7 key principles of solar passive design - Part 2.

Balance it all with local climate and a holistic energy calculation.

If you have not read Part 1 → Click here.

6. Adapted to local climate

All of the first 5 principles should be considered through the lens of the local climate. The design can be informed by regional traditional solutions like specific porches, roofs, window placement. These then can be upgraded to the project's specific needs.

Solar passive principles vs. the Passivhaus standard

No discussion about passive houses is complete without mentioning the Passivhaus standard. People of all countries tried intuitively to build solar houses with more or less success and continue to do so today.

In the end of the 1980s, a small group led by Dr. Wolfgang Feist in Germany assembled an engineering concept called “Passivhaus”. It is based on the first 5 principles I mentioned and it draws an extremely low energy consumption level for all houses:

15 kWh/m2/yr (4.7 kBtu/ft2/yr) for heating & cooling demand.

In order to obtain a Passivhaus certificate a building must go through a rigorous reviewing & test process that demonstrates the buildings energy-efficiency after it was built! In the last 8 years I designed several Passivhaus level buildings that obtained certification and I’m continuing work on such projects.

Passivhaus became a widespread movement with 1000s of PHs popping up in every country but it continually suffers from an overly engineering-heavy approach that births aesthetically unappealing designs.

Some built Passivhaus examples from the passivehouse database

I too had to compromise many times the initial building design on the altar of efficiency, to gain that extra 2-3 kWh of energy reduction, to get below the certification limit. As you might imagine this gets exponentially more difficult as overall efficiency gets better and the end result can leave both client and designer with a sour taste in the mouth.

So lately I am attempting something bold, a holistic synthesis of the old principles, localist building styles with the new methods of Passivhaus energy calculations. This is the holistic approach that underpins the Solarchitecture practice.

This means that all this to work we have to:

7. Balance it all in an energy calculation

The only graph you need to understand:

And maybe this:

The passive house consumes less energy in a whole year than a conventional one in one winter month. Overall around 10x less.

If we analyse things holistically with an emphasis on form and beauty, there's no use cutting another 5% of heat loss off if it transforms the design. Furthermore the owners might have to pay 20% more for something that brings only 5% more of energy reduction.

Some places, like the middle of the forrest may prohibit the house from becoming a passive house. Nevertheless heat-loss can be minimised to obtain a low-energy consumption and a stable indoor climate.

Solarchitect | Sunbeam carpenter @Solarchitects

Analyzing whether my original sun exposure assumptions were correct with the help Sunseeker App.

Modern tools like Sun-seeker app help analyse the local context in great detail, helping the holistic energy-design even more by improved window positioning, sizing, orientation. The energy calculation also shows overheating risks and it is possible to simulate off-grid concepts like PV-array efficiency on roofs with great accuracy.

Conclusions

Wrapping it up, here are the 7 key principles we’ve talked about:

1. Solar gain maximisation & quality windows

2. Continuous thermal envelope

3. Thermal bridge free design

4. Natural & Heat-recovery ventilation

5. Air-tightness of thermal envelope

6. Adapted to local climate

7. Balancing it all in a holistic energy calculation.

A beautiful passive house keeps both the body and soul of the family energised!

Until next time,

Solar

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Sources and in-depth reading about solar passive buildings and passivhaus.