Opinion on Timber frame quotes….

I have two quotes from timber frame manufacturers – Cygnum and Kingspan Century. The house is bungalow circa 3000sq ft. I have looked through the quotes and picked out two possible options which I would appreciate any opinions on.
Cygnum:
8” frame – 46250
Erect - 16270
Plasterboard – 3646
Cellulose insulation – 6808 (quilt equivalent for 8” – 5,310) is cellulose better? Cellulose price includes installation/quilt does not. Both have u-value of 0.2
Service cavity – 1403
Silent home upgrade – 1588

Total – 75,965

Century:
Kit – 69813
Erect (optima option) – 18,946
Optima upgrade – 9619 (u value .15)

Total – 98378

Other features of both quotes seem fairly similar with similar non-erect items supplied. Is there anything in the century quote to justify the extra 25k?. Is the cygnum spec a good system? With blocks on the outside and a cavity, would the u-value be dropped further? And could I spend the extra 20k better on other areas?

Also, I was looking on botanicgp website and their construction diagram has no cavity but has an additional 60mm of rockwool outside the timber frame. http://www.botanicgp.com/heartwood/newdesign/EnergySavings.html. Would this be efficient to add to the cygnum system and what kind of cost would be involved in that?. If it was possible what u-value would I get? or does there need to be a cavity between the frame and the block?

Thanks

sman said:

Also, I was looking on botanicgp website and their construction diagram has no cavity but has an additional 60mm of rockwool outside the timber frame. http://www.botanicgp.com/heartwood/newdesign/EnergySavings.html. Would this be efficient to add to the cygnum system and what kind of cost would be involved in that?. If it was possible what u-value would I get? or does there need to be a cavity between the frame and the block?

Thanks

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Well, according to the Homebond manual, all timber frame must have a clear ventilated cavity outside the TF. You need to check with both Cygnum and Century if they will allow you to eliminate the cavity - I doubt it very much, as to do so would impact on their frame.........

i thought that the cavity was needed also. just curious when i saw it on the other site

galwaytt said:

Well, according to the Homebond manual, all timber frame must have a clear ventilated cavity outside the TF. You need to check with both Cygnum and Century if they will allow you to eliminate the cavity - I doubt it very much, as to do so would impact on their frame.........

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Could you not leave a 110mm cavity between frame and block and insulate the frame with 60mm insulation in the same manner as a standard block cavity wall?

I'm fairly sure www.advancedtimbercraft.com (no affiliation) do this using 50mm eps. They were featured in magazine recently and I'm sure that is what I read.

I think it's a good idea in theory because it contributes towards the reduction of the bridging effect of the studs in much the same way that the german systems use softboard.