Add Radiant floor to sun room / kitdhen ? Please critque!

G Lyons

G Lyons

Add radiant floor heat ot sunroom / kitchen? critique please!

It is necessary to use the sun room as a kitchen. This is 32 ft long and 9.5 feet wide and attached to the house on one side. My plan is to add 1 inch of closed cel foam insulation on the floor, then wire mesh and 1/2" radiant tube at six in centers. Covered with min thickness of gypcrete or cement. I will use the 2- 40 gal dom w/h for heat for now. I will keep the water temp at about 120 deg and use a bronze circulator. Single glass of course. I will see how that works and add some infra red over head if more warmth is needed.

Mark Hunt

120 degree water

will keep you moving on that floor. Your water temp should be MUCH lower than that, probably not more than 80 degrees on the coldest day.

I can almost guarantee that you will experience thermal fly-wheel effect as well unless you use some manner of temperature reset.

I would STRONGLY suggest a plate heat exchanger to keep your heating system seperate from your domestic water. You don't want to make yourself sick.

Mark H

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Brad White_9

I would

carry the insulation up the edges too. That can amount to a huge heat loss especially with the warm slab.

If you use a DHW for the purpose, fine, just do not consider it part of your domestic water system. Dedicate it to heating only or as Mark said, use a plate exchanger. Some codes require a double-wall vented exchanger if connected to potable water so check. Some efficiency is lost as a result.

Given the uncontrollable nature of DHW heaters (uncontrollable meaning manual control, not automatic) I would strongly suggest a mixing valve with OD reset and slab limit control as Mark suggested.


As for floor temperature, I can see a slab no warmer than 85 degrees. This is a typically high maximum number for any habitable room except a bathroom and even that is a maybe.

If concrete, this will give you a heat output of about 35 BTU's per SF. Remember this has to be "usable" space. Under cabinets does not count. Be sure you have enough usable floor area to meet your heat loss (Lord knows what that is..)

To make the floor 85 degrees and with an R value of 1.0 (concrete) in a 68 degree room you will need water at about 102 degrees. Higher than Mark suggests but cooler than the DHW setpoint you suggested. Just an example of what might be. Mix it down. Reset lower from there.

You probably do not have enough net floor area to meet your heat loss if there is a lot of glass, I am just guessing, so prepare to use some panel radiators perhaps.

jp_2

whats the climate?

might work good in tenessee but not work in north dakota?

sounds like you have a lot of glass? whats under the porch?

lots of unknowns to give a good answer.

i assume you are using the hot water heater solely for the floor?

G Lyons

Thank you for your professional input,

We are 20 mi north of Salt Lake City UT..
the sunroom is on a concrete slab, and is north faceing.

Dave Larsen_2

guesswork

no real need to guess at water temp. Do a heatloss calc! it only takes a few minutes of your time and can save a lot of headaches and fuel costs. Minimum slab thickness must be 1 1/2" to 2" ....add insulation underthe slab plus floor covering and yo are closer to 3".....do you have that much room? take a look at Uponor Quik trak or other similar products. Heat exchanger is a must..... don't take any chances with DHW.

Unknown

300 square feet?

Use an electric mat. Problem solved.

These small retrofits are where those mats really shine in cost-effectiveness.

hr

faces north, single glass?

How much glass? Best do a heat load calc. You may well need supplemental heat. These small space, high load rooms can be a bugger to keep comfortable.

Consider a glass upgrade if in fact it is single pane, and a lot of it.

hot rod

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Fred Campbell

North Facing in Utah

Yeah, I guess you don't have to worry about flywheel overheating. Do a heat loss. Insulate well (don't forget the cieling) and new glass if needed. I'm sure it's a beautiful sun room now but to make it a true four season room you have to address these issues, even if it means tearing out a nice beadboard cieling or the roof above to insulate properly.

It's nice you have the room for insulation and overpour. It gives you a little more flexibility with output depending on your floor covering. Good luck, TG