Building Physics of Architecture
Last week I had the chance to eat a delicious slice of nut, egg, dairy and gluten free cake, prepared at my son's school canteen to celebrate his 10-year-old birthday with his colleagues.
A healthy and tasty cake that could be eaten by anyone!
Although it didn't have all the traditional ingredients to achieve that predictable outcome, it had the right consistency, a really good taste and most important it was healthy for all.
In spite of the Architecture and Construction industry slow reaction to the XXI century health paragons, a few things could still be learnt from the fast adaptive food industry I thought.
While making this analogy when talking about healthy buildings and referring strictly to the building physics, two important aspects come to mind:
What are the ingredients used to prepare a healthy architectural recipe?
The building materials and finishes should be assessed and specified against the effects they have on its inhabitants.
It is well known, that some materials conduct energy better than others. A healthy building fabric will require materials that have low conductivity transfer. One basic example could be timber + insulation. Leaving a concrete slab, structural steel members, metal fixings and fasteners uninsulated, we create thermal highways in our buildings, which will lead to condensation and mould growth.
Furthermore, over-specifying on wall and roof insulation, whilst the concrete slab is left exposed to the outside heat & cold, with the windows barely achieving a thermal conductivity of 2.4W/m²K and being reliant only on the natural cross ventilation to eliminate the stale air and condensation, will most likely result in an asymmetric building fabric, bringing future health hazards to the building and its inhabitants.
Concurrently, not all materials are well compatible.
For instance, metal zinc cladding or roofing can react with other metallic fixings that can cause corrosion.
The colour and reflection factors are also important. Darker colours will have higher solar gains when compared with the lighter ones.
Once combined, the material properties need to respond to a number of physical factors: be structurally sound, provide weather protection, have a slow reaction to the thermal gains or losses, be acoustically suitable, breathe and most importantly achieve the just right comfort and temperature balance.
The architectural recipe:
While backing the Built Architecture recipe we should address 5 main building physics characteristics:
Adopt continuous insulation across the entire external envelope - floor - walls - roof;
Eliminate thermal bridges - use engineered timber structural members rather than steel for instance. If steel is used it should be insulated.
Achieve good levels of indoor air quality using mechanical ventilation heat recovery units;
Balance the amount of solar gain and energy losses through the glazing by using well insulated (double or triple glazed) thermally broken windows;
Achieve a tight external envelope and test the building for airtightness levels;
None of the above features should be left behind, if the aim is to achieve a healthy building. External fabric will perform, the building will rely on a small amount of renewable energy equipment, have a reduced carbon footprint, small or no energy bills, good levels of indoor air quality, be healthy and comfortable for its occupants.
If the above 5 characteristics of the recipe are taken to extreme, you will most likely end up at Passivhaus!
Use the right ingredients and the appropriate recipe to achieve the just right details within your built architectural response, and bring truly healthy outcomes to all inhabitants.