Why Is There Frost In My Attic?

At the last four home inspections that I've done, every home had frost problems in the attic. Have you checked for frost in your attic yet this year?  If you live in Minnesota or a similarly cool climate, now is a good time to check your attic for frost.

Temperatures in Minnesota have been in the teens lately, which is plenty cool enough for frost to develop in attics.  Once we get a week of sub-zero temperatures, frost will really start to accumulate in attics.  The colder it is outside, the more frost will accumulate in an attic.   If you already have frost in your attic, I can assure you that it's only going to get worse - winter is still two weeks away.
 

Please excuse me while I digress for a moment.  Who the heck decides when the seasons change?  Yes, I know what the winter solstice is, but what a silly indicator of winter.  Winter in Minnesota should officially start on December 1st or after the first snow fall, whichever comes first.  Half the leaves were still on the tree in my back yard when we got our first snow this year, which happened on November 13th.   That wasn't a light dusting either.  When the ground gets covered with snow, fall is over in my book, no matter what the calendar says.

Frost doesn't do much damage to roofs while it remains frost, but when it melts, it makes a big mess. When the frost melts, there is often enough water to saturate the insulation in the attic and leave stains all over the ceilings.   This is the short-term problem with frost in attics.  The long term problem is that this continual saturation of the roof decking can cause the plywood on the roof decking to delaminate; when this happens, it loses a lot of it's strength and nails are much more prone to pulling out.  The fix for delaminated roof decking is to replace it.

The photos below all show roofs with delaminated plywood; this is caused by frost in the attic.  The last picture is especially nasty.  Click on any of the photos for a larger version.







The way to prevent frost from accumulating in an attic is to prevent warm, moisture-laden air from getting there in the first place.  There are two basics ways of doing this.

Seal attic bypasses  

Attic bypasses are passageways for warm air to leak in to the attic.  A few common places to find these gaps are around furnace vents, plumbing vents, electrical boxes, and electrical wires coming in to the attic.  Any bath fans, kitchen fans, or dryers venting in to the attic space will absolutely wreak havoc.  Even small gaps in any of these vents can bring a lot of moisture in to the attic.  For more tips on locating attic air leaks and sealing them, download this handout.

Lower the humidity in your home

 I find frost problems in almost every single attic where someone uses a whole house humidifier.  That's why I don't like whole house humidifiers.  It's nearly impossible to seal every little bypass to an attic, but when interior humidity levels are kept fairly low, sealing most attic bypasses is good enough.  Here are a few ways to lower humidity levels in your home:

• Turn off your whole house humidifier (duh)
• If you have one, use your kitchen exhaust fan when you're cooking.  Gas ovens add a considerable amount of moisture to the air.
• If you have a crawl space, make sure that a proper vapor barrier is installed on the crawl space floor.
• Turn on your bathroom exhaust fan during showers and leave them on for a half hour after every shower.  If you don't have a bathroom exhaust fan, get one.  While the building code allows an openable window as a substitute for a fan, I don't ;-)
• Install an HRV or a continuous exhaust fan.  Either one of these will dramatically lower humidity levels in a home.

Will adding more ventilation to an attic prevent frost?  No, this won't do squat.  I've been in tons of attics that were completely covered in frost, yet had fantastic ventilation.  To fix the frost in your freezing attic, focus on forbidding the moisture from getting there in the first place.

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

Attic Problems On A New Construction Home In Edina

We recently inspected a new construction, custom built home in Edina.  We did a team inspection at this property, where Neil, Duane, and I all inspected the house at the same time.  We really went over this house with a fine tooth comb, but we didn’t come up with much that was wrong – it was a very well built home.  Towards the end of the inspection, we asked the buyer if they would mind us opening up the attic access panel, which had been sprayed shut.  The buyer was fine with that, as most buyers are.  What we found was quite surprising.

The builder had taken all of the necessary steps to seal all of the bypasses to the attic,  by doing something most builders never do.  Before blowing in loose-fill fiberglass insulation, he had a company spray foam the ‘lid’ to really make sure that any potential bypasses to the attic would be completely sealed.  This isn’t required, but it’s a great idea.  Unfortunately, the person doing the insulation had missed a few areas, and this allowed a ton of frost in to the attic!

The builder was very glad we found this, and quickly had the insulation company back out to re-insulate the areas that were missed.  This is a great example of why it’s so important to break the attic access seal, and why it’s so important to have even new construction homes inspected, no matter how good the builder is.

The best builders will encourage their buyers to have private home inspections performed, and they’ll welcome any feedback from home inspectors.  This will not only prove to the buyer what a good house they’re buying, but can also save the builder from major potential problems in the future.

