Attics and Roofs

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Attic Insulation

(February 1994)

Let's change our work site in the house from the basement to the attic. In this article, I'll discuss proper attic insulation and in the next issue I'll discuss proper ventilation for the attic. Together, proper ventilation and insulation will increase the life of your roof as well as lowering your heating costs. Most of the fixes you might want to make are fairly simple ones that you can do yourself.

Attics, as built in Virginia Hills houses, are not designed as living space. They can accommodate light storage, but their truss construction makes it very difficult to convert them to living space without major work and substantial costs. The attic really does have a function in your house, however, other than to store your old possessions. It acts as a buffer zone between the living space and the outdoors. If it is properly built and insulated, an attic should be the same temperature and humidity as the outside–cold in the winter and warm in the summer. If your attic gets too warm and humid, the wood framing can mildew and rot. Your insulation can get soaked with moisture and lose its insulating value. Proper ventilation will prevent this.

Now is a particularly good time of year to check for attic problems. If the snow on your roof is melting very rapidly, you have either an insulation or a ventilation problem or both. Snow should stay on your roof as long as it stays on the ground. If it's melting faster, you know that your attic is too warm. The first thing to check is whether any kitchen or bathroom vent fans vent into the attic rather than outdoors. If they do, you should have them vented through the roof or through the gable end of the house immediately. Those fans can pump a large amount of warm, moist air into the attic and cause the problems that go with too much moisture. The other source of moisture in an attic is the breathing of your house itself. In the cold of winter, the humidity inside your house is much higher than the humidity of the air outside. This water vapor will try to migrate into your attic. We can either reduce this with insulation that has a vapor barrier attached or increase the amount of ventilation in the attic (more about this next time).

A vapor barrier is nothing more than a layer of material that sits between your ceiling and the attic insulation. Vapor barriers can be kraft paper, foil, or polyethylene sheeting (clear plastic). You can buy insulation with a vapor barrier attached, either the kraft paper or the foil kind. Foil is a bit better, but more expensive. If you have the original rock wool insulation in you attic, it has a kraft paper vapor barrier on it. This will work fine if it isn't torn. Remember, a vapor barrier always goes toward the heated area, so it goes under the insulation in the attic.

The insulation itself keeps your heat out of the attic. There are two types of insulation used today, fiberglass and cellulose. Fiberglass usually comes in rolls or batts. It is naturally yellow, but Owens Corning dyes their fiberglass pink to make it distinctive. Cellulose is a wood/paper product that is a loose fill. It comes in bags and can be poured in or blown in. Both types are good insulation. What you choose depends on your individual preference. Fiberglass is perhaps a bit easier for a homeowner to install and can be purchased with the vapor barrier attached (in which case it is called "faced").

If you use cellulose, make sure it is treated to be fire retardant. You will have to install your own vapor barrier.

Unless you've done an upgrade since your house was built, what you have now is four inches of rock wool insulation with a kraft paper vapor barrier. The ability of insulation to retain heat is measured in R-value, with higher being better. Since each inch of insulation has a R-value of 3, your attic is insulated to about R-12. While this was considered adequate when our houses were built, today energy conservation experts recommend an R-value of about R-30 to R-39 for houses in our region. If you upgrade to more insulation to get to this R-value, it should pay for itself in about two years in savings on your heating costs.

If the existing insulation is in good condition and the vapor barrier is not torn, you can add new insulation directly on top of the old. If you are using batts or rolls, buy R-19 or R-25 WITHOUT a vapor barrier since there is already one below the old insulation. Lay the bats perpendicular to the existing insulation, across the tops of the joists (bottom truss chords). Since warm air tends to rise through your ceiling, you will notice the difference right away! A second alternative is to have cellulose blown in on top of the existing insulation. Again, at about R-3 per inch, you'd need about six inches worth to get to R-30. Try not to compress insulation as that reduces the insulating value.

Next time we'll talk about proper attic ventilation.

