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Radiant heat is not keeping my rooms warm

The radiant heat in my two story home is not keeping the rooms warm enough in the winter months. The home is approx 28x28 and has three zones of heat. Two zones are downstairs one for the attatched one car garage; which by the way is the warmest room of the house maybe because that is where the furnace is located and the heat from it running carries out into the garage; the other half of the downstair is the kitchen-lvingrm-half bath area (with a sliding door and three windows) and the last zone is for the whole upstairs (two bedrooms and a full bath).

The upstairs is usually very cold and the thermostat usually reads a room temp at a balmy 60-62 degrees and appears to struggle to keep it at that temp. i have given some thought to abbandoning the radiant heat in the upstairs and trying to convert it to hw baseboard heat but leaving the downstairs as radiant can that be done with the system i have in place?

The boch heating unit looks like a glorified hot water heater turned into furnace to me -- but i'm as green as the grass about such things. Ideas? what are my options?

Re: Radiant heat is not keeping my rooms warm

Baseboard heat requires a much higher water temperature then radiant heat. Not sure if your heat source could produce the 180 degree water temperature need. Your first step should be to call a professional to see if any of your old system can be used. It is possible to run both baseboard and radiant on the same boiler but it requires controls that are not on your present system.


Re: Radiant heat is not keeping my rooms warm

Just to clarify, this si a boiler not a furnace correct. A furnace heats air, a boiler heats water.

I suspect someone designed or installed your system wrong.

How large is the boiler (BTU's). Does it also heat you domestic hot water?

Where do you live (climate)? You house isn't that large. It shouldn't need more than 50-80 BTU's depending on insulation values and air leaks. IT does sound like the garage is getting a lot of the heat.

Can you balance the zones with flow control valves. So reduce the water flow to the garage and thereby force it to the other zones?

Can you tell if the boiler is run at maximum capacity and running continuously? If not, I suspect either your water pump is too small or you don't have enough radiant loops installed. I'd be suprised if the boiler is undersided. But it could be as simpler is having a larger pump installed or possibly adding a couple baseboard heaters if you're getting enough water flow.

Do you know the water temp leaving and returning from the boiler?

Re: Radiant heat is not keeping my rooms warm


I would agree with the others that you need a professional to come in to look at the system, either the one who originally installed the system, or consult the Yellow Pages under "Heating Contractors", and select someone who is experienced with radiant heat systems.

You will have to determine if the installed system is properly sized for you location, and can produce enough heat to do the job.

The amount of heat you need to adequately heat your home is calculated on many factors, & a heat loss calculation should have been done at the time of installation---this would calculate how many BTUs of heat are escaping each hour thru the walls, ceiling, floors, windows, concrete slab in the garage, etc., and the total square footage of the heated spaces.

Other factors affecting heat loss are the amount of insulation in the exterior walls & the ceilings facing the attic, the number of windows/sliding glass doors, & their age/condition (double pane/single pane); if you are lacking any insulation in the areas mentioned, this should be your first point of attack (R19 exterior walls/R40 in attic/double-pane windows).

The installer of the Bosch system should have calculated a heat loss figure on the above factors; anyone you call now should also make a calculation of these factors, as well as make any minor adjustments that will dramatically improve your heating comfort.

What is your general location? Are you in a very cold climate or a moderately cold climate? What is the BTU rating of the Bosch boiler?

As noted previously, if the Bosch boiler has enough BTU output, & you have reasonable insulation in the walls & don't live in a bitterly cold area, a house 28' X 28' needs approx 30 to 40 BTU per sq.ft. to keep warm: 28' X 28' = 784 sq.ft. X 35= approx 30,000 BTU/hr as a ballpark figure; again, this guestimate can be off depending on the climate, the amount of concrete in the garage, size & demand of the hot water heater, etc.

Garages are NOTORIOUS for being giant "heat sinks" that gobble up all the heat before it gets a chance to get to the other parts of the house; especially if the radiant tubing is buried beneath the concrete garage floor, and especially if the main hot water output of the boiler goes thru the garage slab first, before going to the rest of the house---in any event if the garage piping loops go under the slab, they're probably returning ice water back to the boiler & thus making it impossible for the boiler to catch up & heat the radiant water for the piping loops going to the other parts of the house.

In many cases the 3 heating zones are arranged & controlled by 3-way mixing valves that mix the hot water coming out of the boiler with the cold return flow coming back from the radiant loops---in such a case it should be an easy task to minimize the amount of hot water going to the garage loop, and increase the amount of hot water going to the bedrooms & 1st floor by simply adjusting the knob on the 3-way mixing valves---this would make the garage cooler, but this is as it should be.

Another factor is how the circulating pumps on the boiler/piping loops are set up---better results are often obtained in a radiant system if the circulating pumps are run continuously 24/7 (the pumps used today burn very little electricity); this has the effect of injecting the heat BTUs into the wood flooring & slabs throughout the house on a constant basis for a better distribution of the heat, and also eliminates the threat of frozen pipes during the coldest winter weather.

Re: Radiant heat is not keeping my rooms warm

The info mentioned above sounds good. I have radiant in my upstairs and it works pretty weel. The contractor that installed the radiant insisted that we have an outdoor sensor that will automatically call for heat as the weather changes. He said he wouldn't do the job otherwise as the radiant wouldn't be as efficent and would not react as quickly as a baseboard unit thus upsetting the home owner that made the investment in the radiant. It has worked well so far.


Re: Radiant heat is not keeping my rooms warm

I thought outdoor "resets" just adjusted water temperature. But I could see some benefit to them calling for heat as well within reason.

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