Certified Passive House Consultant · Bucharest
Passive House and nZEB consulting
Energy-efficient homes. Calculated, not guessed.
Semper Supra Initiative designs and checks very-low-energy houses to the Passive House standard and Romania’s nZEB requirements in Mc 001-2022. We work from a complete PHPP energy model, design the HVAC systems and follow the build on site through to handover.
- Certification
- Certified Passive House Consultant, Passive House Institute
- Experience
- More than 40 HVAC projects in Romania, 3 projects in the Netherlands
- Area
- Romania and abroad
- Calculators
- 4 free calculators, no account
Passive House
What is a Passive House
A Passive House is a building that needs very little energy for heating and cooling, because it loses very little heat and makes good use of the sun and of the heat produced indoors. The standard is defined by the Passive House Institute (PHI) in Darmstadt, Germany, and is checked by calculation in PHPP.
The five principles
- Continuous insulation on walls, roof and floor, without gaps.
- High-performance windows, usually triple-glazed, installed in the plane of the insulation.
- No thermal bridges at junctions: corners, plinth, balconies, window installation.
- Airtightness, checked on site with a Blower Door test.
- Ventilation with heat recovery: fresh air all the time, with the heat of the outgoing air recovered.
| Criteria for the Classic class | Limit |
|---|---|
| Space heating demand | ≤ 15 kWh/(m²·a) or heating load ≤ 10 W/m² |
| Airtightness, n50 | ≤ 0.6 air changes per hour at 50 Pa |
| Overheating | above 25 °C in at most 10 % of the hours in a year |
| Primary energy renewable (PER) | ≤ 60 kWh/(m²·a) |
Values refer to the treated floor area, calculated to PHI rules. Source: Passive House Institute.
nZEB
What nZEB means in Romania
nZEB (nearly zero-energy building) is the minimum level required for new buildings in Romania. The requirements come from Law 372/2005 on the energy performance of buildings and from the Mc 001-2022 calculation methodology.
- Since 31 December 2020, all new buildings must meet the nZEB requirements.
- At least 30 % of the primary energy must come from renewable sources produced on site or nearby.
- Each element of the envelope has a minimum thermal resistance R′. For houses, the values are in the table.
| Element | nZEB · Mc 001-2022 | Passive House · PHI* |
|---|---|---|
| External wall | R′ ≥ 4.00 m²K/W U′ ≤ 0.25 | U ≤ 0.15 |
| Roof, flat roof, ceiling under a loft | R′ ≥ 6.67 m²K/W U′ ≤ 0.15 | U ≤ 0.15 |
| Slab on ground | R′ ≥ 5.00 m²K/W U′ ≤ 0.20 | U ≤ 0.25 |
U and U′ in W/(m²K). * PHI criterion for certified components in a cool-temperate climate; elements in contact with the ground use the factor 0.6. In a real project, thicknesses come from the PHPP calculation of the house, not from the table.
Comparison
nZEB or Passive House?
The two can be combined in the same project. They differ in who requires them, what is checked and how.
| Criterion | nZEB | Passive House |
|---|---|---|
| What it is | Legal requirement, minimum level | Voluntary standard |
| Who it applies to | All new buildings in Romania | Buildings whose owner chooses it |
| What is checked | R′ for each element, primary energy, renewable share | Heating demand of the house, airtightness, overheating, renewable primary energy |
| How it is checked | Calculation to Mc 001-2022 and an energy performance certificate | Calculation in PHPP; certification by a PHI-accredited certifier |
Free · no account
Free calculators for the building envelope
Four calculators, one for each element: roof, wall, window and floor. They use manufacturer-declared λ values, climate data for the chosen location and the methods of the European standards. Results appear instantly, without an account.
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U′ and R′ for attic rooms, unheated lofts and flat roofs, including the timber, month-by-month condensation and summer behaviour.
Worked exampleOpen the calculatorAttic with 18 cm of wool between the rafters and 5 cm under them: U′ 0.175 W/(m²K). With 10 cm under the rafters: 0.143.
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U′ and R′ for Porotherm or AAC masonry with external insulation, with the temperature through the layers, condensation and a year of heat loss.