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

RELATED POSTS

• Break Seal At The Attic Access Panel?  Yes.
• Photos of Attic Bypasses
• Frost in the Attic
• New Construction Inspections

Frost In Attics

This Minnesota winter has been an especially problematic one for frost in attics, and it seems that most people don’t understand why it happens or how to fix it.  There is a lot of mis-information floating around about why frost gets in to the attic and how to fix it, but I’m going to give you the real story.

This winter we experienced an unusually long cold spell in Minnesota, with temperatures never climbing above freezing for about a month.  This means cold attics.  When moist household air is allowed to escape from the house to the attic, it condenses on the roof boards in the form of frost.  When this happens for a long period of time, a lot of frost can accumulate.  When the frost melts, it soaks the insulation in the attic, stains the ceiling, and can even leak out through windows (I talked to someone last week who was having this problem).

I’ve heard several homeowners tell me they called their roofer out because they thought the stains on their ceiling were caused by a leaking roof, and of course it wasn’t a roof problem.  Nevertheless, the roofers typically suggest adding more ventilation to the attic space.  This will not fix the problem.  To suggest adding more ventilation to a roof to fix frost in the attic is like telling someone with a leaking water pipe to install a dehumidifier.  Ventilation is not the way to fix frost in the attic.


The fix for frost in the attic is sealing attic bypasses – these are passageways from the conditioned household space to the attic.  Bypasses are what allow moisture in the attic to begin with, and this is what needs repair.  While bypasses are certainly the most common cause of frost, there are other ways it can happen, and these are much more obvious.  Disconnected bath fans can be particularly problematic, and disconnected furnace flues can be catastrophic.  The photo below is one of my favorites – when the roof was replaced, the furnace flue came loose in the attic, which quickly turned the attic in to a winter wonderland.


If you’ve had frost in your attic, wet insulation in your attic, or stains on your ceiling, find your attic bypasses and seal them.  If you're not sure how, read my related posts about attic bypasses or give me call.

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

How To Prevent Ice Dams

After all the recent snowfall, it's a good time to talk about ice dams.  Ice dams are caused by the same thing I've been blogging about for the last several entries; heat loss!  The most obvious sign of heat loss in attics is ice dams - those huge masses of ice that build up at the edges of roofs.  Ice dams occur because heat from the house escapes in to the attic, warms the roof, and causes snow to melt.  When the water gets to the cold overhang at the eave, it freezes.  As the ice builds up, it literally creates a dam.  The trapped water can then leak into the home and cause damage to the roof decking, structural members, insulation, and even stain the ceiling.

   

To prevent ice dams from occurring, you need to stop the heat loss.  The best way to do this is to seal attic bypasses - you can read more about this in two of my recent blogs - Attic Photo Explanations and Insulation Vs. Air Leakage. The other two ways to help prevent ice dams are by having adequate insulation and ventilation.  Insulation will obviously help to prevent heat loss, and proper ventilation will help to keep the roof colder; the colder the roof, the less chance for the snow to melt in the first place.

Older one-and-a-half story houses are especially susceptible to ice dams because there is usually very little access to all of the attic spaces that need attention.  If this is the case, there are still some steps you can take to control the damage caused by ice dams.   The least expensive and most labor-intensive way to prevent ice dams is to remove the snow from the eaves using a roof rake.   It's best to remove the snow right away, when it's light and fluffy.  The longer you wait, the more ice will accumulate.  If you can remove the snow down to the shingles, the sun will usually keep the shingles warm enough to prevent ice from forming at the eaves.



If you're looking for a less labor-intensive method of preventing ice dams, you could install heat cables at the eaves.  These will usually prevent ice dams from forming, but electric heat cables are expensive and use a fair amount of electricity to operate, making them an environmentally UN-friendly solution.   Even manufacturers of heat cables state that they are not the most efficient way to solve ice problems.
The worst way of dealing with ice dams is to get on a ladder and hack away at your ice dams with a hatchet or ice pick.   This is dangerous, and you could cause damage to your roof.  I've seen many roofs with big hatchet marks in the shingles from people chopping too deep.  I don't recommend doing this.
The bottom line?  If you can't stop your ice dams the right way, buy a roof rake.

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

Photos Of Attic Bypasses With Explanations

A few posts ago I included several photos of attic problems in my blog Reasons to Insulate, and said I would come back to them in a later post with explanations.   Here we go!

This photo shows a bypass to the attic space around a furnace flue.  The square piece of metal is not sealed to the drywall, and there is a fair amount of air leaking into the attic space from this gap.  I brushed the insulation away to show the gap for the photo.  The insulation has turned black because of the air leakage - as the warm air passes through the insulation, the fiberglass acts like a filter and collects the dust / dirt particles in the air.  Any time you see darkened insulation, you can bet there is air leakage occuring.  This is often confused with mold because it looks similar.


