Airtight. Insulated. Well Ventilated.
In the Mt Airy neighborhood of Cincinnati, a 3,200-square-foot home uses 7,000 Btu per square foot per year. Most homes in the neighborhood use seven to ten times that!
The house that landed at 7 was designed to three principles. Airtight. Insulated. Well ventilated. At Trilobite, every new-construction and deep-retrofit project starts at those three places. Pretty Good House reaches excellence on all three. Passive House verifies that excellence against a third-party standard and pushes each principle further.
Airtight
A house loses heat in two ways. Conduction moves heat slowly through solid materials, warm side to cold side. Convection carries heat in bulk as moving air.
Convection is faster. A one-inch gap around a doorframe passes the same heat load as a whole wall of insulation, because moving air transports energy in bulk. Conduction moves energy molecule by molecule through a material; convection lifts it in whole volumes and carries it across the envelope in seconds.
Air leakage carries moisture with it. Warm humid indoor air meeting a cold wall cavity drops to dew point inside the framing, and over years that moisture rots structural members and feeds mold behind the finish wall. Tight houses keep moisture where it belongs.
The fix is a continuous air control layer. One membrane around the building, wrapped carefully at every penetration: windows, outlet boxes, plumbing, attic hatches, electrical service entries. After drywall, a blower door test measures how much air leaks through the envelope at a reference pressure.
Code in Cincinnati allows 3.0 air changes per hour at 50 pascals. Pretty Good House targets 1.0 to 1.5 ACH50. PHIUS targets 0.06 cubic feet per minute per square foot of envelope, roughly four times tighter than Pretty Good House. The builder’s detailing carries this number. The air barrier has to come first. Insulation builds on top of a tight envelope.
Insulated
Insulation resists conductive heat flow. R-value is the resistance. Higher R, less heat moves through the assembly per degree of temperature difference.
Two details matter beyond the headline R-value. Thermal bridging: wood studs and steel fasteners conduct heat around the insulation they interrupt. A 2×6 wall filled with R-20 batt insulation performs closer to R-14 once the studs, plates, and headers are counted. Continuous exterior insulation wraps across the framing in an uninterrupted layer and restores the assembly’s true performance.
The second detail is where the envelope meets the ground. Slabs, basement walls, and rim joists are chronic heat-loss paths. A well-insulated house wraps the thermal envelope continuously from roof down the walls and under or outside the foundation, so the insulated boundary closes on itself.
Code in Cincinnati allows R-20 walls and R-49 attic. Pretty Good House runs continuous R-30 to R-40 walls and R-60 attic. PHIUS sizes insulation from a climate-specific energy model, typically pushing assemblies above Pretty Good House levels and detailed so the envelope meets the calculated load in every weather condition.
Windows follow the same logic. A double-glazed aluminum-frame window performs around R-2. A triple-glazed window with an insulated spacer bar and a thermally broken frame performs R-4 to R-5. Multiplied across twenty or thirty openings in a house, the window upgrade is the single largest envelope improvement on most projects.
Well Ventilated
A tight house needs mechanical ventilation because the envelope has stopped leaking fresh air in on its own. That is a feature, and it comes with a system that replaces the accidental ventilation with an intentional one.
An energy recovery ventilator runs continuously. Fresh outdoor air moves in. Stale indoor air moves out. The two airstreams pass through a core that exchanges heat and moisture between them while keeping the streams separate.
In winter, the outgoing warm moist air preconditions the incoming cold dry air, so the heating system picks up a partly-warmed supply. The outside air arrives tempered. In summer, the outgoing cool dry air preconditions the incoming hot humid air, so the cooling system works against a smaller delta in temperature and moisture.
Continuous ventilation earns its own paragraph for what it does beyond energy. The ERV filters incoming air before it enters the house, so pollen counts drop dramatically and outdoor particulate stays outside. It pulls cooking aerosols, bathroom moisture, CO2 from bedrooms, and VOCs from finishes out of the house in real time. Every room gets fresh air every hour, every day of the year. Humidity stays inside a narrow band year-round because the envelope and the ERV are controlling vapor together.
