Recessed radiators with limited insulation

maks

Hello everyone,

I'm switching from steam to water based heating system
My house is made of brick on the 1st floor and stucco on 2nd floor.
I want to install recessed radiators everywhere to save some room, but since I have stucco on the 2nd floor, the thickness of the exteriors walls are no more than 2 inches (max).
My plumber suggested that I DO NOT install recessed radiators on the 2nd floor as there is a possibility of leak or crack. When I spoke to others, I was told as long as its insulated properly (including polyiso foam behind radiators and spray foam under windows), than it should be fine.
In addition, when I checked the OCS website, it says that if you recess the radiators, then buy 20% more sections (but should still be fine)
The Governale website is a little weird, but i think it says to use 10% more.
The house is located in Queens, NYC, where temps can reach -5 in the deep winter.
The plumber is planning to use Pex to connect.
Please help....thank you in advance!

Abracadabra

Was a heat loss performed to figure amount of btus you'll need for each room?

Just curious, but why are you switching away from steam?

Fred

Also, the exterior walls, on the second floor have to be at least five or six inches thick. The stucco may only be 2 inches thick but there is at least a 2"X4" frame structure and lath or wire mesh behind that and then your plaster or sheetrock on the interior.

Jamie Hall

First off... switching from steam to hot water will be a big, expensive and very sad mistake. You will spend a lot of money for a tiny gain in efficiency (perhaps 4 percent overall) and no gain in comfort at all.

However...

You will need to insulate heavily behind the recessed radiators, and even then I would plan on increasing them the full 20 percent. The pipes leading to them should also have heavy insulation between them and the outside wall -- and none between them and the heated spaces.

Further, if you are counting on any efficiency gain at all, be sure that the radiators are properly sized to use relatively low temperature (140 to 150 degree) inlet water; otherwise there is no efficiency gain over steam in colder weather. This means, of course, that the radiators must be considerably larger to do the same job than the steam radiators are.

Again... I hope that you have an awfully good reason for taking out the steam which doesn't involve money or efficiency or comfort...

LionA29

Maybe you need to reconsider your plumber and use a " Pro" from here! You will definitely get the correct resolution for your quest. Find the right PRO and get the job done correctly ONCE!
Good luck.

maks

1. I checked a few websites, but was getting different BTU numbers. Can someone please recommend a good website where I can perform that calculation (btw, I'm assuming my plumber will do they same, but I just want to be sure that we get the same numbers)

2. I lived in a few places that had steam heating and I absolutely hate it. One place made it feel like a sauna (with water dripping on wall). All of the places lost the heat quickly, so I would have to turn it on again. Efficiency is important, but not my top priority.

3. The plumber was recommended by a few people and one person who recommended has a significantly bigger house.

4. @Fred I agree that the total thickness of the wall is over 6 inches, but the radiators will begin approx 3 inches into the wall (2 inches of exterior wall + 1 inch of insulation). If I'm mistaken, please let me know.

Thank you!!!!

KC_Jones

maks said:

2. I lived in a few places that had steam heating and I absolutely hate it. One place made it feel like a sauna (with water dripping on wall). All of the places lost the heat quickly, so I would have to turn it on again. Efficiency is important, but not my top priority.

That problem has nothing to do with the heating system, it's a problem with the house and no new heating system will fix that issue. Also keep in mind your comment about turning it on again, the most efficient and comfortable way for any heating system (especially hot water systems) to work is to run as close to continuous as possible.

All of the problems you list with steam are typically due to some inept contractor hacking up the steam. No system is immune to the phenomena, but some systems are better at "covering up" the hack.

Don't assume they will do a heatloss, if it isn't in the contract they aren't doing it. If you do decide to switch make sure you have a competent designer lay out the system and do all the proper calculations to make sure it works properly. I am with Jaimie you are talking about a serious investment to do the change at the level you are planning.

Also your comment about contractor and house size makes no sense? What does the size of the house have to do with the ability of the contractor. We have seen hacked systems on this website that are in multi million dollar homes. Hacks are everywhere. Just because someone else is happy with the work doesn't mean you will be. What is the other persons criteria for quality? Remember a system that "works" doesn't mean it's right or as efficient as it can be.

