Reuben's Home Inspection Blog

Ice Dams

February 11th, 2014 | 26 comments

I’ve been seeing ice dams all over the Twin Cities, and I’ve heard from a number of homeowners who are having problems with ice dams right now.  I’ve written about ice dams extensively on this blog, so I’m putting together links to my three main blog posts on ice dams in one place.  The topics are how to prevent ice dams the right way, how to prevent ice dams from the outside if you can’t prevent them the right way, and how to get rid of ice dams.  I also have few more ice dam observations; file these under “advanced ice dam prevention”.

How To Prevent Ice Dams (the right way)

Ice dams form when snow is melted on the roof, then freezes again at the eaves.  The main reason the snow melts is because heat is getting to the roof decking from the house.  Stop the heat transfer, and you’ll probably stop the ice dams.  The main way to stop the heat transfer is to have air sealing performed in the attic.  The next step is to have insufficient insulation addressed.  Finally, if venting is improper, consider fixing it… but venting only plays a small role.  Ice dams are mostly about air leaks and insufficient insulation.  Click this link for more information about preventing ice dams the right way.

Anatomy of an ice dam

How To Prevent Ice Dams from the Exterior

Roof RakeIf you live in a 1-1/2 story home in Minnesota, you probably get ice dams.  There’s not much that can be done to prevent ice dams the right way at this style of house, short of gutting the upper level and framing down, or tearing the roof off and framing up.   Homes with vaulted ceilings and other inaccessible attic spaces can also be a real challenge.  In these cases, ice dams may need to be controlled from the exterior.  The standard way to do this is to get a roof rake and pull snow off the roof.  When this is not practical, roof de-icing cables can be used, but should be considered a last resort.  Click this link for more information about preventing ice dams from the exterior.

How To Remove Ice Dams (hire a pro)

There are plenty of hack methods for removing ice dams, so I tried ‘em all out.  The methods I discuss involve an axe, ice pick, pantyhose, salt tablets, heat cables, a pressure washer, and even a blowtorch… just for fun.  I don’t recommend any of these though.  If ice dams need to be removed, hire a pro to steam them off.  Don’t let anyone near your roof with a pressure washer, or the shingles might end up like the ones shown below.

Hack Ice Dam Removal from pressure washer

Click this link for more information about how to remove ice dams.

A Few More Tips

Here are a few more tips on preventing ice dams.  These deal more with the design of a house than anything else.

Valleys Can’t Be Vented

Ventilation plays a small role when it comes to preventing ice dams, because vents can help to cool the roof temperature.  The problem with roof valleys is that they can’t be vented.  If I were to design my own house, it would certainly be a big boring box with a plain hip roof; no valleys.

Plain hip roof

Plain hip roof

Valleys Should Never Meet

Valleys can’t be vented, they have a lower slope than pitched roofs, and ice from two roof surfaces gets concentrated.  Ice dams are always the worst at valleys.  What happens when two valleys meet each other?  The potential for ice dams goes way up.  In my humble opinion, this is just plain stupid design when it comes to performance.

Valleys Meeting

Oh, and don’t get me started on what this means for water management during the summer… never mind, I already blogged about that: Have Your Builder Plan for Water Management.

Don’t vent fans through the roof

What happens when bath fans and kitchen fans terminate at the roof?  Snow melts when the fans run, of course.  This leads to water running down underneath the snow, then freezing again at the eave, or in some cases, right in the middle of the roof.

Bath fans at roof with ice dam

This can be a major contributor to ice dams, or in the case of the photo above, can be the sole cause of ice dams.  The way to avoid this is to have bath fans and kitchen fans terminate at walls, not roofs.  This also applies to clothes dryers; while it has become standard practice to put laundry rooms on the second floor in new construction homes and terminate the vent at the roof, I think this is a bad place to terminate the dryer duct.  It will melt a lot of snow, and there is usually no easy way to clean off the terminal.

