For rigid insulation the guarantee is generally classed as being the same as that of the waterproofing layer. For use inside of a building ie walls or floors they normally suggest that they will last as long as the building.
The main manufactures we have looked at are
U-Values are the most important aspect of insulation and we will cover this in another blog post. There is an excellent App from Kingspan that will help with your calculations and to reach the correct values needed for building regulations. Here is a current breakdown from Kingspan's website on the U-Values needed for Walls, Floors, Pitched Roofs and Flat Roofs. Whether you are based in England, Wales or Scotland information is available for new builds and refurbishments in domestic and non-domestic buildings.
One part of working U-Values out is making sure you account for any openings such as windows. Your always best getting a professional such as an architect or we can get drawings and questions looked at by the Kingspan technical department to work out U-Values.
As again with the flat roof lights none of the BBA Certificates require training as long as they are fitted by a competent Roofer / Builder / Contractor.
The most important part to insulation is the U-Value and strengths of the boards. The most popular insulation is still Kingspan and unlike a few years ago is no longer the most expensive and can sometimes be cheaper than its competitors. Always make sure to check the specification for the project to see if a particular insulation has to be used, if not you are free to use whatever insulation you want, but we always recommend using one of the 3 manufactures in this blog post.