Recticel Insulation explains the importance of being able to trust the competence of anybody calculating insulation thicknesses.
To find out more about U-value calculations, contact Recticel’s technical services helpdesk on 0800 085 4079, or email firstname.lastname@example.org
Insulation is the biggest contributor to the thermal performance and thermal comfort of your home, so it makes sense to be confident about the product being used. If you’re working with an architect or builder, however, it’s common to trust them to specify and purchase the correct material.
Elsewhere in this edition of Progress we talk about the importance of good quality advice when choosing an insulation solution, and installing that solution to get the expected level of performance. Who, though, works out what thickness of insulation to use in the first place?
Typically, insulation manufacturers offer calculations free of charge to demonstrate the performance of their products. Some also have online calculation tools, allowing specifiers and homeowners to experiment with different options for standard constructions. And calculations can be provided by independent assessors and consultants who have appropriate software.
The calculations in question establish the heat loss through construction elements – floors, walls and roofs (pitched and flat). The measure of heat loss is called the U-value (units: W/m2K, or Watts per square metre of surface area, per degree of temperature difference between inside and outside) and the lower the value the better, because less heat is lost through the structure.
How, though, do you know that a calculation has been worked out correctly? Or, if you obtain calculations from different sources and they show different answers, how do you know which one is most accurate?
Depending on the complexity of the construction being assessed, there can be many variables that affect the outcome of a U-value calculation. Insulation is the biggest single influence, but every other part of the specification must be accounted for accurately.
The calculation of U-values is not about manipulating variables to offer the thinnest possible insulation solution; it is about establishing a realistic performance to help guide people towards regulatory compliance (or better), with a corresponding improvement in occupant comfort, energy use and environmental impact from the finished building.
Working for an insulation manufacturer, there is nothing more frustrating than being told that a calculation we have prepared is ‘wrong’ because it shows a slightly thicker insulation product than someone else claims can be used. That is especially true when the other calculation has been worked out inaccurately, or does not follow accepted conventions and simply assumes the best case values for other variables.
In an effort to improve consistency, the British Board of Agrément (BBA) operate a competency scheme for U-value calculations. Membership of the scheme involves a detailed assessment of understanding calculation principles, annual auditing of record-keeping and ongoing checks of calculations sent to customers.
Not all insulation manufacturers are members of the scheme. At Recticel Insulation, however, everybody carrying out U-value calculations is assessed and certified. By meeting the scheme’s requirements and ensuring that technical staff understand how calculations are carried out, we aim to give our customers the confidence that they are being advised correctly and that the proposed solution will perform to the required standard.