The Best Way To Insulate An Attic

Unfortunately, the easiest way to add insulation to just about any place in your home is to install fiberglass batts.  Fiberglass batts are typically the worst insulation for any job, as I complained about in a recent blog.  I mentioned at that time that I would follow up with a blog about the other choices of insulation.  Today I’m going to discuss several different types of attic insulation.

The best way to insulate an attic or pretty much anything else in a home is to use spray foam insulation. There are two types of spray foam insulation; open cell and closed cell. I’ve also heard people call them ‘half pound’ and ‘two pound’ foams, respectively.  Open cell foam has an insulation value of up to R-3.9 / inch, while closed cell has an insulation value of up to R-6.9 / inch.  Closed cell foam will act as a vapor barrier when installed to a depth of at least 2″, while open cell foam won’t act like a vapor barrier at any depth.  For an in-depth discussion of the differences between closed cell and open cell foam, click here open cell vs closed cell foam.

When properly installed, either type of spray foam insulation will act as a perfect air barrier, sealing off all attic bypasses.  Spray foam insulation will also completely eliminate convection; air cannot move through foam insulation.   The downside to using foam insulation is the expense; foam costs way more money than anything else, and it’s definitely not a do-it-yourself product.

I’ve heard some people complain about the flammability of foam insulation; yes, it’s flammable, but it will typically be completely covered in the attic.  The fact that it’s flammable wouldn’t stop me from installing it.  If you’re curious, here’s a quick “don’t try this at home” video.

I’m such a firm believer in spray foam insulation that I had this done at my previous home, which was a one-and-one-half-story house.  For this style of house, foam is definitely the way to go; the insulation gets applied directly to the roof decking, and it’s called a hot roof.  The foam gets completely covered with drywall after that.  For traditional roofs, I’ve made up my own set of standards.

The Gold Standard

For a traditional attic, there is no need to use foam throughout the entire space, as you’ll get the most value out of the first couple inches.  A cost effective way to use foam insulation is to foam the lid of the house, then use loose fill insulation on top.  This means installing spray foam to a depth of at least 2″ on the entire attic floor to completely seal everything up.  After the foam is cured, loose fill fiberglass or cellulose insulation gets installed on top of the foam.  Because fiberglass costs more, has a lower insulation value per inch and makes my skin itch, my preference would be cellulose.

If it’s an older home with only a few inches of space between the tops of the outer walls and the roof, you won’t have much room for insulation here; extra spray foam needs to be installed here to help compensate for this.

Here in Minnesota, the minimum allowable insulation value for a new construction home is R-38 for an attic, but federal standards suggest R-50 for our climate.

Oh, and one other cool thing about spraying closed cell foam on the attic floor is that once the foam cures, you’ll be able to walk on the entire attic floor; not just the truss or floor joists.  I’ve done it.  It’s crazy.  That closed cell foam is strong stuff.

The Silver Standard

Prep the attic before insulation.  Have every attic bypass completely sealed.  Foam in a can is great stuff for most smaller attic bypasses (didja see what I did there?), but watch out for gas vents; they require a 1″ clearance.  Have insulated boxes constructed for any recessed lights – they contribute a ton of heat to the attic.  If it’s an older home where the rafters or trusses only leave a few inches for insulation at the outer walls, you won’t have enough room for proper insulation at the edges; hire someone to spray foam these areas with closed cell foam to get the highest insulation value possible.  Of course, don’t forget to install baffles at the eaves to prevent your soffit vents from getting blocked.

After everything has been prepped, it’s time to insulate.  My preference is cellulose insulation.  If you do it yourself, you can buy the insulation in bags from your local home improvement store, and they’ll probably let you rent an insulation blower for free.  The DIY cellulose insulation method is very dusty, but it’ll get the job done.  If you hire a pro, they’ll use wet-spray cellulose, which adds a small amount of water to the cellulose to help control the dust and to slightly increase the insulation value per inch.

If you choose to use loose fill fiberglass instead, don’t worry; it’s not bad stuff.  There was a widely publicized study conducted by Oak Ridge Laboratories in 1991 that said that loose fill fiberglass insulation lost a lot of its insulation value once temperatures dropped below 20 degrees, making loose fill fiberglass an inferior product when compared to cellulose.  I contacted Andre Omer Desjarlais at Oak Ridge Laboratories about this issue, and he said “This was true 20 years ago but all fiberglass manufacturers have changed their products appreciably since then and this is simply no longer an issue.”  I also contacted several insulation manufacturers about this, and they said the same thing and sent me some great information, which I posted on my web site; click any of these links to read the documents from Certainteed, Johns Manville, or Owens Corning.  Loose fill insulation will still experience convection, but not nearly as much as old fiberglass used to.

The Bronze Standard

Just use cellulose insulation in the attic.  Cellulose does a good job of controlling condensation in the attic and it’s a fairly dense product, so it will cut down on air movement from attic bypasses, but won’t completely eliminate them.

The Brown Standard

Roll out a bunch of fiberglass batts, proudly proclaim “done and done”, and have yourself a cold one.

Oh, and as for the attic access panels or pulldown attic steps?  I’ll cover those in another blog.

Reuben Saltzman, Structure Tech Home Inspections - Email - Edina 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

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

Reasons To Insulate Your Minnesota Home

With the cold weather officially here, it’s a good time to talk about insulation.  This is such a huge topic that I hardly know where to start!  There are so many different aspects to insulation that this will have to take up several blogs.  Today I’ll talk about why it’s important to have a well-insulated home.


Perhaps the most important reason to have a well-insulated home is to reduce greenhouse gas emissions.  While a recent survey conducted by Owens-Corning revealed that most Americans believe transportation and industry to be the largest contributors of greenhouse gas emissions, in truth the largest contributor is buildings!  Buildings use 40% of our energy, according to the U.S. Department of Energy.  The number is even higher in Minnesota - 60 to 80 percent! The most cost effective way to reduce greenhouse gas emissions is to better insulate buildings.  Yes, this is even better than driving a hybrid vehicle, but it's certainly not as hip.


The most obvious reason to better insulate your home is to reduce your heating and cooling bills – especially here in Minnesota.  Adding insulation to attic spaces is often a project that even unskilled homeowners can tackle, and it doesn’t cost a lot of money. Homeowners will typically see a payback in five to ten years. Adding insulation to poorly insulated walls is also a good thing to do and will surely help to save on heating and cooling costs, but this not as cost effective as adding insulation to an open attic area, as this will often require a professional to blow insulation in to the walls.


Arguably the most important reason to better insulate your home is to make it more comfortable. Even if a thermostat says it’s 70 degrees inside the home, poorly insulated walls will make a room feel much colder as the heat from your body radiates out to the relatively cold walls. In older houses with uneven heat, you may even have parts of the house that never warm up enough. I can tell you from experience that insulation makes an incredible difference in the comfort of a home. I live in a one-and-a-half story home with a finished upper level that used to be so cold in the winter that I couldn’t even use it. After re-insulating the upper level last year, I no longer need to heat the upper level! Enough heat rises up from the rest of the house to keep the upper floor so warm that I can shut off all the heat registers and it’s still comfortable.


There are many more reasons to properly insulate your home, but I’ll just mention one more that you’re surely aware of if you live in Minnesota; ice dams. While ice dams are a large subject on their own, suffice to say that lack of insulation can lead to large accumulations of ice at the edges of roofs that cause leaks in the home and destroy gutters.

In my next blog I'll talk about how to determine whether more insulation is necessary, and what critical steps need to be taken before adding insulation. Hint: the photos throughout this blog all show homes with major room for improvement!

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


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