STUCCO: INVASIVE TESTING VS IR SCANNING

I’ve heard of home inspectors in Minnesota offering infrared scans on stucco homes as an attractive non-invasive alternative to standard invasive moisture testing.  Here at Structure Tech, we recently started offering infrared inspections, but stucco scans are something we will never offer.

First, some info on stucco.Stucco homes in Minnesota built since the late 80′s or so have had a nasty history of catastrophic failures.  These stucco homes are more likely to have moisture instrusion problems than other types of homes, and the damage is usually far more serious. The City of Woodbury has an excellent position paper about Stucco in Residential Construction, which should be required reading for anyone buying a stucco home built during this time period.  In many cases, there are absolutely no visible signs of moisture instrusion.

Invasive Testing

My advice to anyone buying a newer stucco home in Minnesota is to have invasive moisture testing performed, which can be done from the interior or exterior (this blog isn’t going to be a discussion of the two methods, although that will be a great future topic).  Exterior testing is done by drilling holes and  sticking metal probes in to the wall to measure the moisture content of the wood.  One such company that offers this service is Certified Moisture Testing, who we have recommended many times over the years.

These holes get covered over with matching caulk after the work is done, and there is virtually no evidence that any work was ever done.  Interior testing is done in a similar manner, where holes are made inside the house and the moisture content of the wood is tested.  As long as the person doing the testing is good at it, the results that come from invasive moisture testing on stucco homes are highly reliable.

Infrared Scans on Stucco

Having a stucco home scanned with an infrared camera as an alternative to invasive moisture testing may sound like a great idea, as there are never any holes left in the walls with this testing method.  The problem is that infrared scans on stucco are unreliable.  Infrared cameras don’t see inside walls; they only show differences in temperature.

For example, the image at right is an infrared image of a window at a stucco home.  You can see a little green at the lower left corner of the window, which means this area is a little bit colder.  This was the worst area of moisture intrusion at the home, and an invasive moisture test found there was no wood to probe here; the wood had rotted away to nothing.

If only an infrared scan had been performed, what would the recommendation have been?  Tear the wall open?  Have an invasive test performed?  This was the only thermal anomoly shown on the entire house, but an invasive moisture test found unacceptable moisture levels in about a dozen other areas throughout the house.

Temperature differences may or may not equate to moisture intrusion.  Conversely, if there are no temperature differences in stucco, should one conclude that there is no moisture in the wall?  Absolutely not.  Infrared cameras are great at finding temperature differences, but not water. Infrared cameras can be used to give clues for places to perform invasive tests at best.

The bottom line is that infrared scans on stucco homes will give unreliable results and should not be considered an alternative to invasive moisture testing.  I’m a firm believer in invasive moisture testing on stucco homes, and I say this as someone with no financial interest in the matter.

Reuben Saltzman, Structure Tech Home Inspections - Email - Infrared Home Inspections

    

THINKING OF ADDING MORE INSULATION TO YOUR ATTIC? READ THIS FIRST.

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.

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.  TheUniversity 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.

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.

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

    

HOW MUCH SNOW CAN MY ROOF HOLD?

After the recent collapse of the Metrodome roof, the collapse of a hardware store roof in Glenwood, and a recent Super bowl commercial from Allstate, some Minnesota homeowners are starting to wonder if they should be worried about their own roofs.  In December, I even received a question on the Structure Tech Facebook page asking how much snow a roof should be able to hold if built to code.

The video below shows the Super bowl commercial; this is what finally inspired me to write a blog on this topic.



The required roof snow loads for Minnesota aren't clearly spelled out anywhere, but the numbers can be found by using Table R301.2(1) of the Minnesota Administrative Rules.  This table says that roof snow loads equal .7 times the ground snow load.  To find the ground snow load, we use section 1303.1700 of the Minnesota Administrative Rules.  The southern portion of Minnesota, which includes the Twin Cities metro area, uses a ground snow load of 50 pounds per square foot.

For the Twin Cities metro area, the ground snow load equals 35 pounds per square foot, or .7 x 50.

So how much snow does this equal?  It depends.  As everyone knows, cold fluffy snow is very light, while wet snow can be extremely heavy.  I've heard that very wet snow could weigh up to 20 lbs per cubic foot, but we haven't received much of that this year.  I just checked a section of undisturbed snow in my back yard, where the snow is about 12" deep.  For the record, we've received over 60" of snow this winter.  According to my calculations, the snow weighs about 10 lbs per cubic foot, which conveniently equals 10 lbs per square foot.

If you have a properly constructed roof, you shouldn't have to worry about your roof collapsing, even if you get some big snow drifts on your roof.   On the other hand, if you know you have structural problems with your roof, this would be a good year to have some of the snow removed from your roof.

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

Recessed Lights Are Evil

I love recessed lights, but even the best ones create a ridiculous amount of heat in attics, which can lead to ice dams.  Until I started performing infrared inspections in attics, I never quite grasped how much heat recessed lights contributed to attics, but now my eyes are wide open.  The main problem I find with recessed lights is that they’re not insulated well enough; on a recent home inspection in Maple Grove, I found a home with forty-six recessed lights sticking up in to the attic, along with some wicked ice dams on the roof.

A standard recessed light will stick up in to the attic about seven inches.  If an attic has fourteen inches of  loose fill fiberglass insulation, how much insulation does that leave on top of the recessed light?  Hang on, let me get my calculator…

At any rate, there’s far less insulation above recessed lights than anywhere else in the attic, and these are the areas that get the hottest, so they should really have more insulation than anywhere else in the attic.   Unfortunately, that never happens.  The combination of minimal insulation and hot light fixtures shows up clear as day using an infrared camera.

The images above show how much heat is leaking through the insulation above an IC rated, airtight recessed light with a 75-watt incandescent bulb.  IC rated means that it’s safe to have insulation directly in contact with the light, but it’s not synonymous with airtight.  You can usually tell if a recessed light is airtight just by looking inside it; if there are a bunch of holes inside the housing, it probably isn’t airtight.

If you can see light pouring through on the attic side, it’s definitely not airtight.  All of these little holes in the housing are passageways for heated air to escape in to the attic; they’re called attic bypasses.

Having said all this, I don’t think recessed lights are truly ‘evil’, but they sure can cause a lot of problems, and there seems to be very little understanding of this in the building trades.   Here’s what you can do to prevent problems:

If you plan to install recessed lights that are going to protrude in to your attic, make sure they’re airtight, IC-rated lights.  After the lights are installed, be sure to double down on the amount of insulation above the lights; you’re gonna need it.

If you already have airtight recessed lights in your home, you probably need way more insulation installed on top of them.  This is usually quite simple to do, but without an infrared camera, it might take a little time to locate all the lights.

If you already have non-airtight recessed lights sticking up in to your attic, don’t worry; there’s a fix for this.   Simply construct an airtight box out of rigid foam insulation, and ‘glue’ it together with spray foam.

Now place this airtight box over the offending recessed light in your attic, and use a bunch more expanding foam to seal it up and make it completely airtight.   Not only will this prevent air leakage from around the light, but it will dramatically increase the insulation level above the light.  While the box pictured below is the ugliest box I’ve ever seen (I built it), it’s still very effective at preventing heat loss.

If constructing and installing insulated boxes throughout your attic seems like too much work, you could always replace any standard incandescent light bulbs with compact fluorescent lights; they produce far less heat, they’re easy to install, and you’ll start saving money on your electricity bills.

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