Do I need a radiator upgrade?

dr_bogenbroom

ThisIsWeird said:

dr_bogenbroom said:

Do you know what… after all of your feedback it’s likely not the radiators that are the problem. With this bout of wind we’re having over here in NI I’ve noticed a few sources of draughts. There is also a small section of inaccessible roof above our WC and cloakroom that has no insulation and I noticed a draught coming in from the light fittings! I’ve no idea how I’ll insulate here though…

Yup, wind affects our 1930s house more than just a low temp too. General draughts, coming up through floorboards, seeping through the carpets, from under skirting boards, stuff like that. You'll notice it coming in from under closed doors from other rooms, for example. 

How do you know that your WC ceiling has no insulation above it?

Tbh, I doubt the issue is from small holes like that, but likely more an overall seepage! Do you have suspended timber floors, for example? Check around the doors to the room using a smoking taper or similar.

I poked a wee inspection camera up and had a look. 

Our internal walls are mostly made of concrete block rather than stud which I’m not used to either… would this make a house colder? External walls are cavity wall with what looks like a polystyrene board (about 50-75mm thick). 

FreeBear

dr_bogenbroom said: There is also a small section of inaccessible roof above our WC and cloakroom that has no insulation and I noticed a draught coming in from the light fittings! I’ve no idea how I’ll insulate here though…

One of two options. Lift part of the roof and shove insulation in. Or take the ceiling down and insulate from below. The advantage of doing it from below is you can get the insulation right up to the edges and make sure it is packed in around the joists - This is what I did over a bay window.

ThisIsWeird

Concrete walls are good - usually quieter, and feel more solid when doors are opened and closed, for example. The internal ones should have no bearing on house temp, certainly not negatively, but possibly helps to keep it slightly more stable by acting as a heat-sunk, smoothing out wide temp swings.
Your outside walls are cavity, with rigid insulation lining the outside surface of the inner skin, so that sounds pretty much ideal - high quality insulation, and still a small, protective, cavity there. Do you know if the inner skin is 'Thermalite' type - much softer if you drill into them? If so, that sounds like the combo we had on our extension, so sounds pretty much like current levels.
Anyway, that all sounds fine. So why is your house cold? Two possible reasons come to mind; one is that it isn't, but you are just not heating it enough, and the other is due to inherent issues like it not being as draught proof as it should be.
For the latter, as I said the easiest way to determine whether a particular room is draughty is to focus on its internal door - you should be able to detect the accumulated seepage going through there in most cases, especially under it. And also check in which direction it flows - in or out of that room.
Does this house have a chimney?
Once you get an idea of each room's draught level, you can track the source - almost certainly coming from under the skirting boards.
As for that cold ceiling, I presume it ain't big? Determine where the ceiling joists are, and note this down - easiest way is to mark the walls on either side with pencil marks or masking tape indicating joist centres, and then cut a sheet of insulated plasterboard to fit as snugly as possible on the underside of the existing ceiling.
Drill a neat hole to feed the lighting cable through as you do this; you can stuff something like a strip of soft foam around the wire in that thick afterwards to make it airtight. Use suitable length p'board screws to secure.
Run a bead of expanding foam around any gap around the perimeter, and either plaster-fill, or mount lightweight coving over it.
2" insulated board will be transformative.

FreeBear

ThisIsWeird said: Does this house have a chimney?

Was looking at a spreadsheet last night that goes in to a lot of detail, and includes chimneys/flues in the calculation. It allowed nearly 2kWh for a standard unsealed flue or a little under 1kWh for one with a restrictor plate.

dr_bogenbroom

Thanks for the advice @FreeBear and @ThisIsWeird - the project for insulating the small roof can be done next year. I spent all day breaking my back and knees topping up my main attic insulation and there’s another layer to do on Wed! 

Good to know my house is set up to be decent at keeping the heat in. The floor is solid so there are no draughts coming from there however I do have a chimney - the Mrs wants to use it once it’s swept but it’s definitely a source of heat loss.

