Passivhaus Myth Busting

Eoin ONeill
Over the past few years, I have heard many myths about Passivhaus, which can cause clients to have hesitations about using the Passivhaus building standard.

What is the Passivhaus building standard?

Passivhaus translates from German to Passive House. The principles were developed by the Passivhaus Institute in Germany. Passivhaus standard is focused on delivering increased building comfort, quality, and lower running costs. The Passivhaus accreditation requires buildings to be built with meticulous attention to detail and rigorous design and construction standards according to the five basic principles which can be seen below.

Why would I spend more money to build a Passivhaus?

New legislation, guidance, and funding schemes are driving the construction industry to reduce both embodied and operational carbon. There are many actions and interventions that can be implemented to work towards that goal, and Passivhaus with over 1,000 buildings underway in the UK, is an excellent and well-established methodology for doing so.

It must be noted that with the right team, a Passivhaus project need not cost significantly more than a traditional build. The focus must be on balancing where the budget is allocated. Additional costs for airtightness and thermal performance (for example, triple glazed units and increased insulation) can be offset against efficiencies in other areas. Great examples are the simplicity of form that we are seeing in Passivhaus designs, resulting in decreased external envelope costs, and the reduction in the amount and size of heating plant and equipment.

Yet that considers at capital cost only. From a cost perspective, the primary reason to build a Passivhaus is because studies and live examples show that the whole life cost reduces, this is mainly due to the decreased energy use costs. Therefore, with a higher quality building and resulting low energy use, we truly building for the future and the business case should reflect the benefit in the value obtained over time.

Does Passivhaus mean my building is Net Zero?

Passivhaus is not Net Zero, however it is a significant and proven step that will get you much closer to your goal. By incorporating the ‘fabric first’ principles of Passivhaus into building design, energy demand will greatly reduce. This is a huge step in the right direction, yet to get to Net Zero carbon in use, the remaining energy requirement needs to be offset.

That offset could be achieved with the use of local renewables such as solar, geothermal, biomass, etc. If this is unaffordable for a project, then management strategies can be put in place to ensure the building owner uses energy from a green supplier with fully renewable means to generate the power they supply (hydro, wind, tidal, etc.).

Isn’t it stuffy? Do I have to keep all the windows closed?

Opening your windows and doors in a Passivhaus building will have the same effect as doing so in a traditional one. However, Passivhaus also delivers improved building comfort and, with the more regulated and constant flow of fresh air, you won’t feel the same need to do so.

Passivhaus are built to have no uncontrolled air draughts in the windows, through the walls or under the floorboards. However, purging the air in a Passivhaus can be done even more easily than by opening the windows – you just turn up the fan in the Mechanical Ventilation with Heat Recovery (MVHR) system for 30 seconds and the air is fresh again. So Passivhaus gives you more choice in your life, and allows you to decide when you want to open your windows

Can the supply chain deliver to this new standard easily?

Many tier one contractors have realised that Passivhaus principles will likely form a major part in the construction of new buildings in the future. Contractors are in the process of upskilling their design managers and site staff by completing the certified Passivhaus designer and tradesperson training offered by the Passivhaus Trust. However, the difficulty then comes with how to impart this knowledge to the subcontractors and tradespersons who deliver the work. They must also meet the quality requirements that Passivhaus demands.

For these reasons, and until the body of experience grows, consideration should be given to early contractor involvement during the pre-construction phase. This will allow greater engagement with the supply chain to ensure costs do not escalate. It will also help set the expectations for quality of workmanship and offer the designers a forum to engage with subcontractors, to explain some of the complex airtightness and thermal bridging detailing involved, and afford the opportunity for subcontractors to offer their own solutions hence managing the risk.

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