What Is Passive House — and Why Does It Matter?

Passive house is a performance standard for buildings — not a style, not a trend, and not a marketing term. It is a rigorous, science-based approach to design and construction that defines specific measurable targets for:

Airtightness:

0.6 air changes per hour at 50 pascals (ACH50) or better

Heating and cooling demand:

limited to 4.75 kBtu per square foot per year

Primary energy demand:

limited to 38 kBtu per square foot per year

Thermal comfort

Interior surface temperatures within 2°F of room air temperature at all points

Meeting these targets requires an integrated design approach — one that treats the building as a single system rather than a collection of independent trades. It requires a contractor who understands building science at a level most never reach.

Alquimia Inc. builds to these standards because we believe a home should perform as precisely as it looks.

The Five Principles Behind Every Passive House Build

Passive house performance is achieved through five design and construction principles. Each one is non-negotiable. All five must work together.

1. Superior Insulation

Passive house buildings require continuous, high-performance insulation without thermal bridges — gaps or interruptions in the insulation layer that allow heat to bypass the barrier. In Houston’s climate, this means carefully designed wall and roof assemblies with insulation values that dramatically exceed code minimum.

We use Rockwool mineral wool and closed-cell spray foam in configurations appropriate to the climate zone, assembly type, and project goals. Every assembly is designed to eliminate thermal bridging at framing, windows, and penetrations.

2. Thermal Bridge-Free Construction

A thermal bridge is any element that conducts heat through the building envelope faster than the surrounding assembly — steel framing, concrete balconies, window frames, and structural connections are common examples. In a passive house building, these are designed out of the assembly entirely or mitigated through strategic insulation placement.

Thermal bridges are responsible for a significant portion of the energy loss in conventional construction — and they are the primary location for condensation and mold formation. Eliminating them is both an energy strategy and a moisture management strategy.

3. High-Performance Windows and Doors

Windows and doors are the weakest thermal links in any building envelope. In a passive house, glazing is specified for solar heat gain coefficient (SHGC), U-value, and frame thermal performance — optimized for Houston’s specific climate: high solar gain in winter, solar control in summer, and robust air and water sealing year-round.

We specify Andersen Windows?

4. Airtight Building Envelope*

Air leakage is the single largest source of energy loss and moisture damage in residential buildings. A passive house building envelope is designed and built to achieve 0.6 ACH50 or better — verified by a blower door test at completion.

Achieving this level of airtightness requires:
– Continuous air barrier at the building envelope
– Careful detailing at every penetration — plumbing, electrical, mechanical, structural
– Air sealing at windows and doors with appropriate tapes and fluid-applied membranes
– Coordination between every trade on the job site

We use Huber ZIP System sheathing as our primary air and water barrier, supplemented by Prosoco fluid-applied membranes at complex transitions and penetrations.

Balanced Mechanical Ventilation with Heat Recovery

An airtight building requires mechanical ventilation — there is no way around this. But the right mechanical ventilation system transforms what might seem like a constraint into one of the most powerful features of a passive house.

A heat recovery ventilator (HRV) or energy recovery ventilator (ERV) continuously exhausts stale indoor air and supplies fresh outdoor air — recovering 80–90% of the energy from the exhaust stream before it leaves the building. The result is a continuous supply of filtered, tempered fresh air throughout every room, with minimal energy penalty.

In Houston’s humid climate, an ERV (which also transfers moisture between the exhaust and supply streams) is the correct choice for most applications. Alquimia has designed and installed ERV systems in passive houses and high-performance projects across the Houston area.

Energy Recovery Ventilators: The Lung of a High-Performance Houston Home

An energy recovery ventilator (ERV) is the mechanical ventilation component of a passive house or high-performance building. It is what allows a tight building to breathe — efficiently, continuously, and cleanly.

How an ERV works:

The ERV simultaneously exhausts stale indoor air and supplies fresh outdoor air through a heat exchanger core. In this core, the two air streams pass each other without mixing — transferring heat and moisture between them. The outgoing exhaust air preconditions the incoming fresh air, recovering 75–90% of its energy content before it leaves the building.

Why ERV rather than HRV in Houston:

In humid climates like Houston, an energy recovery ventilator (ERV) is preferred over a heat recovery ventilator (HRV) because it transfers both heat and moisture between the air streams. This means the incoming fresh outdoor air is dehumidified before it enters the living space — reducing the latent load on your air conditioning system.

ERV system design:

An ERV is not a plug-and-play appliance. Its performance depends entirely on how it is integrated into the building — duct sizing, balanced exhaust and supply flows, filter selection, and controls. Alquimia designs ERV systems from the mechanical drawings outward, ensuring the ventilation performs exactly as calculated.

Passive House and High-Performance Projects in Houston

Alquimia has designed and built high-performance projects throughout the Houston area, applying passive house principles to new construction, whole-home remodels, and targeted envelope improvements.

Stanford Custom Home Renovation

— full gut renovation applying passive house envelope principles to an existing single-family home: continuous insulation, airtight assembly, ERV installation, and high-performance window replacement.

Passive House Design Consultation

— we offer design-phase building science consultation for architects and homeowners planning new construction or major renovations who want to achieve passive house performance.

What Working with Alquimia on a Passive House Project Looks Like

Design phase collaboration.

We engage at the design phase — working alongside your architect or leading the design ourselves — to ensure the passive house principles are built into the drawings, not retrofitted after the fact.

Energy modeling.

We use energy modeling tools to predict the building’s performance before construction begins — confirming that the design meets passive house targets and identifying any assembly details that need refinement.

Construction documentation.

\Every passive house assembly is detailed in writing and in drawings — so every trade on the job site knows exactly what is required of them and why. No assumptions. No improvisation.

Testing and verification.

At completion, we perform blower door testing to verify envelope airtightness, duct leakage testing to confirm HVAC system performance, and ventilation flow measurements to verify ERV balance. The building gets a report card — and it has to pass.