Are radiators energy efficient?

[Lorna3]

I'm doing up my house and wasn't sure about which heating option to choose. I thought that radiators were really inefficient but then I found this report from MARC, what do you guys think?

:


Aimed at assessing the future role of steel panel radiators in an evolving market, the report highlights that:
• Due to their flexibility, steel panel radiators and convectors are the best way of introducing energy-efficient heat generators into existing properties, with renovation and retro-fit accounting for in excess of 90% of the UK and other major western European markets.
• Steel panel radiators work well with low water temperatures, making them an ideal choice for eco-conscious developers and home owners.
• Steel panel radiators have quick reactions to temperature control, with small heat losses, meaning efficiency is not lost with long heat-up times. This is a benefit of the lower thermal mass of steel panel radiators.
• The total energy efficiency of steel panel radiator-heated buildings is excellent.

MARC chairman John Colling said: “During the last 60 years, most technologies have gone through revolutions. With steel panel radiators, it has been more evolution, with the introduction of the advanced welding technologies developed by radiator manufacturers in the 1980s, allowing convector panels to be welded directly onto the radiator waterways. The effect of this was to produce the same amount of heat output from radiators using less primary steel and water content, a major step forward in the drive for energy efficiency and carbon emissions.

“The reason for this is that steel panel radiators work very well and, in reality, nobody has found anything better. While other types of heating system have emerged as popular options, the steel panel radiator can compete on all levels and is still very much the number one choice, thanks to the evolution which has kept it up to speed with the needs of homeowners, legislation and trends such as the drive for a green economy.

“Myths such as steel panel radiators creating a stuffy atmosphere, or not providing thermal comfort throughout a room are simply that: myths.

 

[unguided1]

Radiators are not really inefficient they do what they are designed to do
Its old houses that are inefficient and before you start worrying about the radiators consider the air tightness and the insulation value of your property, dont forget double glazing.

The more heat loss on a building the more your boiler has to generate heat to keep up with the heatloss on your building

 

[MatthewHurt]

As stated above, the more heatloss from the fabric of your house, the less efficient (and more costly) your heating will be.
To make your central heating instillation as efficient as possible, you could get an engineer in to calculate the 'Total Design Heat Loss' for your home, you would then be able to install exactly the right size of boiler and radiators to heat your home without wasting energy.
Also adding things such as T.R.V's on all your radiators (except the radiator in the room with your room stat) will make them more energy efficient.

 

[Big Graham]

Radiators are hugely inefficient.Its the distribution of heat energy that`s important.If you are a fly on the wall at 2m high then its efficient.Why do heat engineers install a a 20kW system when the heat loss calcs require only 10kW.They will say its because they want a quick reaction time.Ab rubbish.If you push a condensed amount of heat into a fairly cool space, automatically the heat rises to the ceiling and you have forced air movement (convection).At molecular level warm agitated air molecules vibrate fast and become buoyant, which mean they force themselves up through cold less agitated air molecules that are slow and sluggish.Eventually the heat will come down to the level of you knees.The heat calcs determines how much heat is required for the fabric of the building.So can any1 tell me how we should heat a 15m high church with lots of singled glazed windows and rubbish U-values for walls and uninsulated roof ?

 

[gaspastemania]

Big graham are you the plumbing version of steven hawking????

 

[Big Graham]

lol nah not really.just a different perspective on how we heat buildings.We need to look closer at the fine detail in what we are trying to do.

 

[gaspastemania]

So i take it you dont like radiators?
My approach is they are a no nonsense solution for heating , they are better now than what they were 20 years ago but you will always lose heat through building fabric/design. The controls are reliable and responsive and for me do the job peole pay for , as for agitating air molecules cant say i have ever had to explain that to a customer lol

 

[Big Graham]

Not particularly !.Your approach is your only approach.I accept that a 92% efficient boiler in a domestic setting is now pretty good.The problem is the distribution of energy and the kind of heat it produces.I am currently designing a heating system in a large church, my heat loss is coming out at 150kW.I know I will have to size it to over 200kW to have a chance in getting some heat into this place.Now I also know that the heat will travel right up through the roof so then I have to re-address the sizing of the system.Now that is not efficiency ?.The requirement is only 150kW from -5C to achieving +18 C internally.So I have to size it to about 220kW.

 

[gaspastemania]

So what are you installing???
Also to add its not my only approach to heating a dwelling/premises what ever spec i get given i install and generally poo poo after its installed to find its not quite hot enough or has poor heat distribution wether domestic or industrial.

 

[Big Graham]

Possibly a dual system, underfloor over a large area and rads (ouch)!.But it is still not the right option.Any Suggestions ?.Getting back to my earlier post.In a domestic retrofit domestic setting, the only option is rads with a condensing boiler.Lol its the best worst approach

 

[gaspastemania]

Easiest solution to this is to dismantle the church and move it to the equator , i think your first gas bills over a 10 year period for heating a huge expansion of cooler air may prove this theory right over time.

