Radiators, baseboard, pex radiant

[Easy Livin’ 3000]

Currently have large iron radiators throughout the house. The house has small rooms, half is 18" thick stone walls, other half is 2x4 poorly insulated on three sides. We could really use the space consumed by the radiators on the ground floor, so we are considering putting in pex under the floor, or baseboard. Is this a bad idea, and what are the pros and cons of iron radiators vs. baseboard vs. pex underfloor radiant?

 

[E Yoder]

Some thoughts off the top of my head-
You can find charts showing the BTU output of cast rads online. You measure the size and design and put in the average water temp in the radiator. It's not hard to do.
Then you know what btu's you had available when comparing other routes.
There are charts for baseboard too. My guess is you'll want more than standard copper convectors.
Panel rads might be a simple option with more btu's. I wish I had home run Pex to panel rads with TRV's and a Alpha circulator in my house. No stats needed and 3/8" Pex would feed most panel rads if they're home run loops.
Radiant floor is nice but you are limited to approx 30 btu's per foot because of max surface temps and that's assuming you can access below. Radiant wall heat might be an option on a wall or two to boost available btu's?
Sorry for the rambles. Just throwing out options. A combination might be best.

 

[Easy Livin’ 3000]

Some thoughts off the top of my head-
You can find charts showing the BTU output of cast rads online. You measure the size and design and put in the average water temp in the radiator. It's not hard to do.
Then you know what btu's you had available when comparing other routes.
There are charts for baseboard too. My guess is you'll want more than standard copper convectors.
Panel rads might be a simple option with more btu's. I wish I had home run Pex to panel rads with TRV's and a Alpha circulator in my house. No stats needed and 3/8" Pex would feed most panel rads if they're home run loops.
Radiant floor is nice but you are limited to approx 30 btu's per foot because of max surface temps and that's assuming you can access below. Radiant wall heat might be an option on a wall or two to boost available btu's?
Sorry for the rambles. Just throwing out options. A combination might be best.

It's rambles like this I was hoping for. I've heard that this is a complicated subject, so I expected some complicated responses.

The real estate inside the house is very valuable to us because the tight dimensions, and the radiators take up just enough floor space to make everything difficult. Also, the massive thermal mass of the stone walls has me worried that anything other than the big radiators will leave us feeing uncomfortable. Perhaps I'll start with the pex underfloor on a separate line in the main living space, and just turn the radiators off to see how it feels before removing them.

 

[E Yoder]

Good idea!
They're not exactly something you'd want to move more than once. [emoji1]

 

[E Yoder]

Ultra-Fin is a full temp underfloor radiant option. You could tie right into the same temp water.

I just ran 180℉ pex under my floor but suspended it down an inch or two on the joists and insulated a tight air space underneath to spread the heat and avoid striping. It works great, but slow to heat up. But so are cast rads.
But I'm not a radiant expert as its all heat pump land down here.

 

[Easy Livin’ 3000]

Ultra-Fin is a full temp underfloor radiant option. You could tie right into the same temp water.

I just ran 180℉ pex under my floor but suspended it down an inch or two on the joists and insulated a tight air space underneath to spread the heat and avoid striping. It works great, but slow to heat up. But so are cast rads.
But I'm not a radiant expert as its all heat pump land down here.

Thank you, I'll check out ultra fin.

I wont be worried about striping, if you saw the floor, you'd know why!

 

[E Yoder]

I was just trying to think of something that would work on the same water temps that you already have for an easy hook up. There might be other products other than ultra-fin but if you look it up you'll get the concept.
And like I said, the limiting factor is how hot you want the surface of the floor.

 

[E Yoder]

A couple runs of O2 barrier Pex might be enough if the floor isn't too thick.
Don't want rugs or carpet.

 

[Lloyd the redneck]

Following. I'm debating walls or floor too. I am re doing my 2nd floor and have to put in new subfloor so I was thinking to snake pex in just like a slab would be. Floor heat is the cats pajamas just don't know if it's worth the fiddling around

 

[E Yoder]

Be sure to insulate underneath or you'll have ceiling radiant for the downstairs...
Radiant goes any direction.

