from a second source quick, It is easier to fix now then when those spaces are full of insulation and the drywall is up. I would also say who ever is the foreman on this job didn't do his job. He let the subs run amok without coordination.
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post #45 of 108 Old 05-27-2012, 05:05 AM
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In this shot you should me able to loosen the clips and slide the red line down a bit

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post #46 of 108 Old 05-27-2012, 05:35 AM
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At first glance, those photos make me cringe! However, keep in mind that an 8" HVAC line is covered with a lot of insulation, so it may not be quite as bad as it looks. Are those openings more than 8"-9"? Don't get me wrong, it's certainly not ideal, but as long as you don't reduce the diameter of the actual duct inside the insulation, then you haven't changed the flow. You've just reduced the insulation value.

As a point of reference, I have a 10" line going into my basement that fills a 16" joist bay due to the insulation around it.

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post #47 of 108 Old 05-27-2012, 02:17 PM
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You're better off having them fix it now than trying to get them to fix it after you've moved in. There's really not much they can do at that point. However, the ideal situation would have been for them to fix the trusses in the first place.

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post #48 of 108 Old 05-27-2012, 02:37 PM
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Quote:
Originally Posted by rabident View Post

. not ideal, but maybe good enough?

Let's say your HVAC has a reduced output efficiency of 30-40%. good enough. Your system will just run longer to make up for the deficit. I'd say a 40% increase in your HVAC electric bill for your life in this house is an easy pill to swallow. I'd demand that it be fixed. Quit looking for reassurances.
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post #49 of 108 Old 05-27-2012, 03:00 PM
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It's unfortunate that your builder didn't take the initiative and have the HVAC contractor fix the ductwork without your intervention. Same with the trusses. But Big's right. You have to live there, not the contractor, the framer, or the HVAC guys. It needs to meet your expectations!

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post #50 of 108 Old 05-27-2012, 05:08 PM
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I'd make them fix it too. At the very least I'd make the builder hire a real mechanical engineering firm to calculate as-built performance.

It might be worth making a switch to a small duct system like Unico.

High Desert Theater - work in progress
Building Bass - Subs

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post #51 of 108 Old 05-28-2012, 11:09 AM
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I'm no structural engineer, but I wonder if you can put a layer of plywood on either side of your trusses and then cut out a hole for the HVAC. Essentially you would be making a short section of each truss like a conventional solid truss so that you can cut out a section for your mechanicals. Obviously your floor designer would have to OK it and give details about how much should be reinforced.

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post #52 of 108 Old 05-28-2012, 07:24 PM
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What style house are you going for?

My gut feel is brown trim would be too much brown. I think it would still look good, but my taste would be to have a different color trim to break things up a bit.

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post #53 of 108 Old 05-29-2012, 10:56 AM - Thread Starter
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Quote:
Originally Posted by BIGmouthinDC View Post

Let's say your HVAC has a reduced output efficiency of 30-40%. good enough. Your system will just run longer to make up for the deficit. I'd say a 40% increase in your HVAC electric bill for your life in this house is an easy pill to swallow. I'd demand that it be fixed. Quit looking for reassurances.

Builder said the crimped and kinked lines will be fixed. The HVAC forum has been encouraging tearing everything out & redesigning from scratch, possibly using metal. Seems kind of drastic. Builder said he wouldn't penalize me for the current install, but I would have to pay the difference for metal if I wanted it. Otherwise they fix what's not right and call it a day.

 

 

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post #54 of 108 Old 05-30-2012, 10:25 AM
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Our HVAC installer has a lifetime warranty on their ductwork (yep, it's in the contract). So, if we have a room that's too hot or too cold, they will come out and fix it. Obviously they hope they can fix it by adjusting dampers, but none-the-less, they come out and fix it. I don't think this is unreasonable as you are paying for their expertise here.

Obviously a warranty like that depends on the HVAC contractor's reputation and how long they've been in business and will stay in business. Does yours guarantee that the install will meet your heating cooling requirements?

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post #55 of 108 Old 05-31-2012, 03:27 AM - Thread Starter
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Always comes down to contract. We have the warranty, that's all.

 

 

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post #56 of 108 Old 06-03-2012, 06:02 PM
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Installation instructions here.

"Avoid bending ducts across sharp corners or incidental contact with
metal fixtures, pipes or conduits. Radius at center line shall not be less than one duct diameter."

I find it hard to believe that a modern home would require so many 8" runs. I would ask to see the Manual J and Manual D calcs and watch for the "deer in the headlights" stare. If your municipality has adopted the IRC, the calculations are required. [Edit: see mech code 603.2]

There are a lot of violations by the HVAC contractor. Pinched lines, as Big pointed out, are not acceptable.

In pic 2 I am seeing most ducts insulated to R-8, but then I see a 4" at R-4.2. Hard to tell what is going on, but deserves a closer look. If you're using the newer codes it's R-8 for supplies and R-6 for returns. If that 4" is for a bath fan it's fine, but I would question it's use in the HVAC system. [Edit: your state requires R-8 supply and return in unconditioned space, see N1103.2.1]

You have a runout that does a 180 turn in pic #3; bend radius is not acceptable.

The whole spaghetti system is not typical of a quality contractor. Your other photos display a fine looking home-- stonework, engineered lumber, plumber looks to have done a nice job; the HVAC install is not commensurate with the quality of the rest of the home.

I would print out the instructions and visit the building department. Tell them you are concerned and ask them to come take a look before it gets too far (but the real idea is to let them know they need to handle this and not do a windshield inspection). Hopefully that keeps you from being the "bad guy".

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post #57 of 108 Old 06-12-2012, 07:11 PM - Thread Starter
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Thanks MrTim. I did a walk-thru with them today and they agreed to change some things. I'll see how it goes.

 

 

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post #58 of 108 Old 08-20-2012, 08:14 PM
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How goes the home building? Are you ready to fire your contractor yet rolleyes.gif I'm told that means you're getting close to being finished.

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post #59 of 108 Old 08-28-2012, 06:54 AM
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Does the ERV run continuously? If not, is there any downside (or negative impact to the ERV) if i's not running when the HVAC turns on? Will it pull untreated air directly from outside?

EDIT: I think what you've got seems reasonable. The only other thing I can think of is the length of the ductwork you are connecting the ERV to. If it's too long, or too restrictive, you can essentially end up with no flow from your ERV.

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post #60 of 108 Old 09-18-2012, 12:12 PM
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Looking good. I'm in the pre-stages of designing our next home (2nd house custom built). I think 12' plus basement height is a must have for me as well. Looking forward to seeing your results. Is your hew home spray-foam insulated?.. and is that why you primarily have fresh air exchanger? Do you have one exchanger or another one for upper floors?

I can understand having builder issues. You want to be a stickler with these guys, but at the same time, if you piss them off, who knows what happens. It's your money (and a lot of it), but everyone's human, and let's face it, subcontractors sometimes aren't the easiest to deal with.

It may be too late for all of this: Do you have a realtor that's getting commission on the home build? We lucked out that we used ours as the primary 'bad guy' with the builder and it helped get things done and changed, when necessary. We had about 1/10th the problems with our new home vs. others with the same builder in our subdivision. Just a thought. Also, keep the subcontractors liking you.. I'd go by every day on lunch or after work and helped keep site clean and foam sprayed all the outlets and wall/floor seams.. just doing whatever I could and not be in their way. I've been inside our same house design in our neighborhood and it's shocking the level of quality ours is vs. others.
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