Infloor radiant heat help

[Mk1390]

I am currently about to lift my house to add a basement , going to put pex in floor for heat, and also adding a slab on grade addition on the side of my house. I am thinking I should have 2 separate zones. One for basement and one for above grade addition, just because I think they may take different amounts of heat? And is it possible to run only one thermostatic mixing valves and possibly just tee off of the mixed water and then pump it to addition when it calls for heat? It will be about 7’ elevation change. Any input would be greatly appreciated. Thank you

 

[Tonty]

I think you’d want them on separate zones. My panel has three zones, one for the garage floor, one for the house floor, and one for the heat exchanger in the air handler. The garage floor and house floor have separate mixing valves, which is nice so that I can set the floors at different input heats. I don’t know if plan to try to heat your main floor above the basement with the basement in floor heat, but that may not work all the time. My house is a slab house with a second floor, and I have to use the heat exchanger in the air handler to heat the second floor on cold days.

 

[Mk1390]

I have a heat exchanger in my furnace that I heat my up stairs up. I think I would be able to run the same input temp to both floors the addition is only 12x20 , so it will only have one loop.

 

[Ashful]

Yes, if you're doing this right and not just cheap, you want as many zones as there are logical divisions in your house. If you're only in one room working from home all day, it might even make sense to get as granular as a zone for that room alone.

The house I live in now has six zones on oil, three zones on heat pump (mini split), and one zone on electric baseboard = 10 zones + 2 wood stoves. This allows us to heat only the portions of the house we're using at any time, staying toasty warm, while saving money letting the rooms we're not using go cold. With zoning, there's no need to heat the master bath and dressing room all day, just to keep us from freezing in the kitchen, if we're only in the bathroom a combined hour in the morning and before bed.

The oil zoning in this house is very simple, a single small circulator off the boiler, then tee'd off to supply every zone, with individual Taco 570 zone valves on each return. The house I grew up in also had four zones on oil, but an older design with a separate circulator motor for each zone, must've been crazy expensive considering the size of those old circulator motors.

I've never done a cost analysis on it, but zoning in hot water systems is so easy and not that much more expensive, that I suspect the payback to be relatively quick. The amount of copper line won't be all that different, top of the line Taco 570 zone valves are only $130 each, and a good programmable thermostat is under $100. If you have the means to pull the wiring, or rig a wireless thermostat, why not?

 

[Bad LP]

In my case 12” centers on PEX dictated how many zones as you can only run 300 feet per run.

 

[Mk1390]

Yes, if you're doing this right and not just cheap, you want as many zones as there are logical divisions in your house. If you're only in one room working from home all day, it might even make sense to get as granular as a zone for that room alone.

The house I live in now has six zones on oil, three zones on heat pump (mini split), and one zone on electric baseboard = 10 zones + 2 wood stoves. This allows us to heat only the portions of the house we're using at any time, staying toasty warm, while saving money letting the rooms we're not using go cold. With zoning, there's no need to heat the master bath and dressing room all day, just to keep us from freezing in the kitchen, if we're only in the bathroom a combined hour in the morning and before bed.

The oil zoning in this house is very simple, a single small circulator off the boiler, then tee'd off to supply every zone, with individual Taco 570 zone valves on each return. The house I grew up in also had four zones on oil, but an older design with a separate circulator motor for each zone, must've been crazy expensive considering the size of those old circulator motors.

I've never done a cost analysis on it, but zoning in hot water systems is so easy and not that much more expensive, that I suspect the payback to be relatively quick. The amount of copper line won't be all that different, top of the line Taco 570 zone valves are only $130 each, and a good programmable thermostat is under $100. If you have the means to pull the wiring, or rig a wireless thermostat, why not?

I like this setup from central boiler. I think I could add a tee after the mixing valve for my addition (second zone). Is there a need for a check valve on the return side of the floor heat, it seems like the way the diagrams is it could potentially back flow , but I think most of those pumps have a check built in ?

 

[Ashful]

Sorry, your original post did not indicate that you’re looking to install hydronic floor heating in a house with a hot air furnace, so I had assumed (logically) that you had a boiler. I have no experience running a hydronic system from a water heater, and while I can easily imagine how it could be done, I have no idea what the costs or potential pitfalls might be on a system like that.

 

[Bad LP]

Sorry, your original post did not indicate that you’re looking to install hydronic floor heating in a house with a hot air furnace, so I had assumed (logically) that you had a boiler. I have no experience running a hydronic system from a water heater, and while I can easily imagine how it could be done, I have no idea what the costs or potential pitfalls might be on a system like that.

One thing is clear and that is the heater is going to run a while while the slab is warming up.

 

[salecker]

Make sure you insulate really well under and the sides of your slabs,
that way your BTU's will go to heating the space you want to heat.

 

[Bad LP]

Make sure you insulate really well under and the sides of your slabs,
that way your BTU's will go to heating the space you want to heat.

Do not underestimate the importance of this.
The loss was amazing when building this house RFH in Gypcrete on the first floor with a full basement below.

Heat will travel down.

 

[Ashful]

Heat will travel down.

Conduction works equally well, down or up. People sometimes miss that. Only convection has an affinity for upward momentum.

 

[sloeffle]

Conduction works equally well, down or up. People sometimes miss that. Only convection has an affinity for upward momentum.

Yep, no water pumps on old JD tractors.