Dear Handy: Has your water heating system just developed these symtoms, or is this an on-going thing. Baseboards generally require much hotter water than radiant floors & radiators, so if you are only getting warm water to zones & DHW, you may have a temperature (boiler) control problem. What temp is your boiler set to produce. More info is needed, to enable anyone to help you. What btu output boiler do you have. What type & efficiency heat exchanger do you have. Scenario: If you have an 85,000btu boiler, and it has been heating your home, it should go on heating your home. 85k is fine for your heating, if it's sized correctly, but you won't get much DHW production. What you may have, is a burnham boiler with a heat exchanger for DHW. I would suggest that you post your question at www.area51hvac.com & www.heatinghelp.com or www.danholohan.com these sites are home to the best heating professionals in the country, who give excellent advice and one of them may live close to you. You may want to consider a separate heat source for DHW. If you do, I recommend Bosch AquaStar as a stand-alone, or in combination with an "Ergomax" heat exchanger. www.ergomax.com (I supply both, but politeness doesn't allow me to advertise here). Ask the guys at those sites, they will steer you right. At Area51, click on "Groom Lake" & post your stuff. Best of luck, Brian, (Your source for electric & gas tankless water heaters, 1-800 851 9891) & happy heating.