SIP construction: considered single leaf or double leaf??

I have recently had a SIPs (structural insulated panel) building put up behind my garage. Quick to put up (4 days complete), wonderful insulating properties, not so good for airborn and impact noise isolation. SIPs are panels of 1/2" pressure-laminating Oriented Strand Board (OSB) plywood with a solid core 'sandwich' of Expanded Polystyrene (EPS) foam using an industrial grade adhesive. The density of the EPS is 1 Lb/cf. So, would a SIP panel be considered a single leaf? Or a double leaf? I want to use this as a single room mixing/recording space (mostly acoustic, non - Led Zep level sounds). I have planned on building a room-within-a room using 2x4 framing and 2 layers of 5/8" sheetrock with GreenGlue between layers on new walls and new ceiling with pink insulation in the 4 inch air space between walls. Before I spend the significant amount of money (for me!) on the room-within-a room I want to make sure I'm not wasting $$ if the SIP panel is considered a double leaf. In that case I would just add 3-4 layers of 5/8" sheetrock to the interior OSB sheathing on the walls and 2 layers on the ceiling with GreenGlue in between each layer. The current interior dimensions are 28ft x 19ft. Walls are 9ft. The interior cathedral ceiling height at the ridge beam is 14.5ft The floor and roof are 10.25 inch thick SIPs and the walls are 6.5 inch SIPs. For the floor, to minimize impact noise transmission I am planning on applying a 3/8" and 1/2" plywood with GreenGlue between each layer and apply cork for the finished flooring. For exterior door reasons I need to stay within 1.125" from the current subfloor therefore am limited to the plywood dimensions. I have read Rod's book (Wonderfully helpful - only wish I had come upon it sooner - nice work Rod. Thank you so much...) HVAC will be a Mitsubishi 'Mr. Slim' ductless unit and either a Mitsubishi or Fantech ERV unit for fresh air. The ERV unit will be located in the adjoining garage to minimize noise. (What is the difference between an ERV and a HRV? Even HVAC people can't give me a consistent answer. They both appear to exchange heat and moisture.)

Welcome! Edit: Deleted some stuff I wrote that was based on ignorance. ;-)

Jeff Chitouras wrote:

What is the difference between an ERV and a HRV? Even HVAC people can't give me a consistent answer. They both appear to exchange heat and moisture.

HRV stands for Heat Recovery Ventilator, whereas ERV stands for Energy Recovery Ventilator. According to Fantech: "HRV's are usually recommended for colder climates with longer heating seasons. ERV's are used for warmer more humid climates with long cooling seasons." According to the map on this page of Fantech's site, you're right on the cusp between "HRV Recommended" and "ERV w/ Defrost Recommended." A note indicates: "When installing ERVs (in ERV areas according to the map), and the outdoor temperature falls below 23°F (-5°C) for more than 2 consecutive days, it is recommended that a defrost option be installed on the equipment." --Keith :mrgreen:

Jeff Chitouras wrote:

I have recently had a SIPs (structural insulated panel) building put up behind my garage. Quick to put up (4 days complete), wonderful insulating properties, not so good for airborn and impact noise isolation. SIPs are panels of 1/2" pressure-laminating Oriented Strand Board (OSB) plywood with a solid core 'sandwich' of Expanded Polystyrene (EPS) foam using an industrial grade adhesive. The density of the EPS is 1 Lb/cf. So, would a SIP panel be considered a single leaf? Or a double leaf?

An SIP is a single leaf........ you might want to add some mass to that inside face before constructing your inner room.

HVAC will be a Mitsubishi 'Mr. Slim' ductless unit and either a Mitsubishi or Fantech ERV unit for fresh air. The ERV unit will be located in the adjoining garage to minimize noise. (What is the difference between an ERV and a HRV? Even HVAC people can't give me a consistent answer. They both appear to exchange heat and moisture.)

