The decisions you can settle yourself, free
Every one of these has a published method and one right answer, so there is no reason to pay for it or to wait two days for it.
- U-values to BS EN ISO 6946 with BR 443 conventions — 300+ materials, a live cross-section, and the condensation check running alongside. The PDF is free too.
- Junction Ψ-values to ISO 10211, drawn rather than picked from a table, for when the accredited details do not match what you have actually detailed.
- The Part L 25% glazing rule — the question that decides whether a rear extension works before anyone draws it twice.
- Table 4.3 for renovated elements, including the 15-year payback test when the improved value is not reasonably achievable.
Where the free stuff stops
A U-value is a calculation. A SAP assessment is an accredited judgement, lodged under an assessor's registration, and there is no legitimate free version of it — here or anywhere else. Same for the EPC that comes off the back of it, for SBEM on anything non-domestic, and for the on-site work: air tightness and sound testing.
We do all of that. The useful part for you is that the fabric numbers you already settled in the tools drop straight into it, so the SAP is not the first time anyone finds out the glazing is 3% over.
When to involve us
Earlier than most people do. A design-stage SAP exists to tell you what the scheme is sensitive to while changing it is still free — at RIBA Stage 3, not at Stage 5 when the windows are ordered. The three that most often come back to bite are glazing area, the junction details you assumed would be accredited, and a heating system chosen for cost rather than for what it does to the emission rate.
If you want a second pair of eyes on a scheme before it goes to Building Control, our compliance pack is the whole set in one price.
Common questions
Can I use the free tools on client work?
Yes. They are free in full, with no account and no time limit, and the U-value PDF is free to issue. If you want the reports to carry your practice name and logo rather than ours, that is what Monkey Pro is for — the maths never changes, only whose document it looks like.
Do you do the whole compliance package or just the SAP?
The whole thing, and usually it is cheaper that way — SAP at design stage and as built, the EPC on completion, Part G water, Part O overheating, air tightness and sound testing. Send the drawings once and get one price and one programme.
Our psi values came from the accredited details. Do we still need a calculation?
Only where the detail you have drawn differs from the accredited one. If it matches, use the published figure. Where it does not — and it often does not once a cavity closer or an insulation zone moves — a calculated value to ISO 10211 is almost always better than the default, and the defaults are punishing.
Not quite you?
- Self-builders — What you can produce yourself, what you cannot, and when each is due.
- Developers & housebuilders — Multi-plot compliance, priced by dwelling type rather than by plot.
- Assessors & consultants — The calculators, the working shown, and your name on the report.