Quick answer: Class A is a result — a label obtained through the Portuguese energy certification. Passive House is a building method — an international technical standard with objective, measurable criteria. A Passive House typically achieves Class A or A+ under SCE calculation, but the reverse is not true. If you're building from scratch and want real comfort with minimal energy use, choose Passive House.
Let's explain in detail, with numbers.
What is Class A
In Portugal, every home (new or existing) sold or rented must have an Energy Certificate, issued under the SCE (Portuguese energy certification for buildings). This certificate assesses the home's overall energy efficiency and assigns a class from A+ (best) to F (worst).
Class A means the home has an estimated energy consumption 25 to 50% below the reference for a new home in Portugal. It's a good class, well above the national average (most homes in Portugal sit in C or D).
Key points about Class A:
- Assigned by simulation under SCE (DL 101-D/2020, successor to REH).
- Considers heating, cooling, domestic hot water and lighting.
- Assumes standardised equipment and behaviour — does not measure real consumption.
- It is mandatory.
- Does not guarantee real comfort or the elimination of AC/heating — only estimated efficiency.
What is Passive House
Passive House (Passivhaus, in German) is an international technical standard created in 1990 by the Passive House Institute (PHI) in Darmstadt, Germany. It defines objective criteria that a home must meet to qualify as Passive House. The main criteria are:
- Useful heating energy demand ≤ 15 kWh/m²/year
- Useful cooling energy demand ≤ 15 kWh/m²/year
- Airtightness n₅₀ ≤ 0.6 h⁻¹ (verified by Blower Door test)
- Overall primary energy demand ≤ 60 kWh/m²/year
- Stable interior temperatures between 20 and 25° C year-round, without active mechanical systems
These criteria require:
- Building envelope with continuous insulation (250-300 mm mineral wool equivalent).
- No thermal bridges — all structural junctions are calculated.
- High-performance triple or double glazing.
- Mechanical ventilation with heat recovery (MVHR) — recovers 80-90% of the heat from outgoing air.
- Optimised solar orientation.
- Adequate summer shading.
The big difference compared to Class A is that Passive House requires real verification — Blower Door test on the completed build, validated PHPP (Passive House Planning Package) simulation, and measurable interior temperatures.
Comparison table
| Class A | Passive House | |
|---|---|---|
| Nature | Result label | Technical design standard |
| Verification | SCE simulation (DL 101-D/2020) | PHPP simulation + tests |
| Airtightness | Not mandatory | Blower Door mandatory |
| Annual heating | 40-60 kWh/m²/year | ≤ 15 kWh/m²/year |
| Annual cooling | Highly variable | ≤ 15 kWh/m²/year |
| Air conditioning/heating optional | No | Yes, in target climate |
| Mechanical ventilation | Optional | Mandatory (MVHR) |
| Construction cost | +0% base | +8-15% typical 0% at Ecoimport |
| Operating cost | €1,800–2,400/year | €350–550/year |
| Summer comfort without AC | Hard in the Algarve | Guaranteed |
What changes day-to-day
The most visible difference isn't in the electricity bill — it's in comfort.
In a conventional Class A home in the Algarve, a typical summer looks like this:
- The interior reaches 28-30° C in south-facing rooms at 5 pm.
- Air conditioning on all afternoons and evenings (June to September).
- Cooling electricity consumption: €800-1,200/year.
- A "cool house" feel only in some rooms.
In a Passive House in the Algarve, a typical summer looks like this:
- The interior stabilises at 22-25° C in every room.
- Air conditioning not needed — if installed (optional), it stays off.
- Cooling electricity consumption: €0.
- Uniform temperature without uncomfortable variations.
The same holds in winter: a Passive House keeps 20-22° C indoors without active heating, while a Class A home needs night-time heating to reach 19-20° C.
Which to choose
The answer depends on three factors:
- Are you buying a home that's already built? In this case, look for Class A or A+ as the minimum. Passive House exists but is rare in existing properties.
- Are you building from scratch and want real efficiency? Passive House is the right choice. Comparable construction cost, radically lower operating cost, much greater comfort.
- Are you building to rent out on Local Accommodation? Passive House is even more attractive — guests value comfort and energy savings flow directly to margin.
