Getting the most out of your radiators

Most of us have them and don’t think much of them. We cover them in cabinets, stick sofas in front of them, hang wet laundry over them.  But how can we get the most heat out of our radiators?  Four key considerations in radiator efficiency are:

  1. The type of radiator
  2. Positioning within the room
  3. Energy-saving accessories

Now, I should probably admit that I don’t think I ever saw a radiator in real life until I was about 27 and living in Nashville, Tennessee.  They’re not really common in the US, and certainly not in California!  So since radiators have been a bit of a “novelty” for me, I always notice them and never cease to be amazed at how lovely the old ones (like the gorgeous cast iron ones in museums around pillars)  and new modern ones are.  I will never forget the first time I saw a towel rail radiator in a bathroom.  I came running out saying “wow, that’s such a great idea! How does it work?  Does it get warm when the shower is on or is there a switch?” much to the surprise of my host who had probably never thought twice about it before!  But I digress…

1. Radiator Types

There are many many types of radiators out there.  If you are starting from scratch, you’ll want to call in a heating professional who can tell you how many BTUs you need to heat your space.  But by far, the most common radiators are white panels.  They’re usually steel or aluminium.  Aluminium heats up more quickly than the steel ones, but they also cool down more quickly.  The most energy efficient design for panel radiators are the convector finned models that increase the convection of warm air, and heat your room more quickly and with less energy, and for me that’s the real key thing to look for in a new radiator.  Only one of our 9 radiators has convector fins, and even though it’s located in the middle of our radiator loop, it is the first to get warm (probably because the others are steel and it’s aluminium, which isn’t a good idea to mix, but never mind) and really heats up the space quite quickly.  This is one radiator type that I can honestly say works better than others!   There are a great many different styles of designer radiators, from more traditional cast iron columns to stone slabs (be still my geologist heart!), so personal style and preference will play a part, but if you’re going for pure energy efficiency, then a finned double panel will be your best bet.  Apparently stone radiators are quite energy efficient, but the scientist in me is quite sceptical, as you need to convect the heat from the radiator to heat the room, so the shape really is quite important.  Sure a stone will retain heat, but unless you’re standing right next to the stone, that won’t really help a large room.  I’d like to hear more about the physics of the air flow for these ones first.

2. Positioning in a room

The thing to remember about radiators, is that it’s all about convection, not radiant heat – despite their name.   Radiators work by creating a convective cell in a room that pushes warm air all through it.  Most older homes will have a radiator or two underneath windows.  My 1930 flat only had one of these thankfully, which I removed a few years back.  If you can put radiators on internal walls, as opposed to external walls, you will likely be better off.  Radiators on external walls will heat both the air and wall.  But you don’t want to waste heating on eternal walls that will bleed your heat to the outside.  Back before double glazing, windows made the room cold, so it made sense to put the radiators near to the windows to start heating the coldest part of the room.  But now that’s not really the case, and the radiator can’t make the full use of it’s convection power with cold window air raining down on it.  Cold air is denser than warm air, so it will fall relative to warm air.  But you ideally want a large circular pattern in your room for efficiency sake and to avoid uneven heating within the room.  So altering this flow isn’t ideal. Not to mention that if you have curtains on the window, then your warm air will rise and get trapped between the curtain and the window instead of getting out into the rest of the room where you’d undoubtedly prefer it.  If you have nothing on your windowsills and radiators below the window, you can tuck your curtains into the sill so that the warm radiator air rising will hit the front of the curtains like a wall and go up to the ceiling, getting a more optimal convective cell forming.

Another factor with placement is the furniture and “stuff” in your room.  While you can’t easily move radiators around, you can move most furniture with a bit more ease.  So try not to stick large items like wardrobes, beds, shelves or sofas in front of radiators.  They’ll absorb and block the flow of warm air coming off the front of your radiator.  Likewise putting wet clothes on your radiators will reduce their efficiency.  But when you live in Scotland and have no tumble dryer, it’s pretty hard to get through the winter without doing this a wee bit!  While I like the idea of making a nice looking cabinet to go over bland radiators, they too block convection and so decrease the efficiency of your radiator.

3.  Energy-saving accessories

Now for the fun part!  There are all manner of items you can try to increase the efficiency of your radiators.  The most important one is the thermostatic control that lets you turn on or off each particular radiator depending on your needs.  These valves can be added to existing radiators too, so one need not replace the whole unit.  These controls allow you to turn off the radiator in a spare room.  Likewise for a lounge, study or dining room that isn’t always used, you can turn the heating down if not off to let your boiler work on heating the rooms that really count for you.

Reflecting foil behind radiatorI have foil lining on the back of my radiators located on external walls.  Yes, I know I just said I removed my only radiator on an external wall.  But living in a flat, I share walls with some lovely neighbours.  While they are nice to chat with, I don’t particularly feel the need heat their flat for them, so the foil lining on radiators that are on these shared walls, helps insure that these radiators are only working on heating my side of the wall.  I’ve had this installed for a few years, but have just purchased a wee bit more to fully cover the backs of the radiators.  Installing this can be a bit tricky as you can’t easily reach behind a radiator, but I used a painting stick to help get in between the radiator and press the foil to the wall.  Some radiator foils come with sticky pads, but I found that a bit of PVA worked quite well, thoroughly sticking the foil to the wall and is easy to clean up.  Have I noticed a difference in my heating???  Honestly no.  But the science behind it is pretty sound.  If you’ve ever cooked a turkey or chicken and put an aluminium foil tent over it, you’ll know the power of foil!

Radiator shelves can be clipped on to the tops of radiators in an attempt to prevent warm air from rising up walls and instead force it into the middle of rooms.  I have had one of these in my bedroom for the past 7 years, and shall keep it there.  Again, I honestly can’t claim that I notice a difference though.  My room is the last on our radiator loop and we have high ceilings, so I’ll try anything to get a wee bit more heat out into my room!  That being said, I don’t have a one of those radiator fans on it.  My unscientific poll of friends who have bought them indicates that they aren’t all they claim to be.  So, I’ll put my energy-saving efforts elsewhere.  I also won’t be painting my radiator black, as I’ve read some people do for energy purposes.  Again, I want to see some science that explains why the colour of paint should impact the heat out put of a radiator…  Glossy vs. matte, sure that might have some super small impact, but colour???  Nah!  I’ll stick to my white thank you very much.

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