How to increase the energy performance of a house

The energy performance of a building is an important feature, as the energy used in a home increases maintenance costs and creates a significant amount of greenhouse gas pollution - the main cause of climate change. So it's not surprising that now, more than ever, energy efficiency is an important part of building design and construction.

To this end, all new buildings, regardless of size, will have to meet minimum energy performance requirements, adapted to the climate in which they are built. These are requirements aimed at reducing the energy needed to maintain buildings, which climate change is driving us to follow. Energy saving measures will benefit the environment, improve air quality, improve people's lives inside buildings and, very importantly in today's conditions, lower energy bills.

Terms increasingly present in today's builders' jargon: ZEB, nZEB, passive house

Modern terms are used to explain the energy performance of houses, terms that are familiar to architects, designers and builders, but not familiar to many of us. They show the very low or even zero conventional energy consumption of a house during operation, i.e. the energy needed to heat and cool the house.

ZEB stands for Zero Energy Building, i.e. a house that uses no conventional energy at all, but only that which it produces from renewable sources or recovers. NZE (Net Zero Energy) and NZE (Zero Net Energy) are variations on the same theme, depending only on the country where they are used. nZEB stands for nearly Zero Energy Building (Near-zero energy building.) I'll get right back to it.

Passive house is a building concept invented by German physicist Wolfgang Feist, a building standard that, if respected, certifies that the building constructed is truly energy efficient, comfortable, affordable and environmentally friendly at the same time. They save up to 90% in heating and cooling energy compared to traditional houses and over 75% when compared to new construction. Find here further information about this concept.

From 2021, the nZEB standard has become mandatory in Romania for all new buildings whose building permit was issued after 31 December 2020, which means that these buildings must have near-zero energy consumption, i.e. they must be very energy efficient and their energy needs must be covered as much as possible from renewable sources.

Key factors that ensure the energy performance of a house

How should homes be built to achieve the safest, healthiest and most comfortable environment possible? By maximising the energy efficiency of the basic components that make up the house. So, to achieve a high level of energy performance, the key factors in house construction are:

• Thicker, quality insulation layers
• Lack of thermal bridges
• High quality windows
• A ventilation system with heat recovery
• Sealed tyre

Thermal insulation

This is a key point for reducing heat loss. Thermal insulation allows the interior of the house to be independent of the outside temperature and thus makes it easier to maintain constant thermal comfort. Once the right temperature is reached inside the house, it should be maintained as long as possible by avoiding heat loss through good insulation of the foundation, walls and roof.

In an energy efficient or passive house, the insulation thickness is considerably greater than in a conventional house. The smaller the insulation, the greater the heat exchange. So the 12 cm usually used to insulate houses is not enough for efficient insulation. Passive houses have at least 15-20 cm of insulation in the walls and 25-30 cm in the roof.

Continuous insulating layer

A thermal bridge is an area of the house through which heat is lost, generally due to faults in the design and workmanship of the construction. A break in the insulation material or a poorly sealed area through which a direct connection is created between the inside and outside of the building (window outline) is considered a thermal bridge. This can lead to problems with damp, condensation and then mould, with negative effects on the house and the health of its inhabitants. The elimination of bridges should be considered at the design stage and followed up with great care at the execution stage.

Thermal bridges can be identified by thermoscanning. With the help of a colour spectrum the areas and the level of heat loss are visualised. Marius Șoflete has some such videos showing with the thermoscanner how much heat is lost around windows, through walls or roofs, especially in old houses.

Good quality windows

Windows can generate the highest energy losses if they are not of good quality and do not ensure tightness. In any house, the weak points are the windows and, in particular, the window/wall junction. But it is not just heat loss at the joints with the wall that occurs with windows, cold can be transmitted through the glass or window structure.

As a lot of heat can be lost through the window glass, double or triple glazed windows with thermal insulation features will be required. In this respect, the architect should guide us to the best option according to the climatic characteristics of the area as well as the needs of the owner. The joinery must have a thermal break system and the joint with the wall must be well sealed. The insulation capacity of the joinery should be checked in full, taking into account the frame as well as the glass. With a properly fitted, sealed and insulated high performance window you avoid heat loss in one of the most vulnerable parts of the house.

Ventilation with heat recovery from the air

This whole concept, which includes high-performance thermal insulation, quality sealed windows, "sealing" by eliminating thermal bridges, can only achieve its purpose together with a proper ventilation system to refresh the indoor air.

In such insulation, natural ventilation is insufficient and must be supplemented by a system that provides permanent fresh air, removes stale air and regulates humidity. Heat recovery ventilation systems exchange stale indoor air by giving up its heat to fresh air introduced from outside. They provide the ventilation needed for a healthy environment and reduce heating costs.

Sealed outer tyre

Energy-efficient buildings have a continuous insulating envelope, like a warm layer that wraps and air seals the building. The envelope of the house comprises all the elements that separate the inside of the house from the outside, supports it, protects it thermally and soundproofing it and seals it from air and moisture.

Tyre components are the walls, roof, windows, doors, foundation, each of which can be made of many different layers and materials. The most important part of any insulation project is sealing. This involves sealing off any places where air could enter or exit the house uncontrollably. Many leaks are found at the joints of envelope components, penetrations for electrical wiring, lighting and sewage. Combined, these can lead to large air leaks.

Sealing a home's envelope is an important step in controlling the indoor environment and reducing energy bills. Sealing measures aim to reduce heat loss as much as possible. A building without defects has a sealed envelope with components that perform their functions efficiently. To check the airtightness of the house, a specific test called a leakage test or blower door test is carried out, which you can find more information about here here.

If we're going to build a new house, let's do it right. Sources of information are now more and more numerous.