From the link I've given it would seem the building was Hospital then a school then back to a hospital during ww1. Its now called Tegfan Old peoples home so that gave me the location via google maps and I had a look at an 1885 and 1900 map and that location is listed as a Union workhouse then Industrial school which tallies up nicely. Its certainly the right area as there is a Windor street and a Lord Windor Public house near by too
Heres how it looked back in the day
Its location via google maps.
From the link I posted
The Soldiers were probably resident at Windsor House in Trecynon that was used during the war as a hospital for wounded servicemen. The military hospital was opened in September 1915 by Lord Aberdare, staffed by the Red Cross there was accommodation for 60 patients.
This site was originally used in as a hospital in 1875 but had been
converted by the Merthyr Board of Guardians for use as an Industrial School. The industrial school had accommodation for 120 pauper children and orphans who would have been taught skills including agriculture and shoemaking to enable them to find gainful employment after leaving