I am planning to install solar panels on a house to be built in NE Georgia.  The house, including the roof, will be built of Structural Concrete Insulated Panels.  I am trying to figure out the best way to install solar panels on the concrete roof.  The pitch is 1:12 and we are not planning to tilt the panels.  The concrete roof will be treated with a penetrating sealer then sealed.  My tentative plans are to drill into the concrete to place bolts/screws after the roof is treated and sealed.  Bolts would be run through an EPDM gasket material and the racks installed.  Then a second coat of the waterproof sealant would be applied to seal the bolts, gaskets and points where the rack touches the roof.

Is this the best way to go about this?  Any comments or suggestions would be greatly appreciated!

R

Exposed metal/concrete interfaces are difficult to seal against water intrusion.

Who's SCIP panel what type of foam core density? What do you mean you are not tilting the panels? How thick gunite?

This is just a guess - drill a hole in the concrete, fill with epoxy, then drop in a stainless steel or galvanized bolt. Similar to how vertical rebar is put into a slab to attach SCIP walls.

Keep us posted - there is a lack of information on SCIPs and concrete roofs.

We are planning on using panels and mortar from Gulf Concrete Technology.  Now that I look at the responses it seems like the solution is clear.

The roof panels will be the PSG panels, which have longitudinal pockets for concrete and rebar.  There is a picture of them here, listed as floor panels:  http://67.205.102.169/~trabajos/gulf/index.php/panels

The solution is to drill into the area of the roof where the concrete 'ribs' are and use epoxy to affix bolts.

Why not use the type of bolts that do not need epoxy?

Alton: Good question!! I need to do a little more research.

I'd be concerned that a hole not filled with epoxy would collect water and crack the concrete when it froze. But perhaps the right combination of gaskets and sealant would prevent that.

Jonr, You made some good points there. My hesitation in using epoxy is that in the cases where I have used epoxy, I meant for it to be permanent. I wonder if a bolt can be removed easily if set in epoxy. I am all for using epoxy if the bolt can be removed without twisting it into. I think a self-sealing membrane under the bolt head should prevent water from entering the hole.

If you're using epoxy, drop the head of the bolt into the hole, then use a nut and washer to hold the racking down.

Why not just have the factory imbed fasteners in the concrete when they make the panels?

void.........

You need to do a static and dynamic load and stress analysis. If you get the dead weight.. width and length per solar panel, diameter of the bolts going through mortar and quantity, and the compression rating of GCT shotcrete and mortar thickness I'll show you how. Need your snow loads and max wind speeds too.

More I think of it you should ask GCT. I have their structures engineers # at home so ....they should have done the engineering and test. I have seen bonded bored threaded cres inserts installed to get the bearing area up, it just depends on your live and dead loads. 1:12 is going to put alot of bearing compression on the mortar skin and foam will do little, you may need more portland cement in those areas added to the mix. This is not a question to ask a forum if you want it done right, we don't have the facts you need for a proper answer.

You don't have to pay or ship in their mortar either there is plenty of data to pass code out there. Just get with a local gunnite pro and get some mix with the proper amount of portland cement or fly ash. The steel reinforced portland cement binder provides the strength for your panels and is the primary structural stressed skin membrane to take loads from the roof to the foundation. You need to be careful adding holes to primary structure, since mortar does not do well in tension or from uplift loads due to winds it is the bigger concern. Some helix fibers here might be a good idea.

I don't know if you are designing solar passive, if so thicken up the inner skin and thin down the outer to gain more mass effect. For example, 1.5" in, 2.5 " out or if you can afford it 4" in 2" out) ORNL showed an energy savings on the latter in your climate zone( see their mass calculator). This just means the inner skin will take more load. This design is superior to ICF ORNL also proved, I don't know why it is not more popular other than finding and training a gunite trade but GCT can help with that. The roof and walls are true monolithic with continuous load paths by the skins with a better thermal bridge foam core than ICF that also does not expose toxic foams to IAQ. Further, in a sandwich structure like ICF and SCIP the center or neutral axis is where the loads are zero-neutral from bending that cause surface tension cracks. Having rebar at this location as in ICF makes little sense, having it in a steel lath mesh and steal vs plastic lateral W-truss configurations as in SCIP makes better sense. Also, the SCIP ductile core provides shock dampening in seismic zones that again keep tension loads away from the skins when buckling.

If GCT is a dead end get me the info. The other option and perhaps the best if you have the room is a ground pod.

Please take some pics and post us on the build. I'd like to see the transition from the roof to the walls. There you want good a steel tie and lateral load paths close by through trusses.

Posted By krom on 25 Jun 2014 07:01 PM
If you're using epoxy, drop the head of the bolt into the hole, then use a nut and washer to hold the racking down.

Why not just have the factory imbed fasteners in the concrete when they make the panels?

Not a good idea with the bolt head and because you would need a floating nut to account for the panel hole tolerances which is not that great in tension, possible but needs a PE stamp. Floating nuts are good for none structural applications. Epoxy in this stack up is non structural. If this were steal and we were installing a heli-coil or fastening a 'structural' rated floating nut plate that be more structural.

No GCT and SCIP use gunite sprayed on a steel metal wire mesh skins laterally attached with 14-16 gage wire zip ties to W-trusses that span from inside skin to outside skin, you can get shapes and spans and pitches you can not with PSG due to lite weight and foam flexure here: http://server3.anexowebhost3.net/~trabajos/gulf/index.php/panels/advantages

Primary load is taken through the steel infrastructure for code approval. The mortar is secondary structure to carry skin loads and air seal. The compression strength for bearing bolts of gunite can yield the same as PSG depending on the amount of binder, the trick is not loosing alot to the ground and have a good guniter. The strength can match PSG, if you add fibers you can get better ballistic proof same as PSG. If you add fibers you open your nozzle up on the hopper.

Here is an entertaining description of trying to get an epoxy embedded bolt out of concrete (but he only went to 4000 pounds). See here for how to design for a bond that will exceed the strength of the bolt.

From another source:

Mechanical anchors require greater spacings and edge distances because of the lateral pressure placed on the drill hole due to anchor expansion. This expansion pressure is reduced with epoxy anchor systems.

Jonr, that is a limited static tensile test in controlled environments. We are in a roof application subject to temperature and pressure fatigue cycles, expansion and contraction, where the bond to the concrete and bolt can fail. Any adhesive bond needs a third party test subjecting the bond to these conditions and GCT mortar/foam or you run the risk of failure over time. Get with GCT use similar binders vs epoxy, they should have the info. Yes, 'the expansion pressures can be reduced" with epoxy since you drill a larger hole to get it in, IF the bond lines hold up which is based on testing for shear, tensile, and fatigue properties. With those allowables the PE can take the actual loads of the installation and size the diameter and quantity of fasteners, or change the hole to a larger one filled with mortar to distribute load to a larger bearing area.

SCIP purchases supports jobs in Mexico build your own goggle u-tube for tooling. You will shoot your kids future in the foot buying foreign.

If you need help PM me you do not need them. Utube tooling shows you how to build the simple panels in a easy assembly jig you weld in your garage, you hire local kids to do that the test results for code are all over the internet.

OP I would encourage you to cancel your order and make your own.