Just a note that there will be a webinar this Thursday on installing radiant heating additions into an existing radiant system, or upgrading existing infrastructure. This should be very interesting because it must deal with most of the design and implementation issues of a new radiant installation, and it must be compatible with an old system, so a very thorough understanding is needed.
The webinar is given by an
Italian company that sells hardware that is specific to radiant heating, so their motivation is to sell their hardware (which is probably good quality), but a learned DIY guy can fabricate his own hardware or substitute his way around problems.
The company maintains an archive of previous webinars on Youtube right
HERE.
There is a free technical manual archive
HERE. Some awesome information.
There is also a free periodical technical publication archive
HERE that has, again, some awesome information.
Best,
-AC