Cast iron and steel radiators - efficient? Where to buy from?

[lizziecupcakes]

Hi all
I am in my next project now - sorting out my suspended floor insulation. But before I dive into it, I am sorting out new radiators.

I want to buy cast iron rads because:
1. they go well with the period property design and look
2. I think they are better at heating period properties overall, and although they take a bit longer to heat up, they stay hot for longer after the central heating is switched off
3. I love the rococo design

If you have bought cast iron rads, do you have any regrets?
Also, where is the best place to buy them from?

I'm also thinking about mixing it up too - the more traffic heavy rooms (living room, dining, hallways) would have cast iron rads, while bedrooms would have steel radiators.

I like the steel ones because they have the look of a cast irone radiator, but I am not sure about their efficiency - can anyone advice? Where can I buy them from?

I would really love your thoughts and experiences.

thank you

 

[aockenden]

We bought a brand new one and installed it in my son's bedroom. Very expensive and extraordinarily heavy to get upstairs, but the floor-stand + single wall-stay installation was infinitely easier than trying to hang modern rads onto wavy, undulating stone walls with bracket systems. Also I never felt quite comfortable mounting rads on brackets against a wall. It always felt like a disaster waiting to happen, so the floor-stand cast iron option was a big weight off my mind. Also they obviously look better and more traditional than newer rads.

Yes it takes a bit longer to heat up and cool down which is a benefit if you are running them for example on a woodburner back-boiler system, where the fire will die at 1 AM and you want to keep some heat input into the bedrooms for longer into the night despite the fire dying. But this advantage basically goes away when looking at modern computer-controlled central heating systems.

We are planning to put another one into our own bedroom, and MAYBE one in our upstairs bathroom.

When you say "efficiency" in relation to a radiator, what do YOU mean by that? People throw that term around in very inconsistent ways, often forgetting the laws of thermodynamics in the process.

 

[lizziecupcakes]

Thanks @aockenden , does this mean you have a mixture of radiator types in your home? .

With “efficiency”, i am referring to keepibg the room warmer for longer? I don’t mind if it take a bit longer to hear it up, since we have wifi controlled combi boiler and can also program when to switch it on in advance based.

What i dont like about my convection heaters is that they’re ugly and once switched off, the warmth doesn’t last as long as I’d hope. Granted, draught proofing needs a bit of work still in the rooms, but I hope that with the cast iron rads (after draught proofing) they’ll keep a room warmer for longer than the convection heaters. That’s my aim.

I am thinking of putting steel rads in the bedrooms (instead of cast iron rads) because on average, 16 degrees is the temp for a good night’s sleep, so I am less woried about keeping bedrooms super warm. I mainly wanted to keep living room, dining and hallway warmer.

As a family, we love to have gatherings together, so these communal rooms are important for us

I agree! I also don’t want to put rads on our solid brick walls and damage the walls. We like that cast iron rads have feet and only need a bit of support into the wall, but thankfully they don’t hang off them.

i am trying to justify their expense I guess (because i really want them)

 

[aockenden]

Thanks @aockenden , does this mean you have a mixture of radiator types in your home? .

With “efficiency”, i am referring to keepibg the room warmer for longer? I don’t mind if it take a bit longer to hear it up, since we have wifi controlled combi boiler and can also program when to switch it on in advance based.

What i dont like about my convection heaters is that they’re ugly and once switched off, the warmth doesn’t last as long as I’d hope. Granted, draught proofing needs a bit of work still in the rooms, but I hope that with the cast iron rads (after draught proofing) they’ll keep a room warmer for longer than the convection heaters. That’s my aim.

I am thinking of putting steel rads in the bedrooms (instead of cast iron rads) because on average, 16 degrees is the temp for a good night’s sleep, so I am less woried about keeping bedrooms super warm. I mainly wanted to keep living room, dining and hallway warmer.

