Changing from Radiator to Radiant Floor In Kitchen

Javelin

Heating Pros,

First - thank you all for your previous help with my questions... This web developer continues to learn a LOT from this forum!

We're planning a kitchen re-do in the next 12-18 months, and I'm starting to think about future heat for the room. Currently there is a BIG old cast iron radiator that pumps out enough heat to keep the room fairly comfortable... the room still lacks insulation/etc., but that will be remedied with the renovation. The issue is that the radiator is just BIG and sort of in the way of what we're planning. I'm guessing I could re-route it somewhere more out of the way, but wanted to ask you pros what would be involved with instead, putting in a radiant floor system.

The floor would be TILED, and I have access to the bottom of the floor in-between the dimensional 2x12 (actual) joists. I've read about some products that get fastened from underneath TO the sub-floor, and others, more traditional that are rolled out above the sub-floor, but below the finish floor.

Are there benefits to either? Also, the room is currently just part of a big master zone that does most of the house. If it changes to radiant, does it need lower temperatures and it's own zone?

Thank you in advance for your advice in pointing me in the right direction.

Jay

Ironman

The first thing you need to consider is whether a radiant floor will produce sufficient heat for the room. That requires that an accurate heat loss calculation be done. There are several factors in determining how many btus a radiant floor can produce: water temp, tubing lengths and space, heat transfer method, floor coverings resistance to heat transfer (aka R value) are some.

Another major consideration is your present boiler and heating system. You have cast iron rads, which means the system is high mass and uses medium to high temp water. A radiant floor is low mass and uses relatively low water temp. Attempting to marry the two takes careful engineering and planning and may require more components than you are expecting.

The general scenario with a house and system like yours is that a radiant floor may be good for warming the surface, but it won't produce enough btus or work in harmony with the system to satisfactory heat the room.

Another thing to take into account is the floor area that will be covered by cabinets. That area will not produce any ( or very little) heat from a radiant floor. Most of the time, that's about 1/3rd of your kitchen floor space.

Most likely you'll need some other type of supplemental heat. Nothing will work as well as the cast iron rad that you have because that's what the system is designed for. A toe kick heater with a low temp aquastat would be another option, but less desirable than your C.I. rad.

Just to bring things into perspective: the rad in your pic will produce 19,200 btus. You would need over 1000 sq. feet of open floor space to get that from the typical radiant under floor system.

Steamhead

Keep it simple- keep the radiator. Seriously, what else would you put under a windowsill like that?

Alan (California Radiant) Forbes

If that were my kitchen, I'd go with floor heating and a nice, big towel warmer.

JeffM

I did a similar project two seasons ago. My kitchen radiator is steam where I think you have hot water, but other factors are the same. I put 3 circuits of radiant in from below with extruded heat transfer plates, and served it as its own circuit with a small mixing device on outdoor reset (that gets higher temp water from the boiler). I could heat the room from the radiant alone, but left the steam radiator and throttled its vent way back so it only puts out much heat when it's really cold. We love the warm floor, and the much more even heat distribution throughout the kitchen.

Javelin

Thank you all for your comments... I guess I'll have to wait a bit to see either a) how much floor square footage will be in the reworked kitchen, or b) if I can work the current BIG radiator into the design..

I do love it, and my boys love drying their damp clothes on it on even having breakfast sitting on it on a cold day... Just want hoping to have something to more evenly heat.

I'm sure I'll be bothering you all again about this sometime!

hot_rod

If you are going to tile the floor, consider adding some electric radiant in the tile set for floor warming and to add to the radiator output.

Warm tile floors, properly designed and controlled, are one of the finest systems you will ever stand on.

Gordy

If the radiator has to go, and the floor is getting renovated I would do over the top radiant in hydronic sandwich form, or electric as @hot rod suggested.

Doing radiant from underneath is cutting your output from the start verses a sandwich style. You will have to push the btus through that tounge, and groove sub floor. Also that style of subfloor is not conducive to have good conduction with the heat transfer plates you need to install.

Keep in mind also kitchen areas in general may need supplemental heat do to decreased radiant floor space because of kitchen cabinets, and appliances.

Also concur with @Ironman on a heatloss as the first step.

Get that done, if the floor space does not provide enough output. There is also radiant ceilings if the ceiling are part of the renovation. I have both floors, and ceilings in several rooms of my house. Mmmmmmm radiant sandwich.