Hi David. No experience of using it myself but there is a detailed calculation method for decrement factor in CIBSE Guide A - Not for the faint hearted though.

Posted By: DEA David I think it is accepted that solar gain control and HRV are necessary with SIP construction as the airtightness combined with impressive u-values can lead to overheating in summer months.

And the very short decrement delays due to very lightweight construction.

Just been talking with our tech guys this week about some of this - we had some European 'active' U-values (no, I hadn't heard of them before) that combines the U-value, Y/psi values and the decrement delay into one 'Active U Value' - apparently its common on the continent. It suggest (rightly) that a buildings walls and roofs real life performance are a combination of things, not just out UK obsession with U-values. Produces some eyebrow raising figures between systems...

I thought decrement delays were not any harder than a U value to calculate - we all did them as staff training once. I will dig out my notes on Monday. I am fairly sure that a version of Usai can calculate them as well.

Can I say, I would have thought as a SIP manufacturer, this technical knowledge should be available.....?