As a family, we love to have gatherings together, so these communal rooms are important for us

I agree! I also don’t want to put rads on our solid brick walls and damage the walls. We like that cast iron rads have feet and only need a bit of support into the wall, but thankfully they don’t hang off them.

i am trying to justify their expense I guess (because i really want them)

Yes we currently have a mixture of rad types, but in the end we will probably end-up with ONLY 3 cast iron rads upstairs + underfloor heating throughout all the downstairs rooms.

Honestly, I think the case for cast-iron rads "keeping the room warmer for longer" when taken in the context of a computerized modern central heating system with controlled water temps is unclear at best. If you want your rooms to be warmer for longer, you need to put heat into them for longer. Changing the thermal mass of the rad (aka switching between modern steel and traditional cast-iron) does not create new heat that didn't otherwise exist.

If your rooms currently OVERHEAT when the boiler is on, and then get too cold when the boiler is off, then the extra thermal mass will help that problem. But in that case why wouldn't you just adjust the water flow-temp on your modern boiler downwards and then just run the system for longer under those circumstances? You end up consuming the same amount of energy over the 24 hour cycle (and therefore incur the same cost), but avoid the uncomfortable temperature fluctuations.

 

[lizziecupcakes]

If your rooms currently OVERHEAT when the boiler is on, and then get too cold when the boiler is off, then the extra thermal mass will help that problem. But in that case why wouldn't you just adjust the water flow-temp on your modern boiler downwards and then just run the system for longer under those circumstances? You end up consuming the same amount of energy over the 24 hour cycle (and therefore incur the same cost), but avoid the uncomfortable temperature fluctuations.

This is interesting.
My temp flow rate is currently 60 degrees. I thought it had to stay at that flow rate? We were advised by the boiler installer to keep it at that.

 

[aockenden]

This is interesting.
My temp flow rate is currently 60 degrees. I thought it had to stay at that flow rate? We were advised by the boiler installer to keep it at that.

I'm not a central heating expert / heating engineer by any means, but what is their stated reason for needing to keep it at that? My understanding is that the fuel / energy / cost efficiency of boiler systems generally improves as flow-temps decrease, meaning that you would have extra reason to run the system for longer but at lower temps. That's baked into the premise of the whole heat-pump idea: aka dramatically lower flow-temps and just run the thing practically 24/7.

Maybe there's something I don't know about combi-boilers which means that decreasing the flow-temp is bad for the system or actually leads to lower fuel / energy / cost efficiency, etc.

 

[a twig]

Depending on how badly insulated your home is and size of radiators you can get to a point where if you lower the flow temp too much then you just end up with the house never getting warm / to your thermostat set point.

60’C is a rule of thumb that is often applied, as you reduce your gas usage but will still get to the desired temps albeit 20-30 minutes slower typically. You can definitely experiment with lower temps on your combi if you so desire.

 

[aockenden]

Depending on how badly insulated your home is and size of radiators you can get to a point where if you lower the flow temp too much then you just end up with the house never getting warm / to your thermostat set point

Makes sense

 

[Lacan07]

Hi all
I am in my next project now - sorting out my suspended floor insulation. But before I dive into it, I am sorting out new radiators.

I want to buy cast iron rads because:
1. they go well with the period property design and look
2. I think they are better at heating period properties overall, and although they take a bit longer to heat up, they stay hot for longer after the central heating is switched off
3. I love the rococo design

If you have bought cast iron rads, do you have any regrets?
Also, where is the best place to buy them from?

I'm also thinking about mixing it up too - the more traffic heavy rooms (living room, dining, hallways) would have cast iron rads, while bedrooms would have steel radiators.

I like the steel ones because they have the look of a cast irone radiator, but I am not sure about their efficiency - can anyone advice? Where can I buy them from?

I would really love your thoughts and experiences.

thank you

When you say steel do you mean the radiators that are designed to look like cast iron radiators?

I started out with the intention of fitting standard convector radiators but once I got my first cast iron rad (brand new for a song on FB marketplace) I was smitten. I love the fact you don't have to faff about with wall fittings (other than a brace) and its those elegant feet that seal the deal for me. A few caveats however, once you get into the higher BTU they're much more expensive and ridiculously heavy making them awkward to fit alone. Just be mindful when assessing the ability of your floor to take the weight, especially on the upper floors.

