How Does Eave Style and Construction Method Affect Ice Dam Formation and Severity?
Eave Construction and Heat Transfer
We have discussed the relationship between eave depth and ice dams previously (Case Study #10). Now let’s look into how different construction methodologies affect the likelihood and severity of ice dams in residential and light commercial construction.
For obvious reasons, eaves are a central topic in the world of ice dams. After all, that’s where 98% of ice dams occur, with the other slice of happening in areas including valleys, flat roofs and low pitch roof pans. There is a reason why older homes are affected more by ice dams then newer homes. That relates primarily to the nature of how the eaves are assembled.
Our grandparents didn’t understand the importance of insulation and ventilation as it relates to the eave. (They were busy thinking about wars and famine). In short, there needs to be enough room between the top plate of the wall and the underside of the roof decking to allow for adequate insulation and ventilation. We know that ice dams are created in large part by the escape of heat from the interior, conditioned spaces of a home into areas where that heat is not supposed to be. Namely, it is not supposed to be in the roof cavity next to the roof deck. Homes with less insulation near the eaves are troubled with ice dams far more than those with adequate insulation and ventilation. In Diagram B, we see an example of common eave construction in modern homes. Notice that the distance between the top plate and the roof deck is quite generous. This is commonly referred to as the heel height. In Diagram A, which shows a hand-framed eave, there is virtually no space for insulation or ventilation. Consequently, heat can easily pass from the room below to the roof system, melting the snow above.
Don’t despair if you have old school eaves. There are options to help prevent or at least minimize the likelihood of ice dam problems in the future. Those can be broken down into two broad categories; Architectural and non-Architectural Solutions. In short, Architectural solutions involve modifications to the thermal performance of the home, including insulation, ventilation and, most importantly, sealing air-leaks into the attic or roof truss cavities. The most effective Non-Architectural solution is simple, cheap and effective. Install a high-quality, self-regulating heat tape system on affected areas.
Ask any experienced residential designer, classic architectural styles are difficult to execute with adequate heel heights. Talented designers can pull it off, but they need to think outside the box. High-end, architecturally refined homes don’t look right with clunky, new construction eaves.
You may notice that the home shown below has some icicles (sarcasm intended). Obviously, when something like this occurs, it is quite likely that you have ice dams as well as a giant insurance claim from the subsequent water damage it has caused. The fact is, the vast majority of the ice dam steaming projects we complete are not on homes with monster icicles. When we arrive we often see quite modest icicles from the ground. The relationship between icicles and ice dams is not difficult to understand when you study the problem for awhile. This Case Study digs into the topic of icicles and ice dam life cycles.
Do icicles mean ice dams? The short answer is NO. While icicles on the edge of the roof are often a precursor to ice dams, they are not always present when ice dams begin to cause leaks through a roof system. Ice dams and icicles are part of the same accumulation but they are not the same thing by any means. This brings us to the normal life cycle of an ice dam.
The characteristics of ice dams change over time. The typical lifespan of an ice dam rangers from a few days to a few weeks. During that time it may get thicker or thinner, icicles may appear and disappear on its’ leading edge, and it may be almost completely hidden under snow or partially or completely exposed. For this reason, there is a big different between a young ice dam and an old ice dam in terms of the presence of icicles. Very young ice dams often have visible icicles on their leading edge. Over the following days most ice dams tend to grow more in depth than thickness, meaning the ice migrates higher up on the roof plane (refer to Case Study #06 for more information). Icicles on more mature ice dams tend to melt away from the affects of direct sunlight or warmer outdoor temperatures. However, while the telltale icicles may be missing, the mass of the ice dam is left behind, frequently hidden under a blanket of snow.
The photos above (A) and (B) demonstrate this phenomenon on two St. Louis Park homes. Virtually no traditional signs of an ice dam and yet you see water leaking down the exterior wall, through the siding and in the wall cavity itself. Bad news.
Case Study #16 examines the important topic of ice migration, from icicles to the interior of your home.
The Relationship Between Sunshine and Ice Dam Formation
Ice dams happen when there is a section of roof that is above freezing (32°) where roof snow melts which then drains to an area that is below freezing, usually the eaves, where it refreezes. The source of this temperature differential is usually the result of interior heat loss, specifically via air leaks and insulation issues. In fact, according to our experience, 95% of our client’s ice dam problems can be mitigated or eliminated altogether through the modification of the thermal characteristics of the home. Still, we see ice dams on certain homes for reasons outside the scope of it’s architectural deficiencies. Homes with what we might call nearly perfect air-sealing, insulation and ventilation still get ice dams. This Case Study describes such a situation.
