External Kingspan K5 what thickness??

stebiz

Hi guys. I'm struggling with deciding what thickness kingspan to get for the outside of my solid wall. I have scaffold up and plasterers ready to start and was going to get 100mm but a few suppliers have said that 50mm is well enough and it is unnecessary to get 100mm. It's also twice as dear. Thoughts please?

bryanb

I'd go for thicker. They used to say 6" of loft insulation was plenty.

MX5huggy

The answer is 100mm (because its the RIGHT thing to do, think of the children) but it depends:-

What's your current wall make up? I am going presume 9 inch solid brick.

This has a u-value of around 2.4 W/m sq K

Adding 50mm of Kingspan gets this down to 0.34 or so (infact this does not meet the required U-Value in building regs but I have not included any render)

100mm of Kingspan gets you down to 0.18 (the level of good new build now).

Now taking a small house I have in the calculation software of 2 floors of 42m sq and giving it 100 m sq of walls:-

With existing walls (2.4) you will use 10300 kWh of heat to heat this high performace house (apart from its walls).

With your insulated walls its 3900 kWh or 3300 kWh the first 50mm saves you 6400 kWh so the extra 50mm saves you 600 kWh per year.

Gas is 5p or so per kWh so the first 50mm saves you £320 per year the extra 50mm saves you £36 per year.

If you are not on gas it changes calculation if your wall area is not 100m sq that also changes the calc.

Now you have to take a view of how long you are going to stay in the property, where gas prices are going over that time, and the value of the money you are tie up in wall insulation compared with putting it the bank or buying gas company shares etc.

Are we going to frack our way to cheep gas? or is Russia going to cut off 30% of Europe's gas supply etc..

stebiz

MX5huggy wrote: »

The answer is 100mm (because its the RIGHT thing to do, think of the children) but it depends:-

What's your current wall make up? I am going presume 9 inch solid brick.

This has a u-value of around 2.4 W/m sq K

Adding 50mm of Kingspan gets this down to 0.34 or so (infact this does not meet the required U-Value in building regs but I have not included any render)

100mm of Kingspan gets you down to 0.18 (the level of good new build now).

Now taking a small house I have in the calculation software of 2 floors of 42m sq and giving it 100 m sq of walls:-

With existing walls (2.4) you will use 10300 kWh of heat to heat this high performace house (apart from its walls).

With your insulated walls its 3900 kWh or 3300 kWh the first 50mm saves you 6400 kWh so the extra 50mm saves you 600 kWh per year.

Gas is 5p or so per kWh so the first 50mm saves you £320 per year the extra 50mm saves you £36 per year.

If you are not on gas it changes calculation if your wall area is not 100m sq that also changes the calc.

Now you have to take a view of how long you are going to stay in the property, where gas prices are going over that time, and the value of the money you are tie up in wall insulation compared with putting it the bank or buying gas company shares etc.

Are we going to frack our way to cheep gas? or is Russia going to cut off 30% of Europe's gas supply etc..

What a great answer. Thanks. :T

It is 9 inch solid.

27col

If 50mm of insulation will "do". Then why do they bother with 100mm. The thicker the better.

MX5huggy

stebiz wrote: »

What a great answer. Thanks. :T

It is 9 inch solid.

No problem, but what is the price difference and what area have you got?