Frequently Asked Questions

What are SIPs?

A structural insulated panel is a sandwich — two sheets of structural-rated OSB with a rigid foam core bonded between them. Structure and insulation in one piece. They replace conventional stud framing, fiberglass insulation, and exterior sheathing with a single factory-built panel that shows up to your jobsite pre-cut and ready to assemble.

How much faster can I build with SIPs?

A SIP shell goes up in days, not weeks. A BASF time-motion study showed a 55% reduction in on-site framing labor compared to stick framing. Panels arrive ready to install — no measuring, cutting studs, insulating, and sheathing as separate steps.

One crew, one process, dried in fast."

Are SIPs Really Stronger?

SIPs work like a steel I-beam — the OSB faces act as the flanges and the foam core is the web. That's an inherently strong design, and it's why SIP structures perform so well in high wind, seismic, and heavy snow load conditions.

The actual ratings on your building depend on the engineering — panel configuration, opening sizes and locations, shear wall design, connections, and your local load requirements.

That's why every Apex project is engineered by a licensed PE for your specific build. We don't hand you a generic rating and wish you luck. We engineer the building to handle what your site is going to throw at it

How do I size HVAC ?

Smaller than you think. That's the whole point of a tight envelope — when the building isn't leaking energy everywhere, you don't need an oversized system to keep up. Work with an HVAC professional who understands SIP construction and will run a proper Manual J calculation. An oversized system in a SIP home will short-cycle, waste energy, and wear out faster

How does ventilation work in a SIP Building?

SIP buildings are extremely airtight — well under 3 air changes per hour at 50 Pascals, which is dramatically tighter than conventional stick framing. That's a good thing, but it means you need mechanical ventilation to bring in fresh air and exhaust stale air on a controlled basis.

Here's what most people don't realize — that's actually healthier than a leaky house. In a stick-framed home, your 'ventilation' is just uncontrolled air leaking through gaps in the framing, bringing dust, pollen, humidity, and whatever else is outside along with it. In a SIP home, all incoming air goes through your ventilation system, where it can be filtered and dehumidified. You control what comes in. That means less mold, fewer allergens, and more comfortable humidity levels year round.

A good HVAC contractor who understands tight-envelope construction will spec the right ventilation system for your build. This isn't optional — it's part of building it right.

What about Fire Safety?

SIPs are a wood-frame building system, and they follow the same fire code requirements as any other wood-frame construction. Residential code requires half-inch drywall on the interior — that's your thermal barrier, and it applies to SIP walls the same way it applies to stick-framed walls. Once the drywall is on, you've met the requirement.

For commercial or multi-use buildings, one-hour fire-rated assemblies are available and tested to ASTM E 119 standards. Your local jurisdiction determines what's required, and our engineering accounts for it.

How are Electrical wiring and fixtures installed?

Electrical chases are cut into the foam core during manufacturing based on your electrical plan. When your electrician shows up, the pathways are already there — they pull wire through the chases the same way they'd run wire through any wall, except they're not spending half the day drilling through studs.

That's why it's important to have your electrical layout figured out before we manufacture your panels. We cut the chases to match your plan so everything lines up when it's time to wire. Outlet locations, switch boxes, fixture runs — all of that gets accounted for in the panel design. If something needs to change on site, minor modifications can be made, but the more complete your electrical plan is up front, the smoother that phase goes."

Does a SIP building roof need to be ventilated?

No, not in the way you're used to thinking about it. In a conventional stick-framed house, you ventilate the attic because the insulation is on the ceiling and the attic is unconditioned space. With a SIP roof, there is no attic in that sense — the insulation is in the roof panels themselves, and everything under the roof is conditioned space. That's one of the big advantages of a SIP roof. No wasted attic space, no soffit vents, no ridge vent trying to manage moisture in a dead air space above your ceiling.

Some builders choose to add a ventilated air gap between the SIP roof and the roofing material — that's called a cold roof, and it's a best practice for long-term durability, especially in heavy snow load areas or hot climates. It's not required, but it's a smart upgrade if the budget allows for it. We can engineer either approach depending on your project and your climate."

Are SIPs code approved?

Yes. SIP construction is recognized by the International Code Council and specifically addressed in Section R610 of the International Residential Code. For applications beyond the scope of R610 — which includes most custom designs, commercial projects, and anything in high wind or seismic zones — an engineered design is required. That's standard practice for us. Every Apex project is engineered and sealed by a licensed PE regardless of whether your jurisdiction requires it.

Here's the thing most people don't think about. In much of rural America, there are no required building inspections. Nobody shows up to check whether your stick-framed house was built right. The only accountability is whoever swung the hammer. Our engineering doesn't depend on an inspector showing up — the accountability is built into the design before the first panel goes on the truck.

How are SIPs supported, are there studs in the panels?

No, and that's the point. A SIP panel is structurally self-sufficient — the two OSB faces and the foam core work together like a steel I-beam. The OSB is the flange, the foam is the web. That design carries the load without studs every 16 inches, which is why there's no thermal bridging in a SIP wall.

Where you do see lumber in SIPs is at the connections — panel edges, corners, window and door openings, and where the roof meets the wall. Those are engineered connection points using dimensional lumber or insulated splines, and they're part of the panel design. But the field of the wall is solid panel, no studs. That's what makes the insulation continuous and the envelope airtight

How Much do SIPs Cost?

This is the question everybody asks first, and it's the wrong question — not because cost doesn't matter, but because the comparison people try to make doesn't work. You can't compare the price of a SIP panel package to a pile of lumber and think you're looking at the same thing. You're not. You're comparing a complete building system to one ingredient in a long, expensive recipe.

Here's what the real cost comparison looks like when you account for everything:

Your framing labor drops by more than half. A SIP shell goes up in days with a smaller crew. That's fewer labor hours on your payroll and fewer days on your construction schedule. And a shorter schedule means less money spent carrying a construction loan — every week you shave off that timeline is real money back in your pocket.

Your insulation cost disappears. It's already in the panel. No separate insulation subcontractor, no scheduling delays waiting for the spray foam crew, no failed inspections because the batts weren't installed right.

Your HVAC system gets smaller. When the envelope is airtight and the insulation is continuous, you don't need an oversized system to compensate for a leaky building. That's a smaller equipment cost on day one and lower energy bills every single month for the life of the building.

Your building subs love you. The shell is dried in fast, the interior is comfortable, and the walls are straight and plumb because they were manufactured that way. Electricians, plumbers, drywall crews — they all work faster and better inside a SIP building because the structure is square and the environment is controlled.

Your jobsite waste practically vanishes. Factory-cut panels mean almost nothing goes in the dumpster. Compare that to the overflowing roll-off at any stick-framed subdivision and you'll see the difference.

And then there's the part that keeps paying you back forever. A SIP home is 50% more energy efficient than conventional framing. That's not for the first year — that's for the lifetime of the building. Every month, every summer, every winter, the homeowner is spending less to heat and cool a house that's more comfortable than what their neighbors are living in.

So when someone says SIPs are too expensive, what they're really saying is they haven't done the math yet.

Call us with your plans and we'll put the real numbers in front of you. 918-984-1717