The "Renovation Wave" is Here

In Europe, the era of endless new construction is fading. The future belongs to Retrofitting.

With the EU's "Green Deal" pushing for a massive reduction in carbon emissions, architects are facing a tough challenge: How to upgrade a 1950s apartment or a 19th-century historic building to modern energy standards?

Enter EnerPHit—the official Passive House Institute (PHI) standard for certified retrofits. Unlike new builds, renovations have constraints (thermal bridges, orientation, facade preservation).

For windows, this means standard double glazing is no longer an option. You need high-performance components that balance heritage aesthetics with Passive House physics.

What is EnerPHit? (And Why It Matters)

You can't always wrap an old brick building in 30cm of external insulation without destroying its character. The PHI acknowledges this.

• Classic Passive House: Heating demand ≤ 15 kWh/(m²a).

• EnerPHit (Retrofit): Heating demand ≤ 25 kWh/(m²a).

The Catch: While the building target is slightly more relaxed, the Component Requirements (especially windows) remain extremely strict. Why? Because windows are the "weakest link" in the thermal envelope.

$U_w$-Value Requirements

For the "Cool-Temperate" climate zone (e.g., Germany, UK, Northern France), the requirements for EnerPHit certified windows are rigorous:

1. Installed Window U-Value (Uw,installed):

   Must be ≤ 0.85 W/(m²K).

   (Note: Classic Passive House requires ≤ 0.80. The difference is marginal!)

2. Glass U-Value (Ug)：

   To achieve the total Uw, you typically need triple glazing with Ug ≤ 0.5 - 0.6 W/(m²K)

3. Solar Heat Gain (g-value):

   Generally g ≥ 50% (0.50)

   Old buildings often have smaller windows. You need high-transparency glass to capture every bit of free solar heat in winter.

 The Renovation Challenge: Thermal Bridges & Mold

In new builds, you design the wall to fit the window. In EnerPHit projects, the window must fit the existing wall—which is often a thermal nightmare.

• The Risk: If you install a high-performance window(Uw 0.8) into an uninsulated old wall, the wall around the frame becomes the coldest spot. Condensation forms-> Mold grows.

• The Solution:

  1. Warm Edge Spacers (Warme Kante): Non-negotiable to reduce edge heat loss (Psi-g).

  2. Insulated Frames: Frames must have excellent thermal breaks(Uf ≤ 1.0).

  3. Correct Installation: The window should be positioned in the insulation layer (if external insulation is added) or carefully detailed with interior insulation on the reveal.

Aesthetics vs. Physics (Historic Buildings)

For heritage-protected buildings (Denkmalschutz), bulky PVC frames are forbidden.

Our Solution for EnerPHit:

We offer Ultra-Slim Aluminum-Clad Wood or Steel-Look Aluminum profiles equipped with high-performance Triple Glazing.

• Look: Respects the historical thin sightlines (Simulated Divided Lites / Muntins).

• Performance: Delivers theUw ≤ 0.85required for certification.

Future-Proof Your Renovation

Renovating to EnerPHit standards is not just about saving energy today; it's about future-proofing the asset for the next 50 years.

Don't let the windows be the reason your project fails PHI certification.

Working on an EnerPHit project?

Let us help you calculate the Uw and Psi-install values to ensure compliance.

Get Your PHI-Compliant Glass Quote