moldy

350mm 0.1 u-value external wall

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Does anyone know a wall make up that could achieve a U-value of 0.1 where the overall width from finished external to finished internal is max 350mm? 

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Posted (edited)

@moldy, you are going to need something like 250mm of PIR/PUR in a timber frame with 50mm eps insulation on the outside and ewi render directly applied (no cavity)

Edited by A_L
typo

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15 hours ago, moldy said:

Does anyone know a wall make up that could achieve a U-value of 0.1 where the overall width from finished external to finished internal is max 350mm? 

 

Is there a specific reason for targeting such a low U-value? It's pretty aggressive - lower by some way than you need to meet the PassivHaus standard.

 

If you're willing to accept a slightly higher value, your options will be far greater.

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15 hours ago, moldy said:

Does anyone know a wall make up that could achieve a U-value of 0.1 where the overall width from finished external to finished internal is max 350mm? 

I can't see how it would be possible with brick and block. We have wall U values of 0.09 but that is with a 495mm overall thickness I-beam timber frame.

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An ICF wall with a 150mm core and 200mm EPS will give you 0.15. for u value of 0.1 you are talking a 450mm thick wall. 

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With brick and block you may get 0.12 - 0.13 with rigid insulation, insulated plasterboard and lightweight block inner leaf.

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don,t think the energy saving would EVER pay for the extra cost of the extra insulation 

I had a few discussions with kingspan tech guy on insulation  for a water tank  and  diminishing returns  for extra insulation

once up to 150mm of pir ,it would never pay to go any thicker  assuming no air leaks .

which will probably explain why cold store walls made from pir are not any thicker

 

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You'd get there in the required overall thickness by having a 140 timber frame filled with PIR and with a 150mm layer of external PIR insulation then a ventilated rainscreen timber facade

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2 hours ago, Ian said:

You'd get there in the required overall thickness by having a 140 timber frame filled with PIR and with a 150mm layer of external PIR insulation then a ventilated rainscreen timber facade

If you changing from block build 

then 200mmsips panels +50mm exterior+cladding/render then on inside  +25mm service cavity+ and 37 or 50mm foam back plaster board.

lots of ways to do it --not sure once walls are down to 0.12 there is any  real need to go lower 

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4 minutes ago, scottishjohn said:

not sure once walls are down to 0.12 there is any  real need to go lower

It's not a question of need but want. Where we live having wall and roof U values of less than 0.1 meant not needing to have a conventional central heating system ie UFH or radiators. This was one of our wants. I ran a lot of iterations of PHPP to arrive at this value. This is of course dependent on shape of house, weather etc, but works for us.

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3 hours ago, PeterStarck said:

It's not a question of need but want. Where we live having wall and roof U values of less than 0.1 meant not needing to have a conventional central heating system ie UFH or radiators. This was one of our wants. I ran a lot of iterations of PHPP to arrive at this value. This is of course dependent on shape of house, weather etc, but works for us.

that,s absolutely your right and choice .

but most decisions are usually a cost versus benefit compromise

that's the only reason for my comment

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On 25/06/2019 at 17:37, moldy said:

Does anyone know a wall make up that could achieve a U-value of 0.1 where the overall width from finished external to finished internal is max 350mm? 

why are you constrained to 350mm? a 350mm i beam filled with cellulose will give you 0.1 u value but will have cladding on outer surface

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