 

[Kearn]

Think you may be meaning aluminium not steel, cheaper and more importantly about 60% lighter.

Steel are not much lighter than cast iron. We only used one as I wanted tall and thin and that was the option that worked.
Interestingly it only came with feeble floor stands or a pathetic wall bracket. We had to improvise and add a stay.

Cast iron give you the flexibility of speccing size and output to what you require as they’re made to order and the range of styles is extensive, but most flexibility is with the Victorian style. Cast aluminium come pre made in a small number of sizes only, and limited styles - basically the Victorian model.

Having one big cast iron per room is a poor idea though. They take a lot of space, which limits furniture and ideal locations Amy not be feasible, weigh more than your floor may be able to carry on point loads, and getting them in place, especially upstairs in no fun.
We used the Genie lift for the one cast upstairs, all 138kg of it, dry.

They also don’t provide equal heat - multiple smaller rads around a room is better for even warmth.

Wet UFH heating is a very good way to keep a low constant heat radiating from the fabric of the building and doesn’t provide hotspots. !but it does necessitate a level of work that is more than just replacing rads.

Equally, how you heat your house - both through choice and physically will matter. Flat modern rads heat up fast, so pump out heat quickly, and are great when you’re heating the air rather than the building - think insulated modern box when you want heating on demand. Conversely something that takes time to heat like cast, or more so a floor slab, requires an ongoing process and can’t be flipped on a whim - way better for old buildings where you’re using the fabric of the building as a heat store rather than than just the air within.

I use UKAA, great service, competitive pricing.

Cast Iron and Steel are Carron rads, Cast aluminium are Arroll.

They only order direct from the manufacturers, so there’s benefit in shopping around.

 

[Flyfisher]

We have a mix of cast iron and steel radiators but the steel ones are column style, which I think looks a bit better in an older property. Apart from the steel ones warming up/cooling down a bit faster than the cast iron ones, I don't believe there's much to choose between them as far as efficiency is concerned. As aockenden noted above, 'efficiency' can be a loosely used term. I've seen 2kW kettles described as more 'efficient' or more 'eco-friendly' as standard 3kW kettles because of their lower wattage but in terms of boiling a given volume of water this is utter rubbish because it takes the same amount of energy to boil a given volume of water regardless of the wattage of the kettle, so the end result is that a 2kW kettle will take longer to boil than a 3kW kettle but both will consume the same amount of energy (measured in kW/h).

It's much the same with radiators. The whole point of a radiator is to 'radiate' heat into a room. It does this by 'losing' heat energy into the room and this can be measured by feeling the flow and return pipes - the flow pipe from the boiler (or other heat source) will be hotter than the return pipe because heat has been 'lost' by the radiator into the room. A small radiator will radiate (or 'lose') less heat than a large radiator, so you might think it would be more efficient than a large one because the boiler will not have to supply as much heat and will therefore use less fuel - but this is not really what 'efficient' means in the context of a heating system, where the whole point is to move sufficient 'heat' from one place (eg the boiler) to another place (eg a room) such that the room gets to a defined temperature. If the room could retain all the delivered heat indefinitely it would quickly get up to temperature and then no more heat would be required, but of course the room cools down over time depending on the quality of its insulation and draughts etc, so heat must be constantly radiated into the room at the same rate that it is being lost through natural cooling in order to maintain its temperature.

Thus, a radiator is just one component of this whole 'heat transfer system' and its job is to 'lose' heat into a room. How 'efficiently' it does this will depends mostly on the surface area of the radiator rather than its physical composition. Yes, a big heavy radiator cast iron radiator will take longer to heat up and cool down than a flat-panel steel radiator, but if they both have the same surface area and are both up to the same temperature then they will both radiate the same amount of heat into the room. The only difference in perfromance will be the thermal lag, ie the time to heat up and cool down. But that's more of a timing issue than an efficiency issue.

