Moving in-set radiators out of walls to improve efficiency?

dbrant

Hi all,
We have several steam radiators that are in-set into the walls (see picture). I've had a suspicion that this placement of radiators is extremely inefficient, since half of the radiator is literally heating the siding of the house, and the cavity that holds the radiator should really be filled with insulation instead, with the radiator being fully inside the room.

The pipes in the basement that lead to these radiators are easily accessible and exposed, so theoretically it should be easy enough to move these radiators inward, and fill in the wall.

My question is whether this theory is valid, and whether such a project would be worth it. Would I gain a good amount of efficiency by moving the radiators out of the walls?

EdTheHeaterMan

The theory is valid. The piping on steam system must conform to certain parameters. You don't want to cause a problem with condensate returning to the boiler, leaving the radiator.

Also... more important... How are you going to close those curtains with a big ole' radiator in the way?

ethicalpaul

It's very valid. I had a much smaller version of yours in my small bathroom. I removed it and insulated the hole and the result was no apparent difference in the comfort of the room (there might have been some net difference of course with the heat coming from the hall to make up for whatever was coming out of the radiator).

Whether it's worth it is a tougher question. What if it only saved $20 per year? Or $5? Myself, I just hated the idea of that cold hole in my wall so the decision was philosophical for me regardless of cost vs effort.

ChrisJ

Aren't those convectors?

If it's a convector it needs the cover and the interior to act has a chimney so to speak, and pull air through it. You would need to buy all new, or used radiators that are the correct sizes.

GGross

ChrisJ said:

Aren't those convectors?

Definitely looks like a recessed wall convector. They would need to build it a little cabinet or purchase a new one.

EBEBRATT-Ed

looks like convectors to me

EdTheHeaterMan

I have seen those as convectors with five or six 1/2" tubes with metal fins connected to a manifold at either end... I have also seen a flatish cast iron block of some design that connects like a standard radiator. Both use the same concept of the "chimney effect" to accelerate air past the heating elements located near the bottom half of the cabinet.

mattmia2

looks like it has already been retrofitted once. might be a cabinet inside a cabinet and you might be able to insulate behind it.

ScottSecor

I cannot prove it, but I think you would not reduce your fuel bill enough to notice. Just for reference, we have removed about thirty free standing radiators or hot water baseboard emitters over the years that were replaced with Sunrad style recessed radiators. The customer wanted more floor space, not have to look at those 'ugly' radiators, never kick another radiator in the dark again, etc. As a matter of fact, we did a builders house years ago and the majority of the brand new house was fitted with Sunrad style recessed cast iron radiators instead of hwbb. I loved the design so much, I happen to have one in my kitchen (with almost no wall space).

Whenever we install a recessed Sunrad type radiator (new addition or retrofit mostly) we install a piece of 1/2" rigid foil faced foam behind it. To date, no one has ever complained that they were using more fuel.

Greybeard

What ScottSecor said. Shove a sheet of rigid foil faced foam in the back of the enclosure and call it a day. I use some behind free-standing radiators.

mattmia2

I suspect air sealing the recess will do far more than insulation.

BobC

The cost of moving those convectors will never be paid for in fuel savings, it will help some but not nearly enough. Adding thin reflective insulation in back of those and sealing up the box so nothing escapes out the back or up into the wall cavity above will cut losses a lot at little cost.

Bob

The Steam Whisperer

I agree with Bob C. I plan on using 1/2 thick duct insulation for the recessed convectors at my church. It is rated to be exposed, which most board insulations are not. If you want you could bond a layer of heavy foil to the insulation with duct insulation spray adhesive.

SteamingatMohawk

Try this. If you can get behind the unit easily. You can just staple it in place.

Hap_Hazzard

No. This will not change the efficiency of the convector. No matter what you do to it, you still get the same number of BTUs per cubic foot of steam condensed. This is a physical constant that can't be changed. All you can change is the amount of steam it condenses, thus the heat output, per hour by increasing or decreasing the airflow. Effectively, this makes the convector bigger or smaller in terms of its EDR.

Any change from the designed configuration, short of installing a fan, will probably result in a reduction in EDR. Convector enclosures are designed to optimize air flow through the convector. The best thing you can do to insure optimal airflow is to remove the cover periodically, vacuum up all the dust and cobwebs that have accumulated, and put the cover back on.

DanHolohan

I’m with Bob C. as well. 

pedmec

Work on these a lot in the Boston area. Always see them installed with foil face paper backing behind the convectors with the foil facing the convector. Can't imagine that of the hundreds that I've seen that the installation would not work as intended and if there was a better way they would have done it. i figure that a lot of the old buildings (easy over 100+ years old) that there in would have changed it if it wasn't a good application. god knows they have had plenty of time to test it.

ChrisJ

pedmec said:

Work on these a lot in the Boston area. Always see them installed with foil face paper backing behind the convectors with the foil facing the convector. Can't imagine that of the hundreds that I've seen that the installation would not work as intended and if there was a better way they would have done it. i figure that a lot of the old buildings (easy over 100+ years old) that there in would have changed it if it wasn't a good application. god knows they have had plenty of time to test it.

They work, sure.
But so did the coal fired snowman boilers.

The in wall convectors could be improved on greatly but it's just not cost effective to modify once they're in place.

For example, radiators installed inside of the heating space next to an insulated wall works quite a bit better.

gerry gill

No you won't increase the efficiency. You have two types of heat at play here. Radiation and convection. You get none of the radiation due to the cabinet. It is really the radiation heating the outside wall. You won't get that heat anyways. What you get is convection air current heat. If you want to increase the efficiency, increase the height of the cabinet. (not really practical under a window)

Jakek

I had a similar situation which I documented in this thread.

A year later I can say the room still looks much, much better but there's no change in comfort in the room and/or fuel savings. The old radiator was leaking slightly between the fins so it probably was worth it regardless.

gassyman

I am an enthusiastic reader and fan of HeatingHelp.com, and though I have worked in HVAC throughout my career, it was with limited formal training. Because of this, I find it easier to see thing from a homeowner's or customer's perspective. My impression of the original question was that the word efficiency was being applied to the entirety of the building, not limited to the heating system. I think the insulation behind the convector is the answer. It would be interesting to see thermal images of the outside of that wall during heating season.