Oh, and whatever you do, don’t place vent terminals for bath fans, kitchen fans, or clothes dryers in a place where the melted snow will pile up in a valley.  That’s almost a sure way to get ice dams, even if everything else is done properly.

Author: Reuben Saltzman, Structure Tech Home Inspections

          

 

How to prevent ice dams from the exterior

March 4th, 2013 | 1 comment

I’ve written about how to prevent ice dams by fixing attic air leaks and insulation, as well as several hack methods showing how to remove ice dams, but I still get a lot of questions about ice dam prevention.  For homeowners with a one-and-one-half story house or a house with a vaulted ceiling and no true attic space, correcting attic air leaks and insulation can be an extremely expensive project.

In these cases, it’s not always cost effective to fix the problems that are causing the ice dams – the ‘repairs’ might outweigh the costs of controlling the ice dams, and even if the repairs make economic sense, it’s not always in the homeowner’s budget.  In those cases, I recommend ice dam control from the exterior.

Remove The Snow

Roof RakePulling snow off the roof with a roof rake will keep ice dams to a minimum. This becomes a constant chore, but it’s better than dealing with water leaking in to the house.  Just raking the first several feet of snow from the eaves is typically enough to prevent the formation of ice dams, but in some cases, this will cause ice dams to form higher up on the roof.  The trick is to get the shingles exposed to the sun; once that happens, the sun will warm the shingles enough to prevent ice from accumulating.

Raking snow off the roof with a roof rake is a safe way of removing snow, as long as you don’t get too close to your overhead power lines.  In theory, a roof rake could cause some premature wearing of shingles by removing the aggregate, but I’ve never seen any real life evidence of this.  Some roof rakes have little wheels at the bottom that prevent the rake head from actually rubbing on the shingles.

Roof Rake

While the roof rake pictured above is the most common type, there are many other variations of this designed to make the work easier – one such version is the MinnSnowta Roof Razor®.

Removing snow from the eaves is an effective way to prevent ice dams, but it won’t work 100% of the time.  Two years ago, I inspected several houses with ice dams forming right where the snow stopped being removed.  This is not typical, but it can happen during especially cold, snowy winters. When this happens, people start to get depressed and wonder why they live in Minnesota.

Second Ice Dam

The fix for this is to have all of the snow removed.

For two-story homes where using a roof rake from the ground isn’t practical or possible, the options are to risk your life getting up on an icy roof to shovel the snow off, hire someone else to risk their life, or install roof de-icing cables as a preventative measure.

Shoveling snow off roof

De-Icing Cables

Roof de-icing cables, also known as heat cables or heat tape, should be considered a last resort when it comes to preventing roof leaks from ice dams.  De-icing cables themselves aren’t cheap, it costs money to have them professionally installed, and they’ll cost money to operate – between five and eight watts per foot.  I’ve also heard that they can damage shingles, but I’ve never seen any evidence of this.

Roof De-Icing Cables

On the flip side, de-icing cables are very effective.  When de-icing cables are properly installed and operational, ice dams won’t cause leakage.   De-icing cables won’t prevent the formation of ice at the eaves, but they’ll keep enough ice melted to create drainage channels for water.

If you choose to install roof de-icing cables yourself, here are a few tips:

  • Measure the areas where you need to install your de-icing cables first, and buy appropriately sized cables.  For a simple 15′ section of roof with no overhang, a gutter, and one downspout with an extension, you will need a 60′ heating cable.
  • The cables should extend 6″ up the roof past the exterior wall line, through the gutters and downspouts, and 2/3 of the way up the valleys.
  • Don’t bother removing the snow from your roof; you could damage your cables, and you could potentially create another ice dam higher up on the roof, defeating the purpose of the heating cables.
  • Don’t expect the snow and ice to melt the way it does in the promotional photo above.  It’s like comparing a photo of a fast-food burger to the burger that actually comes in the fast-food bag.

