Radiator Covers - Leave them or Take them OUT?

gasfolk

According to CDC:

"Temperature is a critical factor in thermal injury. Contact with temperatures in the range of steam radiators can cause an instantaneous full-thickness burn of adult human skin. Children's skin is probably more susceptible than that of adults to thermal injury. In comparison, hot water radiators operate at a lower temperature than steam radiators and present a lower risk for thermal injury.

Risks for burns from home radiators can be reduced by keeping the unit covered and the pipes insulated. In addition, beds, couches, and chairs should be kept at a safe distance from radiators to avoid contact burn injury. Recognition of steam radiator burns in other communities may prompt investigations similar to that in Chicago and improvement of heating systems to prevent burn injury."

<a href="http://www.cdc.gov/MMWR/preview/mmwrhtml/00043779.htm">http://www.cdc.gov/MMWR/preview/mmwrhtml/00043779.htm</a>

Since we have low system temperatures in our hydronic system, we kept the radiator covers for the convenience of a place to rest a book or cup of coffee, but maybe we'll be taking some out after all of the informative comments above.

Thanks,

gf

Victor_7

Hi folks,

I need an expert opinion here and Google has not exactly been very helpful.

I live in a 1925 brick house with plaster over masonry walls. Hot water radiators throughout. All of them have wooden radiator covers with fancy thin metal "lattice-work" on the front. Anyway, my 92% eff. Burnham boiler does not exactly keep the house toasty, as a matter of fact it struggles to keep 65 degrees on a 5 degree day here in PA.

I just had one fellow stop be and he said to take all of those radiator covers off as they are supposedly blocking the heat. On the other hand, I find a lot of companies selling and making those radiator enclosures, advertizing them as making radiators more efficient, not less.

I would really appreciate any and all professional opinions on this subject.

Thank you!

kpc_14

I would...

take them off. They do block heat...esp. the wood ones. They sell a lot of things on the web and not all are good or correct.

Long Beach Ed

Take them off...

If you really want maximum efficiency from the radiators, you'll remove the covers. They generally cause a 5% - 20% loss in heat emission of the radio. There were studies done on this back in the 1920's and charts made that show the decrease in heat emission for each type cover configuration.

I wouldn't be surprised if Dan hasn't posted those charts on this site somewhere.

But covers are not the reason for a cold house. The boiler should simply work harder, burning more fuel to make up the difference.

If the place is cold, there could be several reasons. Perhaps a proper heat loss calculation was not performed and the boiler is under-sized. Maybe the controls are not set properly. Or all the windows are open?

Unknown

This may help.

JohnG_3

I have sheet metal covers with latticework as well. Why wouldn't the covers simply heat up and re-radiate the heat into the conditioned space? The only thing I can think of is that they are acting as insulation, similar to pipe insulation on mains, and they prevent the steam from condensing and giving up its latent heat to the radiator.

Mike T., Swampeast MO

Yes, the covers do "heat up and re-radiate"...

...BUT, at a far less rate than the radiator itself--so much less that covers effectively destroy the radiant output of radiators and turn them into almost pure convectors.

Covering radiators does not affect their efficiency, but it does affect the output. The vast majority of cover designs reduce output--some common ones greatly. Within reason, output can be restored by raising the temperature of the radiator. Most systems with iron rads have quite a bit of room for increasing temperature above the bare requirement, but for any common emitter radiation is maximized when temperature is minimized to just meet the load.

Covers, when used properly, were an intentional part of the design with the size of the radiator adjusted accordingly. In nearly every case, the size will be increased to allow it to work near the same temperature of non-covered radiators in the system.

With a condensing/modulating heat source, minimizing system temperature also increases boiler efficiency. When using such a boiler my advice is to not add covers and remove any that were not originally part of the design.

JohnG_3

Are your comments equally applicable to steam and hot water radiators? The original poster has hot water, I have steam, and it seems like if you are talking about radiator & system temperature then you are also talking about hot water.

jp_2

covers= heat shields

mikes correct. they will act as heat sheilds, like the ones on your car, they get hot too, not as hot as what they are shielding though.

they will also keep the rad warmer so its running output will be less.

this is for any warm surface,steam or electric or etc....

JohnG_3

Makes sense. I think this would have to get reflected back to the boiler as higher steam pressure. The radiators would stay hotter due to the heat shields, resulting in less condensation, resulting in higher pressure.

