We recommend having preliminary calculations done through the early design stage. To make a first assessment of the energy performance at pre-planning stage. To enable informed design decisions through later stages of design and execution. 

Further details get added throughout the design process. Until all missing information has been put in to achieve passive house certification.

The first approach with the calculation tools should be at the concept stage.


Well before the design gets finalised.

When used through the early design stage the building form can get optimised.


The performance of the building can be checked against different design options. For instance, for the form, mass, orientation, fenestration etc.

Different design options can be reviewed against their impact on the predicted energy efficiency requirements. 

This can pinpoint any potential areas of overheating. Or thermal bridges. And can give clarity on the most beneficial design options.

While considering the 6 major passive house principles. 


Even if you don’t want to certify your home. Or if you are not sure you want a passive house after all.

Going at least through the preliminary calculations makes a lot of sense. For any project type. You can refine the solar passive designs of your house. And build a low energy home without any assumptions. You can rely on accurate calculated data. Also taking into account thermal bridges and air leakage.

The preliminary calculations in the PHPP allow the user to enter and test several design options. For single components as well as for a whole building.


For example, deciding the type of glazing for the project. 

Do you need double or triple glazing? Is it enough to only get triple glazing for some of the windows?

Do I need external shading to prevent overheating? And if so, which windows?

This information can also help you to decide on what split system you need. And can also give you valuable data about the MVHR required. (mechanical heat recovery ventilation system)

There is no guess work. You will get a clear scope for your project. This can save you a lot of time and money in getting it right early on. And will also reduce the chances of error.


Passive House Certified buildings are likely to have fewer variations during the construction. There are usually less delays, call-backs and warranty claims. Due to the comprehensive quality assurance process the project went through already. 

The level of documentation during the design and construction phase is more rigorous than conventional construction. And there are also more rigorous inspections.

Any potential problems are usually detected in the design process.

And can be dealt with early to avoid delays on site later.


An extra layer of quality assurance provides the involvement of a Passive House Certifier at an early stage. This will help streamline this process further. 

This high level of quality management means builders of Passive House Certified buildings are also less likely to have dissatisfied customers. 

In the next part of our series I will explain a bit more about the passive house principles. Stay tuned.

P.S. A huge thanks to our passive house designer Shaily, who has been helping me put together all the details for you!