convection encaseing for wall radiators

[lunarhighway]

i've just started renovating my "new" house... it was build in 1938 so it leaves some things to be desired in terms of insulation etc, but generally it was well maintained over the years and renovated about 10 years ago.

it's heated by old radiators, wich seem decent enough, with recent thermostatic valves. they're not a real pretty sight though so i'd like to make an encaseing that runs the entire lenght of the wall covering the radiator and the pipes running to and from them, these can be insulated and the encaseing could house some more wall insulation as well. internally the rad will he boxed in separately with air intakes on the bottom and top of the encaseing. however IS this a good idea? since i've read most of the heat delivered from such a radiator is trough convection a boxed in rad should imho improve airflow, but i can imagine inpropper construction can lead to problems and boxing in the thermostatic valve might cause it to kick out to soon, and perhaps i'll trap the heat inside.

a collegue has a similar setup and he claims it works rather well.

any advice on this??

[wyatt]

If you are going to insulate, you would want to insulate the wall side more so than the room side. Doing this will hold the heat in your home as opposed to helping force heat out through the walls. I have seen different decorative designs for just covering the radiators, and they usually wind up looking like end tables. They have an open bottom, a solid, shelf like top and vertical holes right under the shelf for about 8 inches. A simple google image search returns lots of pictures of how others have done so quite nicely. I don't know how well they work, but there is at least one way to find out...

[almightybmw]

Be sure to not limit the heat potential of the radiator by encasing it and heating the enclosure. Or, institute a thermostatically controlled fan, when the radiator reaches a temp, the fan forces air (slowly so to not waste energy just heating the rad) across it into the room. I remember my old grade school had a sweet setup like this, was awesome when it was -40* outside to just sit on them.

[Peter7307]

LunarHighway,

This topic is well covered by magazines like Finehomebuilder and other books especially from Taunton Press.

Have a look in your local library for some suitable volumes.

We have the opposite problem here just now with the next four days expected to be the hottest in the last 100 years or so.
Temps today 107 and no expected change until Saturday.

Good luck , Pete.

[lunarhighway]

it never gets up to 107F over here... temps are barely above freezing during the day and they'er expected to drop again... a while ago temps went as low as 10F or -10C

makes you think about your radiators

[Piwoslaw]

Lunar, I had radiators in the previous house I lived in (my Grandma's). While renovating, one of the things I did was to put a thermal barrier behind the radiator. It is a piece of styrofoam a few mm thick with aluminum foil on one side. They come in 10m rolls. The 50cm width is about the same as the height of a radiator, just cut the right length. You glue it to the wall behind the rad, with the foil facing the room. I didn't take the rads off for this, so it took some exercise to slip it in. I don't know how your house is built, but at my Grandma's the walls were 50cm thick, but only 40cm under the windows where the radiators were hanging. This means that a lot of heat was being wasted.

Here at my wife's house we have a cabinet in front of the kitchen radiator. I made holes under and above it and the air circulates pretty fast when the rad is hot. But the cabinet gets quite warm inside, which means that a lot of heat is being tranfered through the back. If you put something in front of your radiators, then it is also going to absorb heat, even if there is lots of airflow behind it. That's why I'd vote against covering the rads up, unless it would be something very thin, maybe some kind of screen.

Originally Posted by lunarhighway

boxing in the thermostatic valve might cause it to kick out to soon, and perhaps i'll trap the heat inside.

I've seen radiator valves with the thermostat on some kind of cable, about 1-2m long. This would let you keep the sensor out in the room and not too close to the rad. Or, if you do go along with encasing, keep the valve itself outside of it. A thermostat inside the box will be useless.

[Ryland]

The nice thing about radiators is that for the most part they heat the objects in a room through radiant heat and the air is heated by those objects being warm, put a box around it and it will heat that box an then heat the air and that will make the air feel warmer but not the rest of the house, adding reflective insulation behind them is most likely one of the best things you can do, even a sheet of tin foil will help a great deal.

[lunarhighway]

The nice thing about radiators is that for the most part they heat the objects in a room through radiant heat and the air is heated by those objects being warm, put a box around it and it will heat that box an then heat the air and that will make the air feel warmer but not the rest of the house, adding reflective insulation behind them is most likely one of the best things you can do, even a sheet of tin foil will help a great deal.

the previous owner already installed some reflective film covered foam,

but as i understood their function and backed by some info in the web, a radiators main heat delivery is nog trough radiation, but trough convection. where cold air close to the floor is heated by the "radiator" and than rises and circulates troug the house, cooling and falling as it moves away from the radiator.

this is also why these type of tradiators tend to suck up dust and circulate it trough the house... a collegue of mine who build something similar said one could really feel the hot air being expelled with reasonable force at the top exit opening when the rad was on.

what i meant with a thermostatic valve is that each radiator has a manual valve, sort of like a water tap, to open close the water supply, but these thermostatic valves have a bimetal or similer inside them that opens and closed this valve automaticly depening on the set value... the whole system is controled electronicly from a small wall console that allows one to set the main water temp of the boiler... in my case this is a simple affair with a single twist know, but it will be replaced with something more modern that allows us to program day and night settings etc... when we replace the water boiler wich now runs on oil, but we'll likelt convert to natural gas wich is much cleaner and maintenance free with the option of hooking up some solar boilers on the roof.

but back to the encaseings. lost examples i've seen have a "grill" in the front wich makes sence to allow the radiation heat to exit directly. but what if i where to cover the front panel on the inside with a reflective insulation as well? this would bounce the radiation back and forth in the radiator, heating the internal air faster perhaps.

what i would mainly like to know is how i can improve this natural convection effect? could a larger or smaller intake or exit have an effect on airflow and temperature exchange?

[Ryland]

If you have a cover on the front I would make that absorbent so it heats up as well, maybe with ribs and a dark color, something like flat black painted steel roofing on the inside of your decorative, this would also create more some air flow on either side of that sheet because you want to suck as much heat as possible out of that radiator, not bounce it back in to it.