Man cave insulation

[Mrstauf]

Hi

I'm in the middle of building a large man cave and am ready to order insulation.

The construction is as follows,

28mm loglap cladding,
2x1" batons,
Tyvek breathable barrier,
9mm osb3,
4x2" frame,
insulation, airgap,
100mm block,
dot dab plaster

The building is 11m x 5m and there is block pillars every 2.5m approx and has a flat (well sloping) roof, and it will be heated by 2x gas fired convector heaters (lpg)

My question is re insulation, I am looking at knauf dritherm 37 100mm for the walls, and 100 mm earthwool for the roof, as they are fairly cheap and i can get both for under £500

I have been trying to get my head around the u values and w/mk and kind of understand it, but I'm wondering is it really worth spending double what I'm planning for a better insulation, bearing in mind this is just a man cave and will only really be used on the weekend?
Will it make a massive difference to heat retention and would I ever get a payback?

Thanks

 

[tomfe]

Wahhh, why are you doing a block wall with a timber frame on the outside?

 

[Mrstauf]

Due to planning, it's replacing a old timber barn so had to be timber externally

And block inside for warmth and sound insulation

 

[tomfe]

So is there a reason you need the block wall? Is it close to a boundary?

 

[Mrstauf]

for warmth and sound insulation,
No it's not near a boundary

 

[tomfe]

Blocks are not 'warm' do you need sound insulation?

 

[Mrstauf]

Don't really 'need' sound insulation, but would like it to be pretty sound proof
I know the blocks are over the top, just want to make it feel like proper building and not a shed

 

[tomfe]

I would build it out of 6x2 and insulate between, this will give you a nice fast response time, it'll also be quite sound proof.
If you want to go down the block route then you don't do the osb or 4x2 batons just stick 100mm of pir on the inside.