Colorcoat® Column: Sustainable Refurbishment
There are many reasons to consider the refurbishment of an existing building. The need to refurbish will depend upon the condition of the building and its application. Quite often with industrial and warehouse premises the refurbishment is undertaken out of necessity e.g. for a leaking roof!
Refurbishment should be considered as more than extended maintenance. Instead it should be used as an opportunity to make significant changes and improvements to the building.
Refurbishment of an existing building can provide very significant improvements in thermal performance and reductions in operational CO2 emissions.
How does the embodied and operational CO2 of a refurbished building compare with a new building?
Examination of the embodied CO2 of a warehouse building shows that only 10% is contained within the building envelope. Approximately 75% of the embodied CO2 is associated with the foundations and floor slab. Refurbishment of the building envelope, utilises the existing structure and will save ~ 90% of the embodied CO2 compared with a new build.
The refurbished building will be significantly more energy efficient and have reduced operational CO2 emissions approaching that of a new building and meeting the latest revision of the Building Regulations. The operational CO2 savings over the life of the building will be significantly greater than the additional embodied CO2 from refurbishing the building envelope. In many cases the refurbished building can have a lower overall CO2 footprint than a new building. The exact savings will be dependant on building type, size and application.
Which aspects of refurbishment will contribute most to reducing the operational CO2 emissions from the building?
Industrial buildings, constructed during the 1970s and early 80s have extremely poor thermal performance when compared with current regulatory requirements.
Typically they have minimal insulation with wall and roof U-values in the region of 2 W/m2/K. Air-tightness was not a specified requirement when these buildings were constructed and air-leakage rates in the region of 30 m3/h/m2 are typical. Current regulations require new buildings to have a minimum U-values of wall 0.35 W/m2/K and roof 0.25 W/m2/K and minimum air-tightness performance standard of 10 m3/h/m2.
Refurbishment by either over cladding or a complete strip and re-sheet will show the greatest improvement in thermal performance and associated reduction in CO2 emissions.
Increased fabric insulation will generally show the greatest contribution as the initial U-values are so poor.Air-tightness will also show very significant benefits. For an over cladding refurbishment, a membrane must be installed underneath the additional insulation, otherwise there will be minimal improvements, as the external sheet will not provide an air-tight barrier.
With careful consideration, the operational CO2 emissions of a refurbished building can approach those of a new building and show reductions over the previous building of ~75% of the envelope related CO2 emissions.