The Complete Guide to Part O.
What Part O requires, who it applies to, what satisfies it, and what the Future Homes Standard means for projects completing after March 2027.
What is Part O?
Part O is Part O of Schedule 1 to the Building Regulations 2010 (England), in force from 15 June 2022. It requires that new dwellings limit unwanted solar gains and provide adequate means of removing heat. The associated Approved Document O (AD O) provides compliance guidance.
Do internal blinds satisfy Part O?
No. AD O is unambiguous: internal blinds, curtains and shutters do not count as solar shading under Part O. Only external solar shading is credited. Internal blinds allow solar radiation through the glass before intercepting it. External shading prevents it reaching the glass.
What external shading satisfies Part O?
Any external shading included in a TM59 thermal model that reduces solar heat gain sufficiently to pass the CIBSE criteria. Common compliant systems include external roller screens, adjustable louvre systems, external Venetian blinds, brise-soleil and MicroLouvre® screens (g-value from 0.11).
The Future Homes Standard
Laid before Parliament 24 March 2026, in force March 2027. Expected to tighten solar shading requirements significantly for new dwellings, likely making TM59 modelling the default compliance method. We specify to anticipated Future Homes Standard requirements for any project completing after March 2027.
What we provide
- Product g-values and SHGC data for TM59 modelling inputs
- Product datasheets with full performance data
- NBS specification clauses
- BREEAM Hea 04 compliance documentation
- Written specifications for planning applications