Roofing Solutions for Alpine Regions

Transcription

1 Roofing Solutions for Alpine Regions TRA Snow & Sun 1657 S 580 E American Fork, UT Tel: Fax: Toll-Free: info@trasnowandsun.com Web: Roofing Solutions for Alpine Regions tra07a An AIA Continuing Education Program Credit for this course is 1 AIA HSW CE Hour Ron Blank & Associates, Inc TRA Snow & Sun. The material contained in this course was researched, assembled, and produced by TRA Snow & Sun and remains its property. Questions or concerns about the content of this course should be directed to the program instructor. Please note: you will need to complete the conclusion quiz online at ronblank.com to receive credit

2 An American Institute of Architects (AIA) Continuing Education Program Approved Promotional Statement: Ron Blank & Associates, Inc. is a registered provider with The American Institute of Architects Continuing Education System. Credit earned upon completion of this program will be reported to CES Records for AIA members. Certificates of Completion are available for all course participants upon completion of the course conclusion quiz with +80%. Please view the following slide for more information on Certificates of Completion through RBA. This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA or Ron Blank & Associates, Inc. of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product.

3 An American Institute of Architects (AIA) Continuing Education Program Course Format: This is a structured, web-based, self study course with a final exam. Course Credit: 1 AIA Health Safety & Welfare (HSW) CE Hour Completion Certificate: A confirmation is sent to you by and you can print one upon successful completion of a course or from your RonBlank.com transcript. If you have any difficulties printing or receiving your Certificate please send requests to certificate@ronblank.com Design professionals, please remember to print or save your certificate of completion after successfully completing a course conclusion quiz. confirmations will be sent to the address you have provided in your RonBlank.com account.

4 Course Description This course provides an overview of the problems and solutions associated with roofing in cold climates, including a discussion on the proper engineering of snow retention devices.

5 Learning Objectives At the end of this program, participants will be able to: State the common roofing challenges that are unique to cold climates Discuss the advantages and disadvantages of the everyday solutions to snow and ice difficulties Compare the accepted roof design practices in Europe to those in the United States and Canada Explain the concepts and effectiveness of roof ventilation and snow retention in reducing snow and ice problems List the factors to be considered in the proper engineering of snow retention devices

6 Common Roofing Problems in Cold Climates

7 Introduction Currently, there are no national or state codes relating to snow retention for roofing applications. Consequently, it is very important for architects and other building professionals to take extra care when designing a snow retention system for installations in snowy, cold environments. Presented in this course is an overview of the considerations that are required to facilitate a successful solution to snow and ice issues. This program begins with a review of the common roofing problems that are unique to cold climates. Ice dams Damage from sliding snow and ice Premature roof aging from freeze/thaw cycles

8 What Are Ice Dams? Ice dams are formed in snow climates. They occur when the ice and snow located at the top of the roof melts (as a result of the sun or heat loss from the building) and trickles down to the bottom edge of the roof where it is very cold, causing the water to refreeze into ice. Eventually, as more water freezes, the ice builds up, creating a wall that prevents water from running down the roof surface.

9 Problems Resulting from Ice Dams Ice dams can result in significant problems. Over time, they can cause water backups as melting snow and ice is trapped and pooled behind the ice dam. As illustrated in this image, the pooled water can eventually leak through the roof.

10 Ice Dam Examples In the left image, we can see the ice dam that has formed on the edge of the roof behind the icicles. In certain circumstances, large icicles can be created from ice dams that pose serious safety threats (right image). Ice Dam

11 Damage from Sliding Snow & Ice Another roofing problem associated with cold climates is damage from sliding snow and ice. When snow slides down a roof, or when large ice dams or icicles break loose and fall, they can damage gutters, fascia, and roof penetrations, or cause serious damage/injury to property/people below the roof.

12 Premature Roof Aging Snow and ice can cause roofs to age prematurely as a result of freeze/thaw cycles. The roofing surface can sustain damage (i.e. asphalt granules break loose) when subjected to repeated expansion and contraction.

13 Snow & Ice Solutions

14 Snow & Ice Solutions: Introduction Now that we have reviewed the concerns with roofing in cold climates, let s look at some of the common solutions to these issues. Ice dam protection membranes Manual snow removal Heat tapes Heat Tape

15 Ice Dam Protection Membranes In the United States, homes are required to use an ice dam protection membrane, commonly known as an ice and water shield. This product, applied to the plywood sheet, is used on eaves, rakes and valleys. Ice and water shields act like a bathtub liner that prevents water intrusion. Typically, local building codes dictate that the membrane is applied from the eave edge to two feet inside the exterior wall, though the distance can vary, depending on the region. Unfortunately, this solution does not always prevent ice dams, and it is important to be aware that condensation will be a problem when using an ice and water shield on 100% of the roof when the attic is not vented.

