Winter Weather Roofing: Cold, Hard Facts

Transcription

1 Winter Weather Roofing: Cold, Hard Facts Winter is not a season, it's an occupation. Sinclair Lewis Peter Kalinger, Technical Director Canadian Roofing Contractors Association kalinger@roofingcanada.com

2 Winter Weather Roofing

3 Winter Construction

4 Winter Construction POST WWII Governments looked to construction to stimulate growth and provide jobs. Construction provided a huge untapped industry for labor. Seasonality, winter stoppage of construction presented a significant barrier to full employment.

5 Winter Construction costing the nation (private owners and taxpayers) at least $3 to $4 billion a year in economic waste, creating unnecessary hardship for some 4.6 million workers Except for agriculture, construction has the greatest seasonal variation of any major industry division. Its employment is characterized by summer peaks and winter valleys and the industry takes more money out of the employment insurance system than it puts in. Report by R.J. Myers, Deputy Commissioner of Labor Statistics on construction seasonality

6 Winter Construction In 1967, President Lyndon B. Johnson directed the Secretary of Labor to make a detailed survey of seasonal employment and underemployment and find ways of dealing with these problems. He later directed the heads of various government departments to reduce seasonal unemployment.

7 Barriers to Winter Construction Assumption that : Winter weather requires additional planning and increased costs Traditional construction materials and practices Seasonal patterns in consumer demand Project specifications that inhibit winter work Patterns of distrust and prejudice against winter work among architects, engineers, owners and the public D.O. Mills, M.I.T., 1968 seminar on Seasonality in Construction

8 Benefits of Winter Construction Fights inflation The cost of building in winter must be compared with the cost of building next summer-not last summer Retains key personnel Spreads overhead costs Speeds up supply deliveries (better prices in slack period) Reduces summer overtime Maintains productivity of workers and machines (vs start & stop operation) Eliminates costs of startup and shutdown Provides better use of owners resources

9 Winter Roof Construction

10 Winter Weather Roofing

11 Winter Weather Roofing 1. Getting the work done. Productivity under winter conditions. 2. Materials. Winter weather limitations and precautions 3. Winter weather effects. Thermal, moisture

12 Winter Construction Issues 1. Getting the Work Done: Productivity Snow, sleet, rain Extreme temperatures Reduced daylight Limited work schedule

13 Winter Weather Issues Snow, sleet, rain Annual average snowfall Snowfall Wet days cm inches number St. John's Charlottetown Halifax Québec Montréal (7 ft.) Ottawa (8 ft.) Toronto (4 ft.) Winnipeg Calgary Vancouver Whitehorse (5 ft.) Yellowknife (5 ft.) 118.9

14 Winter Weather Issues Snow, sleet, rain

15 Winter Weather Issues Snow, sleet, rain

16 Winter Weather Issues Snow, sleet, rain

17 Winter Weather Issues Snow, sleet, rain

18 Winter Weather Issues Extreme temperatures

19 Winter Weather Issues Winter Stress Hypothermia Frostbite

20 Winter Weather Issues Portable foot warmer

21 Winter Weather Issues Reduced daylight

22 Winter Weather Issues Limited work schedule

23 Winter Weather Issues Logistics closing in the building

24 Winter Weather Issues Logistics scheduling with other trades

25 Winter Weather Issues Logistics materials protection & placement

26 Winter Weather Issues Logistics roof loading

27 Winter Weather Issues Logistics the challenge of reroofing

28 Winter Weather Issues Logistics temporary protection

29 Winter Weather Issues Logistics drying the roof

30 Winter Weather Issues Logistics- preparing the deck

31 Winter Weather Issues Logistics preparing the deck

32 Winter Weather Issues

33 Winter Weather Issues Logistics temporary protection

34 Winter Weather Issues Logistics temporary shelter

35 Winter Weather Issues Logistics -PLAN, PLAN, PLAN

36 Materials Materials

37 Materials Built-up Roofing B.U.R. and M.B.M. can be applied to temperatures as low as -15 F (-26 C)- CRCA Specifications Manual

38 Single Ply Membranes Minimum installation temperatures determined by worker comfort and safety Temperature at which adhesives can be used

39 Winter Weather Issues Adhesion In a fully bonded system, uniform securement of the components to the deck is crucial for Wind uplift resistance Dissipating temperature induced stresses that cause membrane movement (ridges, buckles, splitting)

40 Winter Weather Issues Wind uplift resistance

41 Winter Weather Issues Adhesion Temperature induced stress

42 Winter Weather Issues Results of thermal movement

43 Winter Weather Issues: B.U.R. Asphalt cooling occurs rapidly under winter conditions A temperature drop 45 to 75 F may occur from the time the asphalt is drawn from the kettle to when it is applied. Need to heat above acceptable limits

44 Asphalt Temperatures Factors affecting heating temperatures: - weather conditions; - distance of the kettle from application

45 Asphalt Cooling During asphalt application in the field, peak contact temperatures were 50 to 75 F lower than the temperature in the asphalt kettle. Under certain ambient conditions asphalt applied to insulation dropped 50 F in temperature in 2 to 7 s. Raising the kettle temperature may be the only effective means of maintaining proper peak temperatures.

