PUF Roofing A Primer

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Myrtle Skinner
6 years ago
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1 PUF Roofing A Primer PUF = polyurethane foam Recent observations by CDW of PUF roofs on commercial buildings seem to suggest that we will be seeing them more often, possibly migrating to residential We should ensure we know enough to effectively advise our clients The following aims to advise you appropriately

2 About Polyurethane According to wikipedia: Polyurethane (PU) is polymerized from monomers of isocyanate and hydroxyl PU is common and versatile, and can have many forms: Low-density flexible foam used in upholstery and bedding Low-density rigid foam used for thermal insulation Soft solid elastomers used for gel pads and print rollers Low density elastomers used in footwear Hard solid plastics used as electronics PU is generally petroleum based Soy-based PU foam is also available

3 About PU Foam From U.S. DOE, spray polyurethane foam can be closed-cell Has bubbles of usually HCFC The R-value is about R-7 to R-8/inch With escape of the bubble gasses over time, the aged R- value can reduce slightly to R-6.5/inch Density = 32 kg/m3 OR open-cell (open to air) Low density = 8 kg/m3 More flexible Lower about R-3.5/inch

About PU Foam Professional foams are 2- component, applied with foam application equipment DIY products include foam-incan One component, low density Also available are 2- component

4 About PU Foam Professional foams are 2- component, applied with foam application equipment DIY products include foam-incan One component, low density Also available are 2- component disposable (or refillable) kits E.g. Froth Pak from DOW These are denser and stronger than single-components, but not equal to, and significantly more costly than, professional versions

5 About PUF Roofing According to NRC, PU rigid foams were first developed in the late 1930 s and used to strengthen aircraft wings Spray-in-place PUF roofing systems were introduced in the early 1960 s! NRCA has talks presented at conferences from as early as 1985 on performance and maintenance of PUF roofs (Army engineers) PUF-based roofing is becoming more prevalent Repair of the Louisiana Superdome after Katrina has included a PUF roof system this, as described by Joe Lstiburek, reduced water damage from exit holes from bullets shot upward during Saints games!

10 About PUF Roofing PUF for roofing is closed-cell, of course much less absorbent, and adequately rigid Specifications by SPFA for foam used in roofing are: Min. density = 40 kg/m3 Min. Strength = 270 kpa Max. open-cell content = 10% Can be used for both new construction and retrofit At this time, at least in GTA, PUF roofing is used primarily for retrofit, overtop existing materials Marketed as green less material in landfill, better thermal efficiency = lower energy costs Cost-effective for client, especially if old roofing is not removed

11 Re-roofing with PUF The NRCA now has a manual on the correct installation of PUF roofing NRCA refers to the system as SPF spray polyurethane foam The manual includes new SPF reroofing details

12 Re-roofing with PUF The existing roof must be clean, and dry, and well bonded to the structure Oil contamination, for example, will prevent bonding Substrate cleaning can include air pressure, vacuum, chemical solvents, sandblasting, manual scraping, etc All wet areas of roofing and insulation must be removed For BUR, the surface is typically power-broomed, during which the gravel is removed Blisters, ridges, etc must be repaired or fastened down Soft mastic must be removed or covered

13 Re-roofing with PUF Metal flashings are typically left in place A urethane-based primer may be specified before the foam is applied to ensure adhesion The foam can be layered to desired thickness in lifts, likely about 1-inch per lift (layer), but NO LESS than ½-inch The foam is said to cure instantly actual time is weather and temperature dependent, but it hardens instantly, and cures substantially within a few hours

14 Protecting the PUF In all cases, the PUF must be protected or it will quickly degrade under UV exposure If it degrades, it will absorb water Protective coating should be elastomeric, allowing it to flex along with the foam and substrate Most commonly, the coating will be spray-applied Often, 2 passes are used base coat and top coat Spray coatings can be proprietary and specified by the foam supplier, who can include such large companies as DOW and BASF, or a coatings manufacturer Appropriate elastomeric formulations include Acrylics, Silicones, Polyurethanes, Butyls The coating could also be a flexible single-ply sheet, like EPDM Non-stretchy material like PVC would not work, and would be too costly anyway

15 Protecting the PUF Coatings are waterproof, of course, and in a high humidity environment, arguably should be vapour impermeable Coatings should be applied after at least 2 hours for foam to cure, but ideally within 24 hours to ensure foam doesn t get dirty or sun-damaged Spray coatings will typically incorporate mineral granules, although it is optional Distributed into the wet top coat Added for mechanical abrasion resistance This presentation shows pictures of 3 different top treatments we have seen in the field

16 Installation Specifications The following are from the SPFA the Spray Polyurethane Foam Alliance You will note that for installing a PUF system over an existing roof, that most of these details illustrate leaving everything in place and spraying over, including curbs, gravel stops, metal counter flashings, etc

19 That would look nice! Go down the front of the building too!

20 (Don t remove foam over)

27 Aka- the volcano

29 Re-roofing with PUF Here s a prudent specification: When detailing skylights or high walls, it is particularly important not to cover weep holes with SPF or coating. Final surfacing is important to prevent ridges and troughs: The final sprayed polyurethane foam surface shall be smooth, orange peel, coarse orange peel, or verge of popcorn. Polyurethane foam surfaces termed popcorn or treebark are not acceptable. (Now would be an appropriate time for a break and snack)

30 1. PUF Roofing with Silicone Coating Ajax industrial building ~50,000 square feet, three roof surfaces 7 years old Original 10 year warranty Supplier of materials was either BASF or DOW Contractor was from Guelph Has substantially improved the building s thermal performance, or so they say No leaks Didn t get cost purchaser thinks it was around $2- $3 / sq. ft. That s LOW. I have NOT confirmed this.

