I have seen a grey metal roof glow in reflected sunlight as if it were gold. As I dimly recall, this effect was most prominent in the early morning and in the evening with the sun at low angles from the horizon. This was very effective in drawing attention to the building, a church.

Dear Pawel,

As far as I know, the topic has been poorly studied. Maybe the best way to get relevant information would be via contacting the manufacturing industries and directly ask them your questions.

There are many aspects to consider, ranging from aesthetic criteria to visual, thermal, environmental, other building physics aspects, etc. Nevertheless, find below a few basic facts to consider as starting point:

1. The so-called " TECU® Gold " is not actually gold. It's made of an aluminium and copper alloy. See:

https://www.kme.com/about-us/news-events/news/news-article/wrapped-in-tecu-gold/

So " TECU® Gold " visually looks like gold.

2. Regarding environmental impacts of "gold" in global scale, see:

http://ec.europa.eu/environment/integration/research/newsalert/pdf/302na5_en.pdf

As stated in the second link:

"

For an ore grade (i.e. metal content) of 3.5 gram per tonne of ore, the study estimated that production of each tonne of gold from non-refractory ore used approximately 200,000 gigajoules (GJ) of energy and 260,000 tonnes of water. It produced 18,000 tonnes of GHGs (CO2 equivalent) and 1,270,000 tonnes of waste solids. For refractory ores, the GHG emissions and energy use were about 50% higher, owing to additional processing steps required. Per tonne of metal produced these figures were several orders of magnitude greater than those for other metals, such as steel and aluminium. However, gold is produced in much smaller quantities, so the total environmental footprint for global gold production is smaller than some other commonly used metals, including steel, copper and aluminium.

"

Also have a look at:

https://en.wikipedia.org/wiki/Embodied_energy#In_common_materials

To put it into perspective let's have a rough comparison between gold and aluminium in cradle-to-gate stages of LCA:

Gold:

200,000 MJ per kg (embodied energy)

18,000 kg CO2e per kg (carbon footprint)

Aluminium (general & incl 33% recycled):

155 MJ per kg (embodied energy)

8.24 kg CO2e per kg (carbon footprint)

As you see environmental impacts of producing (a fixed amount of mass of) gold is much larger than those of aluminium.

Hope it helps.

Best,

Aryan

What are the techniques (the technology) of covering building facades in gold (real gold and imitation) ?

The gilding or gold plating are used in cupolas of churches of Eastern Orthodox church. The cupolas of Uspenski cathedral of Helsinki were gilded rather recently because of the 150 years jubileum of the church.

Gilding is rather expensivive, especially the work. The gold is very thin and the total amount of gold is actually very little. The surface is very seldom flat which is a challenge too.

The total area of Uspenski cathedral's 14 cupolas was 150 m2 and little more han 400 gr of gold was used. Gold was fixed with special oil.

My writing was based on an interview of Harri Virtanen in program:

"Kahden kesken /Kultaajamestari Harri Virtanen osa 5"

Dear Peter F. Colwell,

Thank you for your opinion, it confirms my observations.

Dear Aryan Shahabian,

Thank you for your valuable contribution to my reaearch. I will have to compare gold consumption on façades in relation to other materials.

Dear ulla-maija Rimpiläinen,

Thank you for the informations about cupolas of Uspenski cathedral of Helsinki. They give me an idea of what gold consumption is for gilding.

You're welcome dear Pawel