If fixing the causes of ice dams isn’t a possibility and safe removal of snow isn’t possible, de-icing cables or de-icing panels may be a good choice.  Sometimes this is the most cost-effective way to prevent roof leakage from ice dams.

Author: Reuben Saltzman, Structure Tech Home Inspections  Google Profile

          

How To Prevent Ice Dams (the right way)

December 11th, 2012 | 13 comments

Minnesota got dumped on this weekend with nearly fifteen inches of snow in some areas.  With hardly any snow last winter, we almost forgot what a real snow storm looked like.   I haven’t heard about any concerns over ice dams yet, but I suspect they’ll be coming very soon.  The perfect conditions for ice dams are large amounts of snow and temperatures in the teens and twenties, which is what we’re expected to have this week.

Ice Dam December 11, 2012

Ice dam at a Minneapolis home on December 11, 2012

Two years ago, many Minnesota homeowners experienced ice dams like never before.  The two things that everyone wanted to know was how to get rid of ice dams and how to prevent ice dams.  Today, the focus is going to be on prevention.

How Ice Dams Form

Because it’s been a couple of years since I’ve blogged on the topic of ice dams, here’s a quick refresher: ice dams are literally dams of ice that form on roofs and cause water to back up.  The dams form when the snow that touches the roof melts, and then that water freezes again before running off the roof.  This usually happens at the edges of roofs, but not always.  Here’s a great diagram showing how this works, courtesy of Steve Kuhl.

Anatomy of an ice dam

The best way to prevent ice dams from forming is to address the three factors in your attic that contribute to ice dams; insulation, ventilation, and attic air leaks.

Attic Air Leaks (aka – attic bypasses)

This is the largest contributor to ice dams.  In almost every house with ice dams, there will be attic air leaks directly below the beginnings of the ice dam.  Attic bypasses are passageways for warmed air to enter in to the attic space, and traditional insulation won’t fix this.  The photos below show some common attic bypasses that can be found in just about any older house.  The image series below shows how an infrared camera can be used by a home inspector or energy auditor to locate these bypasses.

Air leak identified with IR camera

The photo below shows one of the largest and most common bypasses – the space around the furnace and / or water heater vent.  Sometimes these are huge. The one shown below is relatively small, but allows a lot of air to leak up in to the attic.

Bypass at furnace vent

In the photo below, you can see several holes in the top plate of a wall that were drilled for wires to pass through.  These holes could all be easily filled with spray foam, but finding these holes all over the attic would be a challenge without first removing the insulation, or performing an infrared inspection with a thermal imaging camera.  The insulation had to be pushed aside to find these and take this photo.

Bypasses at bore holes

With additions, the transitions between the ‘new’ and ‘old’ construction seem to always be sources of attic bypasses.  The gap below was easily identified with the use of an infrared camera, but a lot of insulation had to be moved to get to the bottom of it.

Bypass at addition

When plumbing vents enter in to the attic, the space around the vents needs to be sealed.  This one obviously wasn’t.

Bypass at plumbing vent

Some older houses have whole-house fans that are designed to run on hot summer nights; these fans are gigantic sources of heat loss, because they’re usually not insulated or sealed up.  The photo below was taken from inside the attic without a flash.  There’s some crazy heat loss occurring there, and as you might imagine, there was a huge ice dam nearby.  No infrared camera needed to find this.

Bypass at attic fan

Old ramblers often have stairwells with nothing covering the top – you could fit an entire family in this dead space.  It looked fine in the attic until the insulation was pulled away to show that this area was completely open.

Bypass above stairway

The space around masonry chimneys is also a notorious location for attic air leakage.

Bypass at chimney

What makes many of these attic bypasses so difficult to locate is that they’re almost always buried in insulation.  Finding these buried air leaks can turn in to a guessing game for someone without a lot of experience in digging through attics.

