Posted By HVAC-Engineer on 24 Jun 2013 09:11 AM
I like the idea of peel-and-stick membrane. I assume it would cut some construction times.

Lbear - On this detail, would the membrane go over the top plate to the interior side of the inner EPS and then down the side of the exterior? With The SIP, can you just put roofing directly on top (with proper moisture protection) or would you need an air space for venting? If you're not going to do an attic space and it is conditioned I mean to say. The R-value should be sufficient enough with 12" (48-60) right? I'm just not too familiar with how roof construction changes when you are doing a conditioned space directly underneath (no attic).

The S&P membrane would go over the wood to plate and over the exterior facing EPS and then transition down vertically onto the exterior ICF/EPS wall for a few inches. That's at least my current idea.

If you are using Steel SIPs you don't need an air space for venting. If you are using Wood SIPs, yes, you will need to furr out the roof to allow for venting between the wood SIP and finished roof. If you don't vent a wood SIP roof, you can end up with SIP rot, which has been documented by many studies and the Building Science Journal. It would mostly rear it's ugly head in moisture laden climates but over time can also show up in dry climates.

A 12" SIP with Type 2 EPS should give you a R-48/R-50. Once you use an interior hat channel 1" space with 1/2" of sheet rock on top of that, that will give you another R1/R2 on top of the R48/R50. So you are looking at R50/R52 once all is said and done. If you wanted a higher roof R Value you can use a deeper hat channel cavity and install R13 fiberglass batts and then finish it off with 1/2" sheet rock and you will be in the R60 range.

Posted By HVAC-Engineer on 24 Jun 2013 01:55 PM
Futhermore on roof construction, what do you build to fasten the SIPs to? I've seen a few threads stating you don't necessarily need a truss system but I can't wrap my head around it. I know houses have cathedral ceilings and say I want to have a finished, conditioned space directly under the roof (like a finished attic) how would you build the frame to support the SIPs? *whew* so much to consider when building a house

One part of the SIP attaches to the wall of the home. The other end would attach to a ridge beam at the high point of the roof. The SIP is structural and a steel SIP can span for like 25 feet between attachment points. Wood SIPs need more support and and attachment points vs a steel SIP.

I may be wrong, but I would suggest using open cell foam instead of fiberglass.  The open cell foam would fill the cavity completely.  Open cell foam can be easily trimmed flush with the hat channels.  Yes, open cell foam will cost more than fiberglass but I think it would save more energy.

Posted By Alton on 25 Jun 2013 12:00 PM
I may be wrong, but I would suggest using open cell foam instead of fiberglass.  The open cell foam would fill the cavity completely.  Open cell foam can be easily trimmed flush with the hat channels.  Yes, open cell foam will cost more than fiberglass but I think it would save more energy.

Open/closed cell out in my area is ridiculously expensive and with a R-52/R-57 ceiling I am above code (R48). I will probably leave it at R-52/R-57 but if I choose to go higher, the fiberglass batts are very inexpensive and a DIY job. Plus it allows me to easily run wiring in the cavity by just running the Romex above the fiberglass batt.

At R-52/R-57 I am above what most homes are out there (usually R40) and with the Fiberglass Batts, I would be in the mid R-60 range, especially since there is no thermal bridging and the batts are on the interior portion of the SIP roof.

Lbear,

I hear you.

In my area, for the last few years, we have a new type of insulation that is made from cotton scraps left over from making blue jeans.  http://www.bondedlogic.com/construc...insulation  According to this site, it is also available in the West.  No fiberglass itching with cotton.  Just sharing - not selling.

Posted By Alton on 27 Jun 2013 07:15 PM
Lbear,

I hear you.

In my area, for the last few years, we have a new type of insulation that is made from cotton scraps left over from making blue jeans.  http://www.bondedlogic.com/construc...insulation  According to this site, it is also available in the West.  No fiberglass itching with cotton.  Just sharing - not selling.

Another option is Roxul Wool Batts. They sell them at Lowe's and carry an R-15 value. They don't absorb moisture, are not itchy, much better sound absorption than fiberglass, and have a fire rating of 2,100F.

Stone Wool Batts

One package for $50 covers 60 square feet of wall/ceiling area. With the wool batts and the 12" Type 2 EPS Steel SIP, one is looking at a R65/R67 roof assembly for summer (70F +) and in the winter one is well over R70 (40F and colder).

With the Federal Tax Rebates, you can get $5.00 off per package, which bring it down to $45 per package.

Ok you guys are going to have to educate me a little bit. I understand what hat channels are (I refer to them as furrings), but let me see if I have the construction method down. You're saying once the SIPs are fastened, go in on the underside and attach furrings directly to the SIPs 16" or 24" OC (depending on batt width)? Now I'm assuming you fasten them running vertically(sort of) up towards the ridge beam, but then do you simply use that wire to hold the batts in place? I apologize for not being up on terminology.

