BTU calc help

[Pipedreamer]

Alright chaps,

I’m a bit embarrassed to actually ask this but need some help with something relatively simple.
I need to figure out the Btu’s required for a large open planned room but it’s a bit different from a ‘normal’ room and I’m so used to using a app to calculate sizes and my minds going blank on how to do it properly

The room is a converted garage that has a couple of walls that are stone and block with 50mm insulation and two walls that’s are

The room will then have studding put round internally with 100mm cellotex in.

The room will be open vaulted with a approximate size of ; 5.5m wide, 8m long and 2.4m to wall plate heigh and approx another 3m from there.

I’m unsure whether to work out it as a rectangle and then calculate the upper area as a triangle and double it to work out as a squared area (if that make sense)

And then unsure of how to calculate/allow for the insulation as there sort of two walls/insulation

Sorry if I’m being thick but hopefully someone can help!

 

[Pipedreamer]

Sorry forgot to add it’s siliconed concrete floor and will have approximately 12m square of doors and windows upvc double glazed

 

[exedon2]

The better online heat loss calculators allow you to have every wall different if required also change air change or any parameter you like.
I use stelrad stars but others are available .

 

[ShaunCorbs]

Around 6.4kw

 

[SJB060685]

Around 6.4kw

How have you arrived at that figure so quickly mate?

 

[Pipedreamer]

The better online heat loss calculators allow you to have every wall different if required also change air change or any parameter you like.
I use stelrad stars but others are available .

I’ll take a look cheers

 

[Pipedreamer]

Around 6.4kw

Thank you, but could you explain how you got to that please?

I appreciate the answer but would like to figure it out myself as well if possible

 

[SJB060685]

Do you know the R values of all the materials? If you do you can work it all out accurately. Takes a bit of time though but is a good exercise

 

[ShaunCorbs]

Worked it out approximately 2 outside walls etc

 

[Pipedreamer]

Do you know the R values of all the materials? If you do you can work it all out accurately. Takes a bit of time though but is a good exercise

No just what I’ve given and a rough idea of what’s happening

was hoping someone could give a relatively detailed breakdown of how they get to their conclusion

 

[Pipedreamer]

Worked it out approximately 2 outside walls etc

Sorry I’ve mis typed something there it’s four external walls with three as I stated and the other is one single skin stone wall (don’t ask me why!)

 

[ShaunCorbs]

7.4kw

 

[SJB060685]

Its quite a time consuming and complicated task really and you need to know some data first if you're going to do by hand, although there are websites/software out there that do it for you but they also require the same data, however I would prefer to do by hand. There's two ways a room/building loses heat. 1. Ventilation heat loss and 2. Fabric heat loss. When calculating the ventilation heat loss you need to the total volume of the room, the air changes per hour for that type of room, the design outside temperature and room target temperature. Example.
3m x 4m x 2.4m = 28.8m3, now x that by air change rate, then x that by the design temperature difference and then x that by 0.33 to get your total ventilation heat loss in watts.
Fabric heat loss is a bit more complicated.
The calculation is. Surface area x temperature difference x U value = rate of heat loss in watts.
You would need to know the U value for all materials in the walls and that of windows doors etc.

 

[Pipedreamer]

7.4kw

Any workings?, pretty please

 

[Pipedreamer]

Its quite a time consuming and complicated task really and you need to know some data first if you're going to do by hand, although there are websites/software out there that do it for you but they also require the same data, however I would prefer to do by hand. There's two ways a room/building loses heat. 1. Ventilation heat loss and 2. Fabric heat loss. When calculating the ventilation heat loss you need to the total volume of the room, the air changes per hour for that type of room, the design outside temperature and room target temperature. Example.
3m x 4m x 2.4m = 28.8m3, now x that by air change rate, then x that by the design temperature difference and then x that by 0.33 to get your total ventilation heat loss in watts.
Fabric heat loss is a bit more complicated.
The calculation is. Surface area x temperature difference x U value = rate of heat loss in watts.
You would need to know the U value for all materials in the walls and that of windows doors etc.

Thank you.

 

[ShaunCorbs]

Any workings?, pretty please

don’t work it out long hand I use a program

 

[SJB060685]

don’t work it out long hand I use a program

Admittedly if the program has all the data needed it's quicker but it's more satisfying to do long hand, well for me it is. A room such as that in question would only take 10-15 minutes to calculate and the more you do these things the more it sinks in lol. I am surprised your program has arrived at a figure of over 7kw but then I haven't run the maths.

 

[Pipedreamer]

don’t work it out long hand I use a program

Which one?

 

[ShaunCorbs]

Heat Engineer

www.heat-engineer.com

 

[SJB060685]

So you do use it Shaun. Haven't got round to trying it myself yet.

 

[ShaunCorbs]

Yep or when I’m onsite I use mr combi Heatloss for approximately

 

[Pipedreamer]

On the same place as it’s one big room

Heat Engineer

www.heat-engineer.com

cheers.

one of my questions which I forgot to ask was, on an app where you select, what do you do regarding the walls as it’s technically got two different types.

 

[ShaunCorbs]

The worst

 

[SimonG]

Nope