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PostPosted: Sat May 20, 2017 8:28 am 
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*** UPDATE AUGUST 2017 ***
2nd draft design for RFZ completed. :mrgreen:
Excavation for extending slab complete.
*********************


ORIGINAL POST

Hi all, this is my first post on these forums! I've posted a bit on homerecording forums though and have had good advice there, but it seems quite a lot of those guys post here too! So i thought I'd spread the love.

I'm in the process of building a garden studio for use as a guitar teaching space and jam room for my band. I would like to record in the future and use it as a live room. I'm probably looking to mix in there too, maybe just doing headphone mixing though as I'd like to avoid deadening the sound with treatment much.

Currently I've built a concrete slab as a base. I originally built it with a smaller room in mind just for teaching, but since then I've started playing in a band I'm seriously considering extending the base to make the room more comfortable and 'bigger' sounding.

As it stands the slab is 3.1m x 5.1m to the external walls, this leaves me around 2.5m x 4.5m internal space once I build 150mm external stud wall and 100mm internal isolated wall with 50mm cavity.

I understand it would be extremely benefical to extend the short wall, but I'm bound by me and the wife sharing a house with the in-laws, and therefore I have to negotiate for the garden space. Ha! :wink:

The family are most opposed to extending short wall alot into the garden more, as the garden width is limited, whereas the length is limited only by budget, as we have a very long thin garden.

How would you guys advise me to proceed with the width limitation?
I'm thinking I can negotiate 1m or so extra width putting me up to 3.5m ish internal width.
I understand larger room are always 'better', but could I compensate for a narrow live room by increasing some length. Height isn't fixed but I was expecting around 2.75m ish.
I'll do some drawings once I get some ideas for dimensions.


Thanks in advance all! :D
Dan


Last edited by Waka on Fri Aug 25, 2017 10:29 am, edited 5 times in total.

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PostPosted: Tue May 23, 2017 2:15 am 
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Hi there Dan, and welcome! :)

Quote:
I'm probably looking to mix in there too, maybe just doing headphone mixing though as I'd like to avoid deadening the sound with treatment much.
Mixing on headphones is not really much f an option, as you never hear what other people will hear if they are NOT listening on headphones: You never hear who your mix sounds in the real world.

Also, control rooms should not be "dead". That was a concept from the 70's that thankfully died. Control rooms these days are designed to be neutral. The thinking is simple (and logical!) The control room should not color the sound in any way: it should neither add to nor subtract from the sound coming out of the speakers. It should just transmit that direct sound from the speakers to your ears, perfectly clean, clear, and unadulterated in any manner. So your control room should not be dead.

However, it won't be very live either ... unless you add treatment that makes it so. It is entirely possible to design variable acoustic treatment that can be changed in some way in order to modify the room acoustics: panels that open, slide, flip, rotate, or move in some way or other.

Quote:
this leaves me around 2.5m x 4.5m internal space
That's pretty small, even for a control room. ITU, EBU, AES and other specs related to control rooms all recommend a minimum floor area of 20 m2. That's not to say that you can't build a successful room with less area! You certainly can! I have designed several rooms with less area than that, and John has designed a studio that fits in a shipping container. But the smaller it is, the harder it is to treat, and the lower the quality will be.

Quote:
once I build 150mm external stud wall and 100mm internal isolated wall with 50mm cavity.
Why did you choose those dimensions?

Quote:
I'm thinking I can negotiate 1m or so extra width putting me up to 3.5m ish internal width.
:thu: I would definitely do that! Long thin rooms are pretty lousy acoustically. There's no decent ratios for rooms like that.

I would also make the building structure itself "thinner", so you can maximize interior room width.

Quote:
I understand larger room are always 'better', but could I compensate for a narrow live room by increasing some length.
Take a look at "room ratios" and "modal distribution", and play around with some room ratio calculators: You'll find that long thin rooms don't stack up very well...


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PostPosted: Tue May 23, 2017 7:05 am 
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Hi Stuart,

Thanks for replying. I've been able to get in touch with planning and I'm quite sure I'll be able to extend closer to my boundary. Which is great news!

My external width should be looking now at around 4.1m. With 2 x 100mm studwork with a 25mm spacing (I agree making the walls thinner is a better option) and two inner layers I'm looking at around 3.6m internal. Much better.

I was hoping to do a nice 12degree slope in the ceiling and roof to reduce echo. And hopefully give some assymetry for the room for recording. Internal starting around 2.4m sloping to 3.1m gives me an average height of 2.75m ceiling height. So (acknowleging this likely screws up any 'golden' ratios) plugging in to the ratios in Rod's book I can sortof get second best Louden ratio: 1 x 1.3 x 1.9, if I make the internal length 5.225m. Which only requires extending the room another 0.6m in length. Again good news I think!