If you have these types of bypasses in your attic, my recommendation is to have an insulation contractor seal the air leaks.  They’ll know where to look and how to seal them properly.  If you want to do the work yourself, download this guide from the Minnesota Department of Commerce – Attic Bypasses, and this guide from Building Science.com – Attic Air Sealing Guide and Details.   These guides both give some excellent information on how to properly seal all of these air leaks yourself, and they discuss other concerns that need to be considered when performing attic air sealing, such as combustion appliance safety, knob & tube wiring, and vermiculite insulation.

If you plan to have more insulation added to your attic, have the air leaks sealed first.  This can’t be stressed enough.  This is the driving force behind ice dams, and is even more important than having insulation added.   If your home was built before about 1990, it’s almost a guarantee that you’ll have attic bypasses that need to be sealed all over the attic.  Unfortunately, many insulation contractors just add insulation on top of what’s already there without sealing the air leaks.

Insulation

This is a basic concept that everyone understands; you need insulation in your attic.  If there are voids in the insulation, they need to be fixed.  If there isn’t enough insulation, add more.  The current minimum requirement for new homes in Minnesota is insulation values between R-38 and R-44.  This means about 10″ – 12″ of cellulose, or 12″ – 16″ of loose fill fiberglass, depending on the manufacturer.

I’ll follow up with another post on different attic insulation methods and challenges with insulating older attics in the near future.

Ventilation

Having adequate ventilation for the attic space will help to keep the roof surface cold, which will help to prevent snow from melting, which will help to prevent ice dams.  Ventilation is required for attics, but it’s the last thing that should be considered when troubleshooting the causes of ice dams.

The traditional way to ventilate an attic was to have half of the ventilation provided by vents installed low, such as soffit vents, and the other half at the top, such as ridge vents.  According to information shared at a recent seminar put on by Dr. Lstiburek here in Minnesota, a better way to ventilate the attic is to make the ratio about 1/3 high and 2/3 low.  This means way more soffit venting than ridge venting.

If the soffit vents are dirty, clean them or replace the grills if they’re painted shut.  Grills are cheap.  If the soffit vents are blocked with insulation, install air chutes at the eaves inside to prevent the insulation from blocking the vents.

Reuben inspecting ice damsWhen all else fails…

If you’ve already done everything you can think of to fix your ice dams but they keep coming back, or you hired a contractor to fix your ice dams two years ago but the ice dams have returned, call a home inspector or an energy auditor.  We look at this stuff every day, and some of us even specialize in ice dam inspections.

Reuben Saltzman, Structure Tech Home Inspections

        

Thinking of adding more insulation to your attic? Read this first.

February 15th, 2011 | 9 comments

If you’re tired of dealing with ice dams and you’ve decided to finally get your attic re-insulated, please read this first.  You might save yourself a lot of time and money.

Over the past two months, a large portion of my business has been ice dam inspections in Minnesota.   For most of these inspections, I was hired to determine the cause of the ice dams and to recommend a solution.

I feel extremely fortunate to have spent the past two months doing this.  During this time, I’ve dug through a ridiculous amount of insulation in attics.   I’ve come home with itching arms, neck, cheeks, and red eyes (I’m pretty sure fiberglass insulation was invented by a very evil person).  Most importantly, I’ve learned quite a bit about attics.

I’d like to share the complaints I’ve heard from homeowners, what I’ve learned, and what I’ve recommended.  My goal is to help homeowners benefit from my experience.

What I’ve Heard

I had more insulation added to my attic after last winter, but the ice dams are just as bad as they were last year, if not worse!

I heard versions of this statement over and over from frustrated homeowners.  Just adding more insulation typically won’t fix ice dam problems.  I’ll come back to this.

I just had a new roof installed, and the roofer said they laid down a rubber membrane going six feet up.  Obviously my roofer is a liar, because if they really had laid down a rubber membrane like they said, my roof wouldn’t be leaking.

I’ve heard so many versions of this!  The ‘rubber membrane’ that everyone refers to is actually an underlayment that’s commonly referred to as an ice and water shield.  This underlayment is required by the Minnesota State Building Code; it must be installed underneath the shingles and “extend from the eave’s edge to a point at least 24 inches inside the exterior wall line of the building.”  This stuff comes in a three foot roll, and roofers usually have to lay down two layers of it to get 24″ inside the exterior wall line, so it’s usually six feet.