In short, the thermal rating of the radiator is more important than its construction and is the figure to be used in the system design. After that, just choose a style you like - ornate cast iron, plain cast iron, steel column or whatever . . .

 

[orangepeel]

My temp flow rate is currently 60 degrees. I thought it had to stay at that flow rate? We were advised by the boiler installer to keep it at that.

Does the house actually heat with that flow temperature? Mine certainly wouldnt during the winter. The important thing for efficiency is the return temperature at the boiler, ideally we want this at around 55deg and if the system is designed correctly for a 20 degree temperature drop across each radiator then the boiler should be near full efficiency with the flow at 75deg. Depending on the boiler if its fitted with an opentherm controller(eg Nest) this will take into account the external temperature and adjust the flow temperature accordingly.

 

[paulc]

My temp flow rate is currently 60 degrees. I thought it had to stay at that flow rate? We were advised by the boiler installer to keep it at that.

I run my gas boiler with a variable flow temperature. This evening, it was heating the place up with just over 50°C. Earlier in the year when it was freezing outside, the flow temperature went as high as 55°C. But to make the most of low flow temperatures requires larger radiators to get the same level of heat out of them.
When I replumbed my heating system, I deliberately went for radiators some 50% larger than the calculators were telling me. It has proved worthwhile as I've been getting 95% or more efficiency out of the boiler. Running at lower flow temperatures also means less build up of scale (in a hard water area here), and reduced corrosion - Getting very little sludge in the magnetic filter.

 

[Lacan07]

Think you may be meaning aluminium not steel, cheaper and more importantly about 60% lighter.

Steel are not much lighter than cast iron. We only used one as I wanted tall and thin and that was the option that worked.
Interestingly it only came with feeble floor stands or a pathetic wall bracket. We had to improvise and add a stay.

Cast iron give you the flexibility of speccing size and output to what you require as they’re made to order and the range of styles is extensive, but most flexibility is with the Victorian style. Cast aluminium come pre made in a small number of sizes only, and limited styles - basically the Victorian model.

Having one big cast iron per room is a poor idea though. They take a lot of space, which limits furniture and ideal locations Amy not be feasible, weigh more than your floor may be able to carry on point loads, and getting them in place, especially upstairs in no fun.
We used the Genie lift for the one cast upstairs, all 138kg of it, dry.
View attachment 16417
They also don’t provide equal heat - multiple smaller rads around a room is better for even warmth.

Wet UFH heating is a very good way to keep a low constant heat radiating from the fabric of the building and doesn’t provide hotspots. !but it does necessitate a level of work that is more than just replacing rads.

Equally, how you heat your house - both through choice and physically will matter. Flat modern rads heat up fast, so pump out heat quickly, and are great when you’re heating the air rather than the building - think insulated modern box when you want heating on demand. Conversely something that takes time to heat like cast, or more so a floor slab, requires an ongoing process and can’t be flipped on a whim - way better for old buildings where you’re using the fabric of the building as a heat store rather than than just the air within.

I use UKAA, great service, competitive pricing.

Cast Iron and Steel are Carron rads, Cast aluminium are Arroll.

They only order direct from the manufacturers, so there’s benefit in shopping around.

The modern aluminium rads designed to be attached to the wall don't look much like the cast iron version to me, the feet they provide just look out of place. It would be great if they look exactly the same as they're much lighter.

Did you have to boost the joists for that big one on the upper floor?

 

[Kearn]

The modern aluminium rads designed to be attached to the wall don't look much like the cast iron version to me, the feet they provide just look out of place. It would be great if they look exactly the same as they're much lighter.

Did you have to boost the joists for that big one on the upper floor?

The aluminium ones I have aren’t for the wall, they have integrated feet and are freestanding, but they do look too smooth and precise to me. In hindsight I’d also have painted these, as the grey they come in is very consistent and a touch glossy for my taste. They are a very similar design to the cast iron common Victorian model though.