About the mixing in headphones: I understand you can never really get the true sound when not mixing in a room, but as I'm a real beginner in mixing I'd rather the room have a really good live sound, and then later down the line if needed add additional treatments to improve room mixing whilst maintaining the feel of a nice reverby natural space to record in.

I'm working on a sketchup design at-the-mo that I'd like some opinions on when it's done if anyone has time, please.

Dan


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PostPosted: Tue May 23, 2017 10:11 am 
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I'm in the process of designing the ventilation and cooling/heating system for my studio, but I'm really having trouble sizing my fans.

I was planning on having a portable air cooler/heater to control temperature that I can turn on and off between recording, if it's too loud. This requires ventilation separately.

From Rod's book I know I need around 75CFM of air for a max of 5 people to be comfortable. My idea was to put a wall mounted ventilation fan on the external wall - flexible ducting through to the isolated inner wall running into a boxed baffle in the soffit of the internal wall.

This is the sort of thing I was thinking of:
Attachment:
duct baffle.jpg

But, for my room the ducting through the wall would stop at the outside of exterior wall and fit into a wall mounted fan.

I'll also put a second baffle box in the opposite soffit but without a fan to draw air from.

I know that reducing the velocity of the intake makes the system quieter, but I'm struggling to calculate what I need for a through the wall fan.
For example: A fan like this - http://www.ventilation-system.com/item/247/OV1_150/.

It says it has a maximum air capacity of: 117.8CFM which seems to fit the bill. But I can't see any mention of velocity in the specs.
Quite a bit of the info in Rod's book seems to focus on ducted systems, so I'm struggling to translate this into my requirements.

Can someone talk me through this a little bit please?

Thanks in advance,
Dan


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PostPosted: Tue May 23, 2017 5:03 pm 
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Quote:
I've been able to get in touch with planning and I'm quite sure I'll be able to extend closer to my boundary.
You are in the UK, and I imagine you are going for Class E permitted development? If I recall correctly, you are only allowed a maximum roof height of 2.5m if your building within be within 2m of the property boundary. If you are more than 2m away from all boundaries, then you can go up to 4 if you have a gabled roof, or 3m for other roof types. What's your plan here? Will you be more that 2m form the boundary?

Quote:
I was hoping to do a nice 12degree slope in the ceiling and roof to reduce echo.
I hop you are not very tall! In fact, I hope you are really, really short... :) If you have a 12° slope on a ceiling that starts at a height of 2.4 m, and the room is 4m wide, then the ceiling will be down to 1.5m at the other side of the room. In the middle of the room, it will be at 1.9m...

You might want to re-think your ceiling plans.... :)

Attachment:
12-degree-roof-pygmy.jpg

That's what your room cross section will look like... And that's generous! I'm assuming that you really can get your inner-leaf ceiling as high as 2.4 m....

Besides, why do you want to do that anyway? It's far, far easier to treat flutter echo in other ways.

Quote:
Internal starting around 2.4m sloping to 3.1m
How on earth do you plan to get 3.1m ceiling height, if Class E does not allow that? According to paragraph f, your eaves cannot be higher than 2.5m no matter what, regardless of how close you are to the property line... it's hard to see how you could get 3.1 m height for your ceiling when the roof can't be higher than 2.5 at the eaves! Are you planning to excavate one meter down, then sink your building down into the ground?

Quote:
acknowleging this likely screws up any 'golden' ratios)
There's actually no such thing as a perfect "golden ratio". There are just good ones and bad ones.

Quote:
plugging in to the ratios in Rod's book
Ummmm.... Nope! If your ceiling slopes like that, then there's no way you can use simple calculators to figure out your modal spread. Those tables and calculators only work for rectangular rooms, consisting of three sets of parallel surfaces that are mutually perpendicular to each other. As soon as you angle one of the surfaces significantly, all bets are off.

Quote:
I understand you can never really get the true sound when not mixing in a room, but as I'm a real beginner in mixing . . .
If you are a beginner at mixing, then I would DEFINITELY not try to do it on headphones! As a beginner, you need every single acoustic clue you can get about your mix, and you cannot get that on cans. If you mix in a room, then your left ear hears the right speaker as well as the left, and vice versa. There's ambience, there's decay, there's spatial clues. If you mix on cans, your left ear ONLY hears the left speaker, nothing at all from the right. There's no ambiance, no decay, and no spatial clues. I would only try to mix on cans if you already have experience mixing in a real room. Sort of like learning to drive: if you learn on a manual gearbox, then switching over to an automatic is a piece of cake. But if you start out on an automatic, trying to learn manual later is hell, and you'll never be as good at as you would have been....