 

[pbvermont]

No one has mentioned the importance of using aluminum plates with the underfloor pex. It will make the zone much more effective, responsive and allow you to use lower water temps.

 

[E Yoder]

I was thinking he would want to tie it into the existing full temp piping. But you're right low temp with plates is better.
Mine is high temp with just Pex using the hot air space to spread the heat out. Nice even floor temps in my case. But I'm not disagreeing with you.

 

[Easy Livin’ 3000]

I was thinking he would want to tie it into the existing full temp piping. But you're right low temp with plates is better.
Mine is high temp with just Pex using the hot air space to spread the heat out. Nice even floor temps in my case. But I'm not disagreeing with you.

What about full temp pipes with aluminum plates?

 

[E Yoder]

I think your floor would get too hot with that much contact plus the pipes would squeak in the plates. The idea with suspended PEX is you use the airspace to spread the heat out. The airspace has to be sealed very tightly with good insulation underneath.

 

[Easy Livin’ 3000]

I think your floor would get too hot with that much contact plus the pipes would squeak in the plates. The idea with suspended PEX is you use the airspace to spread the heat out. The airspace has to be sealed very tightly with good insulation underneath.

Good information, thanks.

 

[E Yoder]

Low temp water with plates does heat up quicker, overshoots less, and allows you to utilize storage (if you have it).

 

[leon]

Those stone walls will cool off very quickly and you will not heat up very well.

have you checked into heating grants that would upgrade your wall insulation by installing to 2 by 6 studding and fiberglass batt's of insulation.

I am going to have to suggest that you leave the radiators in place and place a sheet of aluminum backed insulation board behind each radiator.

Panel radiators are going to need insulation if they are not installed with it. The mess my fathers contractors made with his floor heat was abominable as they did not install reflectors and my brother ended up installing foil backed insulation board secured to the basement ceiling joists as the heat loss was terrible.

You have a huge amount of thermal mass there you should take advantage of it as the water is only going to carry so many BTU per gallon to begin with.

If your dead set on removing them which is real shame, the lesser of the two evils is to simply move the radiators to the interior walls in that room specific room put the foil backed insulation board in behind them and then you have created the square foot of space per foot of wall length on the exterior wall that you want.

You should not give up the thermal mass if you have it to use. I would rip out my baseboard in a second if I could afford to install steam or hot water radiators.

All you may need is to have the radiators flushed out with some furnox or hot water and vinegar to break up any dirt in the base and you will have a clean radiator and if they are on the interior walls they will have less heat loss to the windows and most likely you will not have to have as hot a water temperature either if the radiators are cleaned.

Please do not scrap the radiators, you can sell them to a reuse place and they will be put to good use in another home or business to heat it. We have lost too many radiators of both types to the town dumps or the scrappers torch.

If you install the in floor heat your going to lose a lot of it through the thin walls that you have so keep that in mind.

 

[peakbagger]

I have a little experience with folks trying to heat masonry and stone buildings. No matter the hype they are energy sieves. The R value is darn close to zero. Thermal mass it good thing if its designed correctly but a stone or masonry home isn't designed correctly for cheap heat. Unless you put in some real insulation between the stone walls and the interior you are going to be heating the outdoors. Going after infiltration around the home can help but fundamentally you are stuck with the lack of insulation in the walls. Best option is spray foam as it has the best R value per inch. If you don't want to put in inside you can put it on the outside but I expect you probably wouldn't like the looks.

Everything else is band aid. It is amazing how 1" of foam will make a difference, with a masonry wall the heat is being sucked away from you into the wall, add the foam and it going to cut way down on that. One inch of closed cell foam can get over R 6, go with 2" and you have R 12 which is quite respectable, 3 inches is up in the R 18 territory which may be overkill. The foam will also seal any infiltration issues. I expect you will also be able to reduce the overall building temps

 

[E Yoder]

A BTU is a BTU. Thermal mass in radiators heats up slowly and emits slowly as it cools. Net result equals out, right?
Insulating would make the most sense to me.
If you calculate the total btu's of the cast rads then you won't be guessing as to whether what you change over to will heat the place.