I’m going to wait a while before doing any major overhauls to the CH system - at the moment we can’t heat the HW and CH separately and there’s no room thermostat - just some electric manual dial thing so the heating engineer who serviced my boiler today said he can sort all of that and add Google Nest with heating zones. It’s a gravity fed system but seems to do the job. 

We also put a jacket on the copper HW cylinder a few weeks back and this made a big difference. 

FreeBear

dr_bogenbroom said: Good to know my house is set up to be decent at keeping the heat in. The floor is solid so there are no draughts coming from there however I do have a chimney - the Mrs wants to use it once it’s swept but it’s definitely a source of heat loss.

I’m going to wait a while before doing any major overhauls to the CH system - at the moment we can’t heat the HW and CH separately and there’s no room thermostat - just some electric manual dial thing so the heating engineer who serviced my boiler today said he can sort all of that and add Google Nest with heating zones. It’s a gravity fed system but seems to do the job.

A chimney sheep or an old pillow in a plastic bin bag shoved up the chimney will cut the draught down. Just make sure to have a string dangling down in to the fireplace as a reminder.

As for heating controls, I'm far from impressed with Nest or Hive - Both companies have history of discontinuing products and removing support for them. I'd suggest looking at Drayton Wiser as they do a two channel system that can do heating and hot water.

ThisIsWeird

Solid floors is, again, good! Assuming they are insulated, which they must surely be. As you say, this removes the main source of draughts.
A chimney is certainly a draw, so I'd expect any draughts detected coming under sitting room doors will be coming in from other rooms. Worth checking the amounts, out of interest - a gentle draught is good, helping to keep the air fresh and dry. Excessive would suggest leaks, perhaps around/through windows, sockets, things like that.
Nothing wrong with gravity systems - they work just the same. A bit more prone to long-term issues, and if you don't have a magnetic filter fitted to the return to your boiler, it's always worth considering.
That leaves controls - prob the only improvement of significance. I'd do some research, and look to future-proof, using a system that'll match the sophistication of a future boiler - Opentherm, or a similar protocol. 

dr_bogenbroom

FreeBear said:

What I usually recommend is measure up the room sizes & window/door areas. Punch the numbers in to this online calculator - https://www.stelrad.com/basic-heat-loss-calculator/ and note the recommended radiator sizes. Play around with the "System Temperature" and compare the numbers at 40°C (flow temp of 60°C) and 30°C (flow temp 50°C).

Measure the size & type of the existing radiators and take a look at https://www.simplifydiy.com/plumbing-and-heating/radiators/power to get an approximate heat output at a flow temperature of 70°C. The two sets of numbers should be fairly close if your heating system had been properly specified at installation time.

If the numbers are close, but rooms are not heating up effectively, it is possible likely that the system needs balancing. In the meantime, increasing the flow temperature will boost the heat output from all the radiators. Try not to go much above 70°C or you will reduce the boiler efficiency by quite a bit.

Side note - 15mm pipes to the radiators is good, but you also need to know what size the main feed & return pipes are. 15mm pipe will carry ~8kW of heat, and 22mm is good for ~18kW (dependent on pump speed and water temperatures).

Hi @FreeBear

I’m just getting round to doing some calculations in my living room as it’s one of the rooms that never seems to get warm.

I calculated the Watts requirement to be 1503 W according to the calculated on:

https://www.bestheating.com/btu-calculator

I used the following information in the calculator and I’ve added in some extra detail:

Room size:

L: 4.95m

W: 4.16m

H: 2.26m

Window size: 5.2m2 (2 x double glazed) - original to the house built in 1994 (so no Argon). I’ve draft proofed with weather strips temporarily.

Concrete floor - not sure if this will have insulation or not?

2 external walls, double skin with insulated  cavity

Chimney (currently blocked with insulation in a bag)

Room upstairs is a large heated master bedroom. Insulation in the attic is about 350mm.