The winter sun hits Minnesota homes (and all homes in this latitude) at a low angle during the winter. The result is that certain roof slopes never see direct sunlight while others get hit quite directly. The above illustration demonstrates an ice dam situation that relates to the heating effects of the sun. Solar radiation warms the roof slope on the dormer (1), the resulting melt water drains to an area of the home (2) that never sees direct sunshine where it refreezes to form an ice dam (3). These are particularly challenging ice dams to prevent. Often times heat tape, also known as heat cables, are the only affordable option.
In my travels around Minneapolis today looking at ice dam prevention jobs, I noticed a number of homes that already exhibit signs of ice dams. To be more specific, I noticed water and ice coming down the siding and in through the eaves on a number of homes such as the one shown here. This represents a clear signal that water is backing up behind an accumulation of ice on the roof and going where it’s not supposed to go. Want more signs of ice dam issues, click here. With another snowstorm approaching on Christmas, I’m predicting that this might be another troublesome year for Minneapolis homeowners relative to ice dams.
Ice dam removal Minneapolis
What can you do? Unfortunately, once ice dams form and begin to cause problems, the only answer is to have them professionally removed. We use true steamers, machines that superheat water to steam. How do you tell the difference between a high temperature pressure washer used by competitors and a steamer? It’s simple. Does the gun have a trigger or not? If it has a trigger, it is simply NOT a steamer. IDSAFE, a unique organization whose entire purpose is to educate property owners on ice dam steaming, can be found here. The Ice Dam Company is a proud member of IDSAFE. All of our machines have been verified to meet the standards of true ice dam steamers, unlike two of the largest ice dam removal companies in the Twin Cities. (You know who you are!).
Of course the better answer to ice dam removal in Minneapolis is ice dam prevention. We engage in more ice dam prevention work than anybody in the United States, employing both architectural solutions and non-architectural solutions which includes heat tape and heat cable, insulation, roofing, remodeling and general home performance inspections.
Our sister company, Kuhl’s Contracting, engages in the hundreds of attic insulation retrofits and reroofing projects every year in Minneapolis and surrounding communities to address the underlying causes of ice dams. Kuhl’s Contracting also installs heat cable and heat tape on commercial properties and residential properties all over Minnesota. We are proud to sell HeatTapePro, made by Radiant Solutions Company, a premium self-regulating commercial grade heat cable available on a number of online retailers including Amazon. HeatTapePro can also be purchased at The Heat Cable Store, an online direct-to-consumer website that sells a number of heat cable and heat tape products by different manufacturers. Of course, you may also buy HeatTapePro here, at The Ice Dam Company Store.
Click hereto schedule an appointment with our ice dam removal or ice dam prevention teams.
Ice Dams on Mansard Roofs Can be a Seriously Big Headache to Remove
Roof Styles Affect Ice Dam Severity
As discussed in Case Study #16, there can be some serious problems if homeowners decide to remove snow from only a portion of the roof plane affected by ice dams. We call it the ‘Double Dam’, which refers to the fact that ice dams can grow much further up the roof when only lower sections of snow are removed (commonly done with roof snow rakes because they can’t reach high enough on the roof).
Mansard roofs, such as this one from Edina, Minnesota, can create massive ice dams when the steep pitch (B) is cleared of snow. This is amplified when the slope has directional bias towards the north because the sun will not help melt the ice as it accumulates. In the photo, below, we see two ice dam problems on this Edina mansard roof. The traditional location (A) is exacerbated by the low roof pitch (Case Study #09 explores the relationship between roof pitch, or roof slope, and ice dams). Area B has an ice dam that covers the entire span of the roof slope. This took many hours to remove even with our commercial ice dam steaming equipment.
Which Ice Dam Do You Want?
Ice dam #1 is not the one you want. Ice dams like this take hours to remove with steam, which is the most efficient and safe method for removing ice dams. This ice dam is thin but it has grown many feet up the roof. Ice dam #2 is an easier problem to resolve.
