The construction sector is currently very energy intensive and emits a lot of greenhouse gases. The iron and steel industry accounts for 11% of global carbon dioxide (CO2) emissions. Cement for buildings and other uses accounts for another 7 %. Regular insulating materials such as rock wool, fiber wool or polystyrene also are exceedingly energy and carbon intensive. Add to this the many shortages the sector is currently facing…
So current ways of building won’t cut it anymore if we are to cut down emissions to zero and even become carbon-negative by mid century (it may seems far, but it’s only 27 years away).
We need a green revolution in how we build and renovate buildings to sustain cold winters and hot summers without necessaryly resorting to air conditioning. To do so, we need to use denser materials to retain indoor temperature and/or slow down temperatures exchanges. Fortunately, these materials do exist already and just need to be used much more and even become mainstream..
What if we used materials that come from Nature and sequestered vast amounts of carbon dioxide for decades ? What if we used circular economy principles and turned trash to treasure ? Today’s article will serve as an introduction to four of these better, greener materials.
These days, many biobased materials exist, such as rammed earth, cork, sheep wool… with wood being the most used and the most well known. I will not cover these here but just know they exist and each have their own pros and cons. In today’s article I will cover two materials that can give jobs to local agriculture and industry, straw and hemp coming from local agriculture.
Straw is a by-product of our agriculture, whether it comes from wheat, rice or other cereals. It’s a material that stores carbon and can be used to build comfortable homes and buildings. While it has been used for more than a century as a construction material, relatively few houses are built every year with it. Much cheaper than regular construction materials, straw bales homes are also more comfortable, provide a low fire hazard (yes, you read that right) and yes, it can be used for relatively high buildings :
During the course of my technical training I saw many cases of homes and buildings made out of straw and wood, including a massive 2,700 m2 / 29,000 sqft 8-story building that provides 26 appartments in Eastern France. Built ten years ago for 1.4 M€, this building has passive housing certification and comes with solar thermal hot water and geothermal heating. So, yes, the US and Canada and many other countries could build out the missing middle housing in such a way.
Hemp can be used for everything and anything, including in construction. Hemp grows fast and without pesticides. Hemp- based concrete, also known as hempcrete is particularly promising as it sequesters a lot of carbon, provides very good insulation as well as good fireproofing. Various construction modes exists. As an example, hemp can be used as bricks to add external insulation to already existing walls or as filling within a wood frame. To learn out more, please check out this great Grist article.
Materials from recycling
Nowadays 1.2 billion pairs of jeans are sold globally every year. With the boom of fast fashion, some of these are thrown in the trash after just a few years. Of course, many more are sold again to eco-conscious folks. But what happens to really old and worn out jeans ? Thanksfully, denim insulation comes into play. By blending 80% denim with 20% fireproofing and other materials, this green material offers great insulation.
In France, a company is collecting 2 million jeans per year, which is enough to weatherize 4,000 buildings for both renovation and construction. A lot more could be done.
What if instead of being wish-cycled (ie. not really recycled) away, discarded and recycled newspapers and related paper products were reused to insulate buildings ? Given how our societies rely heavily on paper, cartons, newspapers and packaging, the potential here is gigantic.
These days, cellulose from paper is more and more used as a mean to insulate attics. With some borate treatment to make it safe against fire and pests it is better than regular materials for soundproofing. In France we are using 30 cm / about a foot to achieve an RSI value of 7 (39.75 for you non-metrics folks).
With today’s article you will have probably understood while I am very enthusiastic about biobased materials and others coming from recycling. It truly is a great opportunity for our cities and communities.