b'vapour-retarding capability are used. Each successive interior lay- As with anything in construction, with enough money and planning, anything er should have a higher perm rating than the previous layer. The ideal amount of perm rating changes per vapour-retarding layer and is around an order of magnitude (i.e., 0.01 perm to 0.1 permcan be accomplished. However, adding insulation to the walls and roof and then or 0.1 perm to 1.0 perm).For example, if we use a 60-mil-thick TPO membrane (aboutbringing in refrigeration equipment does not address all the considerations that go 0.08 perm) for the roof membrane and the next major vapour-re-tarding layer is a metal roof deck (about 1 perm), the design shouldinto a trouble-free refrigerated space, let alone deep-freeze buildings.work. However, if we use the same 60-mil-thick TPO membrane (about 0.08 perm) for the roof membrane and put a 6-mil-thick polyethylene film (about 0.06 perm) on the metal deck, we can create a possibility for moisture accumulation. This moisture ac- Protective Roofing cumulation can become ice in facilities colder than 32 F.Air SealsMoisture issues directly attributable to water-vapour diffusionSafety Productsare rare. Air leakage (advection) causes a vast majority of problems in cold-storage facilities. During advection, warm, moisture-laden air from the building exterior leaks into the roof and beyond, depositing moisture on any surfaces below the airs dew point. A major part of the design and installation of cold-storage facilities should be preventing air movement between differing sections ofBYthe building and between the interior and exterior.Within the building footprint, air needs to be stopped from moving between areas of the building that are different tempera-tures. Examples include refrigerated space to freezer space, office space to refrigerated space and, particularly, from loading dock to adjacent cooled spaces, even if the loading dock itself is cooled. Even well-sealed loading dock doors can allow warm, moist ex-terior air to enter a facility in copious amounts. Warm air rises by thermal buoyancy, and moist air rises by hygric buoyancy; both factors will cause air to enter and rise to the underside of the roof deck. Once on the underside of the roof deck, this air The PR 100 Guardrail Systemis an efficient and practical perimeter guardrail that allows youto work right to the edge of the roof. Meets and exceeds OSHA & WCB requirements Accommodates: parapets and cant stripsEasy to install Provides unobstructed access to roof edgeThe PR 600 Mobile Fall Protection Systemcan be moved along the roof by pulling the cart to the desired working location, providing a safe working area. The PR 600 meets O.S.H.A. compliance 1926.502D.Roofing & Sheet Metal Super Service CentresEDMONTON, AB CALGARY, AB WINNIPEG, MB WESTON, ON(780) 432-2786 (403) 255-8236 (204) 338-7613 (Weston Road)BARRIE, ON HAMILTON, ON TORONTO, ON (416) 745-4111(705) 792-6683 (905) 560-2858 (416) 534-8421 WESTON, ONOAKVILLE, ON PICKERING, ON LONDON, ON (Signet Drive)(905) 825-0034 (905) 426-4443 (519) 668-3626 (416) 744-2050Photo 1: A field installation of an air-stop detail between a loading dock at 55 F and a food production area at 36 F. Note thewww.sparmarathon.cadeck flutes are filled solid and the membrane has been dropped to the deck to prevent air movement between the areas.ORN THE ONLY SOURCE FOR PROFESSIONAL ICI ROOFING CONTRACTORS IN ONTARIO ONTARIO ROOFING NEWSISSUE 4 2019/20209'