Worked exampleOpen the calculatorPorotherm 25 N+F with 10 cm of white EPS: U′ 0.304 W/(m²K), i.e. R′ 3.29 m²K/W.
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How much sun reaches the window in each season and how much an overhang shades it, hour by hour, from PVGIS data.
Worked exampleOpen the calculatorAn unshaded vertical south facade receives on average between 1,018 kWh/m² a year (Brașov) and 1,101 kWh/m² (Craiova).
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A slab on ground for a house without a basement, to EN ISO 13370, with the soil type, plinth insulation and insulation above or below the slab.
Worked exampleOpen the calculatorA 120 m² house in Bucharest with 10 cm of polystyrene on the slab loses about 1,422 kWh through the floor in a winter, against 3,644 kWh without it.
What the calculators don’t tell you
The calculators describe the physics of a single element in a typical situation. They don’t give ratings or say whether a solution suits your house; that takes a PHPP model of the whole building.
Services
From the energy model to handover
Four services, in the order they come up in a new build or a renovation.
- Stage 1
PHPP energy design
We model the whole house in PHPP, the Passive House Institute’s tool: heating and cooling demand, overheating risk and primary energy. You see the effect of each decision (insulation, windows, shading) before building.
- Stage 2
HVAC design
Heating, cooling and ventilation, sized to the demand calculated in the house’s PHPP model.
- Stage 3
Site checks
We check airtightness, window installation and insulation at the stages when they can still be corrected, before they are covered up.
- Stage 4
Project management
We coordinate the project from concept to handover: the trades, the schedule and the technical decisions that affect energy use.
About
The consultant behind the numbers
Dezideriu Florian Pana
Dezideriu Florian Pana is a Certified Passive House Consultant, certified by the Passive House Institute (Darmstadt). Through Semper Supra Initiative he offers PHPP energy modelling, HVAC design, site checks and project management, from concept to handover.
He has worked on more than 40 HVAC projects in Romania and on 3 projects in the Netherlands, covering both new houses and full renovations. He takes on projects across Romania and abroad.
Questions
Frequently asked questions
What is a Passive House?
A building that meets the criteria of the Passive House Institute in Darmstadt. For the Classic class, the space heating demand is at most 15 kWh/(m²·a) or the heating load at most 10 W/m², airtightness n50 is at most 0.6 air changes per hour, and the indoor temperature exceeds 25 °C in at most 10 % of the hours in a year. The criteria are checked by calculation in PHPP.
What does nZEB mean?
Nearly zero-energy building. In Romania it is the minimum level required for all new buildings since 31 December 2020, under Law 372/2005 and the Mc 001-2022 methodology.
What is the difference between nZEB and a Passive House?
nZEB is the legal requirement: Mc 001-2022 sets a minimum thermal resistance for each element, and part of the energy must come from renewable sources. Passive House is a voluntary standard, checked by a PHPP calculation of the whole building, with limits on heating demand, airtightness and overheating.
What is PHPP?
The Passive House Planning Package, the Passive House Institute’s calculation tool. It works out the energy balance of the house month by month: losses through the envelope and ventilation, solar and internal gains, heating and cooling demand and overheating risk. It is the calculation used for Passive House certification.
What do U and R′ mean?
U, in W/(m²K), is how much heat passes through one square metre of an element when there is a 1 °C difference between inside and outside; a lower value means less heat lost. R′, in m²K/W, is the corrected thermal resistance, the inverse of U′. A wall with U′ 0.25 has R′ 4.00.
Do the calculators replace a PHPP calculation?
No. Each calculator shows a single element (a roof, a wall, a window, a floor) in a typical situation. A PHPP model links all the elements with orientation, shading, ventilation and the local climate, and shows how the whole house performs.
Do you work outside Bucharest?
Yes. We take on projects across Romania and abroad; so far we have worked on 3 projects in the Netherlands.
How do we start?
Email office@sempersupra.ro or call +40 728 988 978 (also on WhatsApp). Tell us what stage the project is at and we will tell you which services make sense at that point.
Updated 24 October 2026
Contact
Book a consultation
Tell us what stage the house is at: an idea, a design in progress or a building site. We reply with the services that fit that stage.