What makes a home high-efficiency?
A short course in modern building science: ACH50, the four control layers, HRV/ERV filtration, continuous insulation, and why most custom homes still get it wrong.
Most custom homes get the big stuff right and the details wrong.
Square footage, finishes, and curb appeal are easy to evaluate. Building performance — the things you can’t see once the drywall is up — is where most custom homes fall short. The wall section, the air barrier, the flashing details, the load calculation. The things that decide whether your house is comfortable, durable, healthy, and cheap to operate for the next fifty years.
Lenders rarely ask about it. Inspectors check for code minimums and move on. Homeowners usually find out about it the first winter the windows fog, the second summer the upstairs is hot, or the year a leak shows up at a window head where the flashing was wrong. We talk about it on day one because the cost of doing it right is small. The cost of doing it wrong is everything that comes after.
“If you can’t see it from the curb, it usually doesn’t get sold. We sell it because it’s where the value lives.”
Water. Air. Vapor. Thermal. In that order.
Joseph Lstiburek’s “Four Control Layers” is the framework every Jacinto Built wall, roof, and floor assembly is built around. The order matters: water first, because nothing else matters if water gets behind the cladding. Air next, because air leakage drives most moisture problems and most energy waste. Vapor third, because in our coastal climate walls need to dry in both directions. Thermal last, because insulation only does its job if the other three are right.
Water
The outermost layer. Weather-resistive barriers, rain screens, pan flashing, head flashing, kick-out flashing, through-wall flashing — all detailed so bulk water drains outside, where it belongs. Most leaks happen at transitions, not in the middle of a wall, so we obsess over transitions.
Air
A continuous airtight layer — taped ZIP System sheathing on the exterior, airtight drywall on the interior. We test every home with a blower door before drywall and again at final, and we share the result with the homeowner. That’s non-negotiable.
Vapor
Coastal San Diego is a mixed-humid climate. Walls need to dry in both directions. We use smart vapor retarders (INTELLO Plus or equivalent) on the interior — closed in winter, open in summer — so moisture never gets trapped.
Thermal
Continuous exterior insulation wraps the whole building envelope, eliminating thermal bridging through studs and headers. A cavity full of R-21 batts without exterior insulation delivers maybe R-13 real-world. We build to effective R-values, not catalog numbers.
If you can’t measure it, you didn’t build it.
We test every home with a calibrated blower door — once before drywall, when leaks are still cheap to fix, and once at final, to verify the finished result. The number we target is 1.5 to 2.0 ACH50 (Air Changes per Hour at 50 Pascals of pressure). For reference: California code is 3.0 to 5.0, the average new tract home is 5 to 15, and Passive House is 0.6.
We hand the homeowner the test results at handoff. If we miss our number, we keep working until we don’t.
- Calibrated blower door, pre-drywall and final
- Taped ZIP System air barrier on the exterior
- Continuous airtight detailing at penetrations and transitions
- Documented test result delivered with the keys
Lower is tighter. We test with a calibrated blower door before drywall and again at final, then hand the homeowner the report.
Build tight. Ventilate right.
A tight house needs a deliberate ventilation strategy — that’s the trade. Every Jacinto Built home gets a balanced heat or energy recovery ventilator (HRV/ERV) that delivers continuously filtered outdoor air to bedrooms and living spaces while exhausting stale air from baths, kitchens, and laundry rooms. We spec brands like Zehnder and Panasonic Intelli-Balance because they’re quiet, energy-efficient, and designed for residential use.
Filter rating is MERV 13 minimum. In wildfire season we move our own homes to MERV 16, which captures PM2.5 down to smoke particle size. Better-than-outdoor air, every day of the year.
- Balanced supply + exhaust, room by room
- MERV 13+ filtration (MERV 16 capable)
- Heat or energy recovery (75–90% efficient)
- Wildfire-smoke-ready by design
R-value on paper vs. R-value in reality.
A 2x6 wall full of R-21 fiberglass batt looks like an R-21 wall in the brochure. Thermal-image one in the field and you’ll see something closer to R-13 effective — sometimes worse — because every stud, header, and plate conducts heat straight through the cavity. The fix isn’t a thicker batt. The fix is continuous exterior insulation that wraps the entire envelope, eliminating the thermal bridging through framing.
We build to **effective** R-values: R-28 to R-35 in walls, R-49+ in roofs, and we detail the transitions — sill plates, headers, rim joists — so the insulation is actually continuous. The number on the spec sheet matches the number you live in.
A window is a hole in the wall. We make it a smart one.
Windows are the weakest link in any high-performance assembly — even great ones. We spec triple-pane and high-end dual-pane from manufacturers built for performance: Alpen, Marvin Elevate, and similar. Target U-factor is 0.20 to 0.25. SHGC stays in the 0.20 to 0.25 range so we don’t cook the house in summer.
Just as important: we install them right. Pan flashing, head flashing, sill slope, sill pan dam, full perimeter air seal. A great window installed badly performs like a bad window.
- U-factor 0.20–0.25, SHGC 0.20–0.25
- Triple-pane on the most exposed elevations
- Full pan flashing and air-sealed installation
- Manufacturer-specific install training, every job
Right-sized heat pumps. Ducts in conditioned space. Zero drama.
Most builders oversize HVAC because oversizing is forgiving — if the load is wrong, the system still keeps up, it just short-cycles, runs loud, and dehumidifies poorly. We do a Manual J load calculation on every project and right-size every system to it. The result is typically 30 to 40 percent smaller than what a contractor would size on a rule of thumb. Smaller is cheaper to install, quieter to run, and dries the house better.
