Low-Energy and Passive New Builds: Running and Maintenance

A low-energy or passive house differs mainly in that it needs very little energy for heating and that living in it is slightly different from living in a standard new build. Running costs are lower, but they depend on correctly functioning ventilation and regular servicing of the building services. Before buying, it is therefore worth finding out how the building is designed, who will maintain it, and how much filter replacements or inspections will cost.

How a low-energy house differs from a passive house

Both types have a high-quality building envelope: good thermal insulation, airtight windows and carefully designed details so that heat does not escape. The passive standard goes further than the low-energy one and sets the highest requirements for airtightness, insulation and controlled ventilation with heat recovery. A passive house can therefore often manage with a very small heat source, sometimes even just by reheating the supply air.

However, the labels "low-energy" or "passive" are not automatically documented for every project. Ask about the building's energy performance certificate, the design documentation, and whether the standard was verified by measurement, for example an airtightness test of the envelope.

Ventilation and heat recovery in everyday use

The heart of the house is the heat recovery ventilation unit. It extracts stale air, supplies fresh air and passes part of the heat back. Residents do not need to ventilate by opening windows, but the unit must run continuously and have clean filters.

• Filters are replaced regularly, usually several times a year depending on the environment and the manufacturer. Their price and availability vary with the type of unit.
• Servicing the unit includes checking the fans and the heat exchanger and cleaning the ductwork. The interval and scope are set by the manufacturer.
• Noise should be barely noticeable in living rooms. Check this during a viewing of a show flat or show house.
• Air humidity tends to be lower in winter. Some people find this bothersome; it is addressed by adjusting the ventilation output.

Heating, hot water and costs

Heat consumption is lower than in standard houses, so the balance of costs changes too. A larger share of energy is often used for heating water, household appliances and the operation of the building services themselves. The heat source is usually a heat pump, a gas boiler, district heating or electric heating. Each solution has different running costs and different servicing requirements.

Actual costs depend on the size of the flat or house, the number of occupants, energy prices and how you heat. Get a rough idea using the calculator, but when planning your financing, also allow a reserve for servicing the equipment. Discuss loan terms and any benefits for energy-efficient housing with a mortgage specialist rather than assuming them in advance.

Maintaining the house and the building envelope

A high-quality envelope wears out more slowly, but it is not maintenance-free. Keep an eye on the following on a regular basis:

• windows and doors – seals and fittings, so they do not worsen the airtightness of the house,
• the façade and insulation – small cracks, damage to the plinth, joints with window sills,
• the roof and terraces – penetrations, drainage, waterproofing,
• shading and external blinds – they protect against overheating in summer,
• technical rooms – pumps, expansion vessels, valves, and inspections according to the manufacturer's instructions.

When making alterations, take care with drilling into the façade, interventions in the airtight layer and changes to the distribution systems. Consult the contractor or the designer before any intervention so that you do not compromise the airtightness or the warranty.

What to ask before buying

In the project catalogue, compare the energy standard that individual new builds declare, and follow up with the relevant developer. Useful questions:

1. What is the energy performance certificate rating, and how was the standard verified?
2. What is the heat recovery unit, who services it and how often are the filters replaced?
3. What is the heat source, and who is responsible for its operation in the common areas?
4. How is shading against summer overheating handled?
5. What does the warranty cover, and what are the owner's obligations so as not to alter it?

Compare the price together with the running costs, not just the purchase price. You will find a rough overview in the section on new-build prices. Have the contractual terms, warranties and the owner's obligations reviewed by a lawyer. The next steps are described step by step in the buying guide.

Frequently asked questions

Do I still have to ventilate or watch the windows in a passive house?

Ventilation is provided by the heat recovery system, so ordinary ventilation by opening windows is not necessary. You can open the windows, but it may temporarily reduce the system's performance. It is more important not to switch the unit off and to keep an eye on the filters.

Is maintenance more expensive than in a standard new build?

There is added servicing of the ventilation and possibly the heat pump, while heating costs fall. The result depends on the specific equipment and the price of services, so ask about the maintenance plan and a cost estimate before making a reservation.

How do I find a suitable project in my area?

Start with the overview of locations and request the energy parameters for the projects you select. If you do not know where to start, you can send a housing inquiry form.