16 Manual Snow / Ice Removal Some choose to shovel the roof each year, risking damage to the roofing surface, endangering those who shovel and those below, and resulting in costly labor expenses.

17 Heat Tape / Cable A heat tape/cable system is another popular solution that is used in the U.S. This type of system features cables that are installed on the roof that heat up to melt snow and ice, providing a tunnel for water egress. This type of system is very expensive in its consumption of energy.

18 Heat Tape / Cable Below is an illustration and image of a heat tape/cable solution. HEAT TAPE OR HEAT CABLE

19 Heat Tape / Cable Unfortunately, a heat tape/cable solution doesn t prevent ice dams, nor will it stop snow and ice from sliding off the roof it simply provides a method of allowing some water to escape. Furthermore, a heat tape/cable system is a costly solution. The heat tape/cable system installed on this roof did not prevent damage to the fascia, drip edge and metal panel caused by sliding snow and ice.

20 Heat Tape / Cable The question we have to ask regarding heat tape is, why are we trying to heat the outdoors? especially when we consider the importance of energy conservation combined with the high cost of energy. According to National Geographic, North America makes up only 7% of the world s population, yet it consumes more than 30% of the energy produced globally.

21 U.S. / Canada Design Strategies

22 U.S. / Canada Design Strategies To address the issues surrounding snow and ice, several design strategies have been adopted in the U.S. and Canada. In this section of the course we will discuss the use of steep-sloping roofs various roofing materials, and snow retention devices, including - dormers - snow brackets/snow fences.

23 Steep-Sloping Roofs In the United States and Canada, structures are typically designed with steep-sloping roofs in mountain areas, and lower slopes in low lands. Steeper roofs allow snow to slide off more easily; however, this solution is designed around the snow and doesn t effectively address the source of the problem. Furthermore, sliding snow and ice presents many disadvantages and dangers to people and property.

24 Disadvantages to Shedding Snow Hazard to People and Property: Sliding snow and ice on a roof is a constant threat to the safety of the home/building occupants and guests, as well as the structure itself. Snow Removal: Snow that builds up on the ground must be removed, which can be costly, time consuming, and labor intensive. Limited Access: Entrance to buildings and homes can be blocked by snow and ice that falls from a roof. No snow on roof, trees or street and no access to the building

25 Disadvantages to Shedding Snow Other disadvantages to shedding snow: Causes damage to roof Less design freedom Loss of snow as an insulator Now that we understand the problems associated with ice dams and sliding snow and ice, let s review the performance of commonly-used roofing materials, beginning with metal roofs. No snow on trees or roof and no view from the windows

26 Metal Roofs Steep-sloped metal roofs are an effective solution to reduce/eliminate ice dams and potential leaks from ponding water, however, they do present some downsides. For example, they do not negate the issue of sliding snow and ice. Along with the dangers it presents, how does one deal with the volume of snow and ice that falls from the roof and surrounds the perimeter of the house? Snow prevents access to the front door of this home, which is buried beneath the snow. This homeowner installed plywood on sliding tracks to cover and protect the windows of the home from snow and ice damage. However, this solution prevents daylight access and impedes views to the outside.

27 Metal Roof Failures Sometimes, if the roof does not have a steep enough slope, snow sliding off can curl over and under the eave and damage parts of a house, such as windows, etc. In these images, notice the visible curling of the snow towards the windows of the home that oftentimes results in broken windows.

28 Metal Roof Failures Snow sliding down a sloped metal roof can sometimes lead to damaged dormers, as evidenced in the left image, where the weight of the heavier sliding snow crushed the lower, weaker part of the roof. Sliding snow can also damage other elements of a building, such as shingle panels, penetrations, and electrical wiring.

29 Metal Roof Failures The snow and ice that has accumulated at the front entrance of this home is a dangerous threat to the occupants and visitors. Serious injuries, even death, have resulted from snow falling from rooftops. This image also illustrates the danger of gas meters being broken/torn from the building, resulting in possible explosions. This image shows metal panels that were pulled off the roof from snow and ice.

30 Alternative Roofing Materials Do other roofing materials work any better? Asphalt Shingle Roofs: Ice dams and icicles can form on asphalt shingle roofs, plus sliding snow and ice can damage the shingles. The asphalt shingle roof didn t stop sliding snow and ice. Sliding snow and ice ripped off the asphalt shingles at the eave of this roof.

