• Nicky Frost

Achieving the gold standard in energy-efficient self-build homes

Soaring energy prices have been making headlines daily, but for some households, heating bills aren’t much of a worry. These are residents of Passivhaus homes – homes that are built – or retrofitted – to an internationally recognised “energy and comfort standard”, which typically involves very high levels of insulation, triple-glazed windows, and an airtight, draught-free structure.



Energy-efficient self-build homes: As climate change awareness now on the forefront of many agendas, Passivhaus designs have become more popular with self-builders and right now there are 1,500 Passivhaus buildings in the UK.


What is a Passivhaus?


To qualify as a Passivhaus in the UK, a building must meet the standards required by the Passivhaus Trust - a non-profit organisation that supervises the awarding of the Passivhaus standard. The building undergoes a strict compliance process with an expert consultant who is an accredited certifier. Passivhaus Trust. The trust is a non-profit organisation that supervises the awarding of the Passivhaus standard in the UK.


Jon Bootland, the chief executive of the Passivhaus Trust explains how it works:


“It’s a way of ensuring that your building or home is very energy efficient, by reducing the energy demand – particularly for heating – down to very low levels while, at the same time, making sure the building is comfortable inside and has high levels of good indoor air quality.
The certifier supervises the process from the beginning, they check the drawings, they check what’s built on-site and they check the end result – and then that gets certified, at that point. It is much more rigorous than the typical building regulations inspections that always occur during the construction of a house.”

A Passivhaus may look no different from the outside, but you can guarantee that the design will have been meticulously crafted.


What will a Passivhaus deliver?

· Reduced utility costs

· Potential rebates and tax credits

· Improved indoor air quality

· More durable homes

· Acoustically sound living

· Less reliance on fossil fuels

· Better value for money over time

· A chance to deliver greener living credentials


To achieve the Passivhaus standard, you need to meet 5 main principles. These principles are the core ways in which you can differentiate a “normal” home from one that has the Passivhaus badge of approval.


1. High-quality insulation

The approach taken in Passivhaus is sometimes called ‘superinsulation’. The aim is to have an ‘envelope’ of insulation, that – as far as possible – is unbroken by any interruptions, so the building can hold in as much warmth as possible. This means that the insulation will usually cover the whole exterior of the building, ideally with no breaks from materials in the structure of the building.


2. No thermal bridging

One of the ways to achieve ‘superinsulation’ is to avoid what’s called ‘thermal bridging’ – using a material that’s less well-insulated than the rest of the house exterior. This could be the frame of a window, for example, which conducts heat more than the other materials around it. That interrupts the insulation ‘envelope’ surrounding the whole building.


3. Superior windows

Windows can often be the weak link in a building. For this reason, using high quality windows is a vital part of Passivhaus standards. This means using windows that are as high quality as possible, to resist the serious heat loss that can so often occur through them.


4. Airtight construction

Another important aspect to the ‘envelope’ is airflow – as this is another way where the protective bubble of insulation can be pricked. This means that you need to pay close attention to airflow at the design stage, as well as using high-quality construction.


5. Mechanical ventilation

Don’t worry – Passivhaus doesn’t mean you’ll be stuck breathing stale air! Instead, Passivhaus keeps the air fresh through a system known as ‘mechanical ventilation’, where a heat recovery ventilator (HRV) continuously removes old or moist air and delivers fresh air. Plus, to make it as energy efficient as possible, the system extracts heat from the air going outwards, to warm the incoming air. This means the air stays fresh, but you’re not losing all the warmth from the air already in the house.


References: https://www.theguardian.com/money/2022/feb/19/passivhaus-how-to-insulate-your-home-against-soaring-heating-bills


https://www.ovoenergy.com/guides/energy-guides/passive-house


https://www.passivhaustrust.org.uk/

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