Air Permeability. Blocks

ht9zni1gs28crp

I have looked and looked but cant seem to find a figure that would suggest how much air actually gets through a block and at what pressure? Ie in an airtight test if one block was left exposed, ie no plaster how much air would this let through?

Or is there a formula such as that of a U Value calculation that will allow this to be determined?

sydthebeat

the block is not the air tight layer, so any result is meaningless

ht9zni1gs28crp

That's true and I understand that fine, but is there a definitive figure on how much a block will leak per m2 under pressure? So could an air loss be calculated? As in surely a block has some resistance to air flow no matter how large or little?

sydthebeat

Wesley Numerous Mesh wrote: »

That's true and I understand that fine, but is there a definitive figure on how much a block will leak per m2 under pressure? So could an air loss be calculated? As in surely a block has some resistance to air flow no matter how large or little?

http://www.harneymasonry.com/Air-Permeability.html

thats the only reference i can find....

MicktheMan

miller_63 wrote: »

but is there a definitive figure on how much a block will leak per m2 under pressure?

No, not really, as air permeability depends as much on the mortor joint quality as anything else.

From testing experience, I wouldn't be surprised to see a > 4m3/hr/m2 difference in a house between when the house was tested before plastering and afterwards

hexosan

Are you trying to work out the air leakage for sealing the electrical chases.

ht9zni1gs28crp

It was more a thought than anything else, the rest of my house is calculated to an inch of its life for target and achieved performance figures, then why so can the air permeability be worked out for all materials and produce a through wall leakage rate? Similar to a U Value.

Thirty years ago U Values were pie in the sky stuff.

sydthebeat

Because the singular most significant factor in air permeability is workmanship.