Give yourself the best possible chance of learning to mix right, by creating the best possible situation for it.

Quote:
From Rod's book I know I need around 75CFM of air for a max of 5 people to be comfortable.
:shock: :ahh: Ummmm... I don't think so! That's just the amount of make-up air that you need! According to ASHRAE guidelines, you need about 6 room changes per hour. Your room will measure about 4.1 x 5.2 x 2.75, as far as I can figure out from what you say, so that's about 59 m3, which is 2100 ft3 very roughly. Six changes per hour gives you 12,600 ft3/hr, which is 210 CFM.

Quote:
I was planning on having a portable air cooler/heater to control temperature that I can turn on and off between recording, if it's too loud.
Is there some reason why you can't use a normal mini-split system in your room?

Quote:
My idea was to put a wall mounted ventilation fan on the external wall - flexible ducting through to the isolated inner wall running into a boxed baffle in the soffit of the internal wall.
How much isolation do you need, in decibels? You can't start deciding on major issues such as HVAC silencer box design until you know that.

Quote:
But I can't see any mention of velocity in the specs.
Do the math... :) You know the flow rate, in CUBIC FEET per minute, you know the cross-sectional area of the fan in SQUARE FEET, so divide, and you'll end up with the speed, in FEET per MINUTE.... (You'll have to get the cross sectional area by using the diameter in mm, figuring the area, then converting to feet.)

Quote:
Quite a bit of the info in Rod's book seems to focus on ducted systems
That's exactly what you are doing! You are taking about a silencer box with ducts and a fan: That's a ducted system.... :) (Yeah, OK, I know: you are thinking of ducted AHU, and you won't have that, but the principles are still the same)...


- Stuart -


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PostPosted: Tue May 23, 2017 6:00 pm 
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Quote:
You are in the UK, and I imagine you are going for Class E permitted development? If I recall correctly, you are only allowed a maximum roof height of 2.5m if your building within be within 2m of the property boundary. If you are more than 2m away from all boundaries, then you can go up to 4 if you have a gabled roof, or 3m for other roof types. What's your plan here? Will you be more that 2m form the boundary?


No no I've received planning permission so I dont have roof eaves height restrictions. I was sloping up from 2.4m internally. The external height at the top of the slope is about 3.6m.

Quote:
Besides, why do you want to do that anyway? It's far, far easier to treat flutter echo in other ways.

As the roof deals with rain water better if it's sloped I just increased the slope to be 12degree, two birds one stone :lol: Also Rod's book seems to show live rooms without parrallel ceilings in his photos, and he says asymmetry is better in live rooms. But a parallel ceiling is of course not an issue if it's a better idea in this case.

Quote:
As soon as you angle one of the surfaces significantly, all bets are off.
That's what I suspected ha!

Quote:
Your room will measure about 4.1 x 5.2 x 2.75, as far as I can figure out from what you say, so that's about 59 m3, which is 2100 ft3 very roughly. Six changes per hour gives you 12,600 ft3/hr, which is 210 CFM.


Ah I see! There's alot of info to digest. I'll work out the actual m3 of the room once I fixed the ceiling issue.

Quote:
Is there some reason why you can't use a normal mini-split system in your room?
Not really no. I was trying keep this system simple with a portable system, but if the airflow requirements are just as complex then it might be worth it to combine the two.

Quote:
How much isolation do you need, in decibels? You can't start deciding on major issues such as HVAC silencer box design until you know that.
Well to match the walls they acheive around STC 63 in rods book. That is using 100mm studs for both walls and 2 layers of drywall (or osb for structural reasons, so maybe a little less.) So I'm trying to bring the silencer box design as close as I can to that within reason.

Quote:
Do the math... :) You know the flow rate, in CUBIC FEET per minute, you know the cross-sectional area of the fan in SQUARE FEET, so divide, and you'll end up with the speed, in FEET per MINUTE.... (You'll have to get the cross sectional area by using the diameter in mm, figuring the area, then converting to feet.)
Whips out a calc :lol:

I'll re-look into mini split hvac systems later on.

I need to get calculating :lol:


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PostPosted: Wed May 24, 2017 12:48 am 
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Quote:
Do the math... :) You know the flow rate, in CUBIC FEET per minute, you know the cross-sectional area of the fan in SQUARE FEET, so divide, and you'll end up with the speed, in FEET per MINUTE.... (You'll have to get the cross sectional area by using the diameter in mm, figuring the area, then converting to feet.)