 

[Big Graham]

If heat was distributed evenly throughout the building then the heat loss requirement could be closer to the 180kW rather than over 220kW.Heat cannot stay at ground level when the cold less agitated heavy molecules are fallimg into the main body of the hall.Back to my Stephen Hawkins mode.Enjoyed the chat gaspastemania

 

[Big Graham]

Just a question for MathewHurt.If someone gets an engineer in to do a heat loss calculation , and the spec is radiators and condensing boiler.The system wont work by what you said.Unless the house is hermitically sealed and the house standard is almost to passiv standard.That means if a 3 bed house requires 8kW, and you suggested that an engineer comes in and puts in the properly sized radiators and boiler, the poor people will be trying to chase a temperature internally that can never be achieved.What would have to be done is the same as usual, over size.If you over size then its not efficient.The ideal system is precision in the controls and the distribution of energy.Heat loss calculations are not relative to radiators.It will never be possible to install the same amount of rads as the heat requirement suggests.

 

[tackleburger]

So i take it you dont like radiators?
My approach is they are a no nonsense solution for heating , they are better now than what they were 20 years ago but you will always lose heat through building fabric/design. The controls are reliable and responsive and for me do the job peole pay for , as for agitating air molecules cant say i have ever had to explain that to a customer lol

I had a similar problem last October and the cost was going up and up. After a meeting with the church committee we agreed that the cost of insulating the roof was money well spent. It was a smaller church than yours but nonetheless the heat calcs worked out to about 70KW and with the correct insulation we got that right down to 45 we fitted a 55KW boiler and in early December it was not quite warm enough then the insulation went in and given we had the coldest winter for years the church was warm enough.

 

[Big Graham]

Great result Tackleburger.Can you tell me the insulation you put in ?.

 

[fuzzy]

if sized and situated correctly radiators are excellent, they wouldnt have stayed around so long if they wernt!

how can they be inefficient? they are an emmitter, if the heat dont leave it goes round again

 

[Big Graham]

Hi fuzzy.Done a bit of digging to find out why they are not efficient.High output from a radiator makes the air rise which means if you are heating up the ceiling.From a cold start the rads cannot heat from your waiste down.The problem is they emit too much heat too fast which means a fly on the wall up 2m is nice and cosy but your feet will be frozen.Look up thermo-dynamics and the transfer of heat and equilibrium if you dont believe me.

 

[fuzzy]

i think your examples are a bit extreem graham.

the rads do not heat the ceiling, they are convectors (badly names radiators as they do not radiate heat). I did say they need to be correctly sized and situated because they are convectors. they heat the air and create a circulation of warm air in the room. they are idealy situated below a window which helps the warm air circulate.

often under floor heating systems and sellers say about the waist up thing as underfloor heating warms the floor and radidates up, underfloor is good but it dont mean rads arent. what you refer to is more to do with comfort conditions and not efficiency. underfloor is prob ably slightly better but most go for rads as they are very good and relatively cheap compared with other installations

 

[Big Graham]

Fuzzy, Get you point on rads being the cheapest and best option, this is tolerable in a domestic environment.However when you say correctly sized what in actual fact you mean is hugely over sized.There is a difference.Can you explain then why my house has a heat requirement of 7kW, my rads are sized to 17kW and from cold start it takes 3 hours to heat the house to 21 C.The calc was based on windows UV of 3.0, Ex walls UV of 1.5, roof UV 1.0 and floor UV 1.0 and from -5C to achieving + 22C.

 

[doitmyself]

Can you explain then why my house has a heat requirement of 7kW, my rads are sized to 17kW and from cold start it takes 3 hours to heat the house to 21 C.

What size is your boiler?

 

[Big Graham]

Its an 12 year old vokera 28kW.74% efficient.

 

[doitmyself]

Its an 12 year old vokera 28kW.74% efficient.

Is it an Excell 96E?

Was the heating range rated to allow for the difference between rad size and boiler output. If you have a boiler chucking out 28kW but only 17kW of rads the return temperature will rise rapidly, so the boiler cuts out. This leads to cycling which could account for the three hour heat-up times.

Range rating instructions are in the installation manual.

 

[justlead1]

Hi. The heating requirements for churches are on the up and up due to the lack of people attending. 0.1kw per person. Get 1500 in there it will be like a oven.

 

[fuzzy]

Fuzzy, Get you point on rads being the cheapest and best option, this is tolerable in a domestic environment.However when you say correctly sized what in actual fact you mean is hugely over sized.There is a difference.Can you explain then why my house has a heat requirement of 7kW, my rads are sized to 17kW and from cold start it takes 3 hours to heat the house to 21 C.The calc was based on windows UV of 3.0, Ex walls UV of 1.5, roof UV 1.0 and floor UV 1.0 and from -5C to achieving + 22C.