In Local Accommodation, the electricity bill difference between Class A and Passive House easily runs €1,500-2,000/year — money that goes straight to the investment's bottom line.
Passive House in the Algarve climate: myth or reality?
A common myth: "Passive House was designed for the cold in Germany, it doesn't make sense in the Algarve heat." False. The standard has evolved over the last three decades to incorporate passive cooling criteria essential for Mediterranean and warm climates. Today there are certified Passive Houses in Seville, Málaga, Athens, Cyprus and Morocco.
In the Algarve, summer is the challenge. A Passive House here includes:
- Heavy insulation (300 mm) to keep heat out.
- Architectural shading (canopies, shutters, strategic vegetation) for south- and west-facing windows.
- Night ventilation to exploit night-day thermal difference.
- Thermal mass in the concrete slab (2 tonnes per m²) that absorbs heat during the day.
- MVHR with summer bypass (renews air without exchanging heat in summer).
Result: an Ecoimport Wood Passive House in Algoz maintains 24° C indoors with 38° C outside. No air conditioning on. Daily electricity consumption: 3-4 kWh, corresponding to appliances and lighting only.
How to tell if my home is really Passive House
A home is Passive House if it meets all the technical criteria and — ideally — is PHI-certified. Many Portuguese builders advertise "Passive House" without meeting the criteria. How to check:
- Blower Door test — ask for the n₅₀ value obtained on the finished build. Passive House requires ≤ 0.6 h⁻¹.
- PHPP simulation — the builder should deliver the calculation in PHPP, not only in SCE (DL 101-D/2020).
- PHI certification — if certified, it has a registration number in the PHI database.
- Contract with performance guarantee — at Ecoimport Wood, we guarantee by contract: Class A + Passive House criteria or financial penalty.
Head-to-head comparison table — technical criteria side by side
The table below compares eight technical criteria exactly as they appear in the regulations for each standard: Class A of the Energy Certification System (SCE) defined by Portuguese Decree-Law 101-D/2020, and Passive House from the Passivhaus Institut. All values are direct regulatory thresholds, not estimates.
| Criterion | Class A (SCE / DL 101-D/2020) | Passive House |
|---|---|---|
| Useful heating energy demand (Nic) | ≤ Nt (varies with shape and climate; ~25–45 kWh/m²·yr in the Algarve) | ≤ 15 kWh/m²·yr (absolute limit) |
| Useful cooling energy demand (Nvc) | ≤ Nv (varies with shading; ~30–55 kWh/m²·yr in the Algarve) | ≤ 15 kWh/m²·yr or overheating frequency ≤ 10% |
| Wall thermal transmittance (U) | ≤ 0.50 W/m²·K (Algarve zone I1, for Class A) | ≤ 0.15 W/m²·K (typical Passive House) |
| Window thermal transmittance (Uw) | ≤ 2.80 W/m²·K (regulatory minimum); ~1.80 for Class A | ≤ 0.85 W/m²·K (absolute limit, triple glazing) |
| Airtightness n₅₀ | Not required; recommended ≤ 3.0 h⁻¹ | ≤ 0.60 h⁻¹ (measured with blower door) |
| Mechanical ventilation with heat recovery (MVHR) | Not required; natural ventilation accepted | Mandatory, efficiency ≥ 75% |
| Mandatory detailed calculation | Yes, official REH spreadsheet | Yes, PHPP (Passive House Planning Package) |
| Certifying body | ADENE (through a qualified expert) | Passivhaus Institut (Darmstadt) or iPHA |
Two practical readings emerge from the table. First, the airtightness and mechanical ventilation limits mark the structural difference: Class A can be met with a permeable envelope and natural ventilation, while Passive House treats both as non-negotiable. Second, Passive House U-values on walls and windows are around three times more demanding, which translates into thicker insulation and triple glazing — the reason construction cost is 8–12% higher but energy demand drops to less than a third.
Conclusion
Class A is mandatory. Passive House is optional, but radically better. On total cost of ownership over 30 years — considering construction, energy, maintenance and comfort — an Ecoimport Wood Passive House in the Algarve is the most efficient investment in new housing in 2026.
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