Passive House Course Day 2 - Our Number One Priority?
What’s our number 1 priority?
The ‘green wash’ we see in the marketplace today can be confusing and misleading. If you occasionally find yourself in a place of confusion, then rest assured you’re not alone. I know I am. I see so many products and materials construed as ‘eco’ or ‘sustainable’. It sounds like you could use anything as long as you can justify it...kinda like a breakfast cereal claiming it’s gluten free so it must be healthy right?! Yet when you scan the ingredients list it’s loaded with sugar!
I want to be as sustainably conscious as possible, but is it actually my main priority? No.
Pause for a minute and consider what we’re actually trying to achieve when building a new home or renovating an oldie. Honestly, what is our number one priority? I believe it is as simple as, “create a comfortable and safe indoor environment”.
Assuming we’re on the same page here, then so is Passive House.
Thermal comfort by definition this “is the condition of mind that expresses satisfaction with the thermal environment and is assessed by subjective evaluation”.
Passivhaus has determined some ideal characteristics for thermal comfort, which in essence provide some design standards to adhere to;
Temperature Range - maintain an indoor air temperature between 20-25degrees - 24/7/365.
Temperature Change - ensure that the temperature difference from indoor surface to indoor air is never greater than 4 degrees. Otherwise the radiation effect from the surface would be perceived.
Stratification - make sure that the sire temperature near the floor is no greater than 2 degrees different from the temperature at head height.
In order to achieve our thermal comfort there are 5 key principles to passive house;
Thermal Envelope - create a fully insulated barrier around your building
Air Tightness - ensure a continuous air tight perimeter to ensure air leakage or infiltration does not occur
Windows & glazing - is typically the weak point of a building, high performance standards are essential
Ventilation - is going to be critical when the envelope is airtight and insulated. Heat Recovery systems will bring in fresh air and expel stale air with minimal temperature loss internally.
Thermal Bridges - conduct from the inside to outside, transferring heat and affecting the heating and cooling loads. Something good design should avoid.
Beyond these principles some well known design considerations are still very effective;
Size - the smaller a building is the less demand it has on heating and cooling, and the less resources required for the build.
Orientation - maximise north, minimise west & east.
Shading - control heat gains in summer. Shoulder seasons also worth considering in a passive house.
The passive house tool (PHPP) will ensure that a comfortable and healthy indoor environment is created, whilst also considering the economics and viability of each building composition. It does not tell you ‘how’ to get there, nor does it prescribe ‘what’ you must use to achieve a satisfactory outcome, it purely uses the science and assesses the physics.