Copyright Doug Boulter, 1994

Attic Ventilation

(April 1994)

In the last issue, we talked about attic insulation. We noted that the correct combination of insulation and ventilation is important for the health of your attic framing and roof as well as for your comfort in the house below. This time, we'll go over ventilation–why it's important, how much you need, and how to get it.

Last time we said that the attic acts as a buffer zone between the living space and the outdoors. If it is properly built and insulated, an attic should be the same temperature and humidity as the outside&ndashcold in the winter and warm in the summer. If your attic gets too warm and humid, the wood framing can mildew and rot. Water vapor that has condensed on the rafters may drip down onto your insulation and ruin its insulating value. Also, if snow covers the roof and your attic is too warm, it will melt that snow. As the melted snow runs down the roof, it will get to the eaves overhanging the house which will still be cold. The water will be trapped by the snow and will re-freeze. However, having no place to go, it will work its way under your shingles and eventually cause leaks in the roof. This freezing is called ice damming. Proper ventilation will help prevent ice dams, wood rot, and ruined insulation.

How much ventilation do you need for an attic? The rule is one square foot of "free vent area" for every 300 square feet of attic floor space if you have a vapor barrier under your insulation. If you don't, you would need one square foot for every 150 square feet of floor space. The typical Virginia Hills house has about 1100 square feet of attic space. If you have a vapor barrier, then, you'd need about 3.66 square feet of free vent area in the attic. If you have the usual gable vents measuring 12" x 18", that's a square foot and a half on either end of the house for a total of three square feet.

Now, here's the problem. "Free vent" means unobstructed. To keep out rain and insects, however, we can't leave unobstructed holes in the house. We need louvers and screening on our attic vents. These together reduce the free vent area by 2/3, giving us only one square foot of free vent and making our attic ventilation pretty marginal.

What should you do about this? If the house hasn't had any problems to date, chances are that you won't get any new problems unless you vent a bath or kitchen fan into the attic. You should check the attic every few months to make sure you don't have any leaks and moisture isn't condensing on the attic framing and causing the wood to rot or mildew. Look for the telltale black spots of mildew and see if the wood of the roof or rafters is spongy.

A good time to add to your attic ventilation is when you are having a new roof installed. The best method for venting an attic is to have vents both high and low. The way this is done today is to cut a continuous vent about 3" wide in each of the soffits where the roof overhangs the house. These soffit vents are your low ventilation. You get high ventilation by cutting away the boards on the ridge of the house an inch or two and installing a continuous ridge vent. Since warm air rises, the warm air from the attic will go out the ridge vent, and cooler air will come in the soffit vents under the eaves, move up underneath the roof, and exit through the ridge vent. This air from the soffits washes the underside of the roof and eliminates hot spots.

Some people try to solve the ventilation with spot roof vents. They cut a hole in the roof and install a vent in one spot up high. There are two problems with this solution. First, some parts of the underside of the roof and the attic won't get much air flow, so hot spots can develop. Second, without the low soffit vents, the replacement air will come through the gable end vents and the lower part of the roof and the attic won't get washed. A thermostatically controlled in fan in the attic will produce much the same results. Some cooling in the summer (but no moisture removal in the winter) will occur, but the roof itself won't be washed. You'll only get an air flow from gable vent to gable vent.

A variant of this solution is to install mechanical turbine vents that the wind or a natural draft turns. Again, you have the problem of uneven ventilation and no low ventilation. Additionally, the turbine vents sold in some home centers are cheaply built. When the bearings wear out, the turbines will make a loud screeching noise. Replacement parts are almost impossible to find, so you'll have to replace the whole vent.

A combination of continuous ridge and soffit vents with good attic insulation and a vapor barrier will work wonders on your heating and cooling bills. It will eliminate moisture problems, reduce ice dams, and increase the life of the roof. When you get a new roof, it's something you should consider.

Copyright Doug Boulter, 1994

New Roof

(April 1996)

In this article, we're going to talk about getting a new roof. It's not something to look forward to, but your roof does protect your investment in your house. We'll talk a little about how to tell when you need a new roof, what you should have done, and what it might cost you.

