Finned Radiators

[stevedo]

I have a total of 20 radiators in my house, 7 of which are finned. The rest are older style ribbed radiators, if you know what I mean?

My question is, as we go through the house and redecorate, is it worth replacing the older syle radiators with new finned ones, particularly are the newer type more efficient? In deciding whether to replace the older type, I will also consider the fact that they all need rubbing down and repainting so it might just be a lot less hassle to replace as part of the cost of decorating a room.

I'm also curious abouth the idea of putting a foil reflector on the wall behind the radiator. Is that worth doing or is it just a waste of time?

Thanks
Steve

 

[Diyisfun]

The cost of replacing a radiator will take quite a while to be recovered through Efficiency.
Things to bear in mind, fined rads are higher output, if you paint the old rads the paint will reduce efficiency, foil on the wall will be beneficial with any rad, remove sludge from old rad will improve efficiency. Now what I would consider the important bits, piece of mind (new rad longer before it corrodes) and what does it look like.

Radiators are not pretty things but the newer ones are more appealing to the eye, so in the end way it up, pay your money etc.

 

[Malc]

New radiators are all metric, so most likely will be a different length to ones you have. Bracket will be different too but that's not so much of a pain as the different pipework.

Finned radiators radiate more for the same size too so if the room temperature is ok at the moment, i.e. when the house is warm that room is warm, so the radiator is the right size for the room, then you will need to go smaller with a finned radiator. Note there is no difference in efficiency, finned radiators won't save you money.

Painting a radiator should make very little difference to performance since radiators are really convectors, that is the warm by convection not radiation (otherwise black would be the best radiator colour and white one of the worst). Compared to the difference in temperature to the air the temperature across a thin layer of paint is negligible (unless you paint REALLY thick ).

Foil behind the radiator will save money so worth doing is the radiator is off (how much does a piece of foil and some wallpaper paste cost?) but not worth the effort of taking the radiator off IMO.

 

[stevedo]

Thanks for the responses.

Currently all rooms heat up sufficiently, so I guess changing the radiator just because a newer one may be slightly more efficient would be false economy.

Where necessary I will rub down and respray existing radiators where they are looking a bit tired. The effect of spraying them should be negligible in terms of efficiency. As part of the clean up process I will flush any sludge that may have accumulated.

Foil on the wall seems to be worthwhile. I will do this as and when each room is decorated. What is the best stuff to use and where can I get it from. I assume kitchen foil is not the stuff we are talking about here.

Why aren't there more radiators with foil behind? We looked at lots of houses and none of them had foil!!

Thanks
Steve

 

[Malc]

Any foil will do. I use kitchen foil. All you need is a reflective surface so the radiator does not heat it up. BTW this only applies to outside walls. For inside walls the heat is given up to the house so there is not loss. For outside walls making the inside over hot gives a higher loss to the outside - hence foil.

You can buy foil with a thin layer of foam but the time to recover the money you spent on the that would be ages so don't bother. Foil is not going to make that big a saving. But since kitchen foil is cheap then it is worth it IMO. I only do the central bit of the radiator so the foil does not show.

 

[croydoncorgi]

As stated, there's no point changing a rad just because it's 'old' .
But if you change your boiler for a 'high efficiency' one, in most cases the ONLY way to actually achieve higher efficiency is to REDUCE the water temperature in the system. Otherwise, the water returning to the boiler will be too hot to allow the boiler to condense (critical temperature = 56 degrees C).
If you've got older rads, these may have been sized for higher temperatures than current practice. So if you then reduce the water temperature, the room(s) will heat up more slowly and may not reach the design temperature at all.

 

[stevedo]

Hi Croydoncorgi,

interesting point. I had the boiler changed in September from a 16 year old Potterton to a nice shiny new condensing Worcester Bosch. What's the easiest way of determining whethet the boiler is in full condensing mode or not. There is a 2 digit readout on the front of the boiler that varies continuously between 30 ish and 90 ish. This seems to indicate how hard the boiler is working and I would assume that if the number is high then it is probably working in the most efficient way?

 

[ChrisR]

COndensing boilers are most efficient when the flue gases are cool enough to condense - which means below 56 ish (I can never remember exactly). So you're best off with big rads allowing the boiler to run cool.

If you paint a rad, use a car-body type primer if needed but don't use undercoat, oil based or otherwise. They aren't flexible enough. Household gloss is ok but yellows, radiator enamel is better. I sprayed a new one with liquid rad enamel which then had to be baked on by running the rad at 80C. (Stinky!) That was 20 odd years ago and it's still like new.