Rockwool vs kingspan insulation

[nvhelectrical]

As my next project i am installing a wet under floor heating system (ufh). The ufh will be sat on spreader plates between the joists. i think it would be a good idea to insulate within the joists before ufh system is installed and would like to know
1. is rockwool rolls or kingspan sheets preferred?
2. why when the Eco drive is on is insulation so costly?
3. any where to get special offers on insulation?

thanks for looking
neil

 

[foxhole]

You need a rigid insulation as a lightweight screed is needed around pipework to make best use of the heat as suspended floors are less efficient than solid when used with under floor heating.
www.centralunderfloorheating.com

 

[nvhelectrical]

not screening going to use aluminum spreader plates.
trying to figure out weather to use board or roll insulation and why it costs so much
thanks for looking

 

[foxhole]

Aluminium is very expensive option and can cause hot spots.

 

[nvhelectrical]

what about weight issues all floors (3) are suspended and fairly large areas would the i need a structural report to determine how much they can take. and how does the heat transfer through the sand cement mix
ta

 

[foxhole]

Its not sand, cement, you use a lightweight granular bed.