I then worked out using the link you provided that my current radiator outputs 3120 W using the following details:

Radiator size:

L: 1.8m

W: 0.45m

Output: 3120 W

This suggests my radiator is way oversized for the room but this can’t be right? I can hold my hand on to the radiator for about 6s before it gets too sore and I have to let go - but even if it was under performing by 50% it should still be enough? 

I’m thinking I’ve done something wrong or missing something here if someone can help?

Thanks.

FreeBear

dr_bogenbroom said: I then worked out using the link you provided that my current radiator outputs 3120 W

Having taken another look at that link and cross comparing numbers from Stelrad & Flomasta via Screwfix, I suspect simplifydiy is using old school ratings based on a flow temperature of 80°C. Modern radiators are rated using a flow temperature of 70°C (a delta T of 50°C). A conversion factor of ~1.3 needs to be applied, so your 3120W radiator produces 2300-2400W at a flow temperature of 70°C.

Bestheating would appear to be somewhat optimistic compared to the Stelrad calculator (which is coming up with 1850W - Still quite a bit smaller than you currently have. However, neither takes in to account the heat lost up the chimney - This could be anything from 800W to 2kW 

Then if there is a vent through the wall to allow fresh air in for a fire, that could be another 2kW of heat being lost. North facing rooms are generally colder than south facing, so the aspect is another point to consider. These online tools can only give approximations. For average rooms, the results are usually fairly close. I have heard that Heat Punk asks for a lot more details, so in theory, should give a more accurate answer. Not used it myself...

One thing you could try - A fan heater blowing out hot air whilst the CH system is running. If a 2kW heater helps to get the temperature up to where you are comfortable, that tells you a 6800BTU radiator needs to be added - That would be a 600mm by 1200mm Type 22. Anything bigger, and prices jump from £80 by a lot.

dr_bogenbroom

FreeBear said:

dr_bogenbroom said: I then worked out using the link you provided that my current radiator outputs 3120 W

Having taken another look at that link and cross comparing numbers from Stelrad & Flomasta via Screwfix, I suspect simplifydiy is using old school ratings based on a flow temperature of 80°C. Modern radiators are rated using a flow temperature of 70°C (a delta T of 50°C). A conversion factor of ~1.3 needs to be applied, so your 3120W radiator produces 2300-2400W at a flow temperature of 70°C.

Bestheating would appear to be somewhat optimistic compared to the Stelrad calculator (which is coming up with 1850W - Still quite a bit smaller than you currently have. However, neither takes in to account the heat lost up the chimney - This could be anything from 800W to 2kW 

Then if there is a vent through the wall to allow fresh air in for a fire, that could be another 2kW of heat being lost. North facing rooms are generally colder than south facing, so the aspect is another point to consider. These online tools can only give approximations. For average rooms, the results are usually fairly close. I have heard that Heat Punk asks for a lot more details, so in theory, should give a more accurate answer. Not used it myself...

One thing you could try - A fan heater blowing out hot air whilst the CH system is running. If a 2kW heater helps to get the temperature up to where you are comfortable, that tells you a 6800BTU radiator needs to be added - That would be a 600mm by 1200mm Type 22. Anything bigger, and prices jump from £80 by a lot.

It could be my windows are letting out a lot of heat due to their age. The chimney is blocked completely with a bag of 200mm insulation so I don’t think I’m currently losing anything up there.

I did a wee experiment in my home office which is much smaller but the rate of heat was loss worrying… not sure if there is anything anyone can infer from the data I collected. It also turns out I’m much more of a geek than I thought as I thoroughly enjoyed this experiment! I’ll do the dam experiment in the living room shortly.

Heating with electric radiator

15 degrees starting temperature 

750W electric radiator

Outside temperature 1 degree

Took 24m to get to 18.3 degrees

Heat loss

18.4 degrees starting temperature

Took 60 min to reach 16.3 degrees 

Room details

L: 2.66m

W: 1.94m

H: 2.27m

- Solid concrete floor (probably little insulation) with laminate on top

- 30 year old double glazed uPVC casement window, size 1.12m

- Heated room above1 external wall which is double skin with insulation

The central heating radiator is single panel with fins 1100mm by 500mm