The process for calculating the u-value of a floor which is in contact with the ground is much more complicated than for other building elements built above the ground. This is because the soil type has a significant effect on the heat transfer through the slab. The heat transfer is multidimensional which makes it more difficult to approximate and therefore calculate than for other building components.

As a result of the multidimensional heat transfer most of the heat loss occurs at the edge of the slab whilst relatively little is lost  towards the centre of the raft. Because of this effect, the ratio of exposed perimeter to overall slab area is one of the most important factors in the calculation. The bigger the raft and its area, the better the U-value and the less insulation that will be required in your raft

Once you have used the GreenRaft U-value calculator and arrived at the depth of insulation needed to achieve that, you can opt to generate a quotation. To do this you need to fill out the second section of the form below including a valid email address. Once complete, press the submit button at the bottom. Upon submission, a quote for the supply of GreenRaft materials will be emailed to you immediately , along with guideline estimations of other associated costs for your project. Providing that all details are entered correctly, the quote will be valid for 90 days from the date of submission.

The calculation is currently based on a standard plain flat insulated raft.  It can be for an above ground structure or for an insulated basement raft foundation.  It does not include for any of the other options available with our foundation systems such as upstands for timber frame & SIPS homes, or the thickened beam edges associated with our revolutionary Post Tensioned Insulated Raft systems.

If you have any questions, please contact us, or have a look in our FAQ.  If you want to see the cost of an insulated raft in the more expensive foamed glass material click here.