31 Alternative Roofing Materials Tile Roofs: As a result of sliding snow and ice, the dormer side of this tile roof sustained considerable damage.

32 Alternative Roofing Materials Wood Shake Roofs: Snow and ice can still move on wood shake roofs, causing damage to the roof itself or to property below. Snow and ice movement damaged the valley and rake. Snow and ice that fell from the roof broke the deck railing.

33 Alternative Roofing Materials In summary, all roofing types have problems associated with snow and ice. Metal Asphalt Tile Wood Shake

34 Snow Retention: Dormers If all roofing materials shed snow, how can we retain the snow? Dormers, an often-used solution, are designed to hold the snow and ice in place, minimizing the possible locations for snow and ice to fall. They are used to shield certain locations (such as entranceways of homes and buildings) to protect those who will be directly underneath, who are susceptible to the dangers of falling snow and ice. Multi-level condo in mountain area asphalt shingle roof (slope of 4/12) with dormers

35 Snow Retention: Dormers The problem with dormers is that ice dams can build up in potential danger areas (indicated below), leading to leaks and damage. They also stop ventilation at the dormer and further up the roof. Hence, dormers are not always an effective solution and often require considerable yearly maintenance. Points of potential danger

36 Snow Retention: Dormers This image shows that although the dormers have isolated the areas to which snow is shed, huge icicles have formed at the eave that present tremendous damage potential. This dormer protected the walkway, but the sliding snow and ice damaged the metal paneling.

37 Snow Retention: Snow Brackets / Snow Fences Other types of snow retention devices include snow brackets and snow fences. Snow brackets lie directly on the roof s surface. Standing seam snow fences clamp onto a metal panel s seam to avoid penetration into the roof s surface; deck mount snow fences attach to the rafter or truss. Snow Bracket: Designed to hold snow in place to prevent glacial movement. Snow Fence: Designed to prevent avalanching snow.

38 Snow Retention: Snow Brackets / Snow Fences Snow brackets and snow fences are widely implemented in Europe as a means of preventing roof damage due to the sliding of snow and ice masses that accumulate on roofs during winter months in alpine regions. However, these snow retention devices can fail if the correct engineering practices and the proper installation methods are not utilized. Presented in subsequent slides are examples of system failures. Note that we will address the engineering and installation considerations of these types of snow retention devices further along in the presentation.

39 Snow Retention: Snow Brackets / Snow Fences Though snow brackets are very strong, without proper engineering and installation, they often fail on all types of roofs. Snow bracket failure on slate roof Snow bracket and snow fence failure on asphalt shingle roofs

40 Snow Retention: Snow Brackets / Snow Fences Even with the installation of quarter-inch plate steel snow brackets, the eaves and roof sustained damage from sliding snow and ice because of lack of engineering of the entire system.

41 Snow Retention: Snow Brackets / Snow Fences Snow fences used alone on these roofs were not able to prevent the damage caused by snow and ice.

42 Heavy Snow Loads on Roofs There are building requirements for the live load in each building location. Are building costs lowered by increasing the slope? No, the costs are increased because of the increase of labor and materials. It is more labor intensive to work on steep slopes. How much are the building costs reduced by the limited load deduction from shedding the snow? Minimal savings. Are buildings strong enough to support the live load weight? Yes, today s structures are engineered to a safety factor of 50 years. So unless there is a 100-year storm, the structure is usually strong enough.

43 European Design Strategies: Opposite of the U.S.

44 European Design Strategies: Introduction The European solution to snow and ice revolves around these key points: Use low-slope roofs in mountainous regions. Stop ice dams by equalizing the roof temperature and outside temperature. Use ventilated roofing systems that incorporate more insulation with greater R-value. Hold snow on the roof with snow retention brackets to create an insulating blanket.

45 Europe s Strategy vs. U.S. / Canada s Strategy As illustrated below, Europe s design strategy is exactly the opposite of what we do in the U.S. and Canada. They choose to use low-slope roofs in mountainous regions to prevent damage to the roof, as well as to retain the snow on the roof as an insulating blanket to promote energy efficiency. Furthermore, by retaining snow on the roof of a building and allowing even snow melt-off, injuries to residents/guests and property below the roof can be avoided, saving money and limiting the possibility of personal loss. This design strategy allows more architectural freedom for windows and entrances into buildings. On low lands, steep slopes with tiles are used to facilitate water egress.

46 Reducing Heat Loss Reducing heat loss from the roof of a building helps to prevent ice dams and minimizes the chances of damage to the roof via sliding snow and ice. The solution is to equalize the temperature of the roof surface to the outside ambient temperature. In Europe, they achieve this by using ventilated roof systems (known as cold roofs) that feature greater attic insulation. Installing more insulation with a higher R-value (no less than R-50) results in less heat loss at the top of the roof.

47 Proper Ventilated Roofing Systems

48 Proper Ventilated Roofing Systems: Introduction Venting below the roof deck increases ventilation and energy efficiency and is commonly practiced in Europe as a solution to ice dams and condensation concerns. Features of a Simple Cold Roof A ventilated system provides greater air movement: cooler air enters at the eave while warmer air escapes through the ridge. Venting below the roof deck equalizes the roof temperature so snow does not melt and re-freeze at the eaves. Cold Heat

49 Cold Roofs Condensation occurs when dew point is reached. A ventilated system provides a means for water vapor to escape before it condenses in an attic or on the backside of a roofing material. Dew Point Cold Vapor

50 Problems with Cold Roof Systems Problem 1: Inadequate size of intake venting Many factors play into the proper design of a ventilation system, including determining the height of the air space needed and the size of the input and exhaust. When the ventilation inlet and outlet is not properly sized, the cold roof system will not work. This chart shows the recommended inlet and outlet dimensions, expressed in inches per running foot, based on rafter length and roof slope. The image shows a soffit vent that is too small for this roof, meaning the inlet is not sufficient for the roof. Intake Vent

51 Problems with Cold Roof Systems Problem 2: Duct size is too small Duct refers to the air space that moves the hot air through the roof from the eave to the ridge. This chart indicates the proper duct size based on the roof pitch and height of the vertical batten boards.

52 Problems with Cold Roof Systems Problem 3: Walls are not vented Walls must be vented; an outlet is always required, even at headwalls. Failing to provide an outlet can result in problems with the cold roof system. Roof venting with clerestory windows

53 Problems with Cold Roof Systems Problem 4: Insulation at plate line blocks air When installing insulation, a baffle must be installed to maintain air intake into the attic. This image shows how airflow is blocked as a result of improper installation.

54 Problems with Cold Roof Systems Problem 5: Combining gable vents with eave and ridge vents If eave vents and ridge vents are used in conjunction with gable end vents, problems will ensue: the gable end vent becomes an inlet instead of an outlet. The gable end vent acts as an intake, drawing moisture and snow into the attic. As the gable end vent pulls in more air than the eave vents, unequal temperatures throughout the attic result in hot and cold spots which create ice dams.

55 Correct Ventilation These images clearly demonstrate the effectiveness of proper ventilation of a cold roof system. Situated in Sun Peak, Canada, these roofs are only 100 yards apart. Not Vented Vented

56 Snow Brackets & Snow Fences

57 Snow Brackets & Snow Fences: Introduction Earlier in the presentation, we introduced the subject of snow brackets and snow fences and showed several examples of system failures. In this section of the course, we will discuss the reasons why these snow retention devices can fail and present the proper engineering considerations that are required for a successful installation. Left: Ventilated system with snow brackets Right: Non-ventilated system with no snow brackets

58 Why Snow Brackets & Snow Fences Fail Poor Engineering The most common reason why snow brackets and snow fences fail is that they are not properly engineered to the roof system. When designing a snow retention system, factors change from project to project: the slope, roof type, sheathing type, and roof snow load. If the snow retention system is not engineered for the variables of the project, it can fail. Roofing Material is Inadequately Secured for the Shear Created by Sliding Snow If the roofing material is not securely fastened to the deck (particularly on standing seam metal roofs), added weight can cause the metal roof to slide off, along with the rest of the roofing material and snow retention system. Screw or Fastener Pullout The thickness and type of the sheathing determine the fastener pullout strength. When designing a layout, ensure the snow retention manufacturer tests the products for these variations.

59 Why Snow Brackets & Snow Fences Fail Fastener Does Not Penetrate the Sheathing The fastener/screw must penetrate the sheathing, otherwise the snow bracket will not have the holding strength for which it was designed. Installation Failure Always ensure that the snow retention system is installed according to the manufacturer s specifications. If the placement and maintenance instructions are not followed, the system may fail. Plastic Bracket Failure UV rays damage the clear brackets, turning them yellow with cracks. These cracks make the brackets brittle, resulting in failures.

60 Why Snow Brackets & Snow Fences Fail Adhesive Failure There are several reasons why adhesives fail. The adhesive will not bond properly if the surface is not dry, or free of dust, dirt, oil, and waterproofing. If the temperature is not above 40 F, the sealant will not cure. The snow guard system may fail if a load is placed on it before the 28-day cure time.

