One Job, Done
Properly
Every feature below exists to answer one question: will this dwelling pass Approved Document O? There is nothing here you will pay for and never open.
The Simplified Method, Without the Spreadsheet
Approved Document O's Simplified Method sets maximum glazing areas and minimum openable free areas, varying by orientation, dwelling type, and whether your postcode sits in a high or moderate risk location. It is arithmetic. It is also fiddly, repetitive, and easy to get wrong at eleven o'clock on a Thursday.
AutoTHERMAL applies the limits from the geometry you have already entered. You get a pass or fail per facade, the number you missed by, and a straight answer on whether this dwelling needs to go to dynamic modelling.
It is the fastest sanity check there is on a house type. For a lot of plots, it is the only evidence you need.
Limits applied for you
Glazing and free-area standards checked per facade, per orientation, per risk location.
A number, not a verdict
Not just "fail". How far over, on which elevation, so you know what to change.
TM59 Dynamic Modelling, Powered by EnergyPlus
When the Simplified Method will not carry a dwelling (a single-aspect flat, a corner unit that does not count as cross-ventilated, too much west-facing glass), Part O's other route is dynamic thermal modelling to CIBSE TM59.
AutoTHERMAL runs that simulation on EnergyPlus, the US Department of Energy's building simulation engine and the reference much of the industry is built on. The model steps through every hour using CIBSE Design Summer Year weather data, with the occupancy, internal gains and window-opening profiles TM59 prescribes already configured.
You get a clear pass or fail, the margin on each test, and the room that is driving the failure.
Daytime comfort
Hours of exceedance against the adaptive comfort threshold, May to September.
Bedroom nights
Bedrooms above 26°C between 10pm and 7am. Usually the one that catches people.
What You Get
All of it, on every plan. No modules to unlock.
Bring your own weather files
Upload the CIBSE DSY or TRY file your assessment needs and AutoTHERMAL runs against it. Drag it in once and reuse it across every dwelling on the site.
Realistic openable areas
Noise, security, fall protection and restrictors all reduce free area, and are all accounted for, including bedrooms that must be modelled closed.
Shading and overshadowing
Overhangs, fins, balconies, external blinds and the building next door.
Batch the whole site
Every plot, every orientation, one run, one schedule of results.
Scenario comparison
Change one variable, keep both answers, and show the client why you chose what you chose.
EnergyPlus engine
Results rest on the same engine the rest of the industry validates against, not a calculation of our own.
Bespoke client reporting
Your logo, your practice name, your standard wording. Issue it as your own document, not ours.
House type library
Save a type once. Reuse it across every site you ever build.
Shared projects
The architect, the assessor and the client can all open the same model.
The Questions People Actually Ask
Do I need to know a simulation package to use this?
No. You do need to understand the assessment: what Part O asks for, how your dwelling ventilates, what a bedroom overheating failure is telling you. That is your expertise and we are not pretending otherwise.
What you do not need is fluency in a general-purpose simulation suite. TM59 fixes the occupancy, gains and opening profiles, and AutoTHERMAL handles the simulation workflow around them.
Replace this with your own wording before launch.
Which Part O route should I use?
Start with the Simplified Method on every house type. It is quick and for many plots it is enough. Where a dwelling fails, or where the glazing limits would force a design you do not want, move it to dynamic modelling. Both routes live in the same model here, so switching costs you nothing.
Will Building Control accept the report?
Reports include the inputs, weather file, assumptions, results and mitigation measures needed to evidence compliance, following TM59 section 2.3.
Replace this with your own statement once you have confirmed your report format with a Building Control Body.
What about TM52 and non-domestic buildings?
TM59 is the residential methodology and the one Approved Document O points to. TM52 covers non-domestic adaptive comfort.
Add your own answer here on whether and when you will support it.
Is this an accredited tool?
Write your own answer here. Be precise about what is and is not accredited. It is the question a cautious assessor will ask first, and a vague answer costs you their trust.
What does it cost?
AutoTHERMAL is in early access and pricing is not published yet. Join the waitlist and you will hear it first.
Bring us a plot that keeps failing
Send us the dwelling that keeps failing and we will walk through it with you.