Thanks for your help so far btw!

So working through this. My current intended internal room dimensions are 2.75m(average height) x 3.6m x 5.23m. This is a total of 51.78m3 or 1828.5 CF.
6 changes per hour is 10971 CF/Hour = 182.85 CFM.

Looking at the fan I listed before would mean I need to upscale to the 250mm fan which has a max air capacity of 630.23 CFM: http://www.ventilation-system.com/item/ ... parameters
The diameter according to the specs is 262mm - which is an area of 53913mm2 or 0.58 feet-squared.

So! If I need 183 CFM through a fan of 0.58 Square feet. 183 / 0.58 = 315 FPM. A bit too high a velocity. I'd be looking for less than 300FPM and nearer to 100FPM would be great.

Rod in his book says you can reduce the velocity by increasing the size of the ducting. Would for example me running the fan into a box baffle with an outlet of 524mm x 262mm therefore decrease my velocity by half to 157.5FPM? If so this seems reasonable and achievable.

So this design would be:

Mount the fan on the exterior wall.
The same diameter round ducting runs through the walls to the isolated internal wall.
Ducting runs into a baffle box attached in the soffit. This box has an outlet twice the size of the fan diameter.
This outlet has a register/grille on it to reduce buffeting.

On the opposite side of the room:
(No fan)
A grille/register is mounted on the exterior wall (should this be the same size as the fan, or same as double size outlet?)
Ducting runs through the wall into another baffle box attached to this soffit. This baffle box also has a register/grille on it.

The fan would be controlled by a speed controller and set to a lower RPM to provide the desired CFM.

Should the fan push new air into the room or extract it out? Or does this entirely make no difference?

Do I need to do anything to combat the fact that the isolated interior wall has been bridged by the ducting, or is the baffle box probably sufficient?

Regards and thanks for any help in advance,
Dan


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PostPosted: Wed May 24, 2017 4:00 am 
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Quote:
The external height at the top of the slope is about 3.6m.
... and how do you plan to support that? :) Even if your trusses used raised collar ties, or are scissor trusses, you'll still get nowhere near 3.6 m at the peak of your inner-leaf ceiling. Not sure what your span is, but rule of thumb says that a raised collar tie should go no more than one third the pitch of the roof, so the lower chord would be at maybe 2.8m, perhaps 2.9m max, if you can get an excellent design that really can transfer the loads and tensions in that configuration. But that's your outer leaf! You still need account for your inner-leaf.... I don't see you being able to get much more than about 2.6 or so as the peak of the actual acoustic inner-leaf ceiling.

Please post your truss layout, so I can take a look at that, and see if there's any way of optimizing it for better height.

Quote:
As the roof deals with rain water better if it's sloped I just increased the slope to be 12degree,


Quote:
Also Rod's book seems to show live rooms without parrallel ceilings in his photos, and he says asymmetry is better in live rooms.
Asymmetrical shape is fine for live rooms, rehearsal rooms, tracking rooms, even isolation booths and vocal booths. But not for control rooms. You can't mix in a room that is not symmetrical. You did say that you want to mix in this room, therefore it cannot be asymmetrical...

That said, you could still have a sloped ceiling if you want, as ong as you arrange the room so that the ceiling slopes symmetrically about the left-right axis, and rises to the rear. In other words, the ceiling would have to be low over the front of the room, where the speakers are are, rising up towards the rear of the room.

Quote:
But a parallel ceiling is of course not an issue if it's a better idea in this case.
If the ceiling can be symmetrical and also sloped, and that would help to increase overall room volume, then it's probably worth doing.

Quote:
I was trying keep this system simple with a portable system,
Portable air conditioners still need to dump the waste heat somewhere! It doesn't disappear into nothingness inside the box: Normally there's a rather large flexible duct on the rear of the unit that has to go out of the room, through an open doorway, or window, or a huge hole in the wall... So even a portable A/C unit is still a ducted system, in that sense. They are also extremely noisy, because the compressor itself is inside the box. With a mini-split, the compressor is outside, in the external unit, so it is much less noisy. And the pipe bundle that links the two units is way, way smaller than the huge duct of portable unit.

Quote:
Well to match the walls they acheive around STC 63 in rods book
Careful with STC.... In fact, forget STC! It is no use at all for telling you how well your studio will be isolated. STC was never meant to measure such things. Here's an excerpt from the actual ASTM test procedure (E413) that explains the use of STC.