Most shingle roofs have a life of about 20-25 years. As the roof goes through the hot summers and cold winters, the shingles get more brittle. They also begin to shed the granules that make up the top layer of the shingle and you'll notice these in your gutter, washed there by rain and melting snow. Walking on your roof may crack these older shingles. Leaks may develop around flashings or where the shingles are cracked or have blown off in a high wind. Small problems can be easily repaired, but when repairs need to be made frequently or you you notice a large number of cracked or missing shingles, it's time to do a replacement.

Your roof is made up of several layers. The bottom layer is the wood decking that supports the shingles. In Virginia Hills houses, this is 3/4" plank. In newer construction, it's a lighter grade of plywood. Unless you've had water leaks, most of your plank should be in good condition, even after 40 years.

The next layer is asphalt paper. It comes in two weights, 15 lb. and 30 lb. The heavier weight paper is thicker, but 15 lb. paper is fine for this area. In fact, some roofers will tell you that it's harder to get all the wrinkles out of 30 lb, and you may get a better appearance with the lighter paper. What asphalt paper does is to form a base for the shingles and, because it's waterproof, a backup layer.

Next come the fiberglass shingles, which are what is most prevalent these days. Shingles are sold based on the warranty. You'll most often see 20 year and 25 year shingles. The shingles with the longer warranty are a bit thicker and a bit better made. You can get these as standard shingles or architectural shingles. The latter have non-standard shapes or colorings to present the appearance of shake, slate, or tile roofs. If your roof deck is a bit wavy, they may also hide that to some degree. While they are more expensive, they allow you to customize your house, and you may find the more decorative appearance worth the minimal extra cost.

Also on the roof are the flashings, which protect penetrations in the roof for vent stacks, chimneys, and skylights. At the front and back edges of the roof, you should also have "drip edge," a piece of metal which protects the edge of the bottom board of the deck from water penetration and rot.

You can have one additional roof put on over one existing roof, but I wouldn't recommend it. Stripping the original roof allows the roofer to inspect the deck and replace any wood which has rotted. After 25 years, there will be some. The roofer should replace it with pressure treated board, and will charge you about $1.25 for every running foot of deck that needs to be replaced. The roofer won't be able to give you a specific figure until the original roof has been stripped. I'd strongly recommend that you not try to save money here. Far better to spend a bit of money on wood than to fall through the roof some time in the future.

A second thing you should have done is replacement of all flashings. Some roofers will re-use them, but this is a false economy. They wear out or can get damaged in the tear-off, but are very inexpensive to replace. Finally, insure that the roofer installs drip edge. That bottom board is the most vulnerable, and again the expense of the drip edge is minimal to protect it.

When you are having the roof replaced, you should give serious consideration to having continuous ridge vent installed. This provides high ventilation for your attic. I wrote about this some years ago, and would ask you to review that article for a detailed explanation. The roofer may provide it as part of the quoted price. There are several new types of ridge vent that can be shingled over and are almost invisible.

Here's the bottom line. The work I've mentioned should cost you under $2000 for a typical Virginia Hills house. This will increase if you want fancier shingles, but your bids should come in near or under that with a standard shingle. Your roofer should be licensed, bonded, and insured. The crew should remove all the debris of the old roof, and, absent any unusual circumstances, should be able to do a typical house in a day. Gutters will cost extra, and the roofer will usually contract it out to a gutter specialist.

Copyright Doug Boulter, 1996


(September 1997)

Many Virginia Hills houses allow access to the attic through a square hole in the hall ceiling called a scuttle. You push up the square piece of drywall and you can climb up a stepladder into the attic.

Unfortunately, there is no insulation above this piece of drywall, meaning that your heat in the winter or cool air in the summer are lost into the attic. Having that piece of drywall over the opening is better than nothing, but not much!

It is easy to build an insulated cover for your scuttle. Take a piece of 1/2" plywood and cut it to the dimensions of the scuttle opening minus just a bit to insure you can freely lift it up in the opening. Take some 2x6 lumber and build a frame around the perimeter of your cover. Fill the inside of the cover with R-19 insulation with a vapor barrier (kraft paper or aluminum foil) facing down toward the floor of the hall. Then secure another piece of half inch plywood to the top of the frame, and you have built an enclosed box that will insulate to R-20. It won't make a huge difference in your heating and cooling bills, but it will add to the comfort of your house.