61 Proper Engineering & Installation Considerations Due to the lack of code requirements pertaining to snow retention systems in the United States and Canada, proper engineering and installation of these devices is critical to avoid system failure. Listed below are the considerations that require discussion with either the snow retention system manufacturer or an engineer. Proper Engineering What is the bracket or fence attached to and what it is made of? What is the pullout of the fastener? What is the fail point of the bracket? What is the slope of the roof? What is the ground snow load? What fasteners are being used? Proper Installation What is the bracket layout? What is the proper physical installation method?

62 Determining the Correct Number of Snow Brackets How does one establish the number of brackets required for a project? The two main factors determining the correct number of snow brackets are the amount of snow at the project location (ground snow load), and the slope or pitch of the roof. This is a chart from Europe that shows the number of snow brackets needed per square meter based on the roof s slope and the ground snow load.

63 Determining the Correct Number of Snow Brackets These graphs are examples of asphalt shingle snow brackets installed on different sheathing materials. Note that more snow brackets are needed when attaching a snow retention solution to wafer board.

64 Snow Bracket Installation Brackets should be spaced throughout the roof from eave to ridge in a staggered pattern. Snow Bracket Type A for Tile Roofs

65 Snow Fence Installation A snow fence is mounted to the roof in rows beginning at the plate line and then repeating approximately every 20 feet from the eave to the ridge, based upon area snow load and roof slope. Snow fences are most effective when used in conjunction with snow brackets. The two most common reasons why snow fence systems fail: 1. The fastener pullout from the rafters is not sufficient for the snow and shear loads. 2. The layout did not specify enough brackets or fasteners for the loads required. Examples of Snow Fence Types

66 Example of Proper Application in Europe Brackets Snow Fence

67 Example of Proper Application This is a ski resort in Big Sky, Montana. The structure on the left has not been re-roofed. The structure on the right has been re-roofed with tile using proper ventilation combined with the installation of snow brackets.

68 Example of Proper Application If you look closely at this image, you can see a space between the blanket of snow and the roof s surface. This system allows for the melted snow to drain properly. The snow brackets are still frozen three inches in the snow mass, stopping the movement of snow. These brackets have been engineered to the roof system for pullout and to withstand the weight of the ice and snow.

69 Example: Partial Installation of Snow Brackets In this example, snow brackets were installed on the left side of the structure only. Notice how the snow has remained where the brackets were installed. The right side, having no snow retention devices, has snow sliding downwards (blue arrow).

70 Example: Partial Installation of Snow Brackets These images of the same structure shown on the previous slide show how snow and ice under the eave is extending beyond the roof, threatening damage to the roof and possible injury to people below. In the picture to the right, snow and ice has broken off at the eave in the area having no bracket.

71 Benefits of Snow Brackets & Snow Fences In closing, we provide a summary of the benefits of designing with snow retention systems, followed by a recap of the advantages of combining these devices with a properly engineered roof. Benefits of Snow Brackets/Fences Stop damage to roof from sliding snow and ice Allow safe access all around the building Provide even distribution of the weight from snow and ice Provide even snow melt-off Create an insulating blanket Provide more architectural design freedom

72 The Components & Benefits of a Successful Roof Installation Proper Ventilation No ice dams or icicles No roof leaks from ice dams No condensation concerns Proper (Engineered) Snow Retention System Reduced snow removal Design freedom No damage to valleys, eaves, rakes or penetrations Insulating blanket energy saver Minimize risk of damage to property and injury to people below the roof Proper Insulation (minimum R-50) Energy savings

73 Review Now, participants will be able to: State the common roofing challenges that are unique to cold climates Discuss the advantages and disadvantages of the everyday solutions to snow and ice difficulties Compare the accepted roof design practices in Europe to those in the United States and Canada Explain the concepts and effectiveness of roof ventilation and snow retention in reducing snow and ice problems List the factors to be considered in the proper engineering of snow retention devices

74 Roofing Solutions for Alpine Regions TRA Snow & Sun 1657 S 580 E American Fork, UT Tel: Fax: Toll-Free: info@trasnowandsun.com Web: Roofing Solutions for Alpine Regions tra07a An AIA Continuing Education Program Credit for this course is 1 AIA HSW CE Hour 2013 TRA Snow & Sun. The material contained in this course was researched, assembled, and produced by TRA Snow & Sun and remains its property. Questions or concerns about the content of this course should be directed to the program instructor. Ron Blank & Associates, Inc. 2013