These single-number ratings correlate in a general way with subjective impressions of sound transmission for speech, radio, television and similar sources of noise in offices and buildings. This classification method [i]is not appropriate for sound sources with spectra significantly different from those sources listed above. Such sources include machinery, industrial processes, bowling alleys, power transformers, musical instruments, many music systems and transportation noises such as motor vehicles, aircraft and trains. For these sources, accurate assessment of sound transmission requires a detailed analysis in frequency bands.[/i]”

It's a common misconception that you can use STC ratings to decide if a particular wall, window, door, or building material will be of any use in a studio. As you can see above, in the statement from the people who designed the STC rating system and the method for calculating it, STC is simply not applicable.

Here's how it works:

To determine the STC rating for a wall, door, window, or whatever, you start by measuring the actual transmission loss at 16 specific frequencies between 125 Hz and 4kHz. You do not measure anything above or below that range, and you do not measure anything in between those 16 points. Just those 16, and nothing else. Then you plot those 16 points on a graph, and do some fudging and nudging with the numbers and the curve, until it fits in below one of the standard STC curves. Then you read off the number of that specific curve, and that number is your STC rating. There is no relationship to real-world decibels: it is just the index number of the reference curve that is closest to your curve.

When you measure the isolation of a studio wall, you want to be sure that it is isolating ALL frequencies, across the entire spectrum from 20 Hz up to 20,000 Hz, not just 16 specific points that somebody chose 50 years ago, because he thought they were a good representation of human speech. STC does not take into account the bottom two and a half octaves of the musical spectrum (nothing below 125Hz), nor does it take into account the top two and a quarter octaves (nothing above 4k). Of the ten octaves that our hearing range covers, STC ignores five of them (or nearly five). So STC tells you nothing useful about how well a wall, door or window will work in a studio. The ONLY way to determine that, is by look at the Transmission Loss curve for it, or by estimating with a sound level meter set to "C" weighting (or even "Z"), and slow response, then measuring the levels on each side. That will give you a true indication of the number of decibels that the wall/door/window is blocking, across the full audible range.

Consider this: It is quite possible to have a door rated at STC-30 that does not provide even 20 decibels of actual isolation, and I can build you a wall rated at STC-20 that provides much better than 30 dB of isolation. There simply is no relationship between STC rating and the ability of a barrier to stop full-spectrum sound, such as music. STC was never designed for that, and cannot be used for that.

Then there's the issue of installation. You can buy a door that really does provide 40 dB of isolation, but unless you install it correctly, it will not provide that level! If you install it in a wall that provides only 20 dB, then the total isolation of that wall+door is around 20 dB: isolation is only as good as the worst part. Even if you put a door rated at 90 dB in that wall, it would STILL only give you 20 dB. The total is only as good as the weakest part of the system.

So forget STC as a useful indicator, and just use the actual TL graphs to judge if a wall, door, window, floor, roof, or whatever will meet your needs.

Quote:
So I'm trying to bring the silencer box design as close as I can to that within reason.
You say you want each leaf of your walls to have two layers of 16mm drywall on each leaf. That works out to a surface density of around 24 kg/m2. Therefore you will need one silencer box made of materials totaling 24 kg/m2 where the duct goes through the outer-leaf, and another silencer box made of materials totaling 24 kg/m2 where the duct goes through the outer-leaf. That's two silencer boxes on the duct. And since you will have two ducts (one for bringing in fresh air, one for removing stale air), you will need four silencer boxes, each of which is made with walls that have a surface density of 24 kg/m2. If you use plywood to make them, then taking into account that the density of plywood is only about 80% of the density of drywall, the plywood will need to be 20mm thick, 2 layers.

Then you will need to check that the insertion loss of the final unit will be high enough, and that the static pressure will not be too high for your fan to handle.

What static pressure can your fan deal with? What flow rate do you get for that static pressure?
Quote:
= 182.85 CFM.
Sounds about right. Call it 200 to be safe.

Quote:
A bit too high a velocity. I'd be looking for less than 300FPM and nearer to 100FPM would be great.
You've been listening to Rod! :thu: Yup, those are good goals to shoot for... but that's about air speed AT THE REGISTER! The speed that the air is moving as it moves through the registers going into and out of the room. The duct speed can be higher.

Quote:
Rod in his book says you can reduce the velocity by increasing the size of the ducting.
Yep! Simple math: If you increase the cross sectional area, then for any give flow rate, the speed MUST be lower.

Not only that, but you MUST change the cross sectional area, several times, in order to get the benefit of the impedance mismatch, which is a great help in reducing the intensity of low frequencies moving down the duct. Those changes must be sudden, for maximum effect.

