Hydronic-radiant-heat-under-carpet, pex radiant heat system faq's. how is radiant heat different from the baseboard heat that i have now? convection. with baseboard, 80% of the heat is transferred by convection and only 20% by radiation. this means that if you place a pair of frozen boots in the middle of your mud room you have to crank the heat up to 74° to get the boots thawed.