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Lbear
Veteran Member
Posts:2740
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| 14 Jul 2013 05:23 PM |
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Posted By joeldunn21 on 14 Jul 2013 09:39 AM
Thanks for all the input everyone! Vented roof for me! Peace of mind well worth it! Will 1" furring strips provide enough ventilation? I'd like to keep my fascia to 6-8" wide, and my panels come from the factory with 6" trim already.
2" furring strips would be better. Remember dimensional lumber is always smaller than the stated lengths. A 2x4 is actually a 1.5x3.5, so with a 1" strip it would probably be 3/4". |
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Alton
Veteran Member
Posts:2164
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| 14 Jul 2013 05:31 PM |
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My understanding is that the thickness of the furring strip should be governed by the length of the roof. Long roofs may require more air space to enhance movement of the air as it expands. This may be more important in hot climates. Maybe Dana1 can enlighten us. |
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Residential Designer &
Construction Technology Consultant -- E-mail: Alton at Auburn dot Edu Use email format with @ and period .
334 826-3979 |
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jonr
Senior Member
Posts:5341
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| 14 Jul 2013 06:43 PM |
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For drying purposes, very little air gap is needed (1/4" is plenty). If you want to remove heat (say for ice dams), then you want lots of space - like 2". |
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Lbear
Veteran Member
Posts:2740
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| 14 Jul 2013 09:48 PM |
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Posted By jonr on 14 Jul 2013 06:43 PM
For drying purposes, very little air gap is needed (1/4" is plenty). If you want to remove heat (say for ice dams), then you want lots of space - like 2".
If you strap/furr out a roof, you typically will need more "bite" in the lumber for whatever material is being applied over it (OSB, etc). A 1/4" piece of lumber will instantly split when you run a screw or nail through it. |
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joeldunn21
New Member
Posts:23
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| 14 Jul 2013 10:33 PM |
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Lbear - I think the lumber yard spec'd out 1x3's for that very reason. I'm going to talk with my SIP supplier to see if they can give me 5" trim detail. Then I can do 2" furring strips without getting too thick for the fascia. |
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Roger R
Basic Member
Posts:131
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| 15 Jul 2013 12:49 AM |
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Lebear,
I have a noise problem as there is a Navy test base a couple islands away from me. Those jets are noisy when they fly over our place - which they do sometimes. Do you think a metal SIP roof would resonate more of that sound than would an OSB SIP roof? |
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Roger R
Basic Member
Posts:131
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| 15 Jul 2013 12:57 AM |
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...another noise transmission question. For my noise problem, would it be better if I furred the SIP roof with those metal sound channels, rather than using a 2X2 wood strip?
Does anybody have a comment to this? |
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Lbear
Veteran Member
Posts:2740
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| 15 Jul 2013 01:48 AM |
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Posted By Roger R on 15 Jul 2013 12:57 AM
...another noise transmission question. For my noise problem, would it be better if I furred the SIP roof with those metal sound channels, rather than using a 2X2 wood strip?
Does anybody have a comment to this?
I think you are confusing the two issues. The EXTERIOR of a WOOD SIP roof should be furred to prevent SIP rot. The INTERIOR of any (wood or metal) SIP roof should have a resilient hat channel design to DECOUPLE the panel and to stop sound transmission into the home. Two different reasons and two different locations of furring; one exterior and one interior. One is for venting and the other is for sound.
Posted By Roger R on 15 Jul 2013 12:49 AM
Lebear,
I have a noise problem as there is a Navy test base a
couple islands away from me. Those jets are noisy when they fly over our
place - which they do sometimes. Do you think a metal SIP roof would
resonate more of that sound than would an OSB SIP roof?
I don't think it matters whether it's a wood SIP or
metal SIP, the SIP noise is due to the monolithic structure of the panel
and how sounds transmit through such materials. The EPS thickness
probably helps to dampen some noise, so a 12" EPS core will deaden
sounds more than a 6" EPS core. Either way you should use a resilient sound deadening hat channel setup for the interior to help stop the noise. |
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Lbear
Veteran Member
Posts:2740
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| 15 Jul 2013 01:50 AM |
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Posted By Roger R on 15 Jul 2013 12:57 AM
...another noise transmission question. For my noise problem, would it be better if I furred the SIP roof with those metal sound channels, rather than using a 2X2 wood strip?
Does anybody have a comment to this?
