What makes a building energy efficient?

With the impacts of climate change becoming ever clearer, and recent gas and electricity prices soaring, the need to make buildings more energy efficient has never been more pressing. The Passivhaus Institute is an independent research institute that has developed rigorous design standards for building properties that maintain an almost constant temperature with minimal energy usage.

The fundamental principles of design that Passivhaus-standard buildings envelope optimises their energy efficiency, and the institute is setting the standard for eco-friendly buildings. Here, we take a look at the key points that make a building energy efficient.


Insulation helps to keep warm air inside our homes, and between 35 – 45% of heat loss occurs via the walls of a building if it’s not been adequately insulated. Uninsulated roofs account for around 20% of heat loss, with a small percentage lost due to poor floor insulation in old properties with stone foundations and cellars. Adding insulation within the walls, roof and floors is one of the best ways to improve your building’s energy efficiency.

Mitigating thermal bridging

One of the core ideas of Passivhaus design is the mitigation of thermal bridging. Thermal bridging refers to the heat energy that flows through a structure by conduction, bypassing the insulation or other thermal barriers in the building. This energy flow can occur through materials such as windows, doors, and other architectural elements. This is both inefficient in terms of energy and costly in regard to bills.
A passive house design must be modelled using the passivhaus planning package. This calculates thermal bridging by calculating thermal conductivity of the envelope of the building. For example a concrete lintel in a doorway could be replaced with foam glass. Concrete conducts heat from a heat source whereas foam glass mitigates that heat loss. This reduces the need for heating and cooling technology to be used, thus reducing the energy needed to operate the house.

Air tightness

When a building leaks warm air, increased rates of energy are necessary to maintain a consistent internal temperature. A Passivhaus is required to have no more than 0.6 air changes per hour, at 50 pascals of pressure. This ensures they are incredibly airtight.
Air tightness can be achieved by using materials like solid concrete, plaster, rigid boards, or purpose-made membranes to eliminate gaps and cracks. Certain products can be passivhaus certified which show they have been rigorously tested. An added benefit of improving air tightness is that cold draughts are minimised, making for a more comfortable living environment.

Triple glazing

Upgrading windows and doors is a great way to ensure your building retains as much warm air as possible. Triple-glazing is the best method of minimising heat loss from windows and from glass panels in doors. Good airtightness of the window and door frames is vital to maximise the energy efficiency of a building, plus, triple-glazed windows and doors can also help to minimise noise pollution.

Mechanical Ventilation Heat Recovery

Mechanical ventilation heat recovery (MVHR) systems draw in fresh air from the outside and extract stale air from inside, while filtering the fresh air to eliminate pollen, dust and other pollutants. They also have a heat exchange function, which means the heat from the existing stale air warms up the entering fresh air.
This helps to maintain a consistent temperature throughout the building, while reducing demand on the property’s heating system. Provided that the building has good rates of air tightness, an MVHR system could reduce heating bills by up to 20%. Due to their inbuilt filtration system, buildings with MVHR systems are also less susceptible to damp and mould problems which can pose health risks.

Energy efficient buildings are eco-friendly buildings

By improving these key areas of a building, you’re sure to improve its energy efficiency and make your property significantly more eco-friendly. As a bonus, you’ll also create a healthier, more comfortable environment to live or work in.

 – Jennifer Collins

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