Advice on what size radiator I will require!

[ianwainwrightjones]

I am currently in the process of building an extension to my house! It's basically across the back of the house, single storey with a vaulted ceiling. Internal dimensions are 3.3 x 5.7 (vaulted ceiling is 2.2 mtr upto 3.0 mtr) basically a lean to. I will be removing the existing patio doors (dining room) and also the kitchen window. Then knocking down the wall between the dining room and kitchen. Making into a large open plan room. I will be removing the existing rad in the kitchen and fitting cupboards, so there will be no room. The kitchen is 3.0mtrs x 3.6mtrs x 2.3mtr high. The radiator is (i think) a type 21 with dimensions of 600 x700. The dining room is 2.7 x 3.2 x 2.3mtr high with another 600 x 700 type 21 rad. This is staying! The rear is east facing and will be fully insulated and have patio doors and 3 Windows. The house is a four bed detached and has a 15.5 kw boiler(powermax) I know that other houses identical to mine have the same boiler and we're built with the garage being an extra reception room.
What I'd like to know is what size rad I will require to heat the new extension and also compensate for the lost rad in the kitchen.
Is this acceptable with regards to building regs?(does the kitchen have to have a radiator?) Can I fit a plinth/kick board heater to get around this??
Any advice would be much appreciated before I put it to my local BCO
REGARDS Ian

 

[PrenticeBoyofDerry]

You will need to do heat loss calculations, so you need to factor in the u-values of the fabric that the external walls, floors and ceilings are formed with, this will include the type of insulation and the depth of this. This would include heat loss U-values of your window and door types, rule of thumb would be a value of 3.
There will also be the temperature differential to work out, normally applying a -1 factor for external temperature.
There would also be surface air temperature of internal and external walls to be considered and air changes within the space.

Or simply input in to an online calculator such as http://www.cityplumbing.co.uk/heatLossCalculator

Plinth heaters can be used, you have two options, one that purely works on electricity or one that requires both central heating connection (flow/return) and a electrical power source for the controls. The second will operate as and when the central heating comes on.

 

[ianwainwrightjones]

Thankyou for your response, really give me something to work on! Does the kitchen have to have a radiator? If the other 2 rads
can fulfill demand?

 

[ianwainwrightjones]

It says heat loss is just under 7000 btu just 4 the 5.7 x 3.3 extension. with this in mind do I go for a larger radiator or stick to around this size? Sorry for all the questions!

 

[PrenticeBoyofDerry]

Thankyou for your response, really give me something to work on! Does the kitchen have to have a radiator? If the other 2 rads
can fulfill demand?

If you size the heating panels/radiators correctly then if it is an open space, the heat given off by the radiators should allow the cold air within the kitchen to get warm.

But I would consider plinth heating if you cannot locate a rad on kitchen wall.
"Smith" plinth heaters are not bad.

 

[PrenticeBoyofDerry]

It says heat loss is just under 7000 btu just 4 the 5.7 x 3.3 extension. with this in mind do I go for a larger radiator or stick to around this size? Sorry for all the questions!

Ideally when sizing radiators you want to slightly oversize to deal deal with the demand, whether this is done with one larger rad or multiple rads will depend on wall space and suitability.

 

[Agile]

A well insulated building needs about 100w per sq m. An older building with solid walls etc. about 150w per sq m ( or even more ).

There is no advantage in not over sizing so I would recommend using 150w per sq m floor area.

The thermostatic valves will compensate for any oversizing.

In large areas using two or more rads helps to heat evenly as does using long single panels rather than double panel types.

There is also a good increase in boiler efficiency when you replace with a condensing boiler soon if radiators are oversized.

Tony