Quote:
Mount the fan on the exterior wall.
The same diameter round ducting runs through the walls to the isolated internal wall.
So where is the silener box on the outer leaf? You didn't mention that one....

Quote:
A grille/register is mounted on the exterior wall (should this be the same size as the fan, or same as double size outlet?)
Ducting runs through the wall into another baffle box attached to this soffit. This baffle box also has a register/grille on it.
You seem to be forgetting the silencer box on the inner-leaf, in this case.

Quote:
The fan would be controlled by a speed controller and set to a lower RPM to provide the desired CFM.
It's always good to have a speed controller, yes, but do check that your fan can handle the static pressure that the system will present to it.


Quote:
Should the fan push new air into the room or extract it out? Or does this entirely make no difference
There's pros and cons both ways. You can make good arguments for having a fan pushing air in, and you can also make good arguments for a fan sucking air out. Personally, I usually prefer to put the fan at the far end of the exhaust duct, sucking air through the room.

Of course, if you chose to use a ducted AHU outside the room, then you can recirculate a lot of the air through that, save money, etc. and use smaller ducts for the make-up air coming on from outside, and the corresponding exhaust air going overboard....


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PostPosted: Wed May 24, 2017 6:09 am 
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Soundman2020 wrote:
Quote:
The external height at the top of the slope is about 3.6m.
... and how do you plan to support that? :) Even if your trusses used raised collar ties, or are scissor trusses, you'll still get nowhere near 3.6 m at the peak of your inner-leaf ceiling. Not sure what your span is, but rule of thumb says that a raised collar tie should go no more than one third the pitch of the roof, so the lower chord would be at maybe 2.8m, perhaps 2.9m max, if you can get an excellent design that really can transfer the loads and tensions in that configuration. But that's your outer leaf! You still need account for your inner-leaf.... I don't see you being able to get much more than about 2.6 or so as the peak of the actual acoustic inner-leaf ceiling.

Please post your truss layout, so I can take a look at that, and see if there's any way of optimizing it for better height.


Sorry we've crossed lines here I think :wink: the height is 3.6m external at the top of the eaves. I just mentioned that height as you'd said about permitted development height being restricted. I have planning permission for the height externally. The internal height on my design is around 2.4m up to 3.1m internally.

Here's some sketchup images of the sort of thing I was thinking. The roof joists have a max clear span of 5.08m. Mine are clear for around 4.5m for external and less for internal. Do you mean that the supporting wall won't handle the lateral stress?
Exterior Timber Frame:
Attachment:
Exterior Timber Frame.png


Interior Timber Frame:
Attachment:
Internal Timber Frame.png


Here's a link to my google drive that has my sketchup file if you'd be able to have a look.
https://drive.google.com/file/d/0B8fOTP ... sp=sharing

Bear in mind I designed the above with 150mm studs at 600mm spacing before deciding that 100mm studs would be a bigger benefit for the room size even at 400mm spacing.

Quote:
Portable air conditioners still need to dump the waste heat somewhere! It doesn't disappear into nothingness inside the box: Normally there's a rather large flexible duct on the rear of the unit that has to go out of the room, through an open doorway, or window, or a huge hole in the wall... So even a portable A/C unit is still a ducted system, in that sense. They are also extremely noisy, because the compressor itself is inside the box. With a mini-split, the compressor is outside, in the external unit, so it is much less noisy. And the pipe bundle that links the two units is way, way smaller than the huge duct of portable unit.


Ah of course. I have been looking at the Mini Split systems and they look like a good fit. A little draw back though is that the sound reduction I'm attempting is just as much to keep noise in as it is to keep it out. And I'm not sure I'd be able to get away with a 50dB condenser outside when my family are trying to enjoy the garden etc. I assume it's possible to have the condenser in it's own sort of isolation box to cut that down to below 30dB ish?

Quote:
So forget STC as a useful indicator, and just use the actual TL graphs to judge if a wall, door, window, floor, roof, or whatever will meet your needs.


Will do!

Quote:
You say you want each leaf of your walls to have two layers of 16mm drywall on each leaf.