My wife is not going to be impressed when I tell her we should remove our attractive radiator covers to get better heating efficiency.

John_173

Dave's link

Please consult Dave's link to consider the effects of rad covers. To simply say a cover acts as a heat shield is inaccurate; at least according to the information provided by our host (at the link and in various HeatingHelp publications). Design of the cover is key.

Also consider that rad covers & paint choices can be used to tune comfort in particular locations.

Thanks, Dave, for your link of February 27.

Peace.

[Deleted User]

We've been successful

w/ getting many customers to remove, or modify, the solid tops on most radiator enclosures. One customer asked us to design covers. He now makes them for his apartments. Makes the top, front, & sides, w/ coverleaf design aluminum sheet & minimal framing. Works well.

Victor_7

Dave, thank you very much for the link and everybody who posted for their insght. I really appreciate it.

It looks like all of my radiator covers are "the worst kind" wich require 30% compensation.

They are going out the door!

JohnG_3

Thanks, the information is also in We Got Steam Heat, a few pages ahead of where I am in the book. I'll be getting to it any day now...

Mike T., Swampeast MO

Again, covers do not change the efficiency of the radiator, they change its output. If the covers result in reduced output, then such can be restored merely by increasing the supply temperature. The efficiency of the radiator has not changed--merely the conditions under which it operates to achieve a given output.

Increasing the supply temperature does however affect the efficiency of the boiler. In general, the lower the temperature requirement, the higher the efficiency. This is especially true with condensing/modulating boilers.

In the case of steam radiators where the supply temperature is essentially fixed, covers that were not considered in the original design could reduce radiator output enough to cause the boiler to short-cycle on pressure thus reducing boiler efficiency. The efficiency of the radiator still hasn't changed--but since it cannot give off heat as rapidly it stays hotter and a hotter radiator condenses steam less rapidly.

jp_2

but mike the definition of

efficiency, as you know, is output divided by input.

if you reduce its output, how is that not effecting its efficiency or its ability to heat?

are we assuming these covers were built 100% correct?

how do you define Radiator efficiency?

D107

but if there are couches/obstructions in front of bare rads...

I removed all my covers a few years ago. They were the worst kind according to Dan's illustrated info sheet. I recently realized that if the rads are blocked by furniture, then much of the radiant heat may be lost, so I'm not getting the full output of a bare rad. For many of us space is a premium, and we don't have the luxury of keeping rads free and clear.

So looking at Dan's page, at the 3rd rad from the left in the first group--which apparently increases output by 5% (says 'deduct 5%) perhaps it would be smarter to get those kind of enclosures, which work more by convection and which might increase output not only by 5% but more if the rad is currently blocked.

I'd only ask what effect even the best rad covers would have on the house benefitting from the capacity of cast iron to hold --and give off--heat for a long time if they're acting more as convectors.

Thanks,

David

Mike T., Swampeast MO

Glad you asked jp. Who knew it would be you?

Covering a radiator does not affect its efficiency, it affects only its output.

Yes, efficiency is "output divided by input".

In the case of an emitter however the input of the emitter is exactly equal to its ability to liberate energy under the current conditions. Input = Output so efficiency = 100% The emitter may not be efficient with regards to mass or space, but it is still 100% percent efficient in its ability to liberate heat under the given conditions.

Emitter output is relative to not only to the ambient conditions but its ability to liberate heat at a given temperature under those ambient conditions.

----------------------------------------

All hot water space heating systems control supply temperature as their prime variable.

----------------------------------------

If the boiler can supply energy more efficiently at a lower temperature and the temperature requirement of the emitter is lowered by removing a cover then and only then will system efficiency increase. You have NOT however changed the efficiency of the emitter--you have changed the conditions under which it operates.

jp_2

Ok mike

sounds fishy and pseudo science like but I see what you mean.

thing is, generally, we(I) think of the effect on heating the room, not just the radiator in of itself. of course thats the way I see it.

Jim_64

Neither fishy nor pseudo-science.

You will find the very same statement that covers do not affect the efficiency of the emitter--only its output--in standard references. The difference is subtle, difficult to explain and until you "see" the underlying concept of changing the conditions under which the emitter operates, it does sound "fishy".

Jim_64

jp:

You said, "they will also keep the rad warmer so its running output will be less"

Think of the seeming contradition in that statement--your radiator is hotter but it has less "running output". Common sense tells you that a hotter radiator will put out more heat...

