Gray energy of a new house: 50 to 100 years of heating!

[Christophe]

I counted 120 m2 on the ground. With 1 floor, it's 240 m2.

It's still a lot ... I think 50 is possible ...in fact the more the house is well insulated (therefore consumes little energy) the longer this duration (logic: bcp more gray energy and bcp less annual bill).

For a passive house it is ... infinity

So what does an average with infinity give? No, I'm joking...

[bpval]

Hello

If that can give an idea

House 145 m2 living space / 169 m2 net floor area (gross floor area)

Total reinforced concrete (incl. Floor)

150 m3 of concrete including 50 m3 in foundations
Good 50 m3 of concrete in foundations is not the norm for a flat ground (but it is not my case)

Take average reinforcement of 15 to 20 kg of steel per m3 of concrete

And that´s it

Hello

[loop]

Hello

To give an order of magnitude of the gray energy necessary to manufacture a purchased product, I proposed the following hypothesis
1 euro = 10 KWH spent, i.e. 1 liter of fuel (e.g. fuel oil)
or 1KWh = 0.1 euro

In the case of a house of 200 euros, if we consider that half of the price is attributed to construction materials (the rest is the land + MO) there are 000 euros of concrete, concrete blocks, scrap metal, wood of framework, roofing, joinery etc ...
By applying the above rule, we obtain 1 KWh of gray energy expended

For info, the m3 of concrete delivered is invoiced 100 euros
This gives you an idea of ​​the gray energy expended in the manufacture of cement, the extraction and transport of sand, gravel, water, mixture

A+

[jean63]

For info, the m3 of concrete delivered is invoiced 100 euros
This gives you an idea of ​​the gray energy expended in the manufacture of cement, the extraction and transport of sand, gravel, water, mixture

exact and in addition the cement factories are very energy-consuming and polluting.

It is for this that I built my wooden house (Douglas of the country except exterior cladding in red cedar from Canada).

For such a wooden house, I think the "cost" in gray energy is much lower. Concrete only for the concrete "studs" every 3 meters and 80 cms deep + concrete outriggers 50 cms high + ground floor slab on backfill with heated floor slab.

No trace of concrete from the floor to the ridge: wood, insulation, glass, ...

wooden joinery, wooden shutters (oregon pine)

[loop]

Hi John

Thank you for these details on your construction which demonstrates that a house can very well do without the concrete that is systematically poured everywhere

For the slab on the ground floor I think we could do without it, because I find it completely inappropriate when you know:
- the gray energy of the concrete (and it takes a few m3)
- the irreversible aspect of the screed (try to break a piece)
- the huge thermal bridge made on the ground
- the final cost for a poor result

PS: Jean could you make a sketch of the insulation of your floor in relation to the ground and outside?

A+

[bpval]

Hello

So according to your calculations the cost of purchasing materials for a concrete structure

Concrete 150m3 * € 100 = € 15000
Steel 150m3 * 20kg / m3 * 1 € / kg = 3000 €

Either € 18 * 000kwh = 10kwh or 180% of the gray energy spent

The remaining 82% is therefore excluding concrete ...

Hello

[jean63]

Hi John

Thank you for these details on your construction which demonstrates that a house can very well do without the concrete that is systematically poured everywhere

For the slab on the ground floor I think we could do without it, because I find it completely inappropriate when you know:
- the gray energy of the concrete (and it takes a few m3)
- the irreversible aspect of the screed (try to break a piece)
- the huge thermal bridge made on the ground
- the final cost for a poor result

PS: Jean could you make a sketch of the insulation of your floor in relation to the ground and outside?

A+

I am not good at sketches.

On the concrete screed (thin) poured on the embankment, there is a special insulating floor heating (I forgot the thickness) and also on the sides to prevent thermal bridges to the outside, and on 12 cms d 'thickness is poured the actual heating slab. The network of pipes is dense to allow the use of water at low temperature and avoid circulatory pbs for the legs.

I think all heated floors are made like this.

Indeed, the PC is an option that I chose because the most realistic to give a little inertia to a house that does not have one and in addition poorly connectable to any boiler system or solar collectors producing water at low temperature. In addition it frees up all the wall space, distributes the heat well throughout the room, it's very comfortable.

Indeed, a wooden floor is more comfortable to touch than an icy tile, but also less easy to maintain.

Normally there is no reason to break such a concrete floor (PER pipes are guaranteed 50 years). The house has been built for 25 years.

Indeed if one day there is a problem, there it is the disaster, it is necessary to replace by radiators "low temperature".

In the bedroom, floating floors have been laid on the slab, but heating is not used in this room.

[Christophe]

1 euro = 10 KWH spent either 1 liter of fuel (fuel oil for example) or 1KWh = 0.1 euro

(...)

By applying the above rule, we obtain 1 KWh of gray energy expended

I like your method: fast and fairly effective.*

But it only works in the worst case obviously (100% of the material load = energy and 0 margin for the contractor) ... now your 1kWh = 0.1 € is overvalued so it must compensate a little.

0.1 € is not the cost of energy of a cement factory for example .... it should rather be 0.02 to 0.03 ... or 25% and therefore the rest is margins and other charges .. .so it sticks

If I were a teacher I would say: you were lucky but 0 anyway because reasoning erroneous! I know I had sadistic teachers ...

* if you want we could think about it to generalize it thanks to some correction coefficients according to the field of activity?

ps: otherwise you had seen that? https://www.econologie.com/forums/airshow-un ... t4868.html

[loop]

Hello

Reply to bpval

Either € 18 * 000kwh = 10kwh or 180% of the gray energy spent

Sorry, I didn't understand the percentage calculation, or what it refers to?
My method (if you can call it that) simply allows you to estimate the amount of gray energy of a manufactured product

Response to Christophe and bpval

For example for the cement (little margin, no extra in the price), you buy a bag of 25 Kg at 5 euros, this means that 50 kwh were necessary for the extraction of the components, their transport to cement plant, manufacturing / processing, packaging, logistics etc ... (i.e. 5 liters of fuel oil for example)
It must of course be understood that the energy spent on site (coal cement plant?) Represents only a part of what will have been necessary. Besides the functioning of the whole system and sometimes more demanding than the simple manufacturing of the product itself.
My reasoning amounts to saying that whatever the object purchased, if we subtract the part of the price that has nothing to do with its manufacture (R&D, marketing, etc.) we only pay for energy.
Most raw materials are very expensive for extraction, processing, transport, etc.
The mine itself is worth nothing.
Even if the industry buys cheaper energy (zero-rated oil) than the individual, it bills it sooner or later.
Depending on the area, it is undoubtedly wise to apply a coefficient, but it is the order of magnitude that counts, in particular to estimate the return on "ecological" investment of one solution rather than another.
The reference to the price of electric KWh is a good average, I think.

A+

[Christophe]

For the method I just created a specific subject: https://www.econologie.com/forums/methode-de ... t4897.html