Low-Energy Houses

Nowadays, we are faced with ever-increasing energy prices and the limited availability of fossil fuels, so the demand for energy-efficient buildings is continuously growing.

Environmental awareness and the need to significantly reduce greenhouse gas emissions into the atmosphere are resulting in the growing construction of low-energy buildings.

Low-energy prefabricated houses are energy-efficient homes. They are examples of sustainable construction, from building materials whose production does not harm the environment to their energy efficiency and rational use of increasingly expensive energy sources.

The goal of building a low-energy house is to optimize energy consumption and make the most of available energy.

What is needed to build a low-energy house?

An energy-efficient house is based on a quality layer of insulation, high-quality windows and doors that prevent heat loss, an air circulation system that provides ventilation while also conserving energy, and the use of renewable energy sources.

Insufficient thermal insulation leads to increased heat loss in winter; the outer structure becomes cold, condensation damage occurs, and in summer the space overheats. The structure deteriorates, living conditions become uncomfortable and unhealthy, and the cost of using and maintaining the building increases.

Additional investment in improving energy efficiency and reducing heat loss in new construction is highly cost-effective. An increase in construction costs of 10% can result in energy savings of 50-80%.

By building a low-energy house, energy consumption is optimized.

Low-Energy Houses

In Croatia, a low-energy house is defined as a house that consumes less than 40 kWh/m² per year for heating.

Such energy consumption can also be expressed as the equivalent of 2.7 liters of heating oil per m², which is why a low-energy house is sometimes called a “three-liter house.”

In Germany, a low-energy house (Niedrigenergiehaus) has a heating energy consumption limit of 50 kWh/m² per year, while in Switzerland this limit is defined by the MINERGIE standard and must not exceed 38 kWh/m² per year.

Nearly Zero-Energy Buildings

A nearly zero-energy building is one that has very high energy performance.

This almost zero or very low amount of energy should be covered to a very significant extent by energy from renewable sources, including energy produced on the building itself or nearby, as required by current regulations.

The designation for a nearly zero-energy building is nZEB (nearly zero-energy building).

From December 31, 2020, all new buildings must be nearly zero-energy buildings.

Historical Context of Construction

Due to building characteristics and the lack of regulations, between 1950 and 1980, many buildings were constructed with high average energy consumption for heating.

The energy performance of existing buildings has been analyzed depending on their age, construction type, and the existence of thermal protection regulations.

Buildings built before 1940 often have poorly insulated exterior walls. Stone masonry bore the structural load and, due to its thickness, provided sufficient insulation for the conditions of that time. Buildings were made of brick or stone without thermal protection. Windows and doors were usually wooden with single glazing. Average heat losses in such buildings range between 200-250 kWh/m² per year.
Between 1940 and 1970 construction intensified; new technologies and materials developed, but there were still no regulations on thermal protection or energy savings. Structures were thinner, made of reinforced concrete, and lacked any energy concept.
In the period between 1970 and 1987 the first thermal protection regulations were adopted, and thermal insulation began to be used modestly. Structures were slim, with large glass surfaces, making them very energy-inefficient. Heat losses in buildings from this period often exceed those of older buildings, reaching over 300 kWh/m² per year.
From 1987 to 2006 all projects and constructions had approximately the same thermal quality, with heating needs ranging from 100-150 kWh/m².

Average old buildings consume 200-300 kWh/m² per year for heating, standard insulated houses consume under 100 kWh/m², modern low-energy houses consume under 40 kWh/m², while passive and nearly zero-energy houses consume 15 kWh/m² or less.

With the amount of energy used to heat a standard insulated house today, we could heat 3 to 4 low-energy houses or 8 to 10 passive houses.