Ice and water shield will not prevent roof leakage from ice dams. Ice dams can cause leaks above the underlayment, or even right through the underlayment; I’ve seen it happen.  According to Certainteed, the manufacturer of Winterguard underlayment, it “provides your first line of defense.”  It’s not a guarantee against leaks.

If you have ice dams and your roof leaks during the winter, don’t blame your roofer.  I can almost guarantee you that it has nothing to do with the way your roof was installed.

Why do I live in Minnesota?

This last weekend was a great reminder of why we live in Minnesota.  The temperature shoots up to 40 degrees and it feels like summer is around the corner.

What I’ve Learned

Gutters don’t cause ice dams. Ok, I always knew this, but I’ve noticed plenty of ice dams with no gutters this year.  Ice dams will show up whether gutters are installed or not.  I mention this because I actually heard a ‘professional’ guest on a local radio show say that gutters cause ice dams, and that homes without gutters won’t get ice dams.  I’m sorry, but that just ain’t true.  You should have seen me ‘calmly’ disagreeing with my radio when I heard this.

Ice dam with no gutters 3

Ventilation has little to do with ice dams. I’m sure I’ll get plenty of indignant feedback for this blasphemous statement.  I’ve always been taught that you won’t get ice dams if you have enough ventilation, and I even used to preach this myself.  This is a concept that is deeply ingrained in the minds of contractors, roofers, and home inspectors everywhere.

Nevertheless, from all of the houses I’ve been to, I’ve seen little to no relationship between attic ventilation and ice dams.  Sure, attic ventilation is required.  Attic ventilation will help to cool the attic space, which helps to cool the roof decking, which helps to prevent snow melt, which helps to prevent ice dams… but this is a very small part of the equation.

The Minnesota Department of Commerce lists attic ventilation as a non-solution to ice dams.  The University of Minnesota Extension says that “only small amounts of roof ventilation are needed to maintain uniform roof surface temperatures.”

Adding more ventilation probably won’t change your ice dam problems.  Shoveling the snow off your roof vents probably won’t change your ice dam problems either.

Adding more insulation to your attic probably won’t fix your ice dam problems. As I mentioned at the beginning of this blog, I’ve been to a ridiculous number of houses this winter where insulation was added, but the problems didn’t go away.

If an attic lacks insulation, it’s probably an older attic.  Not always, but usually.  If it’s an older attic, it’s pretty much a guarantee that there are attic bypasses present.  Attic bypasses are passageways for warm air to get in to the attic, and they’re the driving force behind ice dams.  In almost every home that I inspected this winter, attic bypasses were at the root of the ice dams, regardless of how much insulation was present.  Through the use of an infrared camera, I’ve learned that insulation can’t make up for air leakage.

It doesn’t matter how much insulation is present in an attic; if there are air leaks, warm air will pass through traditional insulation.  The images below help to illustrate this; this was a very small attic bypass, but it still shows up plain as day through 14″ of loose fill fiberglass and another 4″ of cellulose on top of that.  I have hundreds of image sequences just like this.

Attic bypass

Recessed lights are huge contributors to ice dams. I recently wrote about this in another blog – Recessed Lights Are Evil.

What I’ve Recommended

I’ve recommended the same thing over and over; seal the attic bypasses.  They’re the main cause of the ice dams.  When insulation has already been added to an attic space, this becomes an extremely difficult, if not impossible chore.  To access and seal the attic bypasses, you first need to know where they are.  When they’re buried under one to two feet of insulation… forget it.

An experienced insulation contractor might be good enough at their job to know where to look for most of the attic bypasses, and could spend their time digging through the insulation to find most of them, but without completely removing the existing insulation, there is no way to seal all of them.