What Frost Melt Patterns Can Tell You About Your Home
Insulation and Ice Dams
At their most fundamental level, ice dams are the result of the interaction of heat loss and snow on your roof. An experienced Ice Dam Company Thermographer can use photos like these in conjunction with infrared imaging to see the weak points in your home’s thermal envelope. If you have a moment on the next frosty morning, take a few photos of your roof from a few angles before the sun hits it. Those photos may end up saving you time and money if you are hoping to fix the root cause of ice dams and home heating inefficiencies. Of course, ice dam prevention involves more than simple insulation job, but understanding the basics through frost pattern analysis, thermal imaging and a good site inspection is a great place to start.
Observations on the Effectiveness of Ice Melting Compounds on Ice Dams
Can Dad’s Old Pantyhose Save Your Home?
Over the past 25 years we have seen many different methods used to address ice dams. More often than not those measures are reactive, not proactive. Thus is the case of the lowly salt sock, otherwise known as a cloth tube of some sort filled with an ice melting compound of some sort.
Salt socks work on the principle that the ice melting compound is contained in a linear form which, when laid across an ice dam, will melt a channel through the ice. That path would then presumably be used as an escape route for water that may tend to get trapped behind the ice dam. The purpose of the sock is to hold the ice melting material in place, thereby concentrating the melting action. (Yes, that was a cross-dressing joke about dad).
Concept Vs. Reality
The only problem with the sale sock is that it simply doesn’t work. The examples below show typical results. In theory, salt socks seem like a great idea. In practice, however, using them to deal with an ice dam is not practical. One problem is that in order for them to do their intended job (Cut channels through the ice dam) they need to be placed somewhere meticulously, every 16″ or so. That’s a lot of socks. Next, we see that they tend to only melt about 90% down through the ice dam and then putter out. We have no idea why they don’t melt a clean slot right down to the roofing material but it never happens? The net result is that the melt water that causes ice dams, and the leaks that follow, still can not find a way off the roof. That’s bad. Perhaps the most dangerous part of using salt socks (outside of balancing on a ladder to position them all perfectly) is that they create a false sense of hope. Homeowners tend to ‘install’ them and not look back. That is, until water is dripping through the ceiling.
These salt socks didn’t melt down to the roof, resulting in massive water damage to the interior walls. (Can you find the ice on the siding?)
Sad and ineffective pantyhose, encased in ice.
Here’s the bottom line: Don’t use salt socks or pantyhose filled with ice melting compounds to manager your ice dam problem. It simply doesn’t work.
How Roof Pitch (Roof Slope) Affects the Impact of Ice Dams on Standard Residential Construction
Fact: The Flatter the Roof, the Less Ice it Takes to Cause Problems
As discussed in previous Ice Dam Company blogs and Case Studies, there is a strong relationship between roof slope and the timing and likelihood of damage as the result of ice dams. Specifically, low roof slope areas are far more susceptible to damage by small ice accumulations than areas of steeper slope. Why? It comes down to basic geometry. Study the diagrams, below. You can see that the high slope roofs (C) require a pretty thick ice dam to form before water will begin leaking into the home. Eave depth plays another important role. See Case Study #10 for more information.
Ice dams create leaks when melted water from higher on the roof slope hits a dam of ice and is forced to travel backwards, up and under the plus of the roofing system (typically asphalt shingles). When that backward motion occurs outside the plane of exterior wall (dotted red lines in diagrams), the water runs down the exterior wall or through the soffits (zone indicated by happy face). As soon as the water falls on top of the top plate of the wall it seeps down through the wall causing damage to insulation, finishes and flooring (zone indicated by sad face). Truthfully, water coming through your soffits is nothing to be happy about. The next step is the interior of your home so it is considered an emergency in terms of the progression of the ice dam. As mentioned before, if you see ice coming through the soffit or down the exterior wall, it’s time to get that ice dam removed.
Wayzata Residence with Low Pitch Roof Suffers the Consequence
Seen below is a home in Wayzata, Minnesota where we steamed an ice dam a couple of years ago. The construction assembly was typical 2×6 walls, 12″ eaves, 6″ facia with a 2/12 roof pitch. From the ground, no ominous, threatening icicles could be seen, just a couple of pathetic whiskers of ice off the face of the gutter through the soffit (D). Pan out and you see that the entire exterior wall was bleeding ice through the siding. This is bad. This home had massive damage to the interior insulation, drywall and flooring systems.
As discussed in Case Study #06, low pitch roofs also tend to create ‘deeper’ ice dams (E), where the ice has grown further up the roof. Deep ice dams take far longer to remove.
No icicles does not mean no ice dams.