Fred

@maks said: 4. @Fred I agree that the total thickness of the wall is over 6 inches, but the radiators will begin approx 3 inches into the wall (2 inches of exterior wall + 1 inch of insulation). If I'm mistaken, please let me know.

The rads will require a 2" cavity on the inside wall. If done properly, the installer/carpenter should remove (cutout) any stud(s) up to a height and width that accommodates the rad and he/she should build a wood header above the rad, substantial enough to support the studs that were shortened. That may mean removing inside plaster 4" to 6" above the actual rad and then replastering those areas. The insulation will go in the cavity behind/around the new rad. That cavity is already there and it sounds like you will have 2" to 3" of space already there, when the internal wall is opened and behind the rad, to fill with insulation. keep in mind the interior plaster wall is typically about an inch and old studs are typically really 4" deep so your rad will only sit 1" to 2" into the actual frame cavity.
I'm not advocating for this conversion at all. I agree with what the others have said about keeping the steam but you should have correct facts about the process.

Jamie Hall

maks said:

1. I checked a few websites, but was getting different BTU numbers. Can someone please recommend a good website where I can perform that calculation (btw, I'm assuming my plumber will do they same, but I just want to be sure that we get the same numbers)

2. I lived in a few places that had steam heating and I absolutely hate it. One place made it feel like a sauna (with water dripping on wall). All of the places lost the heat quickly, so I would have to turn it on again. Efficiency is important, but not my top priority.

3. The plumber was recommended by a few people and one person who recommended has a significantly bigger house.

4. @Fred I agree that the total thickness of the wall is over 6 inches, but the radiators will begin approx 3 inches into the wall (2 inches of exterior wall + 1 inch of insulation). If I'm mistaken, please let me know.

Thank you!!!!

On item 1 -- your plumber won't do a heat loss unless it is specifically in your contract. SlantFin, however, has a decent on line calculator.

On item 2 -- as @KC_Jones said, all of the problems you list for steam are due entirely to some contractor or service person who didn't know what he or she was doing. This can be a problem for any type of heating system, and we see a lot of it here.

On item 3. -- you don't want a plumber. They do water supply and drains. You want a very experienced heating contractor. There are a few men and women who do both, but be sure that the individual is really experienced.

On item 4. -- you're not mistaken. You will have a maximum of an inch of insulation between the radiator and the outside wall. In that situation, you will need to have considerably more heat sent to your radiators than you heat loss calculation will suggest, since it is based on the assumption that you do have a real heat barrier. In my previous note, I mentioned a 20 percent boost in radiator size. In my judgement, given this application and the minimal insulation you are proposing, I would recommend that the radiators be upsized by at least 50 %, and that the boiler also be oversized by about 50 % to compensate for the losses through the wall.

And I will keep my previous comment: this will be a very expensive mistake, for no improvement in comfort or efficiency -- but as they say, the customer is always right, and it's your money, not mine.

JUGHNE

This is a steam system converted to hot water, house was on the market and supposedly checked every day by the agent last
winter.
This was second floor and rads are sitting away from the walls.
The first floor ceilings may have come down. Even if a steam boiler fails, most of the water would drain down into the boiler in the basement.....perhaps not as freezable as 2nd floor.

jumper

If you already have hot water type rads,you can improve one steam heating by feeding steam at top of radiator like in the second picture above. Hot water heating is okay but it's more sensible to fix existing steam heat. Especially after the building envelope is improved. Then the radiators are over sized and you can put shelves on the radiators.That should increase the radiant/convection ratio. Radiant is more comfortable than convection.

That second picture looks like it was originally a two pipe system. So somebody modified a Cadillac into a Ford?

JUGHNE

You can see a steam trap on the floor.
Yep it was, then the Ford turned into a Yugo. This house was probably brick veneer with 2 x 4 stud walls, lath & plaster, maybe back plastered to reduce air infiltration inside wall cavity.
The house itself was a nice old Cadillac that probably lost a lot of resale value. The insurance companies are probably still pointing fingers at each other after a year.

Perhaps even a pump failure could have caused this.....slim chance that the boiler was still hot and caused some gravity convection that may have prevented this. But once it popped the auto feeder would have kept doing it's job.

brandonf

KEEEEEPPPP THE STEEEAAAMMM!!!!!