No, i meant correctly sized, if i meant hugely over sized i would have said so.

If the heat requirement is 7k including 10% for initial heat up, if not add this on, still rads should equal 7.7kw and therefore be correctly sized. Your outside temp is a bit extreem, where abouts do you live, we normally use -1 or maybe -3/4 for the highlands of scotland at max. Inside temp is normally 21 design temp
The reason it is taking so long is because you have used the wrong size radiators, there is too much water in the system, or should i say, more than you needed. so you have proved my point for me, thanks.

 

[fuzzy]

many people think my rads are undersized, they look so small comapered to other houses. they get hot real quick and then gently raise the temp of the room, i use it with a programmable room stat and we never know its on, the heat in each room is equal and comfortable. people want massive rads to feel it bouncing like you would a fire, poor design. correctly size rads lead to equal comfort temps which dont over and undershoot, leading to poor efficiency and rarely being in your comfort zone

 

[unguided1]

Buildings such as churches would benefit from a MVHR system to bring the heat back down to earth

 

[tamz]

Or maybe just the old bit 2 or 3" run through the pews off a 1 pipe. Because it is old don't mean it doesn't work in the "modern" world!
Overhead radiants work too if you can fit them discreet.

 

[fuzzy]

ive worked in churches and they all have large 1 pipe systems to my knowledge

 

[unguided1]

rather than using radiators they may benefit from using fan coils

 

[fuzzy]

skirting board heaters etc, all work pretty well

rads are great domestically, and large column rads look good and work well in big open spaces

 

[Big Graham]

Fuzzy, not long moved into new house, so its an existing system which i will rectify.I`m in Scotland, we had a full month this year when it did`nt go above zero.We had long periods of time where we were below minus 10.The climate does seem to be changing.2 years in a row we have had freezing conditions for a month at a time.Time to amend your calcs guys.As for the churches, I have been looking at the skirting stuff, a friend mentioned another product which uses far radiant heat, apparently its fairly cold to touch but produces this kind of heat.Need to research that 1 !!!

 

[Big Graham]

Radiators cant heat a large volume space efficiently, You can design them any which you like but this is an impossible task.Remember the word being efficient !!!.The problem with large fans at ceiling height creates horrendous levels of convection i.e. the old lady sitting at the back of the church lets rip (breaks wind) 10 seconds later the vicar is choking, smelling her cabbage, potatoes and ham from the night before.I`ve came to the conclusion the radiant heat is best.The product to use is a difficult choice.

 

[fuzzy]

i dont understand how your example affects efficiency?
If you are refering to comfort conditions of best type of heat you may have an argument but i dont get why you say efficient?
i would also argue rads are good for large open spaces, but it depends on the type of open space. often large open areas such as reception areas use convectors fan assisted, this is to improve heat up time as rads are slow but effective way of heating the space. with doors opening frequently they loose the heat fast so need a fast heat up time to componsate
most churches have rads, and 1 pipe systems, which is only the same as a rad in a tube!

 

[Big Graham]

Ok, Lets talk efficiency.You install a condensing boiler thats lets say 92% efficient.8% lost from fuel going in and transfer loss within the boiler mechanism.Get back to my large church, efficient, comfort.If the church at ground level is 15 C, then thats not comfortable.But ur rads 15m up have produced 22 to 23 degrees below the roof !!!!!!!!!!! Rads have kept the pigeons warm but the poor church goers are freezing.Defending a technology thats ur bread and butter is all fine and well, but rads are not efficient.The church will need a minimum of 220kw thats keeping the pigeons warm.Thats potentially on a sunday for 3 hours 660kwh and the people will probably still be cold.Lets now install a biomass boiler with a dual system of underfloor and a suggestion of skirting heating.We now need around 180 kw maybe less.3 hours and we have a total of 540kwh and radiated heat is better than convection rads.And there may be a payment from the RHI.660 ? or 540 ?.Your last post you said rads are slow but effective, which is it slow? or effective ?.

 

[Big Graham]

Convected heat from rads can travel around 0.3 to 0.7 meters per second, by the time it rises in high rooms, it will lose a lot of its energy .Perhaps through a long period of time the heat will build up from the top working its way down to floor level, after all if a roof has a U-Value of 1.0, its losing heat constantly by then how many kW have been emitted to create that heat build.Thats not to mention that someone doesnt keep opening and closing the doors and letting the heat out.Then we get the people that say as long as the place is insulated rads are great.So when we go the plumb centre and asked for a 28kW boiler, 7 rads and oh give me 20 rolls of rockwool.Wheres the insulation in the rad manual.