Difference between hydronic radiant floor installation types?

PieCa

Hello -

I see online that there are many different ways to install radiant heated floor with engineered wood. I would like to have your point of view of what would look like the right choice in my situation.

So this is the main floor of my house. The surface is about 12x38, all one big open space room (kitchen-dinning-living all connected without walls in between). The current hardwood floor will be removed and a new engineered bamboo floor will be installed. Under this space is an unfinished basement, no insulation. I can see and have easy access to the joist of the main floor from there. The current boiler is a new (2016) McLain ECO 70.

So, what are the criteria to pick a system that are between the joists, or something in the subfloor, something with a slab or overpour, "warmboard" versus any other? Is that only cost?

Thanks!

Zman

Underfloor with plates is going to be way simpler. When you go on top, you need to consider built-up height, door clearances ect. If you have good access underneath, go underneath.

PieCa

Thanks!

And in term of efficiency, will they all yield the same results?
I just have one door to replace with the change of height Because of the nature of the project, there is a new opening to create on the back to add a patio door, but we have not yet open the wall, so we will be able to accommodate any new height.

CMadatMe

Under floor less material cost, labor increase, above floor more material cost, less labor, they're a wash in the end. A 10 degree supply water temp difference dependent on sub and finished floor R-Value will have zero effect on the systems efficiency.

PieCa

I assume that the type of installation does not influence to type of boiler right?
I talked to a contractor earlier today and he mentionned that he wanted to change the boiler too. It was a quite pricy quote. I had the feeling he was trying to upsale me a new boiler. But quite frankly, I have no idea. Thanks for your messages!

kenjohnson

I did an underfloor retrofit, and I can tell you it is absolutely comfortable without needing high temperatures. You'll need to run PEX down and through joists, which will require a couple of friends to help you. And make sure to buy the thick aluminum plates to install the PEX into.

PieCa

I see, I live in Ontario. Outside temp usually gets to -5 °F and a bit lower too in the mid winter. Should that influence my choices?

nibs

You can do an overpour slab, but concrete or gypsum do not like flexing and wood joists are going to move around, can be done but prone to problems.

PieCa

I guess I'll opt for retrofit with aluminum heat transfer panels. It's not a big surface, the price of the plates + tubing should be around CAD2,600. Now I have to find the right contractor to do the work None of you are around GTA/Toronto area?

hot_rod

It wouldn't be a bad idea to do a heat load calculation for the space. That will give you an idea on how much heat, the space needs.

SlantFin.com has a free calculator.

So let's say that 456 Sq feet calculates to 10,000 btu/ hr input required on a -5 day.

That would be 22 BTU/ sq ft the floor needs to transfer, a doable number for radiant floors.

Then the floor covering needs to factor in as it is basically R-value over the heat emitter.

With all that a supply water temperature SWT will be established.

There are free software programs to do a load calc and system design if you want hard data. Or hire one of the contractors on this list to do a load and design for you.

The design tells you plate spacing, loop length, GPM flow rate required and SWT. it is sometimes better than the guesstimate method, takes a few hours to do the number crunching.

Occasionally you come across rooms or spaces that cannot be heated with floor radiant alone, generally over 25-27 btu/ sq ft becomes the high end without overheating the floor surface.

Rooms with a lot of built in that cover the floor surface can throw you for a loop also. The available un encumbered floor space is the number that becomes the radiant panel.

nibs

@PieCa
T O Went to Harbord High school more than 1/2 a century ago.
Come to BC, it is much nicer. Cheers.

Zman

PieCa said:

I assume that the type of installation does not influence to type of boiler right?

I talked to a contractor earlier today and he mentionned that he wanted to change the boiler too. It was a quite pricy quote. I had the feeling he was trying to upsale me a new boiler. But quite frankly, I have no idea. Thanks for your messages!

The boiler size should be determined by performing a heat loss calc. It is probably a moot point unless your home is > 2,500 sq ft your boiler is likely oversized.

kenjohnson

I did a room-by-room heat loss calc in Excel using known insulation values for walls, floors, ceilings, windows, etc. It was remarkably accurate (maybe even a little conservative, probably because I underestimated the window insulation value) but I had the walls open and knew what I was putting in there.

Once you know room-by-room heat loss, you can make some assumptions about required delivered BTU/hr through your floor. Realistically, the values mentioned before are near the upper limit of what you want (~20 BTU/hr/sq foot).

Then, you or someone else will have to design the radiant plate and piping layout. I did this myself in Visio.

All this can be done if you have patience, willingness to learn, and can do some basic math. Excel proficiency is a plus.

In my area, I could never have found a contractor to do these calculations and do the plate/PEX install (I tried). Realistically, the contractors in my rural area just want to do what they know. I did the PEX install myself with some helpers I hired, and then hired someone to connect it to a GSHP.

Ironman

You probably don't need a new boiler, but you'll probably need to create a separate, WATER TEMPERATURE zone for the floor using a mixing valve since it's gonna need cooler water than the rest of the house.