Pretty Good House and PHIUS both require continuous balanced ERV or HRV ventilation. PHIUS additionally specifies the system’s recovery efficiency and requires commissioning to verify performance on the installed equipment.
Heating and Cooling
A tight, insulated, well-ventilated house has a small heating and cooling load. The mechanical system that serves that load looks different from a code-minimum furnace and air conditioner.
Heat pumps move heat. They capture thermal energy that already exists in the outdoor air, compress it with a refrigerant cycle, and release it inside the house. Because the heat pump is relocating heat, it delivers three to four units of heat for every one unit of electricity it consumes. That ratio is the coefficient of performance, or COP.
A gas furnace works differently. It burns fuel to generate new heat, and the most efficient modern furnace delivers about 96% of the fuel energy as usable heat. Its effective COP caps at 0.96 by definition, because every unit of fuel energy can produce at most one unit of delivered heat.
At 30 degrees outdoor air temperature, a modern cold-climate heat pump operates at roughly COP 3. At 47 degrees, closer to COP 4. Averaged across a Cincinnati heating season, heat pumps deliver roughly three units of useful heat for every unit of electricity.
In a Passive House, the heating load is small enough that the heat pump itself is compact. Wolfgang Feist, the physicist who set the original Passive House threshold in 1990, specified the standard precisely by that comparison: a house that heats itself with the equivalent of a hair dryer.
Pretty Good House and PHIUS both default to electric heat pumps sized from an energy model. An oversized heat pump short-cycles in a tight house and creates humidity problems by running too briefly to dehumidify the air. Correct sizing comes from the model, which accounts for the envelope, the glazing, the ventilation rate, the equipment loads, and the occupancy.
Pretty Good House
Pretty Good House began in Maine in 2011. A group of builders and designers led by Dan Kolbert agreed they were tired of arguing about which certification to chase. They shared the performance targets they thought reached excellence on most houses in most climates at a modest construction premium. The framework is a book, a community of practitioners, and a set of targets.
Verification lives with the builder and the homeowner, confirmed on site with a blower door test at completion. The philosophy is that three principles applied rigorously reach excellence for most homes at a modest premium over code construction.
Pretty Good House works on discipline. The team agrees the targets are correct for the project. The design reaches those targets on paper. The builder delivers the assemblies to specification. The blower door test at completion confirms the envelope.
Passive House
Passive House started in Germany in 1990. Wolfgang Feist set a performance threshold: a building that heats itself with the equivalent of a hair dryer. PHIUS adapted the standard to North America, and since 2015 has used climate-specific performance targets tuned to each zip code, calibrated to the climate the house actually sits in.
PHIUS certification is verified. A certified rater reviews the energy model, conducts the blower door test, and signs off on the as-built performance. The certification stays with the property, recognized by appraisers and utility incentive programs across the country. Utility rebates in Ohio and neighboring states cover part of the construction premium. Grant programs for affordable housing, tax credits for high-performance building, and climate-focused funding increasingly require PHIUS certification to qualify.
A certified Passive House holds temperature through long power outages. Three days into a winter grid interruption, a PHIUS-certified building in climate zone 4 typically sits around 60 degrees with zero backup heat running. The envelope is doing the work.
Where Each Fits
Pretty Good House is the floor Trilobite writes into every new-construction and deep-retrofit contract. It fits inside a normal design-build workflow at a modest premium over code. The resulting house uses a fraction of the energy of a code-minimum build.
Passive House is the upgrade a client picks when they want verified performance, utility rebates, eligibility for grant programs and tax credits, resilience through multi-day outages, and a certification that stays with the property through resale.
Either path starts from the same three principles. Airtight. Insulated. Well ventilated.
Measured Results
Our Mt Airy Passive House, a 3,200-square-foot single-family home in Cincinnati, uses 7,000 Btu per square foot per year before onsite generation. One of the lowest measured residential numbers its certifying engineer has logged in the region. After the solar array was installed in December 2025, the home is now net zero.
A mastering studio we designed to the same principles in a different program type lands at 11,000 Btu per square foot per year. Offices and audio equipment draw differently than bedrooms and showers. The same three principles run both buildings.
Either way, the house runs on less.