Ductwork – Embodied Energy
Embodied energy environmental impact of differing insulated HVAC ductwork specifications
Embodied energy is a measure of the total amount of energy consumed by a product during production and installation. It includes the energy used during the extraction of raw materials, transportation, and manufacture through to the installation of the product.
The lower the embodied energy of an insulating product, the lower its overall environmental impact and the faster its environmental payback will be. The environmental payback for an insulating product occurs when it has effectively conserved more energy by restricting heat loss or gain, than its initial embodied energy figure.
In the case of insulating products in energy saving applications the environmental payback period is generally extremely short, compared with the lifetime of the application. After the environmental payback is complete, the insulating products can go on saving energy for many years more. Because of this, the energy saved over the lifetime of an application is mostly far greater than the embodied energy of the insulating products saving that energy. Embodied energy is therefore usually irrelevant in the specification of insulating products.
In comparing the embodied energies of materials, the concept of a functional unit must be taken into account. In the case of ductwork insulation, the functional unit depends upon firstly, the density of the insulation and secondly, the thickness of insulation required to achieve a defined heat loss / gain. This thickness will vary depending upon the thermal conductivity (k-value / λ-value) of the insulation material. Thickness and thermal conductivity are used in calculation of the material thermal resistance (R-value) of the insulant, by dividing its thickness by its thermal conductivity.
The embodied energy content of mineral fiber and rigid thermoset phenolic insulants vary significantly. Some mineral fiber insulants have been quoted as having an embodied energy content of 5.9–11.8 MJ/lb / 13–26 MJ/kg, whilst rigid thermoset phenolic insulants are quoted as having an embodied energy content of 45.4 MJ/lb / 100 MJ/kg. Whilst these figures would seem to suggest that the mineral fiber insulant is the more ‘environmentally friendly’ product, since it has the lower embodied energy content per unit mass, this is not the case in the case of insulated ductwork.
If a comparison is to be made between ductwork fabricated from The Kingspan KoolDuct System, and ductwork constructed from galvanized sheet steel and insulated with mineral fiber duct wrap, then the functional unit must not only include the insulation as specified above, but also the sheet steel, which is absent from ductwork fabricated from The Kingspan KoolDuct System.
On this basis, the embodied energy of ductwork fabricated from The Kingspan KoolDuct System can be less than that of ductwork constructed from galvanized sheet steel and insulated with mineral fiber duct wrap – up to 30% less.
It is clear that, as a result of the findings described above, the Kingspan KoolDuct System should be considered the product of choice for insulated HVAC ductwork systems where embodied energy is a key requirement.