Loft room heating problem

[jpdw]

Hi - Hoping someone can give me some advice on a problem with our CH system, which is struggling to heat our 2nd floor loft-conversion room of our victorian terrace.

- Boiler is only a year old and heats the rest of the house OK.
- The rad in the loft room is blead and gets an even hot temperature top-bottom.

Even with all other rads 'off' it doesn't make much noticeable difference.

If we let the room temperature drift down during the day (e.g to ~16C) it then takes ~4 hrs in the evening to rise up just 1.5C to 17.5C.

Once up to temp it's better - a half hour of 'boost' every couple of hours through the night at the moment (our baby daughters are currently in our room, so we are keeping up the night-time temperature).

Alternatively if we tried to keep the room temp constant 24hrs (to save the ~4hr re-heat, the heating would be running probably 18 of 24hrs.

Room size:
- 3.6m x 5.4m,
- ceiling about 2.1 m across the dormer half, sloping across the pitched half
- Exposed to the south (pitched) and north (dormer)
- Neither neighbour have a loft conversion, so I guess 4-sides exposed!
- Using the rad calculator at http://cultfollower.net/radcalc2/BTUcalc.htm it gives about 5000 BTU but how do I account for the sloping roof?

Does 5000 BTU a reasonable estimate for this size & type of space?

2/ Is the radiator hopelessly undersized for the job?

- The radiator is apparently a slimline. It was fitted before we moved here so all I know is:
- 1000m wide by 600 high, single panel with 1 set of fins (It does look slimmer than a normal single panel)

Can anyone suggest what the BTU is likely to be for a slim panel this size?

3/ Any other suggestions? Or is it just a lost cause because it's a loft room?

Thanks

 

[gas4you]

What boiler/system have you got?

I would say it needs to be a pressurised system boiler or combi with a loft radiator.

 

[jpdw]

What boiler/system have you got?

I would say it needs to be a pressurised system boiler or combi with a loft radiator.

Sorry... Already my post was rather long!

It's a system boiler (Greenstar... either the biggest or 2nd biggest in the range); Sealed/pressurised - the loft rad is the highest point.

The boilder/flow-return also feeds a circuit to the heat exchanger in the megaflow cylinder (The HW circuit is off during the evenings when we are trying to heat the loft - so this isn't the issue)

 

[htgeng]

Hi - Hoping someone can give me some advice on a problem with our CH system, which is struggling to heat our 2nd floor loft-conversion room of our victorian terrace.
Thanks

I'll lay £1 on the answer, but first how old is the conversion. Do you know if it was done as a proper conversion with planning permission or as a 'storage area'.

 

[jpdw]

Hi - Hoping someone can give me some advice on a problem with our CH system, which is struggling to heat our 2nd floor loft-conversion room of our victorian terrace.
Thanks

I'll lay £1 on the answer, but first how old is the conversion. Do you know if it was done as a proper conversion with planning permission or as a 'storage area'.

Lack of insulation I'd guess would be your answer. Maybe but I'd hope not.

To answer your question, about 3-5 years I think (we've been here 1.5 and it was done by the previous owners that were here about 5 years. I have the actual date on paperwork somewhere if it becomes significant). As for planning permission -- yes, all above board, I know for a fact from when we bought as this was something our solicitor suggested we specifically & explicitly checked (he had a real 'belt and braces' approach).

So what answer does your £1 lay on?

 

[Agile]

I am surprised neither you nor any of the replies have noticed or calculated the rad heat output!

A 600 x 1000 is about 950 watts and I would want to put about 2 kW in that space.

You may well be able to make it into a double panel with about 1750 watts output.

My preference would be to add a second 600 x 1000 further away because the space is too large to heat very uniformly with just a single 1000 mm wide rad!

Make sure all the loft rads have TRVs!

Tony

 

[jpdw]

Actually I think solving the heating problem is only part of it.

I'm sure there are ways I can reduce the heat losses (better window blinds, thermal blinds in the velux, maybe check insulation in the void below the loft room floor etc).

But we also did a test tonight with an old 2Kw electric heater. In 20 minutes it did what the radiator took 4 hrs to do yesterday. So whatever heat output the radiator gives it's nowhere near the same...


I'm more and more convinced the rad size is an issue (maybe not the only one).

 

[jpdw]

I am surprised neither you nor any of the replies have noticed or calculated the rad heat output!

A 600 x 1000 is about 950 watts and I would want to put about 2 kW in that space.

You may well be able to make it into a double panel with about 1750 watts output.

My preference would be to add a second 600 x 1000 further away because the space is too large to heat very uniformly with just a single 1000 mm wide rad!

Make sure all the loft rads have TRVs!

Tony

Hi Tony,

The BTU of the existing rad is something I've been suspicious about (See post I wrote at same time as yours mentioning the 2kW elec that was doing a good -- if expensive -- job). I did some lookups on the radiator panel size to try to find the BTU but of course any vendor advertising is doing so because they have a super-dooper high output rad. Whereas I suspect the rad we've got, albeit only a few years old, is going to perform somewhat less.

You mention 950... which is such an order lower than any of the BTU-by-area calculators that it explains why the heating in that room only works when it's relatively warm outside.

I didn't mention positioning -- the rad is at the dormer end of the room so a full 5m from the other end. There's a bit of wall space at this other end where we could site another rad and just behind this location I've noticed a pair of plastic pipes which I suspect are flow & return going to the en-suite bathroom (which are not lagged and appear to be running the perimeter of the conversion rather than the shortest route).