Low pitch roofs present higher risks in terms of how quickly small ice dams can cause big problems.
Ice or water coming down the exterior wall in below freezing conditions is bad. Very, very bad.
How to Figure Out if the Leak is from Ice Dams or from Something Else?
As discussed in Ice Dam Company Case Study #03, ice dams can form in many locations on the typical home. The eave (lowest edge of the roof) is the most common area for ice dams but we find them around other areas including skylights, in valleys and in low-pitch roof pans and saddles. Many times a winter we get calls from concerned property owners who are experiencing leaks – or at least that is what appears to be happening – because they see water, moisture or discoloration on the ceiling. It’s logical, after all, to assume the roof is leaking when one sees that sort of thing. But the fact of the matter is that winter roof leaks can be attributed to a few potential sources. Here are a few of the common sources:
Is the leak in close proximity to a plumbing fixture, water supply or drain line? The most common sources of plumbing related leaks in homes are associated with failing shower pans, over-flowed bathtubs and faulty caulking or bad wax rings around toilets. Water can travel many feet from the source before it finds the path of least resistance and shows up. It’s typical to see water coming through penetrations through the ceiling such as recessed lights and at sheetrock seams many feet from the leak source. Plumbing failures can occur at any time during the year. When they happen in the winter, homeowners often assume its an ice dam. Plumbing leaks can be tricky to find and fix. Our favorite tool to find this type of leak is the thermal imager. This is a special camera that sees through walls and ceilings to detect differences in temperatures.
Attic Frost and Attic Condensation
If possible, it can be tremendously helpful to peak into the attic. A healthy attic with good ventilation (Ice Dam Company Case Study #17) should not present moisture or frost on the framing members or roof decking. The photo, right, shows a poorly insulated, ventilated and air-sealed attic. Notice the frost on the underside of the roof decking? This is not good. Attic frost can cause tremendous damage and is most likely to accumulate when temps are quite low (below 10°F). Warm, moist air meets the ice-cold roof deck and freezes into frost. This cycle continues until as much as 1/8″ and 1/2″ of frost has built up. When outdoor temps rise above freezing, all of that frost melts and has nowhere else to go by the interior of the house. This type of ‘leak’ is tricky because it is actually not a leak. We have seen clients spend thousands of dollars trying to resolve a roof leak that was in fact nothing more than attic condensation. Future Ice Dam Company Case Studies will discuss how we fix this issue.
Exhaust Vent Condensation
This is a very popular source of the winter roof ‘leak’ phone call we receive. Similar to attic frost-related leaks, this problem is related to the accumulation of frost inside an exhaust vent, commonly a bath vent duct where it travels through an unheated attic. A quick review of the temperature variations from the previous week is a good clue that we may be dealing with an exhaust vent condensation issue. If we had a number of days with extreme cold (highs in the single digits) followed by a thaw (highs in the mid-high 30’s) our first guess without even visiting the home is that the source of the moisture is a condensation issue, not a roof leak. Of course, a thorough site inspection is essential in confirming our suspicions. In almost all cases when exhaust vents are the culprit the leak shows up in the bathroom. Future Ice Dam Company Case Studies will discuss how we fix this issue.
Last but Not Least…Ice Dams
Do you see icicles on the eave near the leaking area? Do you see an ice dam? While not always the case, ice dam causing leaks are usually plainly visible from the ground (See Ice Dam Company Case Study #20). The steeper your roof pitch, the more ice it takes to create interior leaking (See Ice Dam Case Study #09). If you have a low-slope roof area, accumulations as little as 1″ thick can cause problems. Likewise, a heavy blanket of snow can hide the significance of an ice dam, making it hard to ascertain it’s size. Ice Dam Company Case Study #01 and #02 describe some easy things to look for in determining if you have an existing ice dam issue. In our experience, it is unusual to get roof leaks cause by ice dams when no appreciable ice accumulations can be seen from the ground. It can happen, however. It is common to see water/ice coming through the soffit or down the exterior wall when ice dams have developed to the point where they are forcing water to back up into the roofing system.
Removing Ice Dams in Minnesota: We Serve Many Areas in the Minneapolis Metro
The Ice Dam company based out of Hopkins, Minnesota, about 5 miles west of Minneapolis. We've done gutter ice removal, roof ice removal and ice dam removal all over the Twin Cities, on new houses and old ones.
Some of the more frequent places we've done ice dam services are: