I agree that the heat would dry out a normal rubber underlay quicker than a made for purpose one but if its only a cheaply carpet going down, how long will that last?
Price will always be an issue when it comes to UFH underlay. Trouble is the heating companies/plumbers conveniently omit the fact that the customer will need to spend extra dosh on flooring when using UFH. Us flooring guys are left with the task of breaking the good news. Technics is indeed a good product but due to its thinness, I always feel it puts more wear on the carpet and if you get a customer insisting on using gripper you end up with a nasty line right round the room as the underlay is thinner than the gripper :-(
You will have that problem with all low tog underlays as they are all thinner than the gripper. I would still rather stretch fit than double stick the whole house, as you say its another extra cost.
The tog rating of the underlay and the carpet combined has to be less than the tog rating of the heating system being used.
£31-90 + me, so close, think I'll just go for a rubber u/lay. spoke to customer today, they don't know the output of their heating, and are happy with that option. The carpet is .11kk? apparently according to Condor, how does that translate to tog? btw, just realised I started this thread in general discussions, now we are discussing prices could someone move it to trade section?