Help with radiator output needed

[Best]

Looking at a 1960s bungalow with converted roofspace that may need some new rads. No idea if what is there is adequate as guy has just bought the place & he wants to put hardwood flooring down in some rooms. Just wanted an approximate second opinion, please, on output of just one room as an example, as they are fairly long rooms.
Living room is 5.75m. x 4m x 2.4m high. It has 2 outside walls (one is north facing), insulated brick cavity walls, wooden joist uninsulated floors, plastic double glazed patio doors leading into a heated conservatory, bedrooms above & unused sides of attic 100mm fibreglass at ceiling & bungalow is near the coast.
All of the similar rooms have just one rad at one end of rooms at present. Getting different outputs with online calculations.

 

[mountainman]

Pick the highest calculated output, choose an appropriately sized radiator and stick a trv on it.
Job done IMO

 

[Best]

Pick the highest calculated output, choose an appropriately sized radiator and stick a trv on it.
Job done IMO

I agree, that it's better to oversize but I am concerned about just one rad in each of the large rooms & biggest rad may not be enough (one of the rads is below a window & is 15" high max) as they probably will be borderline or worse & I think anyhow it would be better with heat either side of room from 2 rads which he may not like unfortunately.

 

[Dotty]

If he's banging new flooring down can you not put ufh in no?

 

[Best]

If he's banging new flooring down can you not put ufh in no?

Heating pipes are imperial & probably as old as the bungalow & they are poorly done. Add to that, the hall & kitchen floors are nicely tiled, so impossible to do much. If it was mine, I would rip everything up, but few people would want to spend more.
Just started as needing new rad valves & has developed into needing pipes to valves renewed & more output, so new rads.

 

[Best]

If he's banging new flooring down can you not put ufh in no?

Heating pipes are imperial & probably as old as the bungalow & they are poorly done. Add to that, the hall & kitchen floors are nicely tiled, so impossible to do much. If it was mine, I would rip everything up, but few people would want to spend more.
Just started as needing new rad valves & has developed into needing pipes to valves renewed & more output, so new rads.

 

[mountainman]

I agree, that it's better to oversize but I am concerned about just one rad in each of the large rooms & biggest rad may not be enough (one of the rads is below a window & is 15" high max) as they probably will be borderline or worse & I think anyhow it would be better with heat either side of room from 2 rads which he may not like unfortunately.

Your heat calculation will be for the room requirement only regardless of the number of radiators you choose to fit.
If your calculated requirement is 7kw and the custard only wants one radiator that can only supply a maximum of 4kw then the result is a cold room.

 

[Best]

Thanks Mountainman.
Issue I have is I will be telling him what output is required & I really don't want to insist on extra rads if he can manage with one & I obviously don't want rooms too cold, as once the floors are down nothing can be done.
The calculator I use is out of date but does keep on the high side & the online calcs are low IMO & vary.

 

[mountainman]

Everything is subjective Best, your cust may be happy with 18 degrees in January, but you can be certain that his family and friends won't.
You won't be perfect but give your professional opinion nonetheless, if your customer chooses to overrule you then make him fully aware of the potential consequences.

 

[mfgs]

What heat loss did you get from your calculations?

 

[Best]

What heat loss did you get from your calculations?

Only did basic calculations & they are varying from 2300 watts. I would think that particular room would need around 3500 watts to be on the safe side as TRVs will be fitted.

 

[tamz]

The calculator I use is out of date but does keep on the high side & the online calcs are low IMO & vary.

The mears ones do over size but i've never had a a complaint of being too warm. The online or longhand way of doing it is a bit too tight for my liking.
If you recon it will be under tell him and leave the decision to him.

 

[tamz]

The mears works out around 2750 for uninsulated floors allowing for just under 4m2 of glass. It will be a bit less than that as there is a bedroom above but better over than under.

For a 15" rad a 390 x 2165mm Myson premier DC or for a 12" a 300 x 3000mm Stelrad K2.

Although 2 may be better, 1 rad will spread the heat no problem in a room that size.

 

[Best]

The mears ones do over size but i've never had a a complaint of being too warm. The online or longhand way of doing it is a bit too tight for my liking.
If you recon it will be under tell him and leave the decision to him.

Thanks Tamz. I will follow my instinct & tell him it's 2 rads for the both living rooms with my chosen higher output if he wants nice & warm when we go to minus numbers outside. Just didn't believe the online calcs & that knocked my confidence. No point in 1 rad at far end of room anyhow, it really will need 2 rads & the larger rooms all have had 2 rads in the past, albeit they were probably singles, as the holes are still in the floorboards & pipes are capped below.

 

[Best]

The mears works out around 2750 for uninsulated floors allowing for just under 4m2 of glass. It will be a bit less than that as there is a bedroom above but better over than under.

For a 15" rad a 390 x 2165mm Myson premier DC or for a 12" a 300 x 3000mm Stelrad K2.

Although 2 may be better, 1 rad will spread the heat no problem in a room that size.

Cheers for that Tamz, & thanks for taking the time.
That is what I got with my calc for that room - about 9500btus which means the rad in it at the moment, which a previous owner has fitted, is a decent size - an old Veha 20x78 DC which I estimate at about 10000btus. That shows my calcs are okay, but think that rad is badly placed on the warm end of the room. Something to think on, but personally I would have put 2 middle sized rads spread about. Other rooms in bungalow are worse for existing rad size & will need new rads with totally different outputs. (the 15" high rad I mentioned earlier, is in a near identical sized room - a 15x69DC which is well wrong & will need extra rad for sure)