Not quite, An ERV is an Energy Recovery Ventilator......... they generally work with a dissicant system to dehumidify fresh air coming into the building - although they really aren't considered dehumidifiers. What they do is transfer moisture from the humid air stream (incoming outdoor air in the summer) to the exhaust air stream. They (therefor) lower energy costs because your air conditioning does not have as great a latent heat load. Less latent heat load equals less run time for the compressor equals lower energy costs. A HRV is a Heat Recovery Generator - they use a heat exchanger to capture the heat or cold as the case might be) from exhaust air that would normally be lost to the outside world. They generally have a double sided chamber in contact with the coil - and thus can cool incoming air (in the summertime) or heat incoming air (in the winter time) to recapture what would be lost. An HRV does NOT dehumidify air - although it will (slightly) affect humidity levels by adjusting relative humidity (slightly less RH in the warmed winter air - slightly greater RH in the cooled summer air). They are 2 totally different animals working in a totally different manner. I hope that helped. Sincerely, Rod

sharward wrote:

It appears you have those panels on each side of your frames. Therefore, you have a two leaf system right now. Adding another wall frame on the inside and applying drywall to it would make a three leaf system (not good). Is there a reason you covered the outer leaf frames on the inside faces? Ideally you would have left the frames open on the inside and then framed inner leaf walls and ceiling isolated from the outer leaf framing. :roll:

Keith, there is no frame - there is only the single leaf panel making up the wall - ceiling and floor assemblies. The foam is sandwiched between the 2 panels. No air between what so ever. Sincerely, Rod

OK, I got it now. I thought those panels were two layers, but after more careful reading I see that they are three layers -- OSB, EPS, and OSB. So, there are no studs in those walls? :shock: How can that be? :? Edit: I just looked it up and I get it now. "Structural insulated panel to panel and SIP to deck connections usually require the recessing of a dimensional member, like a 2-inch by 4-inch stud, into the edge of the SIP. These edge studs are adhered to the foam and then the overlapping OSB of the panel surface is face nailed to the inset stud. This solid wood edge band then becomes the nail surface for attachment to other panels, decks, and floor assemblies. Alternatively, connections at vertical panel edges can incorporate an OSB spline rather than a wood stud as the connector. Gutter spikes and long screws provide the connections at corner intersections." (Source) Neat! 8) --Keith :mrgreen:

Thanks for such quick responses. This is a wonderful resource. "Structural insulated panel to panel and SIP to deck connections usually require the recessing of a dimensional member, like a 2-inch by 4-inch stud, into the edge of the SIP. These edge studs are adhered to the foam and then the overlapping OSB of the panel surface is face nailed to the inset stud. This solid wood edge band then becomes the nail surface for attachment to other panels, decks, and floor assemblies. Alternatively, connections at vertical panel edges can incorporate an OSB spline rather than a wood stud as the connector. Gutter spikes and long screws provide the connections at corner intersections." My SIP structure (panels are 4 ft wide x whatever length you require up to 24ft) has two 4" splines running down each exterior side of a panel that interlock with the next panel. For the SIP floor panels (10.25" thick) I have 2x10s imbedded into each side of each panel, rather than the splines. This means there is effectively a 4x10 "floor joist" running every 4 ft across the width of the structure.

Got pictures of the construction taking place? It would be really cool to see that from the inside out. ;-)

Thanks Rod for your comments (and clarification ERV vs HRV). I now plan on putting 5/8" on the interior OSB sheathing. Would you suggest using GreenGlue between these two surfaces or can I "get away" with screwing to sheathing and using acoustic caulk on the seams?

How about... All of the above? ;-) You'd then only have one leaf though. You'd need a second leaf. --Keith :mrgreen:

I wasn't clear. I still plan on building a room within a room with 2 layers of 5/8" (GreenGlue between layers) for the interior wall creating a 4" air space (filled with fiberglass insulation) between it and the exterior SIP wall. My question is whether it is a waste of $$ to use GreenGlue between the additional layer of 5/8" I now plan on adding to the interior OSB sheathing (exterior wall)? - Re: Rod's comment: "you might want to add some mass to that inside face before constructing your inner room." By the way Keith, reading your studio building thread has saved me quite a bit of research. Appreciate it.

Jeff Chitouras wrote:

My question is whether it is a waste of $$ to use GreenGlue between the additional layer of 5/8" I now plan on adding to the interior OSB sheathing (exterior wall)? - Re: Rod's comment: "you might want to add some mass to that inside face before constructing your inner room."

Jeff, Seeing as you have (for all intent and purpose) basically no mass in the existing outside leaf, And Seeing as 2 layers of 5/8" drywall with GreenGlue gives you (for all intent and purpose) the isolating value of 4 layers of drywall - My answer would be - "No it is not a waste of money to use GreenGlue between 2 layers of drywall on the inside face of the exterior panel." Sincerely, Rod