I think you are confusing the two issues. The EXTERIOR of a WOOD SIP roof should be furred to prevent SIP rot. The INTERIOR of any (wood or metal) SIP roof should have a resilient hat channel design to DECOUPLE the panel and to stop sound transmission into the home. Two different reasons and two different locations of furring; one exterior and one interior. One is for venting and the other is for sound.
Posted By Roger R on 15 Jul 2013 12:49 AM
Lebear,
I have a noise problem as there is a Navy test base a
couple islands away from me. Those jets are noisy when they fly over our
place - which they do sometimes. Do you think a metal SIP roof would
resonate more of that sound than would an OSB SIP roof?
I don't think it matters whether it's a wood SIP or
metal SIP, the SIP noise is due to the monolithic structure of the panel
and how sounds transmit through such materials. The EPS thickness
probably helps to dampen some noise, so a 12" EPS core will deaden
sounds more than a 6" EPS core. Either way you should use a resilient sound deadening hat channel setup for the interior to help stop the noise. This is done with using resilient hat channels with rubber isolators as seen here: Resilient Sound ClipsYou are creating an (1) air space and decoupling the SIP from the drywall by using rubber isolators (2), this stops noise by using those two methods.  Here is an older GBA THREAD on
this exact topic. It is my opinion that resilient decoupled hat
channels are MANDATORY to stop unwanted noise when using SIPs. The above
product when installed correctly can improve sound by 20 STC points or a
8-10 db. drop. |
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jonr
Senior Member
Posts:5341
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| 15 Jul 2013 10:35 AM |
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If you add a clip/channel to a SIP, you may have created the dreaded triple leaf wall (it makes things worse). Some of this is non intuitive - I'd want to see data that specifically tests with SIPs and various combinations of double drywall, high STC drywall, Green Glue, clips/channels and fiberglass fill. With actual STC ratings, not anecdotal results.
Basic summary of here - there is no easy fix, SIP isn't a good choice for noise attenuation. |
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Lbear
Veteran Member
Posts:2740
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| 15 Jul 2013 06:58 PM |
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Posted By jonr on 15 Jul 2013 10:35 AM
If you add a clip/channel to a SIP, you may have created the dreaded triple leaf wall (it makes things worse).
Some of this is non intuitive - I'd want to see data that specifically tests with SIPs and various combinations of double drywall, high STC drywall, Green Glue, clips/channels and fiberglass fill. With actual STC ratings, not anecdotal results.
Basic summary of here - there is no easy fix, SIP isn't a good choice for noise attenuation.
That is why I keep emphasizing that it should be a resilient sound isolation clip in order to decouple the assembly. A standard hat channel is not decoupling it, although it is creating a space for air. If a decoupled clip is used, it will NOT make things worse if properly utilized. Here are actual studies done by Orfield Labs where
they used the clips to achieve a gain of 15 STC points. As mentioned before, the clips will gain you at least 15 - 20 STC points: Soundproofing CompanyFour Elements in SoundproofingA standard 6" SIP will have a rating of around STC 26. If you use a resilient sound clip on the inside to decouple the assembly. Then hang 1/2" or 5/8" drywall, you will bring that rating up to around STC 41 - STC 46. If you add batt insulation you can bump that another 4-5 STC points or STC 45 - STC 50. The fix is quite simple if you plan ahead. In and of itself a SIP is not the perfect sound deadening building material but following some simple design details will make it a very well performing sound proof building method. |
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jonr
Senior Member
Posts:5341
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| 15 Jul 2013 07:17 PM |
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Neither of your links mentions SIPs. Evidently you are taking data from other walls and assuming it will have the same effect on a SIP. Adding another layer can increase sound transmission in some cases and I've yet to see evidence that SIP + clips/channels isn't one of them (although my guess is that it would help some). |
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Lbear
Veteran Member
Posts:2740
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| 16 Jul 2013 12:44 AM |
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Posted By jonr on 15 Jul 2013 07:17 PM
Neither of your links mentions SIPs. Evidently you are taking data from other walls and assuming it will have the same effect on a SIP. Adding another layer can increase sound transmission in some cases and I've yet to see evidence that SIP + clips/channels isn't one of them (although my guess is that it would help some).
