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DTS Part 13 & glazing calculations
Deemed-to-Satisfy energy efficiency for extensions and alterations — often a simpler, faster path than a full NatHERS rating for small additions.
What we deliver
Compliance without the full rating
The NCC Housing Provisions (Part 13) set out Deemed-to-Satisfy requirements for building fabric, glazing and sealing. For many small extensions this is the quickest way to show compliance.
- Glazing calculations (window U-value and SHGC)
- Building fabric and insulation requirements
- Building sealing requirements
- Documentation for your building surveyor
FAQ
Common questions
Can my extension use DTS instead of a NatHERS rating?
Often, yes — especially for small additions. Your building surveyor decides what’s acceptable, and we’ll recommend the path most likely to comply simply.
What do you need for a quote?
Drawings of the existing house and the extension, window sizes and orientation, and the site suburb.