choosing new radiators

[BasinHaircut]

to improve the layout and increase available wall space of our downstairs, we've decided to get those tall narrow radiators to replace the short wide ones we currently have.

Im a bit confused about double or single radiators. whats the difference? Do the double ones give out double the heat? can I take 2 single radiators out and replace with one double and still be as warm? How do you know which ones to choose? Is there an unwritten rule? e.g. double downstairs, single upstairs?

We are only replacing downstairs radiators and they are currently a mix of double and single. I don't really plan to reduce the number of radiators, just change existing traditional style ones for 'upright' ones.

Any ideas?

tall, narrow radiators are very good for warming the ceiling. Low, wide radiators are better for warming the room.

Larger radiators can run at a lower temperature and keep a more even warmth.

You can look up the nominal power output of your radiators by measuring them and looking on a radiator sales website. For example a single radiator, 600mm high, can give out about 1kW of heat if it is one metre long; and 2kW if it is two metres long. The nominal outputs in the catalogue are at least 10% less than you will actually get due to the way it is measured.

A double radiator gives out more heat than a single, but not double.

Unless your rooms are currently more than warm enough even on the coldest days, I'd usually get bigger radiators than you already have. Housebuilders usually fit minimum sized radiators to cut costs and increase profits. TRVs will prevent them overheating the room. Modern boilers modulate their power according to demand, and are usually more powerful than older boilers.

Give the system a chemical clean before removing the old radiators to help remove sludge and sediment.

"The nominal outputs in the catalogue are at least 10% more

Thanks PigletJohn, are the tall radiators a bad idea then? We are in a 1930s house with high-ish ceilings and end of terrace. We haven't spent a winter here yet so im not sure how warm the house usually is but are you saying that they aren't going to keep us as warm?

I don't want to make the wrong choice here as we will plan layout around the fact that radiators are either in their current position or not. BUT on the other hand, there isnt really a layout that works with the current radiators unless they are hiding behind furniture, so I was thinking that an unobstructed tall radiator might be better than a low wide one between the window and the couch?

I don't mind radiators behind furniture, as long as there is an air gap.
A shelf above the radiator helps to break up the warm airflow so it mixes better.

If you have antique furniture, solid, rather than modern veneered chipboard, it should be kept away from sources of heat or the joints will crack.

The external wall at the end will get quite cold, unless you have it insulated, which at that age might be external cladding as it is probably not a cavity wall.

We have one tall radiator in the living room. It does warm the ceiling nicely, but it also warms the room really well and for us it was the best decision spacewise, so they can work - but maybe overspec it a bit to make sure.

Ha ha thanks grumbleina!

We have just replaced a wide with a tall. Totally agree with increasing the BTU's, the calculators can under spec and it's best to have over warm and turn down then cold.