Friday, April 30, 2010

Concrete and Steel VS Wood

As an answer to Annoms Question: which material is better for the environment: concrete and steel or wood.
I did some life cycle analysis (LCA) calculations, and this is my starting point:
building life time: 35 years
Materials calculated with their Maintenance cycles (from the gain (start) to the use of the material to the demolition of it (recycled or ends as waste).
I calculated the hidden milieu costs, these costs are the prices you pay to remediate the milieu problems. This way you get one number out of the 14 milieu effects.
I compared a beam that can strain 6 meter with 14 KN/m pressure. ( for 100 pieces).
Steal beam: HEA 280
Milieucosts: 220
To make steel fire proof it need a fireproof painting, otherwise the construction can bend when its get to warm. This painting i didn't calculated because its not always needed.
After steal is used we calculate with a change of 20% recycling.
Wooden beam (with FSC mark)700x280mm
Milieucosts: 107
This wood is from a Forrest with a good forest maintenance.
Every 5 year a painting and fixing.
When a wooden construction gets burned it creates a charred bit from around 20 mm, this char protects against fire so the construction doesn't need fire protection.
The wooden beam has some thermal treatment so it protects against the weather, and it makes it stronger.
After the 35 year we calculate with a 100% waste
Wooden beam (without FSC mark) 700x280mm
Mileucosts: 250
This wood is from a heist cut.
Concrete beam 400x200mm
Mileucosts: 160
Concrete beam with steel reinforcement, the concrete is made for 40% out of recycled old concrete.
Concrete construction are well protected against fire.
The bad thing about concrete is that's heavy so the building gets heavier and you need more concrete to hold its own weight.
After the 35 years we calculate with a 10% recycling.
S0 the wood with the FSC mark gets the lowest milieucosts, the most milieu effects come from the diverence in young trees and old trees (CO2 decrease). The transport is also a milieu effect. because we calculate with a mix of origin (countries from around the world). If you decide to get the wood from a forest close to the building location the milieu costs would get lower.
What we don't calculate are the milieu costs to build the factory, tractor etc. This is a discussion on my work how we going to calculate these things as well. Once these are implemented, steel and concrete will have more milieu costs added.
Wooden construction for a fabric hall.


cybrbeast said...


You say
"When a wooden construction get burned it creates a charred from around 20 mm this charred protects against fire so the construction don't need a fire protection."

AFAIK wooding buildings aren't very fireproof, they burn like.. wood.

annom said...

Very nice. I see you did your magic trick.

So a concrete beam is about as good as a wooden beam without FSC mark. Is there such a thing as "FSC" concrete? I know there is a lot of CO2 produced in the production of concrete, but they may be able to reduce this or easily store it.

I think the fire-proof thing makes sense against collapse, as the internal structure will probably stand during a fire. But that first 2 cm burns like hell and makes sure everything in you house or building is lost, although it may not collapse.

I guess you have all seen

Not a very good commercial for a wooden stadium.

annom said...

56 people died.

"One of the main outcomes of the inquiry was prohibiting the construction of new wooden grandstands at all UK sports grounds."