COLUMN BUILDING SCIENCES FIGURE 2 Map of Freeze-Thaw Risk. Freeze-thaw damage needs water and freezing temperatures. The greatest risk are regions with more than 20 in. (508 mm) of annual rainfall coupled with cold and very cold climates. The shaded area of the map combines rainfall with cold and very cold climates. Historic folks like the term reversible because they can " undo " whatever is done later. Of course, they shouldn't because the " intervention " saves the building. The discussion often gets quite animated-we will leave it for later-with the understanding that " saving the building " is more important than " preserving a dumb detail. " Speaking of dumb details, check PHOTO 6 (Top Left) Notre-Dame Basilica of Montreal. Look closely at the horizontal " bands. " They were supposed to act as drip edges. PHOTO 7 (Top Right) Notre-Dame Basilica of Montreal. Deuxieme partie. Original drip edges did not work. They got retrofitted with lead-coated copper drips. PHOTO 8 (Bottom Left) Legislative Assembly of Ontario. We got it wrong in Toronto on our Legislative Assembly a hundred years later and had to add drip edges. PHOTO 9 (Bottom Right) Canada Life Building in Toronto. We messed up the building during the depression years, but fixed it with retrofitted drip edges. Yeah! As much as I want to pick on folks from Montreal (because the Habs keep beating my Leafs), they got it sorted out. Look at the retrofitted drip edges that are going hand-in-hand with the energy-efficient window replacement and interior insulation (Photo 10). And guess what? It has caught on in New Zealand (Photo 11) and in Czech Republic (Photo 12). Roof edges are a big deal. We have been retrofitting " reversible " parapet coping drips (Figure 3 and Photo 13). 50 ASHRAE JOURNAL ashrae.o rg N O V E M B E R 2021 out Photo 14. Wow, dumping the roof rainwater runoff right on the wall. Ouch. Good news-got fixed. An elegant fix that is pretty much invisible. A minor kick out with a major impact-a short diagonal metal roofing ridge directing water away from the roof/wall interface (Photo 15). The entire point of all this is that we can do seemingly minor changes from an aesthetic perspective that have major impacts on the flow of rainwater on building surfaces, reducing the concentration of rainwater and thereby reducing the amount of rainwater absorbed by materials. If we do this we can safely insulate old buildings and not damage them from freezethaw. Even if we don't insulate old buildings, we can save them from water damage. If we do this right, no one will know we were even there.http://ashrae.org