I wasn't going to be using 16mm plasterboard. My actual design was planning on being:
Inner leaf:
9.5mm Plasterboard
9mm OSB (Oriented Strand Board) - This is mainly useful for hanging things on the wall with.
Moisture Control Membrane - (Stops condensation entering the structure of the wall)
100mm Stud with 100mm of Mineral Wool between studs

25mm Air cavity

Outer Leaf:
100mm Stud with 100mm of Mineral Wool between studs
9mm OSB - Sheathing is structural here and also negates the need for noggins between studs.
9mm OSB - Second layer of mass, must also be structural to support facing material.
Breather Membrane

Facing (Not airtight)
50mm Battens every 400mm Vertically
These support horizontal Shiplap/Loglap cladding

Quote:
That's two silencer boxes on the duct. And since you will have two ducts (one for bringing in fresh air, one for removing stale air), you will need four silencer boxes

Ah! I didn't realise that. I only thought they were required on the inside. But that does make sense so that'll be in the design.

Quote:
Then you will need to check that the insertion loss of the final unit will be high enough, and that the static pressure will not be too high for your fan to handle.

What static pressure can your fan deal with? What flow rate do you get for that static pressure?


I realised the fan I was looking at isn't from the UK lol so I have a new one here:
http://www.fansandspares.co.uk/shop/pro ... -axial-fan

The above fan has two pressures listed in the manual with flow rate:
Static Pressure of 0 Pa - Airflow: 0.268 m3/s or 567 CFM
Static Pressure of 50 Pa - Airflow: 0.1 m3/s or 211.89 CFM

Do you think the silencers would increase static pressure to above 50Pa (0.0073 Psi) :?:

Quote:
Yup, those are good goals to shoot for... but that's about air speed AT THE REGISTER! The speed that the air is moving as it moves through the registers going into and out of the room. The duct speed can be higher.
...
Not only that, but you MUST change the cross sectional area, several times, in order to get the benefit of the impedance mismatch, which is a great help in reducing the intensity of low frequencies moving down the duct. Those changes must be sudden, for maximum effect.


Ye I've tried to design some for the vents in my roof on the sketchup file if you take a look. If you hide the outer skin you can see what I made inside.

Quote:
Of course, if you chose to use a ducted AHU outside the room, then you can recirculate a lot of the air through that, save money, etc. and use smaller ducts for the make-up air coming on from outside, and the corresponding exhaust air going overboard....

That also is a good suggestion, but I'm trying to have as little impact on the experience for my family if possible, by isolating noisy things from the outside world as much as possible too.
And I think a fan with a silencer box either side of it shouldn't produce much noise. *I say optimistically* - The specs of the fan I linked shows 44dB at 3m when running 1400RPM - being the lower RPM model. I assume this goes down even further if I slow it down to reduce flow to what I require.

So for me at the moment the big problem to resolve is my cooling requirements whilst not causing much noise in the garden whilst running. Could I build a miniature exchange room/box possibly in the corner of the studio? With a through-the-wall / window system. Is there a limit to how small this room can be? For example could I build just physically large enough to fit the system and ducts in. Like 0.5m cube in the corner of the room. In theory wouldn't this also take care of fresh air supply?

Thanks for your time again Stuart, you've been a great help so far.


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PostPosted: Thu May 25, 2017 9:25 am 
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Location: Surfleet, UK
So I've been thinking about my cooling and ventilation requirements some more and the exhange room method may be feasable for me.

This is a quick sketch I did to illustrate:
Attachment:
20170524_235740~2-600x694.jpg


If you can't quite read the writing, the design involves extending the room 1m in length to accommodate an isolated exchange room. The exchange room inside would be 0.9m x 3.6m This allows a door to open into the room for access.

Btw can I put storage in this room as long as I dont block the fan/A.C.? Would be a nice place to store guitar cases etc. when playing.

The room would have an internal through wall AC. That has an 130mm intake vent and 130mm exhaust vent.

In the left bottom corner of the room would be a fan drawing the good air out through a silencer into the live room. The old air would travel through a lined duct opening at the other end of room back through another silencer above the doorway in the top right of the room and into the exchange room for exhaust by the AC unit.

The AC I'm looking at is this: https://www.hygienesuppliesdirect.com/p ... oC7S3w_wcB
(sorry for long url I couldn't remember how post a short link)

This AC has max airflow of 320 m3/h which is 188 CFM just above my 183.5 we worked out I wanted earlier (too close?). And cools/heats 10,000 BTU. I only need around 8500 btu max so that's fine.

Does this system seem ok to you?

It seems to tick the boxes for me.
Noise kept inside to not disturb garden users.
Noise kept out of live room for music.
I can breath the fresh air.
People get somewhere to store their coat/guitar cases.

Anything I've missed?

**** EDIT ****
According to the documentation I must have 2m free space in front of the unit for circulation. I will instead hang on the left side of the exchange room on the short wall blowing across the room.
*************


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PostPosted: Fri May 26, 2017 2:27 am 
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Posts: 43
Location: Milton Keynes, UK
Hello Waka

Looks like you are in the same stage as me although i am currently framing my garage.