46 Asphalt Temperatures Factors affecting rate of cooling: Asphalt application temperatures Quantity and thermal properties of the asphalt Ambient temperature and wind speed Temperature and thermal properties of underlying components

47 Asphalt Cooling A S P H A LT MODEL: VARIOUS SUBSTRATES Substrate: 1. Concrete 2. Steel 3. Plywood 4. Felt/PUF 5. Fiberglass T E M P ( F) COOLING TIME (s) (air & substrate temp are 19 F, wind speed = 0 m/h)

48 Asphalt Cooling Asphalt often needs to be above recommended kettle temperatures to obtain EVT SP fallback occurs at these temperatures. Dangerously close to flashpoint temperatures (CSA-500 F)

49 Single Ply Adhesives & Primers

50 Membrane Adhesives Single Ply solvent based adhesives temperature limits, flash-off, condensation

51 Solvent Adhesives & Primers Blushing -solvent based Adhesive Evaporative cooling of the material during drying lowers the surface temperature at or below the dew point temperature. Water vapour in air condenses on the surface of the adhesive inhibiting adhesion. Greater risk of blushing in early morning and late afternoon (less solar radiation). Scheduling the application of adhesives near midday when the difference between ambient and dew point temperatures is greatest.

52 Low VOC Adhesives Prolonged exposure to freezing temperatures can cause the adhesive to thicken. Drying time is affected by temperature, clouds/sun, humidity, and shade. Low VOC Bonding Adhesive takes more time to flash off. Must be stored unopened at elevated temperatures. Typically 60 to90 F.

53

54 Polyurethane Adhesives

55 Polyurethane Adhesives One component polyurethane Moisture cured Minimum application temperature of 33 F and rising Not suitable for winter construction Two Component Chemically cured, exothermic reaction Winter and regular grade formulations Steel decks must be clean and free from ice, snow.

56 Polyurethane Adhesives Two Component: Reaction time varies with temperature

57 Polyurethane Adhesives

58 Elastomeric Membranes

59 Plastomeric Membranes

60 Mod-bit Membranes

61 Mod-bit Membranes

62 Mod-bit Membranes

63 SA Membranes Minimum application temperatures range from 14 F to 25 (-10 to -4 C) Type of substrate and substrate surface temperature affect adhesion

64 SA Membranes

65 Materials All roofing materials have cold weather limitations In-service performance will depend on how they were installed under cold weather conditions Installations must be closely monitored Know when to quit

66 Construction Generated Moisture

67 Winter Weather Performance

68 Construction-Generated Moisture

69 Condensation and Cool Roofs

70 Condensation and Cool Roofs

71 Wetting Vs. Drying Wetting from vapor diffusion

72 Air Leakage

73 Air Leakage

74 Air intrusion When conditioned indoor air enters into a building envelope assembly but cannot escape to the exterior environment.

75 Waterborne Adhesives

76 AIR Research Study Partnership of NRCA, CRCA, SPRI, and NRCC to carry out extensive research on air leakage and intrusion in mechanically fastened single ply systems.

77 Limiting Moisture Accumulation Construction and in-service moisture accumulation due to diffusion, air leakage and air intrusion can be controlled by: Adequate ventilation during construction Dehumidification prior to building occupancy Sealing gaps between building envelope assemblies gaps around penetrations and steel deck end laps Using multiple layers of insulation (a minimum of two) with staggered joints to help retard warm, moist air flow from the interior of the building into the roofing assembly

78 Mod-bit Membranes

79 Increased Insulation National Energy Code for Buildings (2010) 79

80 Increased Insulation Thickness Increasing insulation thickness may adversely affect roof performance. 80

81 Increased Insulation Thickness 81

82 Winter Weather Roofing Conclusions Winter weather roofing is difficult, costly and high risk We ve been attempting to find solutions since the 1950 s Advanced materials and techniques have not been a panacea Perhaps it s time to think out of the box.

83 Prefabricated Roofing

84 Winter Weather Roofing Winter is nature's way of saying, 'Up yours Robert Byrne Canadian Roofing Contractors Association