The cover has changed the conditions under which the radiator operates--not its efficiency. The rad's "running output" will always be exactly equal to its "running input".

Neither "fishy" nor "pseudo-science"--it's law that can only be understood via relative comparison.

Mike T., Swampeast MO

Unfortunately, most covers I've seen--both advertised for sale and in use--are of the "worst" variety. But even these are better than many built by well-intentioned carpenters. I've even seen wooden covers made that have no ventilation openings save cracks.

Mike T., Swampeast MO

I daresay there are hundreds of thousands if not millions of children living in the U.S. who have grown up with uncovered steam radiators. Despite numerous web searches, I have never been able to find even an anecdote regarding anyone--adult or child--being seriously harmed by contact with a radiator.

Schoolkids have been melting crayons on steam radiators for as long as both existed--they might get sent to the office, but not the nurse...

gasfolk

Hi Mike,

From the same CDC article...

"In 1993, an estimated 1881 children visited emergency departments for treatment of burns related to nonvehicle radiators in the United States (3)....

Of all emergency department visits for burns related to home radiators in the United States during 1993, 22% resulted in hospital admission, and 68% involved children aged 0-4 years. Among children aged 0-4 years who visited the emergency department for such an injury, 16% slept in a bed that was too close to a radiator (3).

Unprotected radiators and their pipes were directly related to injury risk for the children in this report. Building codes in Chicago require radiators to be covered in public places (e.g., churches, day-care facilities, and schools) but not in private or public housing."

We recently had (and enjoyed) steam heat. Since we have small children, this seemed only a small safety consideration regarding covers for steam radiators. The original question related to a hot water system, so sorry for the off topic post.

gf

Mike T., Swampeast MO

Thanks gf. Am a bit surprised that never came up in any of my searches.

jp_2

but mike

if you insulate a pipe, doesn't its surface temp increase?

does that mean it looses more heat?

this reminds me of a discussion I had with a draftsman, he claimed the the shape of a steel frame member doesn't effect the strength of the structure, cause steel has a single strength regardless of shape!

you are looking at the radiator exclusively, I am looking at the room. and there lies the reason we don't agree here, apples and oranges......

JJ_4

Kids and Steam Rads

My kids each touched them....once. The cats, however, sleep on and under them.

Mike T., Swampeast MO

Hydronic emitters have to obey the same laws that govern every other emitter.

Say you have an electrically ideal resistance heater.

You supply 100 volts; it draws 10 amps and emits 1,000 watts (about 3.4 mbh) of energy.

You cut the voltage to 50 via a power supply that still has at least 10 amps of output potential The element now draws 5 amps and emits 500 watts (about 1.7 mbh) of energy.

In both cases, the emitter is 100% efficient as it is consuming exactly the amount of energy it is liberating. You have simply changed its output by varying the conditions under which it operates. While more amps were available when the voltage dropped in half, the element could not utilize them and thus the power supply did not produce them. The emitter only gave off the energy it consumed even though more energy was available. An emitter cannot waste what it cannot use.

A radiator connected to a hydronic system follows the same laws. Change the conditions under which it operates and the BTUs it does consume from the supply water--thus cannot emit--are still contained in the return water.

JohnG_3

Mike, I understand and have no quibbles with what you are saying about emitter efficiency, but what I am concerned about is overall system efficiency. Or, in more practical homeowner terms, should I remove my radiator covers to reduce my fuel consumption at a given level of comfort?

jp_2

yes and no

reducing a heaters voltage is not the same as covering the heater, the boiler has already made the energy conversion that looses energy by the second.

the covered rad will reject the hot water, but you can't just keep circulation that hot water til its needed; theres the difference, theres the loss.

seems everyone here is talking about system eff not just whats going on at the rad. who cares about it of itself!!!

no need to re-explain, I got it the first time.

John Ketterman

Everything Mike T said is correct.

But I am wondering if the OP's problem is the radiators. He says that the boiler struggles to heat the house. I don't know what that means.

Is the boiler smaller than is required? In that case the aquastat would never kick in, the flame would be lit all the time. If so, removing radiator covers won't help.

Or is the radiation inadequate as the OP has assumed? In that case the pump runs all the time but the boiler does not (aquastat has shut off the boiler), and if so then removing the covers will help.

The OP needs to find out. It's not so difficult to figure it out.

