Filling cavity under radon?

Selfbuilderx

Hi, Can anyone help.

My build has a 6" cavity and two courses inside and one course outside up to radon and i was told buy the groundsman yesterday to fill the cavity up to the level of the outside 9" block. My question firstly is this right and secondly is it ok to fill with 2" down or would screening be better. the radon went down yesterday so ill have to act soon....

sydthebeat

Selfbuilderx wrote: »

Hi, Can anyone help.

My build has a 6" cavity and two courses inside and one course outside up to radon and i was told buy the groundsman yesterday to fill the cavity up to the level of the outside 9" block. My question firstly is this right and secondly is it ok to fill with 2" down or would screening be better. the radon went down yesterday so ill have to act soon....

are you saying youve only 1 block course between the top of your foundation and your radon??

is this a raft foundation?

Selfbuilderx

Hi sydthebeat,
Ya, well we have 2 blocks on inside and one on outside and then back filled the house, then screening and the radon over all that coming over the two inner blocks and down onto the one on the outer course. Another one course will go in the inside and two more on the outside, then insulation and pour floors. If all that makes sence to you..

sinnerboy

Is this sketch right ?

If so fill the "?" part with concrete or better yet - buy some 150 thick EPS board and cut it to slope .

If you are using bead fill to the cavity above ground use cut EPS like this behind all stepped dpcs.

Selfbuilderx

sinnerboy,
Thanks so much for going out of your way to do the sketch, Ya you're spot on with it. I filled most of it with 2" down and some of it with screening, i had to make a call. The blocks are starting tomorrow or Friday. Do you reckon this will suffice or do you recommend I try and take it all back out? Pity I wasn't talking to you before today as the insulation idea is really good. I would appreciate the advice on whether to take it out or whether it's ok. Thanks again.

BryanF

selfbuilder,
may i suggest you lay a row of quinlite's or similar above the radon layer on the inner leaf. that way you'll have a better continuation of thermal resistance. (Do check with your engineer re correct strength of block)

Selfbuilderx

Hi BryanF
Im pumping insulation into the cavity after, should that help with thermal resistance, not that i'm 100% on what thermal resistance is...

BryanF

Selfbuilderx wrote: »

Hi BryanF
Im pumping insulation into the cavity after, should that help with thermal resistance

yes thats the whole point of insulation, however what I'm saying (clearly in the absence of you hiring an architectural technician to detail/specify this) is that between your floor insulation and wall insulation there is an inner block that does not have any insulation properties. so I'm recommending you use a 1 row of 'quinlite' blocks or similar product (as it has better insulation properties) at the location where the floor and wall insulation should meet..

Selfbuilderx

Hi BryanF,
Thanks, ill look into that for sure, what do you think of what i backfilled the cavity with? do you think it will do?

sinnerboy

Selfbuilderx the cavity below ground level is vulnerable to crushing. So it must be filled with something to resist those forces. I thing you've filled it with hardcore ? This is not good. Concrete is the "usual" way but high density EPS would work too.

Selfbuilderx

Thanks sinnerboy,

I didn't realise this i'll try and take it back out and mix some cement through it and put it back in, or would the eps be a better job.

sinnerboy

The Psi value means heat flow through a junction. Like U Value measures heat flow through a wall / roof / window - Psi measures the heat flow where each building part meets .

I've looked at 4 option

1. fill below radon with concrete - Psi 0.37 W/mK
2. fill below radon with EPS - Psi 0.29 W/mK
3. As 2 + one course of Quinnlites to inner leaf above Radon - 0.23 W/mK
4. As 1 + one course of Quinnlites to inner leaf above Radon - 0.26 W/mK

So what do these funny little numbers mean ?

Suppose you heat the house with an oil fired boiler. You'll pay today around 10cents / Kwhr.

Average year round temp in Ireland is 9 degrees - desired indoor temp being 20 degrees we therefore get

((20-9) x 24 x 365 )/1000 = 96.3 Kilo Kelvin hours per year temp difference to make up

So

1 .Psi 0.37 x 96.3 = 35.63 kwhr @ 10 c = €3.56
2. Psi 0.29 x 96.3 = 27.93 kwhr @ 10 c = €2.79
3. Psi 0.23 x 96.3 = 22.15 kwhr @ 10 c = €2.24
4. Psi 0.27 x 96.3 = 26.00 kwhr @ 10 c = €2.60

Reminder - this is the rate of energy flow - money flow - at todays oil prices - for EVERY metre run of this detail.

If you can work out a per meter cost to
1. place concrete or
2. place EPS
3. use 1 course QL's

You will have your answer.

Would you mind "returning the ball" by costing the above ?

Selfbuilderx

Thanks sinnerboy,

Will (try) work it out and get back.. Thanks for all your help, i'm on my own with the build at the moment as my engineer let me down..

Thanks again

BryanF

Selfbuilderx wrote: »

Thanks sinnerboy,

Will (try) work it out and get back.. Thanks for all your help, i'm on my own with the build at the moment as my engineer let me down..

Thanks again

here we go with the engineers again:) if only there was any architectural technicians with any spare time in the country:D

( no offence ment Selfbuilder)