We spec heat pumps and heat pump water heaters by default — California’s 2025 Title 24 cycle pushes that direction anyway, and the math works. Ducts live inside the conditioned envelope wherever possible, so we’re not heating an attic. Mini-splits where they make sense, ducted systems where they don’t.
Water gets in. We make sure it gets out.
Bulk water management is the first job of the wall assembly. Most leaks happen at transitions — window heads, sill plates, kick-outs, deck ledgers, parapet caps — not in the middle of a wall. We obsess over those transitions. Weather-resistive barriers lap correctly. Pan flashing has a back dam. Head flashing kicks water away from the wall. Kick-out flashing terminates roof-to-wall intersections so water can’t track behind the cladding.
We use a smart vapor retarder (INTELLO Plus or equivalent) on the interior so the wall can dry in both directions — closed in winter when it’s humid inside, open in summer when it’s humid outside. Coastal mixed-humid climates demand assemblies that breathe.
- Pan, head, sill, kick-out, and through-wall flashing
- Continuous WRB with rain screen on cladded walls
- Smart vapor retarder on the interior
- Detail-checked at every transition
Engineered for this climate — code, wildfire, and coastal air.
California’s building code is the most demanding in the country. Title 24 Part 6 sets energy. Part 7 (Chapter 7A) sets wildfire-urban-interface (WUI) requirements for any home in a fire-prone area. CalGreen layers in indoor air quality, water efficiency, and material requirements. We design to all of it, exceed most of it, and document the rest.
In WUI zones we spec ember-resistant vents (Vulcan or BrandGuard), Class A roofing, ignition-resistant exterior materials, and defensible-space guidance. On coastal projects we detail for salt air, marine corrosion on fasteners, and wind-driven rain.
- Title 24 Part 6 (energy) — exceeded
- Title 24 Part 7 / Chapter 7A — full WUI compliance
- Vulcan or BrandGuard ember-resistant vents
- Class A roofing on every WUI project
- CalGreen-aligned material and IAQ specs
The air in your home should be cleaner than the air outside.
We spec low-VOC paints, no-added-formaldehyde (NAF) and ULEF-rated cabinetry and millwork, and finish products that don’t off-gas for the next ten years. The HRV/ERV pulls fresh air in continuously and filters it. We can install continuous IAQ monitoring (Airthings, Awair) so the homeowner can see PM2.5, CO₂, VOCs, and humidity in real time.
Combine that with airtightness and balanced ventilation and you get an indoor environment most homeowners have never experienced — measurably cleaner than the air you breathe walking outside.
Our performance standard, side-by-side.
The complete table. Compare us to a tract home, to code minimums, and to Passive House.
| Metric | Tract Home | Title 24 Code | Jacinto Built | Passive House |
|---|---|---|---|---|
| Airtightness (ACH50) | 5 – 15 | 3.0 – 5.0 | 1.5 – 2.0 | 0.6 |
| Effective Wall R-Value | R-10 – R-13 | R-19 cavity | R-28 – R-35 effective | R-40+ |
| Window U-Factor | 0.30 – 0.40 | 0.30 | 0.20 – 0.25 | ≤ 0.14 |
| Window SHGC | 0.40 – 0.60 | 0.23 (CA) | 0.20 – 0.25 | 0.25 |
| Mechanical Ventilation | Bath fans only | Bath fans + exhaust | Balanced HRV/ERV, MERV 13+ | Balanced HRV/ERV, MERV 13+ |
| HERS Index | 85 – 100 | 65 – 85 | 35 – 55 | 20 – 35 |
| Duct Leakage (% CFM25) | 15 – 30% | 6% | ≤ 3% (or interior ducts) | Interior ducts |
| Blower Door Tested? | No | Yes (required) | Yes — and we share the result | Yes |
Questions we get about high-efficiency homes.
How much more does this cost than a normal custom build?
Typically 3 to 7 percent more on the building envelope, partially offset by right-sized HVAC — we install smaller, less expensive systems because the load is lower. Over ten years, energy savings alone usually cover the premium.
Do I have to pursue Passive House certification?
No. We build to Passive House principles on every home and can pursue formal PHIUS, DOE Zero Energy Ready Home, or ENERGY STAR certification if you want the badge. Most of our clients don’t certify — they just want the performance.
Will the house feel stuffy if it’s that tight?
The opposite. A tight home with a balanced HRV/ERV running continuously delivers more fresh filtered air than a leaky home — the difference is the fresh air is filtered, tempered, and delivered where you need it, not randomly leaking through walls.
What’s the HRV/ERV filter rated?
MERV 13 minimum. In wildfire season we swap to MERV 16 on ours. Captures PM2.5, smoke, pollen, and most allergens.
Do you build to Title 24?
Yes. We exceed it. Title 24 is a floor, not a ceiling.
Do I have to go all-electric?
California’s moving that way under 2025 Title 24, and we recommend it. Heat pumps and heat pump water heaters are what we spec by default. If you have a reason to keep gas, we’ll discuss it.
What about wildfire resilience?
If you’re in a WUI zone, we build to Chapter 7A — Class A roofing, ember-resistant vents (Vulcan or BrandGuard), ignition-resistant exterior materials, and detailed defensible-space guidance.
Will you work with my architect?
Yes, and we prefer it. We’ll also recommend architects who understand high-performance detailing if you need one.
Want to dig deeper into how your home can perform like this?
We’ll walk you through what it would take on your specific project.