Posted By HVAC-Engineer on 28 Jun 2013 11:40 AM
Ok you guys are going to have to educate me a little bit. I understand what hat channels are (I refer to them as furrings), but let me see if I have the construction method down. You're saying once the SIPs are fastened, go in on the underside and attach furrings directly to the SIPs 16" or 24" OC (depending on batt width)? Now I'm assuming you fasten them running vertically(sort of) up towards the ridge beam, but then do you simply use that wire to hold the batts in place? I apologize for not being up on terminology.

The furring hat channels should be installed as per the manufacturer recommendations and for the drywall loads. The batt insulation can always be cut to size. Also, the batt insulation is not necessary unless you want higher R-Values.



Here is the company that sells really good metal decoupled hat channels:

Steel Hat Channels

Typical Hi-Hat installation on SIP ceiling / walls .................

Posted By cmkavala on 28 Jun 2013 05:42 PM
Typical Hi-Hat installation on SIP ceiling / walls .................

Chris, are those 12" oc? How deep are those channels?

Posted By Lbear on 28 Jun 2013 11:41 PM

Posted By cmkavala on 28 Jun 2013 05:42 PM
Typical Hi-Hat installation on SIP ceiling / walls .................

Chris, are those 12" oc? How deep are those channels?

1-1/2" on walls and 7/8" on ceiling , both @ 24" o.c.
steel RC-1 channel works better for de-coupling and "Z" furring works better for adding insulation

If you want to create a gap to fill with insulation, it seems to me that foam furring would perform (thermally) a lot better than steel.

I would consider dense pack or wet sprayed cellulose over fiberglass bats. But it is less DIY.

Posted By jonr on 29 Jun 2013 10:01 AM
If you want to create a gap to fill with insulation, it seems to me that foam furring would perform (thermally) a lot better than steel.

I would consider dense pack or wet sprayed cellulose over fiberglass bats. But it is less DIY.

just laminate foam sheets and use longer screws to attach drywall

I'm really sold on the steel SIPs for structure and thermal performance. When it comes to roofing, I assume you'd be able to put down any type you'd want. Asphalt shingles are most common in my area. How would you do this? Would you simply nail down your moisture barrier (tar paper) and then nail your shingles onto that as in standard construction?

Let's go further. If I wanted more insulation, instead of doing the fiberglass on the inside what if I did 1"-2" of XPS on the outside? Would this be feasible? I assume I could simply glue the XPS to the steel, but how would I attach the roofing? It seems I would need to place a layer of sheathing to the XPS for strength and then apply my roofing in the standard fashion?

What do you experts think about both of my approaches?

Posted By HVAC-Engineer on 02 Jul 2013 08:58 AM
I'm really sold on the steel SIPs for structure and thermal performance. When it comes to roofing, I assume you'd be able to put down any type you'd want. Asphalt shingles are most common in my area. How would you do this? Would you simply nail down your moisture barrier (tar paper) and then nail your shingles onto that as in standard construction?

Let's go further. If I wanted more insulation, instead of doing the fiberglass on the inside what if I did 1"-2" of XPS on the outside? Would this be feasible? I assume I could simply glue the XPS to the steel, but how would I attach the roofing? It seems I would need to place a layer of sheathing to the XPS for strength and then apply my roofing in the standard fashion?

What do you experts think about both of my approaches?

Any roofing can be used , I have shingles on my own personal home , any attachment is with screws, wafer head screws for shingles

instead of doing the fiberglass on the inside what if I did 1"-2" of XPS on the outside?

Sure, but you can't beat the price per R value of fiberglass or cellulose. EPS is next, XPS or polyiso is more. Plus, loose fill is beneficial for sound blocking.

I may be mistaken, but it looks like they're not putting down any underlayment. Is that possible with steel SIPs?

By the way thanks for the pics. They are really helpful. Chris, are you a rep or a dealer?

Posted By HVAC-Engineer on 02 Jul 2013 09:59 AM
I may be mistaken, but it looks like they're not putting down any underlayment. Is that possible with steel SIPs?

By the way thanks for the pics. They are really helpful. Chris, are you a rep or a dealer?

HVAC-Engineer,
If the panels are watertight as in this roof, then shingles are for cosmetic puposes only.
if the roof has a valley, then I would recommend an underlayment
I have 2 companies - Marquis Const. for supply and installation of steel SIPs and SIP Supply Inc. (Florida) where we sell steel SIP packages to other builders/ owners in the US and Caribbean

John, I suppose you're right. You would have to install hat channels anyway for the drywall right? Or can drywall be directly fastened to the SIP as well?

Chris, you wouldn't happen to deal in the OKC area would you? Or know anybody reputable SIP dealers in the area?

Posted By HVAC-Engineer on 02 Jul 2013 11:15 AM
John, I suppose you're right. You would have to install hat channels anyway for the drywall right? Or can drywall be directly fastened to the SIP as well?

Chris, you wouldn't happen to deal in the OKC area would you? Or know anybody reputable SIP dealers in the area?

HVAC-Engineer,
the closest steel SIP manufacturers are in the Atlanta area.