These are foil backed on both sides and are by far and away the most popular selling. The Celotex GA4000 range and Kingspan TP10 range are to all intents, indistinguishable, from a thermal performance perspective. The new regulations have meant that greater and greater thickness are now required to achieve the required U value. For walls this is likely to be in the region of 70mm of insulation but this is very much dependent on the wall construction (i.e. brick or block cavity or non cavity)
If you select a plasterboard backed product to go on your wall the main factors to think about are "How am I going to fit the product?" and "How thermally efficient is the product?":
Key to making the right board choice is understanding thermal efficiency of boards. Boards use different insulants which perform differently. These range from lower efficiency expanded polystyrene to high efficiency phenolic foam. The better the efficiency the more you pay; and the thinner the product is, therefore the less space you lose for the same amount of insulation.
Your choice is often arrived at by weighing up the merits of space lost and the price of the boards. The better the performance of the insulation materials the higher the price.
Kingspan TP10, TW55 and TF70 (all the same board) are high-performance, rigid PIR panels with a thermal conductivity of 0.022 W/mK. They are an ideal home insulation product for use as wall insulation, floor insulation, and pitched rooves and ceilings, and are the equivalent of Celotex's GA4000 range.
Celotex GA4000 range (previously GA3000) is a multi-purpose PIR insulation board, and is the equivalent of Kingspan's TP10/TF70/TW55 range. It is ideal for floor, walls, and pitched rooves and ceiling and has a thermal conductivity of 0.022 W/mK.
The Kooltherm K-range is an extensive range of premium performance rigid phenolic insulants (a different type of foam to the ones used in the Therma range and a little more thermally efficient). There is often a Therma alternative to each of the K-range of boards:
In performance terms, the K-range products can be considered to be industry leading, premium insulation. They have a thermal conductivity of 0.018W/mK.