Radiator covers are often found in older houses that are typically overradiated (many were designed on the expectation that the windows would be open at night). So the covers were seen as improving not just aesthetics but also comfort (cast-iron boilers require 180F water and then overrradiation results in short bursts of excessive heat, the covers help moderate the bang-bang effect). If that is the case, then even with the covers in place there is enough radiation, and removing the covers won't help.

Mike T., Swampeast MO

John. Sorry, but without knowing more about your system it's hard to say what effect removing the covers will have on system efficiency.

You have a steam system, correct? Are all of the rads covered? If not, are there balance problems between rooms served by covered vs. uncovered rads? Can you tell if the rads were designed to be covered--remember that original covers may well have been replaced.

Do you have any idea if the covers were in place when the current boiler was installed? If so, do you know if the effect of the covers was taken into consideration when the boiler was sized?

In my experience, residential steam radiators especially in "public" rooms of systems installed after 1900 or so are the most likely to have been covered originally.

If yours was a hot water system using a condensing/modulating boiler then I would say, "Absolutely remove any covers that weren't original and perhaps even those that were." In this case--and with appropriate adjustment of the boiler's reset curve--the increase in system efficiency could be quite significant.

If yours were a hot water system using a conventional boiler then I would say, "Removing the covers will likely improve comfort somewhat, but you're unlikely to see much change in system efficiency."

Mike T., Swampeast MO

the covered rad will reject the hot water, but you can't just keep circulation that hot water til its needed; theres the difference, theres the loss.

Sorry to keep on, but there's no loss associated with the radiator itself. The "rejected" hot water just goes right back to the boiler via a return temp that is warmer than before. While such reduces the efficiency of a mod-con, such is not necessarily true with a reasonably-sized conventional boiler--particularly when the radiation is often vastly oversized and its ability to liberate energy (at a "standard" say 170F average emitter temp) already exceeds the boiler's ability to produce it. Removing unplanned covers from such a system probably won't have much affect on system efficiency and might even decrease it slightly by forcing the boiler to work in conditions further and further away from the conditions at which its efficiency is rated (e.g. the AFUE test).

GansDitrixGanher

What enclosures increase the efficiency of the system/rear panel


Ok, I understand what most are saying on this thread. I am curious what cover will increase system efficiency?

On a related topic, why is it so difficult to locate radiator reflector panels (for between the wall and the rad). It would
seem that you can save a bunch from diverting the heat back into the room (instead of an outside wall).

Thanks
Will

GansDitrixGanher

what covers improve system efficiency/reflector panels


So what covers increase system efficiency and why is it so difficult to find radiator reflector panels (for the back of the radiator). And I know I can 'build' on with foil but I am looking for an 'engineered' solution (other than Novitherm).

John Ketterman

> but you can't just keep circulation that

> hot water til its needed;


That makes no sense. Of course you can. Where would the energy be lost to? There is nowhere for it to go except into the house ultimately.

John Ketterman

> efficiency, as you know, is output divided by

> input.


Nonsense. You can't take the output of one device (radiation) and compare it to the input of another device (the boiler).

In the case of the radiation the issue is with the RATE of output (how fast the radiation releases the heat). But all heat is ultimately released.

jp_2

NON SENSE???

MR cricket you are too funny...

what you read into "output divided by input" is beyond me?

jp_2

higher running temps

equal higher fuel usage.

Mike T., Swampeast MO

jp:

You know I've always been one to hammer home the point of system efficiency.

To properly understand system efficiency though you must also understand that you cannot change the efficiency of an emitter--you can only change its output by changing the conditions under which it operates.

Depending on the nature and design of the system, it is possible that intentionally reducing the output of an emitter will result in higher system efficiency.

Unless you have a heat source proven to provide higher efficiency at lower average system temperatures (e.g. a mod/con) it is impossible to make blanket assumptions like "removing the covers will increase system efficiency". In a number of scenarios I can imagine change in system efficiency is either negligible or even slightly negative.

Think of this:

The ideal emitter of radiant heat has no mass.

The ideal conductor of heat contains no heat.

I eagerly await your reply...

johnnyge

I want to find out about radiator covers also and I was reading This Old House Magazine Webpage and they show you how to built one. They suggest to put a galvanize sheet metal on the back of the radiator cover to reflect the heat back into the room and not the outside wall. After reading all the imput on this treat I may put only one radiator cover on the babies room, because the radiator is between the beds, as a safety. I will paint the other ones.