I am not assuming anything. A standard 6" SIP with just 1/2" drywall attached directly to it achieves a rating of STC 28/29. Numerous tests were done and this is the standard for a SIP. I've also spoken with sound engineers and adding a decoupled clip to the SIP will increase the STC rating by at least 15 points or a STC 43/44. Here is a SIP study (ASTM E90) showing the STC rating of SIP: SIP Sound Transmission PDF Here is another one showing the STC rating of STC 28/29: R-Control SIPs PDFThe important factor here is that the sound proofing design MUST be done prior to the install of the SIP. Like anything, if you plan ahead, it is much easier and less expensive than retrofitting it later on. Here is a study that showed the decoupling channel works, even when they did it outside (due to occupants living inside and the drywall was already installed). Ideally you don't want to decouple from the outside but from the inside. The study clearly showed that greater STC ratings are possible if the decoupling is done on the inside and not sandwiched on the outside like they did it. Even so, they still achieved a STC 43 rating. Phoenix Labs SIP retrofit PDFSIP buildings do a good job of reducing ambient noise but don’t do so
well with the low frequency sounds. This is easily fixed with decoupling clips and drywall. This will give a STC 43/44 rating which is above a standard insulated wood framed wall. I don't see this being such a big dilemma or problem. Every building technology/material has its pros and cons. Low frequency transmission is the con for SIPs but it can be solved by the above mentioned method. |
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jonr
Senior Member
Posts:5341
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| 16 Jul 2013 11:03 AM |
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Ideally you don't want to decouple from the outside but from the inside. The study clearly showed that greater STC ratings are possible if the decoupling is done on the inside The source side is typically the BETTER place to do noise control and that case study did everything on the outside. Where does it show "that greater STC ratings are possible if the decoupling is done on the inside"? If you add batt insulation you can bump that another 4-5 STC points or STC 45 - STC 50...make it a very well performing sound proof building method. The Phoenix Lab study did add bat insulation and only achieved a STC of 43. Very poor when compared to other upgraded wall designs that actually do achieve STCs in the 50s and even 60s. I'll agree that OSB SIPs plus clips/channels/bats being approximately equal to a standard stud wall sounds about right. |
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Lbear
Veteran Member
Posts:2740
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| 17 Jul 2013 02:38 AM |
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Posted By jonr on 16 Jul 2013 11:03 AM
Ideally you don't want to decouple from the outside but from the inside. The study clearly showed that greater STC ratings are possible if the decoupling is done on the inside
The source side is typically the BETTER place to do noise control and that case study did everything on the outside. Where does it show "that greater STC ratings are possible if the decoupling is done on the inside"?
"the resilient channel is “sandwiched” between two layers of OSB. With more traditional gypsum board applications, “sandwiching” resilient channel is strongly discouraged. This configuration restricts the resilient channel, negating its effectiveness may produce unfavorable resonances in the system. In instances where resilient channel is “sandwiched”, the installation of fiberglass batt between the channels is also uncommon."
So in essence the sandwiching on the outside was done for drainage plane reasons, not for resonance or soundproofing. The sandwiching had a negative effect on the STC numbers. Even so, they achieved the STC 43 rating. If the resilient channel was done on the interior, it would not have been sandwiched and the STC numbers would have been higher, as it would allow the resilient channel to work effectively as it should.
Posted By jonr on 16 Jul 2013 11:03 AM
The Phoenix Lab study did add bat insulation and only
achieved a STC of 43. Very poor when compared to other upgraded wall
designs that actually do achieve STCs in the 50s and even 60s.
I'll agree that OSB SIPs plus clips/channels/bats being approximately equal to a standard stud wall sounds about right.
A typical insulated exterior wood frame wall achieves a STC 36 rating. An ICF wall (6" concrete core) achieves a STC 50 rating. So to have a roof assembly achieve a STC 43 rating. I wouldn't call that "very poor" by any means.
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jonr
Senior Member
Posts:5341
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| 17 Jul 2013 08:36 AM |
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> If the resilient channel was done on the interior, it would not have been sandwiched
OSB, channel, drywall = sandwich |
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Lbear
Veteran Member
Posts:2740
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| 18 Jul 2013 06:00 PM |
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Posted By jonr on 17 Jul 2013 08:36 AM
> If the resilient channel was done on the interior, it would not have been sandwiched
OSB, channel, drywall = sandwich
According to the engineer I spoke to, you are incorrect. He said that with a SIP, 3" channel, R13 fiberglass batt, and 5/8" drywall, it would not be a "sandwich" and that it would be around a STC 50. I don't disagree with you in that a SIP without a decoupled channel/air space is a bad sound insulator. This is indisputable since the STC ratings of a SIP is around STC 28, which is pretty bad. Where I (along with the engineers I spoke to) disagree with you is in methods on how to fix the sound issues with simple channel decoupling, fiberglass batts, and drywall. Once that is done you are around a STC 45-50 or higher. Problem solved. |
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