There's a few members here with, like myself, a Touchwood Home's frames and there were quite a few more over at eBuid, but with MBC dominating the discussions over there it possibly suppressed discussion on other manufactures and build types.
Our frame went up this year (2016) during July and August and I'd rate my experience with Touchwood as a success.
Our build is a Conversion of a portal framed cowshed, and the frame design and erection was complicated by the existing structure, that obviously needed to remain in situ during the build. Visible below is the original primary steel frame with roof purlins:
The TH Design process was far more precise than I expected for the construction industry. I was able to laser scan the original frame and prepare an as-built CAD model for TH to then work around. This was invaluable, since the original frame was a long way from square and plumb with the top of the portal frame being as much as 115mm out of position in places.
With my model imported this into their frame design software they were able to confidently design their frame dovetailing around the existing structure, and confident we weren't going to have some unexpected clashes on site.
The original structure and especially the haunches at the joints, required bespoke detailing of the timber frame to incorporate and guarantee a robust airtight layer. The TH design process allowed all of these conditions to be assessed and solutions agreed before a single piece of timber went up on site.
During the design process we exchanged 3D models back and forth to agree solutions and to ensure compatibility to raft and drainage etc. I also have from them a full 3D model of the final frame design that has informed follow on trades and helped decide MVHR duct, plumbing and cable routings.
This didn't however stop me from being nervous during the first stages of the frame erection when it would become obvious if my as-built model and their frame were sufficiently accurate. But I shouldn't have worried, the two fitted together perfectly.
Taking a step back, our decision on what build process to use, what type of insulation to use and what performance targets to set took around 9 months after our planning was approved.
Once we had decided on timber-frame with cellulose fibre insulation and Passivhaus levels of insulation and airtightness the list of companies capable of delivering this and giving guarantees was surprisingly small. Having removed many of the variables, we actually found it relatively simple to compare quotes. There were slight differences with what was and was not included, but these were all relatively simple to assign a value too, to allow comparison.
A huge positive I found with TH is there has been no extra charges from their initial quotation. If anything, the content probably grew a little during the design stage, but everything must have been within a contingency they had allowed for, since they didn't ask for anymore money.
With the majority of issues foreseen and resolved before the frame erection started, the frame build went without a hitch. Their frames are a mixture of pre-cut and cut on-site to a cutting list (whichever is more cost-effective), and stick built. I believe they're on site around 4 weeks for a "normal" build, it was a little longer for mine. While a panelised process may take less time on site, the overall timing would be around the same. For me, they turned up on the day they said they would and finished about a week later than expected.
I'm looking forward to the airtightness test. Unfortunately, due to a hiccup with the roof lights I'll not be able to test with the structure still open, so remedial work will be a little more difficult, but I have high hopes. The airtight layer on a TH frame is "simple by design", and looks very robust. I believe their claim to generally be better than 0.2 ACH @ 50Pa, and sometimes be better than 0.1 ACH, but the proof of the pudding...