For many, the idea of building a home to Passivhaus standards may seem very difficult and expensive compared to a normal home. A recently published analysis of construction costs by the Passivhaus Trust in the UK, however, has found that costs are reducing as the methodology is becoming more widely adopted.
Back in 2015, a study by the Passivhaus Trust, found that the costs of building a Passivhaus was between 15 and 20 percent more than when building to other standards used widely across the UK. This is because, at that time, the standard was quite innovative—something that often comes with extra costs. Thankfully, it looks as though this is rapidly changing as people become more familiar with the methods. In their most recent study, the Passivhaus Trust found that the best practice costs of Passivhaus homes were 8% higher than comparable projects in 2018, and they think it’s possible to reduce this to 4%.
This shift in cost is quite a significant and helps to increase the affordability of efficient, comfortable and sustainable home designs. But what is it that makes them more expensive in the first place? This is complicated and will depend on the specific project but can typically be associated with several factors. These include better quality wall and room insulation, glazing of windows and doors, airtightness, extra site supervision and, of course, Passivhaus Certification throughout the project. It’s important to note that these initial extra costs are what lead to a high-quality, efficient design that will usually have long-term savings in relation to running and maintenance costs. And that’s not even considering the benefits for the climate and our health and wellbeing.
Source: the Passive House Trust
If you are planning to build a Passivhaus soon, the last thing you want is for it to end up blowing over your budget and not getting certified. So let’s look into what you can do to ensure your home is designed to the necessary standards without going over budget:
1. The initial brief
Ideally, the choice to design your home to Passivhaus standards should be made as early as possible so it’s part of the initial brief. This will ensure proper consideration of the requirements are made right from the very beginning of the planning process.
2. Passivhaus designer
As early as possible, ensure there’s someone on the project who has a good understanding of Passivhaus standards. An architectural practice that specialises in Passivhaus designs, like Leanhaus, is ideal but not a requirement.
3. Simplicity
Simple homes are typically much more practical and affordable than complex ones. Familiar materials, and simple strategies for more technical elements like airtightness should be utilised to make sure no time consuming or wasteful mistakes are made.
4. Ventilation design
Ensure the design of the Mechanical Ventilation and Heat Recovery (MVHR) system is done by someone familiar with MVHR systems and the Passivhaus criteria.
5. Summer comfort
A particularly important consideration here in Perth, the design needs to be realistic about how much cooling is possible with passive methods like cross-ventilation, and function should always be prioritised over form. External shading and glazing orientation, in particular, should be carefully considered. At Leanhaus, we also recommend having a back-up method in place for particularly hot days.
6. Airtightness
Throughout the building process airtightness should be taken particularly seriously and careful planning is crucial. Several tests throughout the build are also advised so any leaks can be caught early on when they’ll be most affordable to fix.
7. Educated team
The entire team you work with should be familiar with Passivehaus principles and, in particular, understand how the principles will impact their part of the project.
8. More than just design
Even if your initial plans and design are of the perfect Passivhaus, a lack of expertise on-site can lead to a bad final product. Throughout the design, someone should be appointed to monitor progress, ensure work is of a high-quality and make sure the key elements are properly enacted.
9. Collaboration
Good communication between the designer and contractor is important on any site, but with the specialised knowledge needed for a Passivhaus design, it’s even more so. If the designer doesn’t properly explain what’s needed, or the contractor doesn’t understand, there’s bound to be issues.
10. Appoint a certifier early in the project
The Passivhaus certifier shouldn’t just be viewed as someone who comes to look at the project after completion to either provide certification or not. They should be found early in the project and be involved throughout, clearly setting out requirements at each stage and providing advice where necessary.
With early planning, the right team and consideration throughout it’s more than possible to build a home to Passivhaus standards without breaking the bank. If you’d like to learn more about how we can help you do this, get in touch.
This piece was written to summarise the findings by the Passivhaus Trust. To see the full report, go to their website here.