Roof insulation manufacturer Dow Building Solutions has released a new guide on making U-value calculations for inverted flat roofs.  Authored by Dr Steve Johnson, Technical Manager for the STYROFOAM and XENERGY extruded polystyrene producer, the paper outlines key considerations to bear in mind, including:

1. U-values: Location, Location, Location.
2. Design and declared lambda values: know the difference.
3. Roof build up and potential condensation effects.

“We are all aware of the importance of U-values when it comes to the long term energy performance of well-constructed buildings,” said Dr Johnson.  “With the spotlight turning on the actual energy performance of buildings – not just the designed performance – ensuring U-value calculations are robust is a responsibility the industry must take seriously.

“The inverted flat roof is a building element with many unique aspects, which must be tackled at the outset in order to avoid errors when making U-value calculations.  Water vapour movement as well as heat transfer should be calculated, and in addition condensation issues need to be satisfactorily addressed if a robust design solution is going to be achieved.”

The paper includes information on making corrections for rainwater cooling and moisture absorption, key issues to bear in mind for the inverted roof application.  Copies of the paper are available by clicking here or emailing dbsuk@dow.com.

For support with making or reviewing U-value calculations for inverted flat roofs and advice on relevant correction factors, contact Dow Building Solutions’ technical helpdesk on FKLTECH@dow.com or 08707 104 553.  Visit www.styrofoam.co.uk for product literature and technical data sheets.