10 keys to a Positive House

1) Climate
First, the climate of your location is very important.
It’s not the same to build on the coast of Spain than to build on the mountains of Andorra.
The climate data are official chart values accepted by the Passive house German institute.
Here it’s also added the elevation above sea level data.

2) Square metres
All surfaces of your house are taken into account.
That means square metres of indoor spaces, facades and windows.
But not only the values, but also orientations, shadows…
To give you an idea how this is done in a mathematical way, let me explain how we do this.
Once your house design is finished (so, no changes to be made); we build a simplified 3D digital model of your house by using Sketchup. Then, the model is geolocalized by using Google Earth.
Secondly we use a special plugin inside Sketchup (called DesignPH) to calculate the model (note that to use this plugin you must have the official Sketchup, not a free version or cracked licence).
Finally, the model is exported into a complex excel chart that already has all square metres of facades, roofs, interior surfaces, windows, floor slabs and (very important) the shadows.
After this, then it’s time to insert the thermal behaviour of materials.

3) Thermal behaviour of materials
All thermal values of all surfaces are calculated.
That means that every different composition of wall, roof and flooring is specially designed and also specially calculated in terms of thermal behaviour. Let me give you an example here.
When you’re outside during summer and your bare feet touch a piece of aluminium, it burns. When you step on a wood plank it doesn’t burn that much. That’s because the aluminium highly transports the energy of the sun along its matter while the wood does in a lower value. This value has different names: thermal transmittance, thermal conductivity or U value (let’s just call it U value). Its units are calculated in W/mK.
But of course your house wall, roof and flooring is not made only by aluminium or wood planks. Instead, it has layers of different materials and thicknesses. Let me give you an example. Let’s say your house has 10cm of Contra Laminated Timber (CLT), 15cm of insulation and 1cm of stucco. Then the U values are calculated according to each U value multiplied by its thickness. Finally we get the combined U value of your house wall. 

4) People
One important data is also the number of people living regularly in the house.
That is to count the heat gain that every human produces inside the house.
Imagine how refined this simulator is, that it even takes your heat production to calculate your comfort!.
I’d say every different person produces different heat values. My husband, for example, is a walking radiator! (very handy in winter).

5) Construction system
As you probably already know, there’re different construction systems you can choose for your house: timber frame, CLT, ceramic bricks, concrete, cellular concrete bricks (we’ll be soon having a post about this).
The construction systems are organised into three categories: light, mixed or massive. These categories also define the ability to retain heat inside during summer. Then light construction systems dispel the heat better than massive construction (ceramic bricks and concrete).

6) Ground 
Also the ground down your house has different thermal abilities.
Depending on the soil type, the ground could help your house dispel the heat during summer.
This data is taken from the geotechnical study (you may check our post Geotechnical Study).

7) Shading
Shadows projected into windows are very important.
On one side you have the permanent shadows projected by other buildings or trees around. But also those part of your house design: pergolas, sides and tops of your window frames (your architect will call them jamb and lintel).
On the other, the temporary shadows such as louvres and awnings. Please note that inside shading like curtains or inside blinds have no effect to protect from the sun in summer.

8) Volume
Positive and passive houses use air to spread the fresh air with recovered heat. So, the amount of volume of air that the house needs to move to deliver comfort is a very important data.

9) Machine’s efficiency
Biggest part of a passive house is the machine’s efficiency.
On one side the simulator counts the primary energy consumed by the production of hot water, climatization, and the ventilation system. Also, all the appliances’ primary energy consumption.
On the other hand, it also counts how climatization, ventilation and hot water is produced, and how this affects the comfort all year long. This means if machines or pipes produce heat to deliver hot water for instance, then this is also accounted against your comfort in summer.

10) Renewable energy
Although this is not mandatory for the Passive House Classic, it’s a must to get a positive house (which is the same as getting a Passive House Plus certification).

 

 

Conclusion
I understand this can be very complicated to digest.
Let’s just say that your positive house is a very sensitive comfort machine that runs with very low energy.
Let me bring all those technicalities down for you in our next post ‘6 musts for your positive house’.
On this new post, we’ll be summarizing the 6 key designing aspects your positive house must have.

 

 

Hope this post ‘10 keys to a Positive House’ is helpful!

Best of luck on your positive house adventure.
See you in the next post,

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