Top 5 Sustainable Building Materials All Architects Need to Know

As a junior professional in the architecture & building industry, thoroughly engaged in green-building rating and energy performance, I have come across a wide range of building materials specifically used in high-end residential & mixed-use projects. The majority of the projects I've come across are heavily dependent on reinforced concrete and steel as the foundation materials to resilient and sturdy structures. From high-rise towers to private residences and villas, concrete forms the body and envelope, from foundation to slabs, walls and roofs. This is undoubtedly due to the materials' structural strengths and capacities to resist atmospheric pressures such as wind, it's ability to be highly fire-resistant and other qualities.The production of commercial concrete however releases into the atmosphere tons of Carbon Dioxide annually; a major greenhouse gas and a contributor to climate change and environmental disasters. So the main issue in question is how can we as sustainability-driven architects and building professionals use resilient building materials while minimising the effect on our environments?

From infrastructure to superstructure, be it low-end or high-end projects, these heavy duty materials remain essential in characterising the physical strength of buildings. But what about the environmental strength? Where does sustainability locate its narrative in a built environment based purely on material resilience and physical form?

Terra Verde collated five of the most sustainable building materials from structure, to glazing & fenestration in this short article and we aim to guide green-thinking architects, builders and designer to choosing energy-smart, fire-resistant and Zero-CO2 materials.

1. Insulating Concrete Forms (ICFs)

According to The Portland Cement Association, Insulating Concrete Forms (ICFs) result in cast-in-place concrete walls that are sandwiched between two layers of insulation material. These structural systems are strong and energy efficient and can range in use from industrial to commercial and residential at a multitude of scales. We might argue that yet again there is a dependent use on concrete which releases greenhouses emissions through its production, but the way in which sustainable building standards have redefined the typical concrete block work allowed for terms such as 'energy efficient' and 'green' to describe Pre-insulated concrete forms.

A typical pre-insulated concrete block work starts from a minimum of 200 mm thickness and a minimum Extruded Polystyrene (the insulation layer) thickness of 60 mm. This will ensure the projects meets the low U-Values (measured by W/M2.K) and minimising thermal bridging that all sustainability professionals and architects aim to attain. And here is what this system brings to project owners and end-users:

- Structural strength and resilience,

- disaster resilience and safety

- energy efficiency and thermal comfort control,

- fire-resistance and,

- overall comfort

Here is what Pre-insulated systems bring to contractors and builders:

- the efficiency of production and assembly on site,

- flexibility of working with the material to meet project requirements and design intent,

- being a lightweight system, Pre-insulated blocks are easier to transport and to build,

- meeting sustainability requirements and energy-performance compliance established by local authorities.

2. Rammed Earth

Rammed Earth is essentially constructed by 'ramming' a mixture of selected aggregates, like gravel, sand, silt and a small amount of clay, into a pre-designed formwork. This is a structural technology that locates its existence in the earliest of civilizations, particulary in Syria, Iraq and Iran, but has been widely used in modern times due to its resounding efficiency and sustainablity. In fact, it is historically considered the most sustainable, cost-effective and thermally comfortable material where perhaps access to higher-end materials was and still is less accessible.

In modern use, rammed earth attains its physical stability from an added amount of cement (5-10%) to increase its strength and durability. The actual quarrying of the raw material and transporting it to site encompass the majority of the energy use its construction, and despite rammed earth's ability to cool internal environments in summer rather than to heat, it is nevertheless an excellent thermal mass.

3. Structural Glass Systems

The glazing and fenestration systems are the elements of transparency that allow us to interpret the interior life that a building holds within its enclosure. But besides the poetics of space and the aesthetics of envelope design, there is a multitude of factors that determine glazing selection be that for windows and/ or curtain wall systems. It is crucial for architects in particular to pay attention to the qualities of vision glazing, its performance data and technical information and its effect on sustainability and energy efficiency. And a particular attention to detail needs to be given to projects that have over 90% of their facades glazed.

Structural Glazing Systems utilise stainless steel fittings, housed in countersunk holes, to fix the glass façade back to the structure instead of using the more conventional aluminium-framed systems.

Vision glazing utilised in the form of windows, curtain wall facades or roof-glazing should be examined from the basis of sustainability rather than mere aesthetics and appearance. Below are some of the crucial factors every architect and contractor needs to understand in glazing assessment:

1- Visibile light transmittance (%):

(%Tvis) percentage of incident visible light directly transmitted through the glass

2- Reflectance outside and inside (%):

% Reflectance Indoors = percentage of incident visible light directly reflected from the glass back indoors, % Reflectance Outdoors = percentage of incident visible light directly reflected from the glass back outdoors

3- Solar Energy:

% Reflectance Out = percentage of incident solar energy directly reflected from the glass back outdoors
% Absorbance = percentage of incident solar energy absorbed into the glass
% Transmittance = percentage of incident solar energy directly transmitted through the glass

4- U-Factor/ U-Value:

also refered to as the U-Value, it is a measure of the heat gain or loss through glass due to the difference between indoor and outdoor air temperatures. It is also referred to as the overall coefficient of heat transfer. A lower U-factor indicates better insulating properties. it is measured in W/M2.K in metric system

5- Solar Heat Gain Co-efficient:

The percent of solar energy incident on the glass that is transferred indoors both directly and indirectly through the glass. The direct gain portion equals the solar energy transmittance, while the indirect is the fraction of solar incident on the glass that is absorbed and re-radiated or convected indoors.

Here is an example from Guardian Glass on what performance data sheet look like advising architects and clients on the details to which they should pay attention:

4- Compressed Earth Blocks

Compressed Earth Blocks, also called CEBs, are another example of using naturally-derived materials to construct a structural system. CEBs are comprised of "mixed dry subsoil, clay, and waste aggregates, such as building rubble, compressed with machine press or hydraulic compactor at high pressures." This earth-derived material in the forms of structural blocks are sustainable and eco-friendly, have an exceptionally lower pollutant emissions per brick volume and lower embodied energy in comparison to typical kiln and country fired bricks.

As earth and soil are locally-sourced, CEB are produced on site (in-situ Blocks) and may well not require transportation from factories or not transported from further distances. Moreover, the cost, time and energy-effective material embodies a masterful art in its production distinguishing it from conventional building material.

5 - Trombe Walls:

A Trombe Wall is essentially a solar wall; it combines two of the sustainable materials we discussed above in a very effective and energy-effective system of construction: Masonry and Glass. A typical Trombe wall consists of an 203.2- to 406.4mm thick masonry wall coated with a dark, heat-absorbing material and faced with a single or double layer of glass. The glass is placed from about 19.05 mm to 152.4 mm away from the masonry wall to create a small airspace. Heat from sunlight passing through the glass is absorbed by the dark surface, stored in the wall, and conducted slowly inward through the masonry.

This passive solar system allows inhabitants of a designed space to experience year round thermally-balanced internal temperatures and general comfort due to the materials embodied insulatory characteristics. Not only will the dependence on air conditioning reduce exceptionally during summer, but also the dependence on central heating during winter; both of which typically consume the most energy produced by residential buildings.