In most cases, I’ve told homeowners that they can hire an experienced insulation contractor to seal up all of the attic bypasses that they can find, and to keep their fingers crossed.  This will probably be enough to prevent leakage from ice dams again, and it will be a good repair, but not complete.  For a complete repair, all of the existing insulation needs to be removed so all of the attic bypasses can be located and sealed.

If you’re going to have insulation added to your attic, be sure to seal the attic bypasses first.

Reuben Saltzman, Structure Tech Home Inspections – Email – Maple Grove Home Inspections

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Preventing Ice Dams From The Exterior

January 4th, 2011 | 6 comments

I’ve been doing a lot of attic inspections for Minneapolis homeowners with water leaking in to their houses, and in almost every case I find obvious problems in the attic that should be addressed to either prevent or significantly reduce ice dams.  I mentioned most of the stuff that I look for in last week’s blog about preventing ice dams.

Occasionally I’ll come across a house with no attic space in the areas where heat loss is occurring, or there isn’t access to the attic areas.  In these cases, it probably isn’t cost effective to fix the problems that are causing the ice dams – the ‘repairs’ would outweigh the costs of controlling the ice dams.  In those cases, I recommend ice dam control from the exterior.

Remove The Snow

Roof RakeIf you rake the snow off your roof, you’ll keep ice dams to a minimum.  This becomes a constant chore, but it’s better than dealing with water leaking in to your house.  Just raking the first several feet of snow from the eaves is usually enough to prevent the formation of ice dams, but in some cases, this will cause ice dams to form higher up on the roof.

I have one very low-sloped section of roof at my own house where even closed-cell foam wasn’t enough to prevent the formation of ice dams, so I get out there with a roof rake and pull the snow off my roof.  This is a perfectly safe way of removing snow, as long as you don’t get too close to your overhead power lines.

This is also a very effective way of preventing ice dams, but it won’t work 100% of the time.  This year,  for the first time ever, I actually had another ice dam begin to form higher up on my roof just past where I had stopped raking.  That was crazy.  I ended up removing almost all the snow on my roof with a super-long roof rake, and that worked very well.

For owners with two-story homes where using a roof rake from the ground isn’t practical or possible, the options are to risk your life getting up on an icy roof to shovel the snow off, hire someone else to risk their life, or install roof de-icing cables as a preventative measure.  I say go with the de-icing cables.

Men Shoveling On Roof

De-Icing Cables

Roof De-Icing Cables Promotional PhotoRoof de-icing cables, also known as heat cables or heat tape, should be a last resort when it comes to preventing leakage from ice dams.  De-icing cables themselves aren’t cheap, it’ll cost money to have them professionally installed, and they’ll cost money to operate – between five and eight watts per foot.  On the flip side, they’re very effective; it’s pretty much a guarantee against leakage from ice dams.  They won’t prevent ice dams, but they’ll keep enough ice melted to create drainage channels for water, if installed properly.

If you choose to install roof de-icing cables yourself, here are a few tips:

  • Measure the areas where you need to install your de-icing cables first, and buy appropriately sized cables.  For a simple 15′ section of roof with no overhang, a gutter, and one downspout with an extension, you will need a 60′ heating cable.
  • Roof De-Icing Cables Real Life The cables should extend 6″ up the roof past the exterior wall line, through the gutters and downspouts, and 2/3 of the way up the valleys.
  • Don’t bother removing the snow from your roof; you could damage your cables, and you could potentially create another ice dam higher up on the roof, defeating the purpose of the heating cables.
  • Don’t expect the snow and ice to melt the way it does in the promotional photo above.  The photo at right, which I took at a real house, is what this stuff is going to look like.  Don’t worry, this is normal.

If fixing the causes of your ice dams isn’t a possibility and you can’t safely remove snow from your roof, install some de-icing cables or de-icing panels.  This is oftentimes the most cost-effective way to prevent leakage.

Reuben Saltzman, Structure Tech Home Inspections – Email – Minneapolis Home Inspections

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