More and more now I'm thinking that soon as we can do without the heating I need to replace the existing rad, and as you suggest, add another one. Same time I can either lag the existing pipes or replace with a shorter run (and lag). Meanwhile a timer & the electic 2kw is probably more effective than running the CH (for this room) nearly 24h.

If I remember correctly we slightly oversized the boiler so adding a rad or two should not cause any issues there either.

Regarding TRVs - the rad has a TRV but it's actually set to max, for a good reason. The loft room has it's own thermostatic control & each floor of the house is an independant zone (with stat) on the flow/return (the ensuite is on the same wet circuit but no TRV so there's always some path through the circuit even if the TRV was inadvertantly closed).

 

[Agile]

If you agree to add another rad than I would suggest you add a 600 x 1000 double convector with TRV.

There is little extra cost involved and over a number of years the greater heat out will enable the boiler to operate more into condensing and so the small extra cost will be recovered.

The TRV on the double panel can be set at a lower setting so that it starts to turn off before the thermostat and leaves just the other rad.

Lagging plastic pipes is less important but still worth doing if they pass through unheated areas.

Once you have fitted the new rad to the wall its only about two hours work to partially drain and make the connection to the flow and return. I suppose if you must use push fit connections its less than an hour to make the final connection!

Tony

 

[mogget]

You mention 950... which is such an order lower than any of the BTU-by-area calculators that it explains why the heating in that room only works when it's relatively warm outside.

Just to clarify, Tony is talking about Watts, not btu/h. 950 Watts is around 3240 btu/h according to http://www.onlineconversion.com/power.htm - I can never remember the multiplier for this one.

In a room that size, a 950 Watt radiator will be hopelessly undersized unless the room has a very high standard of insulation.

I agree that adding another radiator would be the best all-round solution, and that swapping the existing radiator for a double would be the easiest.

 

[jpdw]

You mention 950... which is such an order lower than any of the BTU-by-area calculators that it explains why the heating in that room only works when it's relatively warm outside.

Just to clarify, Tony is talking about Watts, not btu/h. 950 Watts is around 3240 btu/h according to http://www.onlineconversion.com/power.htm - I can never remember the multiplier for this one.

Hi mogget,

A little while after posting I realised we (or I) was probably mixing BTUs and watts. But by then the PC was off ( it was 2am!).

In this case, I think, the only different it makes to the verdict is how much undersized it is !

In a room that size, a 950 Watt radiator will be hopelessly undersized unless the room has a very high standard of insulation.

I agree that adding another radiator would be the best all-round solution, and that swapping the existing radiator for a double would be the easiest.

I would guess it's just "average" insulation for a conversion of it's age.

My preference is as you suggest - replace the old and add another. As it happens I've realised the best wall for the additional rad has the en-suite's "towel warmer" on the other side, so there must be flow/return nearby. Though this would mean retaining the plastic flow/return that takes a 5m detour [unlagged] through the unheated eaves space. Maybe this is also an opportunity to re-route this pipes so they are more direct and don't pass through the eaves space. Then, even if I keep them in plastic, I can lag them.

Agile,
I like the comment about partially draining the system (as opposed to fully draining, I guess). How do you judge how much is enough - other than finding out when you disconnect a pipe you think it empty... but isn't?


To you all, many thanks for the comments. I'll go away and plan this now. Meanwhile I think we'll be using the 2kw elec heater for this room - especially if it's as cold as the past week. Just now need to convince mrs jpdw that we do it soon -- she favours waiting till we dont need the heating -- which is months away and after we've burned more £££££ with the naff radiator !

 

[gas4you]

Assuming bedroom temp of 18C and the conversion is fully insulated to current standards (I'm too lazy to read back over all the posts ) and allowing for 3 outside walls, I get the result to 1650 watts.

I would therefore specify either a 600 x 1000 K2 or 450 x 1200 K2 rad for this room.

If the insulation is totally lacking and you have the equivalent of 3 terraced solid walls, then it works out to 2550 watts, which would be 600 x 1400 K2 or 600 x 1600 K2, to be slightly over the top.

 

[jpdw]

Assuming bedroom temp of 18C and the conversion is fully insulated to current standards (I'm too lazy to read back over all the posts ) and allowing for 3 outside walls, I get the result to 1650 watts.

I would therefore specify either a 600 x 1000 K2 or 450 x 1200 K2 rad for this room.

If the insulation is totally lacking and you have the equivalent of 3 terraced solid walls, then it works out to 2550 watts, which would be 600 x 1400 K2 or 600 x 1600 K2, to be slightly over the top.

Thanks gas4you,
The only rad in the space is 300 x 1000 (so same size you would spec). But it's definately not a K2. I dont know the brand (doesn't look like the stelrad we have fitted elsewhere last year). But the general design is similar to a Stelrad K1 (single panel, 1 set of fins).

We can't tell what insulation was installed, so probably a good idea for us to aim towards the "totally lacking" end of things -- I assume too much heating capability is not a big issue so long as the rads are controlled (one way or another) to turn off when the job is done.

Mr jpdw can get Stelrad's at a good price through work so we'll probably go for 2 K2s - one the same size as the existing (600x1000), the other as big as we can fit in the space (up to 600x1000).

Just got to convince her to let me fit them!