Never go digging for a U-value or rooflight table again
Carry out your own area-weighted U-value calculations and compensatory calculations in minutes, with 100’s of pre-programmed products from the most popular manufacturers, and new ones added regularly. Downloadable and printable PDFs to provide to your Building Control Officer or Inspector at no extra cost. No manual maths, no clunky spreadsheets.
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| Element | Area (m²) | Notional (W/K) | Proposed (W/K) |
|---|---|---|---|
| Floor | 20.0 | 3.0 | 2.4 |
| External wall | 35.0 / 33.0 | 6.0 | 5.0 |
| Roof | 20.0 | 2.4 | 2.0 |
| Openings | 5.0 / 7.0 | 7.0 | 8.4 |
| Total | 18.4 | 17.8 |
Illustrative sample calculation
More manufacturers and ranges added regularly.
Work across borders without relearning the regs.
Offset is modelled individually for Scotland, Northern Ireland, England and Wales, with the most up to date U-values built in for domestic and non-domestic projects alike. All values and methods come directly from Scotland’s Technical Handbook, Northern Ireland’s Technical Booklet F1, and Approved Document L in England and Wales.
Everything a compensatory calculator actually needs
Pick the nation and edition, Offset automatically applies the right calculation method and U-values.
U-values and dimensions sourced from manufacturer literature for popular suppliers including VELUX, Korniche, The Rooflight Co. and FAKRO. Pick a product, the figures calculate for you.
Every calculation generates a title-blocked, submission-ready report: notional vs proposed tables and a clear pass or fail.
Invite colleagues into your practice, or belong to more than one. Everyone in the office can access and update saved calculations seamlessly.
Start free. Upgrade when you’re ready.
Free forever
For trying it out and self-builders.
£48 billed annually (save 20%)
For sole practitioners and freelancers.
£144 billed annually (save 20%)
For small to mid size practices.
Per-seat volume pricing for larger practices, and for universities and colleges teaching architecture and technology.
No VAT is charged. Cancel any time from your account.