Hell yeah for support, that’s about 160kg from memory when full. To make things more interesting, when floors were added to this barn 400 years ago, they decided the final joist didn’t need to meet the wall, and our floors are lower than the nearby plate on the wall, so that doesn’t pick up the board ends either! Therefore a decent chunk of oak went in while we did the post repair here.

 

[DaveG]

I only have the 1 cast iron rad. It was experimental, it’s big, and is insanely heavy. It sits in a hallway with lots of space to heat, with a great deal ending up going upstairs most likely.
Primarily I wanted it for the looks. It makes a great feature and it seems to do its job well. With the hallway being original quarry tiles on limecrete I have no interest in eventually underfloor heating that space like other ground floor areas.
For me it seemed like a future proof thing to buy a big oversized rad that will still be able to heat well at lower flow temps. My boiler is 17 years old so am hoping to move across to heat pump tech eventually.
As others have said, the smoother curve in the way the heat output rises and falls I think compliments an old stone house better too.
I will speak to the heat pump peeps about the appropriateness of using similar rads in some of the upstairs bedrooms. The windows are bay shaped so for me it’s the perfect place to sit a radiator as it’s dead floor space and frees up the wall that currently hangs a radiator. Sitting them under a window also seems like a good idea for single pane leaky windows.
I have considered reclaimed rads but was put off when it was mentioned they may be full of all sorts of corrosion and not been a great shape internally so will probably stick with the cast iron radiator centre unless anyone suggests better options elsewhere.

 

[mardinor]

We only have cast-iron rads in our victorian home. Put them all in ourselves 25 years ago - refurbished originals from a now-defunct company that restored them from salvage yards.
Hugely expensive but one of the best things we spent money on. They just look right and you see them everyday. Just had a new oil boiler fitted yesterday and rads flushed for first time in 10 years - water came out clean, no corrosion.

We love the slow heat release as it matches the house structure - 20 inch stone walls that act as a big thermal store. We keep the heating 'on' (via single thermostat) all day at 18C and down to 16C at night, controlling each room via TRVs. Quick on/off fast-response heating doesn't work in a place like this. PS we have no insulation, even in the loft. We value period features and fresh air and are happy to pay a few hundred quid a year for comfortable living in a nice environment.

No regrets. Would absolutely do it again in a period house.

 

[paulc]

We love the slow heat release as it matches the house structure - 20 inch stone walls that act as a big thermal store. We keep the heating 'on' (via single thermostat) all day at 18C and down to 16C at night, controlling each room via TRVs. Quick on/off fast-response heating doesn't work in a place like this. PS we have no insulation, even in the loft. We value period features and fresh air and are happy to pay a few hundred quid a year for comfortable living in a nice environment.

Got TRVs on all my radiators. One thing I did notice was the boiler would short cycle after a couple of the TRVs operated. Leaving them all set at max doesn't increase the energy consumption by any appreciable amount. Where as, having the boiler short cycling does impact on efficiency and increases wear & tear. That said, with an oil fired boiler, it is unlikely to modulate (there are only a handful that can), so I suspect short cycling will be less of an issue.

On the subject of loft insulation - It makes a very noticeable difference in cutting heat loss. Up to 25% !
A few rolls of fibreglass or mineral wool doesn't cost much, and will reduce your heating bill.

 

[orangepeel]

Got TRVs on all my radiators.

Unless you have an automatic bypass fitted this is not recommended and may invalidate the boiler warranty depending on manufacturer.

 

[mardinor]

On the subject of loft insulation - It makes a very noticeable difference in cutting heat loss. Up to 25% !
A few rolls of fibreglass or mineral wool doesn't cost much, and will reduce your heating bill.

Agree. Trouble is, the loft is jam packed with 'stuff' and insulating means clearing it all, raising on stilts and boarding. It's on the list, but there's no economic payback and I'm hoping the junk i so tightly packed it has some insulating value! (Yes, weight is supported on a platform between trusses, not on ceiling joists. Used to hold victorian watertank so good for a tonne or so!).