I am looking to use a HRV system to supply air to my room, i plan to bypass in the summer as being in the UK like you I do not need any bloody cold air coming in while i work :)

I have been looking at this company https://www.bhfunlimited.co.uk/product- ... hrvu-kits/

Today I gave them a call as I need a bigger duct size than 4" and they say they can make custom units. Its another option, low power quite quiet <30db and can live in the loft space.

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PostPosted: Fri May 26, 2017 6:30 am 
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Posts: 42
Location: Surfleet, UK
dsp wrote:
Hello Waka

Looks like you are in the same stage as me although i am currently framing my garage.

I am looking to use a HRV system to supply air to my room, i plan to bypass in the summer as being in the UK like you I do not need any bloody cold air coming in while i work :)

I have been looking at this company https://www.bhfunlimited.co.uk/product- ... hrvu-kits/

Today I gave them a call as I need a bigger duct size than 4" and they say they can make custom units. Its another option, low power quite quiet <30db and can live in the loft space.


That's a good idea, as ventilation probably means drafts! The air con I was looking at doesn't provide fresh air I've established so again back to square one! I'm considering ust my initial idea of a portable unit and turning it off when recording. Unless I can find a way to isolate the noise of a window/through wall unit without it overheating.


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PostPosted: Fri May 26, 2017 6:49 am 
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Posts: 42
Location: Surfleet, UK
For AC I'm possibly going to have to bite bullet and get one of these:
http://www.arredatutto.com/en/olimpia-s ... 62622.html

27dB to 38dB depending on speed sounds good in UK with our rarely hot weather (suprisingly having a hot end of may though!) will probably be low all the time.

Add a fan for ventilation and some silencers and we're set I think.

I might get a HRV system later if it's too drafty in the winter.


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PostPosted: Wed May 31, 2017 7:59 am 
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Location: Derbyshire, England
Nice find on the HRV system, DSP! I've been trying to decide what to do for my studio room that's cold all year around so I won't be needing an air con for cooling, although the dehumidification might help. I shall look into the HRV thing instead of an electric radiator..

Waka - I'd found the below when I was looking which looks a bit cheaper than the one you've found. I emailed the company who confirmed it can be self installed: "The easy fit systems are quite straight forward to install if you follow the instructions to the word. If you are a capable DIY'er you should find that its no hassle.

The most important thing to remember and the most common complaint we receive from people who purchase these units is you HAVE to make sure you tighten all the pipe connections properly to gain the appropriate seal otherwise refrigerant will leak and the unit won't work properly. if that is done then the rest is relatively straight forward. there's no gassing or pressurising needed, It's literally, Wire the indoor unit to the outdoor unit via a hole in the wall and away you go. the good thing with the easy fit systems is that your warranty stays intact even though you fitted it yourself where as the other units like the LG's etc need to be installed by a professional."

http://www.ixus.biz/easyfit/high-wall-h ... erter.html

Good luck!

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PostPosted: Thu Jun 01, 2017 9:33 am 
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Location: Surfleet, UK
garethmetcalf wrote:
Waka - I'd found the below when I was looking which looks a bit cheaper than the one you've found. I emailed the company who confirmed it can be self installed: "The easy fit systems are quite straight forward to install if you follow the instructions to the word. If you are a capable DIY'er you should find that its no hassle.

The most important thing to remember and the most common complaint we receive from people who purchase these units is you HAVE to make sure you tighten all the pipe connections properly to gain the appropriate seal otherwise refrigerant will leak and the unit won't work properly. if that is done then the rest is relatively straight forward. there's no gassing or pressurising needed, It's literally, Wire the indoor unit to the outdoor unit via a hole in the wall and away you go. the good thing with the easy fit systems is that your warranty stays intact even though you fitted it yourself where as the other units like the LG's etc need to be installed by a professional."

http://www.ixus.biz/easyfit/high-wall-h ... erter.html

Good luck!


Thanks for the link Gareth. I was interested in mini split systems like those but opted against them as the outside unit is loud (52db for that one you linked). The Inside noise is good though. I live in a quiet area of the countryside so can't reasonably install a condenser outside without disturbing the family and neighbours in their gardens, it's also not really possible to isolate the unit due to overheating. The system I linked is actually an all-in-one system. It requires no outdoor system at all, only ducts to the outside world. which I will put silencer boxes on. In my situation I require the system to have low inside dB AND outside dB ha! I'm trying to have as little impact on my surroundings as possible :)


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