31 Application process According to maintenance guy: The foam is about 1.5 thick, thicker at flashings Top coat = 2 thin layers of silicone based film first layer was dark grey top layer was light grey for reflectivity Ceramic granules applied, during spray of top coat

32 Interesting how the structure telegraphs through

33 Really should have removed sleeper first

35 Manufacturer suggests small repairs be made with tube-grade silicone

36 Blister between foam and coating

39 Textbook cap flashing

40 This would have been far better if the fan was removed first

41 Prior coating repairs loose granules are swept up and applied to still wet silicone patch

43 Foam debonding from parapet wall

44 Is this popcorn or tree bark??

45 A few larger areas where the granules have worn off were noted surface is shinier

46 Coating sample

47 Coating is flexible, but easily ripped

48 2. PUF Roof with Acrylic Spray Coating Same process as previous In this case, the coating was very thin, probably consisting of an elastomeric acrylic paint with mineral granules Age of system estimated at 5 8 years More wear of the coating was noted than the previous silicone-based material, for similar age Water getting under foam at perimeter repair is required

51 Clearly this is orange peel

52 Accumulated worn-off granules

54 Void

55 Foam over old roof Foam debonding from substrate Pre-existing gravel stop flashing

57 Coating worn through

63 3. PUF with EPDM I believe I ve shown these before, but to recap in this context Topcoat is EPDM glued to hardened PUF EPDM flashings were not detailed in the usual single-ply fashion the sheet was cut around the protrusion, then the seam was foamed over, and sprayed with protective, granulated coating

64 Foam flashings Micro-ponds PUF with (dirty) EPDM roof coating

69 Maintaining PUF Roofs Protective coats Longevity of system dependent on maintenance of coating Vulnerable areas include edges, drains, overhanging vegetation, foot traffic at rooftop equipment Small and routine coating repairs can be done by maintenance personnel Silicone coating - make small repairs with tube silicone Acrylic spray coating - owner should keep pail of coating on hand for brush application EPDM easily patched with extra material and glue Larger repairs should be re-sprayed by original installer or approved contractor likely $1-$2 p.s.f, minimum $500 to $1,000 Ponding should be avoided will weaken coating

70 Maintaining PUF Roofs - Foam Water, mechanical or sun damage to foam should be repaired The manufacturers and associations suggest small repairs be made with compatible caulking Cut out damaged coating and foam, on 45degree bevel Fill hole with caulking, with slight mound and feather the edges Top coat after full cure of caulking, if required They seem to specifically NOT want repairs made with DIY foams

Maintaining PUF roofs - Foam Curiously, the defect used to illustrate the caulking repair is this one That s a lot of caulking I suggest careful use of a DIY spray-foam, with a reapplication of the

71 Maintaining PUF roofs - Foam Curiously, the defect used to illustrate the caulking repair is this one That s a lot of caulking I suggest careful use of a DIY spray-foam, with a reapplication of the protective paint/layer after the foam has dried However, this could void the warranty For repairs to larger areas, professional re-spray would be advised, taking care to remove all damaged foam, ensuring substrate is dry and clean, etc Re-coat required after foam repair

72 Blisters in PUF Roofs Per SPFA, blisters can occur Between lifts of foam Between foam and substrate In substrate (old roof underneath) Blisters can be caused by Moisture, oil or grease under a foam layer Moisture in the substrate Foam layers less than ½ Spraying over incompletely cured or damaged foam often weather related Low application temperatures

73 Blisters in PUF Roofs Lower level blisters probably don t need to be fixed until they get large and are at risk of cracking or breaking under load Blisters near the top of the foam thickness, or in thin layers, are flexible and can easily break these should be repaired Cut out bad areas Ensure surface is clean and dry Re-spray with original material Re-coat

74 PUF Roof Lifespan Uncertain strongly dependent on installation quality, maintenance level and exposure Low if installation is poor, coating is thin and not well maintained extended sun and water exposure of foam may negate opportunity for local repairs Replacement could be required within years, in worst case scenario For a well maintained, low-traffic roof with longerlasting coating (10-15 yrs before re-application), perhaps foam will mechanically withstand 2+ coating lives?? Report that higher maintenance is expected, as coating integrity is vital to system performance, and coating is relatively easily damaged

75 Resources More information can be obtained at: CUFCA Canadian Urethane Foam Contractors Association SPFA Spray Polyurethane Foam Alliance US Dept. of Energy A foam manufacturer - National research council - National Roofing Contractors Association -

To ensure warranty eligibility, each job must be approved by American WeatherStar before it begins.

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