Thursday, 17 November 2011

Critical publication review:Traditional, state-of-the-art and future thermal building insulation materials and solutions – Properties, requirements and possibilities (Bjørn Petter Jelle a,b,∗ )

In this article the Jelle outlines the advantages and disadvantages of thermal building insulation materials. He investigated traditional, state-of-the-art and possible future materials. The table attached compiles all of the various properties, requirements and possibilities analysed. This table is intended as a reference table and a learning tool for insulation materials and will be updated over the course of my studies.

Currently there is no single material that is capable of fulfilling all requirements. The new materials being introduced have their limitations, and Jelle stresses the importance of knowing these.
Jelle notes how recent studies point out that insulation of buildings is more cost-effective than the creation of renewable energies. It makes good fiscal sense to take account of these advances and for investment to be put into thermal products.

Thermal background in brief:
The main key property of thermal building insulation materials are the thermal conductivity (W/(mK)) and a low thermal transmittance U-value (W(m2K)).

Traditional insulation materials:
Traditional thermal insulating materials were robust with respect to perforation vulnerability and flexibility. They generally have a thermal conductivity value of between 30 and 40 mW/(mK). However this increased with an increase in moisture content.

State of the art insulation materials:
The author is most impressed with vacuum insulating panels (VIPs) and Aerogels. VIPs can achieve a thermal conductivity of between 3 and 4 mW/(mK) when in good condition. However, vacuums have a problem with maintaining their thermal conductivity over a long time period (vacuum can be lost with air and moisture penetration due to diffusion). Perforations also create an increase in thermal conductivity to 20mW/(mK).
Aerogels can achieve a thermal conductivity of as low as 4mW/(mK) at a pressure of 50 mbar. Aerogels conductivity does not increase over time, and perforations present no problem. As Aerogels can be manufactured in a translucent state this may mean that their application may be considered for projects where clients may be willing to pay higher costs.

Future Materials:
Currently the Nano insulation materials (NIM) solution seems to be the best high performance, low conductivity thermal material for the foreseeable future.
Dynamic insulation materials (DIM) and NanoCon also show good potential, due to their thermal insulating properties and their good load-bearing properties respectively.

The author concludes that NanCon, the theoretical insulating material is the most desirable solution. I think that the DIM shows the most potential for global use due to the fact that its thermal properties can be altered in relation to the geographical climatic conditions.
The Passive House Standard is a standard that is global. It has been well discussed that Ireland does not require the very high standards set out by the Passive Institute. There may be an option to build using materials that have the potential to reach the standard when needs arise, but are of a much lower standard than needed in mainland Europe.

If the properties of the DIM (for thermal adaptability), NIM (Nano Insulation Materials: for strength and thermal conductivity), and the Phase Change Materials (PCM: these change from solid to liquid when heated and then when cooled release the energy used as heat back into building thereby keeping internal temperature constant), while also having a material that could adapt to moisture content, we would have the ideal solution. 

Link to the table of Insulating materials

Link to "Traditional, state-of-the-art and future thermal building insulation materials and solutions – Properties, requirements and possibilities"


  1. Eimear,
    Its interesting to note that the author tells us that the insulation of buildings is more cost effective than the creation of renewable technologies such as solar photovoltaics and wind energy. This is quite a broad statement and if one were building a large house, using say Aergel insulation (which we are told is expensive) maybe a less expensive insulation and a small wind turbine or solar panel would be more cost effective?
    Also, as you know, sound wind and air tightness are critical to any insulation type's performance.
    Your post is well structured, informative (table of thermal insulation materials) and easy to read and understand.

    Well done

  2. Shay,
    Good point about the less expensive insulation, coupled with the wind turbine. I think that insulation and the building fabric should always be most important, as they are static (whereas energy demand is volatile), and play the biggest part in energy efficiency.

    I think that the Jelle's point was more about where your money is better spent. It is better to have a house that requires very little energy where you to have to pay small bills, than to have a house that requires more energy, but you have to depend on a renewable energy source. This energy source will probably only contribute to the required energy for the house, and not supply all of it. For example current wind turbines would have difficulty reaching the demand of a five bed house in Ireland, and generally they would have to be supplemented by more traditional energy sources to meet the energy demand.

    In this situation one would be leaving themselves in an uncertain long-term situation financially. If you install the wind turbine with less insulation, the excess energy needed that you have to pay for may be affordable at the moment. But at some point in the future your energy demand might increase (more children in the house for example), or the price of your secondary fuel (oil or gas for example) may rise, and your costs to run the house could multiply greatly.

    It you insulate the house to a higher standard, your dependency on an energy source to maintain comfort and standard of living is drastically reduced, and you can budget more effectively in the long-term , and are more likely to spend less.

    Jelle also notes in his article that Aerogel is very expensive and proposes that it be used on larger projects, commercial ones for example, where budget is not a major issue. He does not recommend them for dwelling houses, but does say that they have great potential if developed correctly.

    Thanks for your comment, you have certainly got me thinking about the whole energy demand of the house!