If you have pull-down attic stairs, you can replace them with newer stairs that are insulated, or you can build a box over the stairs. This is a fairly carpentry-intense project. At a minimum, you should weather-strip around any cracks at the edges to prevent the loss of your heated or cooled air into the attic.

Copyright Doug Boulter, 1997


(November 2000)

Fall is always a good time of year to talk about gutters. You know you need to clean them, but somehow getting up on the roof or on a ladder doesn't seem like much fun. In this article, we'll talk about some of the things you can do to improve your gutter system and some of the ways you can reduce or avoid gutter cleaning.

Most gutters on Virginia Hills houses are four inches wide. If the shingles hang over the edge of the roof a bit as they should, that four inches doesn't give your hand very much room to get in the gutter to clean it. Next time you install new gutters, consider a five inch wide gutter. This isn't much more expensive than the four inch version, and will carry away a lot more water besides being much easier to clean. Five inch gutters clog less easily because of the larger size opening at the downspout. The downside to larger gutters is that they come in fewer colors.

When cleaning gutters, the first thing you should check is the bottom end of the downspout. It needs to be clear; cleaning the leaves and debris out of the gutters does you no good if the end is clogged. Make sure each end empties out at least three feet from the house, the further the better. Almost all water-in-the-basement problems are caused by water from the roof running down the foundation. The further away from the house that the gutters empty out and the cleaner they are, the less likely you are to have a basement water problem. If you see water running over the edge of the gutters in a rain storm, you know you're inviting basement problems and you need to get those gutters cleaned quickly.

Most gutters are hung with the "spike and ferrule" method. That is, a long thick nail goes through the gutter into the fascia board and, it is hoped, the rafter/truss tails. The ferrule is a piece of metal tube that goes over the spike inside the gutter and helps strengthen it when a ladder rests against the gutter. I said "it is hoped" because often the spike misses the rafter tail and is held only by the fascia board. Even if the spike hits the tail, end grain of a board doesn't hold nails well. As a result, the weight of a lot of water or ice in the gutter can pull the gutter off the house.

The good news is that there is a replacement for the spike. You can buy a gutter screw that can be used as a replacement for the spike. It's roughly the same length as the spike, but with an aggressive screw thread on the tip that will really hold your gutters. I haven't seen these screws in home centers yet, but I'm sure they will be there soon. You can get them from McFeely's (a great source for all kinds of screws and fasteners).

Now what about all these products that keep leaves and debris out of the gutters and relieve you from the task of ever having to clean the gutters again? These are usually of three types: screens that go in the downspout opening, screens for the top of the gutters, and solid covers for the top of the gutters that use surface tension of the water to direct it into the gutter but let the debris silde off and miss the gutter.

Given that most clogs occur where the gutter empties into the downspout, I've never seen anyone have any real success with the downspout opening screens. At best, they may buy you a bit of time before you need to clean. At worst, they clog earlier than the opening would otherwise.

Screens over the gutters keep out the larger leaves, but things like pine needles usually go right through them. If you have a minor gutter clogging problem caused only by a tree or two, these may work for you, or at least reduce the amount of cleaning you need to do. One warning. If you do have to clean, getting the screens off may be a major task that adds more time to one cleaning than it would take to clean three or four times.

The trend today is toward the solid gutter covers. These work reasonably well in all but the heaviest rain storms (over 6" per hour of rain). Some installers will guarantee that you'll never need to clean your gutters again if you let them install their product. My concern with such devices is that the installers charge an arm and a leg for them. I've heard quotes of up to $3000. That buys a whole lot of gutter cleaning! The good news is that you can buy them inexpensively and install them yourself. Prices should run you under $2.00 a linear foot. A good source for these is, a web site that has lots of good information on all kinds of gutter problems.

I still clean my gutters by hand. If you have any experiences with any gutter protection systems, I'd like to hear about them.

Copyright Doug Boulter, 2000

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