A vestibule is a completely enclosed unconditioned space that separates the interior of a building from the exterior. It creates an air-locked entrance and acts as an entryway into a larger space, such as a lobby. Its purpose is to reduce stack effect (air movement caused by warmer air rising and colder air falling), and the amount of air infiltrated by wind at a building’s primary entrance. The primary entrance of a building has the highest volume of pedestrian traffic and is typically used by the general public, as opposed to private entrances and doors used by employees.
https://ccpia.org/vestibule-inspection/

Among all existing species tambours can be divided into two large groups: cold and heated structures. The first option does not affect the microclimate in any way, but protects against rain, wind, allows you to take off your shoes or clothes without going into the house. Heated vestibule have a heating element in the form of a radiator or underfloor heating system, glass structures are equipped with double glazing.
https://pacificlight.ru/en/otaplivaemyi-tambur-v-chastnom-do...

The heated vestibule enables members of our College community accessing campus for approved activities to wait for the bus in a warm & nearby space during inclement weather & after dark.
https://twitter.com/Confederation/status/1352365115639644163

Service Entrances: Each large service entrance with overhead doors (or equivalent) that allows
large quantities of outdoor air infiltration shall be accompanied by a heated receiving room. The
same considerations regarding freeze protection shall be applied here. Each smaller service
entrance shall be provided with heated vestibule unless the frequency of usage is expected to
be low, in which case it shall simply be served by one or more dedicated heating units as required
for a low-usage public entrance.
https://nebraska.edu/-/media/projects/unca/offices-policies/...

This project involved removal of exterior metal, re-framing the front awning, installing 2 motion activated sliding doors, constructing a heated vestibule space, finishing the exterior with a 3 colour stucco application with wood accents, re-roofing the entire building and prepping and wiring for new signage.
http://www.vocedevelopments.ca/project-07.html

The stay was absolutely fantastic. Nice, big and clean room, with heated vestibule where you can put your skiing equipment.
https://www.tripadvisor.com/ShowUserReviews-g1593089-d575325...

11 East 57th Street New York, NY
Scope of work: Installation of new storefront and heated vestibule
http://www.oculusdesignconstruction.com/miu-miu/

Our lobby renovations added a heated vestibule to our main entrance, and relocated our volunteer greeting desk front and center demonstrating the importance of volunteers in welcoming guests.
https://www.rmhc-swo.ca/mediafiles/agm-report-interactive.pd...

As simply 'sas' or 'sas d'entrée' this must have come up countless times.

I think 'airlock' says it all, i.e. the double door system locks air in and out, thus keeping the temperature inside a building stable. The text locates the airlock as adjoined to the main lobby, so it is pretty obvious this is not about pressure difference or contamination which MIGHT need qualifying if the context is not clear.

What country is this for? While draught lobby (or vestibule if lobby is used for the hall d'accès principal) might work, it might be too specific for, I don't know, places with temperatures of 40-50° (we're getting there) and/or Canadian prairie type winter temperatures where the issue is not so much draught as hot/cold air.


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Note added at 7 hrs (2022-03-11 18:39:16 GMT)
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If a qualifier is felt to be needed, how about 'weatherbreak vestibule' ?

"Because of frequent coming and going, THE LOBBY NEEDS A WEATHERBREAK; a vestibule or revolving door. Because the lobby may serve as a horizontal exit to the outside, a hinged door is required in addition. The hinged door should provide for the delivery of bulky packages and level passage for the handicapped."

"The principal element being that of outdoor space and yard. Combining this with the requirements of a WEATHERBREAK between the weather and the heated interior spaces and additional hobby, play and storage space the concept of entry into a "yard" has been proposed"

Suggestion based on the references cited below.

This page gives me a bit of inspiration for this:

http://www.naturalbuildingblog.com/airlock-entryways/

... sas on its own is "airlock entrance", of course. But your drafter seems to want to emphasise somewhat the eco-credentials of the unit they're going to install. Perhaps (speculating wildly) to recommend a rather more expensive unit.

I think "airtight" conveys this idea. In the link I referenced it stresses the (very obvious!) need to make such units as airtight as possible if they are to justify a) the extra cost and b) the extra claim to environmental virtue.

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Note added at 1 day 5 hrs (2022-03-12 16:19:05 GMT)
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And, just to add: I was simultaneously puzzled, intrigued and amused the first time I learnt that "moteur thermique" is (one) translation of ""internal combustion engine". It is certainly true that an internal combustion involves "heat". But using such a terse expression in such an oh-so-Cartesian process of abstraction struck me as quite funny.

Just a thought, to suggest that "thermique" doesn't therefore necessarily mean that a reference to heat has to be present in the English expression, which might be slightly more, er, straightforward potentially.