Timber frame wall insulation

[GrantMcscott]

Hi

In between the studs in my timber frame I have used Thermaframe 40 is the adequate insulation?  The architect specified Thermaframe 35 but i order the wrong one will this make much difference.  There is no insulated plasterboard either on the walls just 15mm thick.

 

So wall make up is Thermaframe 40 - VCL - service cavity then plasterboard

 

Also people have questioned why it is not PIR insulation between the studs tight fitted

[Mr Punter]

You will need more insulation than that to pass Building Control.  What did your SAP say the wall  u value would be?

[BMcN]

Is this a new build? Wouldn't achieve minimum u values at that. 

 

Presuming it is 150mm studs, I'm not sure 35 alone would pass either. Prob need 25mm PIR, then your VCL and strapping. 

 

 

[GrantMcscott]

The Architects spec say this

The external walls above DPC level shall comprise amixture of types, single leaf of 100mm thk. cutstonework or rendered blockwork or timber cladding,50 mm vented cavity, TF200 Thermo BreatherMembraneor similar, 9mm sheathing ply, 140mm timber frame, 140mm fill Thermframe Roll 35, 45x35mm timber battons (service void).15mm vapour checked plasterboard. All window/door lintels toStructural Engineers design. Catnic or similar steel lintols to be used in stonework leaf.Minimum Overall U-Value –0.22 W/m²K.

 

The SAP Certificate says

exposed timber framedwalls to achieve U-value of at least0.22W/m2K using 100mm Thermawall TW55

[MikeSharp01]

1 hour ago, GrantMcscott said:

The Architects spec say this

The external walls above DPC level shall comprise amixture of types, single leaf of 100mm thk. cutstonework or rendered blockwork or timber cladding,50 mm vented cavity, TF200 Thermo BreatherMembraneor similar, 9mm sheathing ply, 140mm timber frame, 140mm fill Thermframe Roll 35, 45x35mm timber battons (service void).15mm vapour checked plasterboard. All window/door lintels toStructural Engineers design. Catnic or similar steel lintols to be used in stonework leaf.Minimum Overall U-Value –0.22 W/m²K.

 

The SAP Certificate says

exposed timber framedwalls to achieve U-value of at least0.22W/m2K using 100mm Thermawall TW55

 

Feels slightly confused - two types of insulation seem to be in the game plan, you will need to know the areas of each buildup, but essentially your main insulation is just 140mm thick and that bit gives you a U value of something like 0.28 { U = 1 divided by (Thickness in m [0.14 in your case] divided by K value [.04 for your insul / 0.035 for the stuff the architect specified] ) } To get the whole wall you need to work it out for the whole buildup. In which case it is 1 / Sum of (Thicknesses / K values) Here is a sample calc for you to look at and there are myriad calculators out there for you to play with. https://www.thenbs.com/knowledge/what-is-a-u-value-heat-loss-thermal-mass-and-online-calculators-explained

 

PS the U value of the thermawall specified is 0.22 on its own without the rest of the build up!

 

 

[GrantMcscott]

Not 100% sure what you mean but if I tight fit say 50mm pir  insulation into the studs and compress the frametherm would that be OK

Edited July 6, 2021 by GrantMcscott

[GrantMcscott]

or Could go for this make up

 

TF200

9mm OSB3

140 mm frametherm 40

Polythene vapour barrier.

50 mm PIR.

Battened service cavity.

[A_L]

43 minutes ago, GrantMcscott said:

or Could go for this make up

 

better, U=0.18W/m²K, do not compress mineral wool as it increases the thermal conductivity by an unknown amount

 

 

[GrantMcscott]

31 minutes ago, A_L said:

 

better, U=0.18W/m²K, do not compress mineral wool as it increases the thermal conductivity by an unknown amount

 

 

what calculator is this?

Edited July 6, 2021 by GrantMcscott

[A_L]

26 minutes ago, GrantMcscott said:

what calculator is this?

 

No longer publically available.