How to Tell if You Have Adequate Roof Ventilation in Your Soffits
Proper roof ventilation is an essential component of ice dam prevention. It is possible to get ice dams even when you have normal or even above average insulation in your attic. Passive heat loss will build up in your attic due to the stack effect (tendency for heat to rise). Therefore it’s important to let the attic breath so that warm air can be evacuated properly. Here is a quick way to check your attic for proper soffit, or eave ventilation:
Go up into your attic and look around in the dark. Here is what you should see:
If you can see a lot of light through your eaves (A) you have half of your attic ventilation addressed. The other half is the ventilation up near the peak of the roof either in the form of box vents mounted to the roof deck or an open ridge vent along the majority of the ridge. It’s common to see the eave ventilation clogged with blown in insulation. Another common hindrance to proper eave ventilation is compressed or collapsed air chutes. This Eden Prairie home had problems with air-sealing and attic ventilation. We fixed the problems.
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.
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.
The Truth About Gutters and their Relationship with Ice Dams
In 2011, Ice Dam Company owner Steve Kuhl wrote a nationally published article about ice dams for the Journal of Light Construction. One of the topics that receieved the most attention was the notion that gutters have nothing to do with ice dams. Here is a deeper look at that assertion.
There is a great deal of confusion and misinformation about the relationship between gutters and ice dams. Many people are under the misconception that gutters cause ice dams or that gutters filled with ice can cause water to back up into homes. Not true. We repeat. Gutters have nothing to do with ice dam formation or severity. For this reason, buying systems that heat gutters in order to prevent ice dams is a total and complete waste of money.
We know that ice dams occure when:
Escaped heat from the inside of the home warms the roof deck.
Melting snow results in water that runs down to a cold, unheated area of the roof (frequently the eave, as shown below).
That water freezes, forming ice. After many of these cycles, that ice piles up to form an ice dam.
Study the illustrations below. These are identical eave designs, one with gutters, the other without. The Area B in the diagrams below is referred to as the ‘cold edge’ of the eave because heat from the interior of the home doesn’t travel that far. Fact One: Whether or not a home has gutters, a cold edge will still exist and this is where ice dams form. Fact Two: leaks from ice dams occur in Area A, at the leading, top edge of the ice dam where water–with nowhere else to go–is forced up under the roofing material and into the home. Put another way, if the home in Figure 2 had bad leaks inside, those leaks would not be eliminated whatsoever if we took a chainsaw and cut off the gutters along the red dashed line (C). Moreover, if we heated the gutters using a fancy electrical system, the likelihood of ice dams and the subsequent leaking would NOT be affected. Spend money on heat cables for the lower edge of your roof, not on heating the gutters only. High quality heat cables can be quite effective in preventing ice dams.
Figure 1: Ice Dam Without Gutters; Figure 2: Ice Dam With Gutters
None of this is to suggest that ice in gutters are harmless. We have seen many gutters damaged or destroyed by ice dams and that is a problem most homeowners would like to avoid. The point here is that, all else held equal, if a home is likely to get ice dams the addition or deletion of gutters will be of no consequence to the formation or severity of said ice dams. Likewise, for this reason, installing heated gutters or adding heating systems to existing gutters will have no affect whatsoever on the occurrence or severity of ice dams.
To read more Case Studies click here.
Where Do Ice Dams Normally Happen on Homes? A List of the Most Common Ice Dam Locations
Where ice dams happen…and don’t happen:
Ice dams seldom occur over unheated areas such as garages and porches (A).
The valley areas of dormers frequently get ice dams (B).
Ice dams often occur both below and above skylights. Ice dams above skylights are hard to see from the ground, making them some of the sneakiest to discover (C).
Any openings through the roof – such as pipes and vents – are a good place for small ice dams for form (D).
Valleys are very common areas for ice dam formation. It is important to never use hammers or chisels near valleys as the difference between a thorough ice removal job and valley damage is fractions of an inch (E).
On roofs with a low pitch (angle) even a 1-2″ ice dam can cause significant leaking and interior damage (F).
The eaves edge is the most common place to see ice dams. 80% of the dams we remove are found here (G).
Interior rooms with vaulted ceilings are frequently associated with large ice dams. Bathrooms are often the worst. If you had recessed lighting to a vaulted ceiling, you are much more likely to have ice dams (H).
Ice dams occasionally form around chimneys and furnace flues. Any place heat escapes through the roof line. Ice dams in these locations can be very, very small and still cause leaking (I).
I’ve been working on a new graphic to describe the basics for homeowners in Minneapolis to identify a problematic ice dam. It’s true that some ice dams cause no problems. The key consideration in determining whether or not an ice dam is a current problem is all about where you see ice. Study this drawing closely and you will see that any ice behind the facia is a bad sign. Ice through the soffit, down the exterior wall or through the window frame is very bad thing. Leaks caused by ice dams minneapolis
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: