What hospital opens their windows? The proper ventilation system in a hospital or in patient multi story health care facility is not the same as typical commercial building or residential systems. First of all there is no return air system. It works with outside air at the intake going across the coils and the cooled sir distributed throughout the ventilation system. No air return is done as a hygiene measure. You don't want virus and bacteria in your air. The building is slightly pressurized and that pressure is released through entrance doors and the elevator shafts.
The biggest thing that hurts hospitals is under sizing the capacity of the A/C plant itself as an initial cost cutting measure in construction. In a typical US hospital we're likely talking anywhere from 300-1000 tons of cooling needed depending on how large the facility, what type of equipment is operating in the way of electronics, and if adjoin office buildings are hospital physical plant dependent. In other words adding say a CT Scan machine, etc would add to heat load. The UK is likely adding equipment but not increasing their tonnage capacity in cooling.
Heat loads on these buildings by outside weather factors have not gone up. Many things can substantially increase or decrease the heat load though such as overcast skies, closing curtains on the side of the building the sun is hitting allows for significant lower temps.
The biggest risk to a hospitals A/C isn't global warming. It's power failures that are the threat and most generator can not cover the large power capacity to run the units. After about 12 hours of no A/C in a hospital with a concrete floor the floors begin to sweat. That too is dangerous. But if the unit itself break down or units and need several days to repair them that generally can be remedied within about 12 hours by bringing in a flatbed tractor trailer with a portable chiller on it. Most hospitals have set up to allow for this remedy in the US.
Uhh, don't know where you live, but that's not the way the hospitals work here in FL. I spent three years consulting for a problem hospital in South FL, and I can guarantee you the building has lots and lots of return air ducts in it.
The building is slightly pressurized and that pressure is released through entrance doors and the elevator shafts.
If a large building is cooled using 100% fresh air, it won't be "slightly pressurized," it will be highly pressurized, and there will be pretty much a gale exiting whenever an outside door is opened.
Not saying it wouldn't be a good idea to operate hospitals this way, simply that it's not actually how they work.
In fact, here in FL the state regulatory agency has a requirement that hospitals operate at neutral pressure to the exterior. It's a remarkably stupid requirement, since among other things it's just not possible, but the requirement is there.
In a hot/humid climate, hospitals, like all other buildings, should operate on a slight positive pressure to help prevent intrusion of humid air, and to ensure that building envelope cavities are generally filled with dry "inside air" rather than humid "outside air."
Properly run hospitals do, of course, have specially pressurized rooms for immune-compromised patients (positive pressure) and highly infectious patients (negative pressure).
Not sure what they do when the patient is both immune-compromised and highly infectious. Start making funeral arrangements, I guess.
Can't speak to UK hospitals or buildings in general, but in USA, at least in FL, a much more common problem is oversizing rather than undersizing AC systems for the load.
Doing so greatly reduces the ability of the system to control humidity, which, regardless of what this article implies, is much more important to the health of the occupants (and the building itself) than the temperature.
BTW, in any large building, opening windows around the perimeter will do little or nothing to control temperatures in the center of the building.