Passive House principles
Most of you might already be aware of the Passive House Principles but for a quick recap:
Understanding the Passive House Principles
Passive House follows FABRIC FIRST DESIGN APPROACH.
1 A continuous Building Envelope without any gaps
The woolly jumper for your house.
2 Airtightness
This plays a vital role in eliminating draughts and heat losses from your house. And also protects the building fabric from condensation.
3 Using thermally broken high performing Windows (double/triple glazed)
To maximize winter heat gains and minimizing overheating in summer. The quality of windows depends on two components. The U value (frame and glazing – the lower the better). And the g-value (measures how much solar gain is admitted through the glass).
4 Controlling Solar gains
Orientation of windows and shading devices has a big impact.
And can help with winter heat gains as well as overheating in summer.
5 Thermal bridge free detailing
Eliminating weak and leaky areas in the thermal envelope.
6 Fresh air with heat transfer
MVHR (Mechanical ventilation with heat recovery) is important to not only avoid condensation in the airtight building envelope. But also, to improve the indoor air quality.
How does the analysis process start?
While it may sound complicated. It is not rocket science. It is simple building physics.
The first step in the process is a Site Analysis. Which is no different from designing any other low energy building.
The passive house standard can be achieved with various orientations and built forms. But is easier if the house is well positioned on the site. Making the most of the passive solar design principles.
Passive houses as well as solar passive houses make use of solar energy during the heating season.
Hence it is always a good idea to start thinking around those basic parameters.
However, there might be situations where optimal positioning might not be possible. Due to site constraints. While you will struggle to get a great performance out of a passive solar home with poor orientation and solar access. You can still design a high performing passive house.
If the orientation is poor, other design considerations must be taken into account though. For instance, the house might need to be more compact in size. To reduce the heating and cooling demands. You might have to reduce your glazing area. Or you might have to go for high performing triple glazing throughout. Whereas many passive houses with optimal solar access only need high performing double glazing.
The key thing is to make the most of the site. And try to optimise solar access.
For this reason, the PHPP tool requires accurate Site Information (location, shading, exposure). And to model a building’s energy demand.
What next? Integration with the principles:
The next steps are based on “Component Performance Criteria”
The key criteria known as ‘The Evaluation Criteria. Which integrates with the Passive House Principles that we talked about earlier.
The calculations in PHPP are based on 4 main evaluation criteria:
1 Specific heating demand
It is the total required energy to heat the building for a year.
2 Primary Energy Renewable (PER)
Based on renewable energy supplies. It is calculated based on energy supply from renewable sources. And the final energy demand at the building.
3 Renewable Energy Generation
It is the sum of all created energy. It is divided by the Projected Building Footprint. Which is the vertical projection of the thermal envelope towards the ground.
4 Airtightness
It is a measurement of the air leaked through the building fabric (walls, roofs, and floors).
Why is it a Holistic Design Approach?
A design can be developed through every stage of the process. Without any guess work. And the tools can give feedback on how well the house will perform. How healthy and comfortable it will be.
The effects of any proposed changes can get accurately checked and verified. You can make better informed decisions. Depending on the impact of the proposed changes. For instance, on what they mean for the performance of the house. What impact they have on the overall build cost. Or whether they may lead to delays for the project.
And all this can be done and trialled preconstruction. So, you have more quality assurance upfront. Which means that in most cases the actual construction goes much smoother.
The decision making is less of a “guessing game” and more of a “quality assurance” approach. For both the design and the construction phase.
Even if you are not aiming or a certified passive house. The calculations are invaluable. And can help you to improve and optimise the performance of any home. Even if you are ‘just’ aiming for a solar passive or low energy building.
Once all the data is entered, the PHPP tool will tell you whether your project complies with the passive house criteria. In terms of heating, cooling and PER (primary energy demand). Or, if not, where it goes over.
And this is where the fun begins. The point where you can start to investigate possible design changes. And how they affect the performance of the house.
P.S. A huge thanks to our passive house designer Shaily, who has been helping me put together all the details for you!