In this photo the gap around the plumbing vent is allowing air in to the attic.  Notice the dark insulation?  An easy fix would be to fill the gap with expanding foam.

This photo shows several holes that wires pass through to get to the attic.  These holes could easily be sealed up with expanding foam.  I didn't move any insulation to find these holes - this is exactly how the insulation looked when I climbed in to the attic, so there is obviously missing insulation here too.   The recommended insulation depth for loose fill fiberglass is 18", but the silver areas have no insulation at all.

This is another attic space in desperate need of more insulation.  Someone probably moved the insulation away to install a ceiling fan, but never bothered to put it back.

There is a major attic bypass around this furnace flue, and this is one of the most common bypasses that I find.  You can clearly see the walls on the floor below, and you can even see the basement ceiling from this opening!  To correct this bypass, the owner will need to install a large piece of wood, metal, drywall, or any other material that air won't pass through, and caulk all of the joints to make it airtight.  This wasn't obvious just by looking, but I always make a point of pulling the insulation away around furnace flues to look for bypasses.  The fiberglass batt on the right side of the photo was sitting on top of this opening.


Hopefully these photos have helped to illustrate exactly what attic bypasses are and how to correct some of the issues.


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

Insulation vs. Air Leakage (Attic Bypasses)

With winter officially here, I’m on a big insulation kick.  This is the time of year when I can really tell which houses have attic problems, oftentimes just from looking at the house on the outside!  Today I’ll talk about a few things I look for when inspecting an attic when it comes to air leakage, insulation, and ventilation.

When I inspect houses in the winter, the first thing I look at is the roof.  I do this out of habit, and I can usually identify a house with attic problems without even going in the house.  The most obvious things to look for on the outside are ice dams, icicles, and patches of unevenly melted snow or frost.  These are all signs of heat loss from the house to the attic space.

If I find a Minnesota house with obvious problems on the outside, I look for two conditions in the attic which cause heat loss; lack of insulation and attic bypasses.  Most people readily understand what lack of insulation is, but attic bypasses are generally less understood, and much more time consuming to correct.  An attic bypass is a passageway for heated air to rise in to the attic – insulation won’t fix this.

To understand how attic bypasses work and why insulation doesn’t help, think about wearing a knitted sweater on a cold windy day; the wind will cut right through the sweater, but if you wore a thin windbreaker over the sweater you would be much warmer.  The same principal applies to attics – warm household air will pass right through a foot of fiberglass insulation, but if the air is stopped by a physical barrier (such as the drywall at your ceiling), it won’t pass through the insulation.  According to the Minnesota Department of Commerce, attic bypasses can reduce the overall effectiveness of insulation by as much as 70 percent!  This is why it’s critical to fix attic bypasses before adding more insulation to an attic space.

When I evaluate the insulation in attics, I focus on areas with missing or minimal amounts of insulation.  Any gaps can drastically reduce the overall effectiveness in the attic.  Attics in new homes should have insulation that provides an insulating value of at least R-38, which equals out to about a foot of fiberglass rolls, or a foot of loose-fill cellulose, or about eighteen inches of loose-fill fiberglass.  If I can see the bottom chords of trusses in an attic, this is an obvious sign that the attic needs more insulation.  While I don’t have any hard and fast rules for my recommendations, I generally say that an insulation level over R-38 is good, between R-19 and R-38 is marginal, and less than R-19 needs correction.

Attic bypasses are much more difficult to identify because they are usually covered by insulation.  While national home inspection standards don’t require inspectors to move insulation, I always make a point of doing this anyways because this is typically the only way to identify them, and they’re important to know about! While bypasses are major sources of heat loss, they can also allow moist household air in to the attic space, which will often condense on the roof boards, creating a frost covered attic space.

   

In the summer there is never frost in the attic, but a dead giveaway that frost accumulates in the winter is small black stains around the roofing nails. The frost in attics will form the heaviest around nail heads because they’re the coldest components.  Possibly the worst bypass that I frequently find is a bath fan exhausting in to the attic – these pump warm moist air in to the attic at a ridiculous rate.  Another common place to find bypasses is around the furnace or water heater vent.  I frequently find gaps around the vents that are several feet wide, and these areas are always covered with insulation.  The Minnesota Department of Commerce puts out an excellent brochure on finding bypasses in the attic and how to fix them, which you can download here.

The last thing I look for in an attic space is ventilation.  Attic spaces are almost always unconditioned spaces, so they need to be ventilated to the exterior.  Attic ventilation helps to keep the roof cooler throughout the year, which will help to minimize ice dams in the winter and help prolong the life of the roof in the summer.  While the traditional reason for ventilating an attic space was to prevent condensation in the attic, I’ve read a number of studies lately that say that this may not be as important as we once thought.  I always verify that proper ventilation is in place, and I make suggestions on how to improve ventilation when necessary.

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