What homeowners should know about attic ventilation.

Attic ventilation provides a means for airflow throughout your attic space. It is important that the entire space is considered ventilated because if only a portion of the attic space “breathes” then it is no benefit to you.

So why ventilate at all?

There are many reasons sited as reason to ventilate the attic space. The most important reason in my opinion for attic ventilation is moisture control. In fact, this is the reason the attic ventilation discussion began in the 1930’s because as homes became better insulated moisture issues surfaced. Moisture can form in the attic space as the moist air from the house condenses in the attic space. You can sometimes see this in the winter as water droplets form on the nails protruding through the roof deck. Excessive moisture can degrade the life of the roof deck and cause other moisture related problems such as mold.

Ice damming is another major issue that proper ventilation can help resolve. Ice damming is a condition that is created when snow melts at the upper roof, where heat build-up raises the roof temperature above freezing, and refreezes at the lower roof creating a dam of ice. This in turn prevents water from snow-melt to reach the gutter system and instead backup under the roof shingles. This can create leaks in the home and cause considerable damage. Attic ventilation creates an even temperature in the attic space to promote even snow-melt.

Proper attic ventilation can also reduce the overall temperature of an attic. This can help in maintaining cool conditions in the summer time in the upper levels of a home. This can lower the amount of air conditioning required to cool the same space. When talking energy efficiency, attic ventilation should be considered in conjunction with attic insulation.

Another reason often sited for attic ventilation is extended shingle life. It is my opinion that there is not enough scientific research to support this. Shingle color, roof orientation, and geographic location have more impact on shingle life and shingle temperature than attic ventilation. Nevertheless roofing manufactures and organizations continue to beat this drum of extended shingle life and as a result you will find some roof covering warranties require proper ventilation. It would be more accurate to state that proper attic ventilation is needed to maintain roof shingle warranties rather than life expectancy.

So how much ventilation is enough?

The predominate theory and the one prescribed by most code officials is 1 square foot of ventilation for every 150 square feet of attic space expressed as 1/150. Or, if there is a vapor barrier installed under the attic insulation 1/300 is required. This calculation originates from a 1940’s document published by the FHA (Federal Housing Administration). Even though it does not seem to have much basis in scientific research it has persisted to this day and is considered the final word in ventilation requirements.

Types of ventilation.

There are many different ways to provide ventilation and no one method works for every roof type. The types of ventilation can be broken into two major categories; passive and active.

Ventilation needs to address the whole space. This is resolved by the methods applied drawing in airflow from the lower sections of the roof, as in the eaves, up to the upper sections of the roof. Continuous soffit venting, shingle vents, or can-vents can accomplish the lower roof section venting. Ridge vents and can-vents might be used on the upper section. Gable vents are an older approach and not as effective as other means. They also should not be used in conjunction with other vent types.

The previous approaches are all examples of passive venting. Active vents are powered vents with a thermostat and possible a humidistat, wind turbine vents that spin when the wind blows, and fan assisted gable vents.

You should consult a reputable roof contractor or home improvement contractor to determine what will best work with your roof type.

Common problems.

One of the most common problems with attic ventilation, especially in retro-fit situations, is a lack of eave venting. It is common for roofers to sell homeowners a ridge vent but with a lack of eave ventilation it serves no purpose. Other problems with eave venting can include the vents rendered ineffective by painting them shut. In the attic often insulation is blocking airflow. Baffles installed in the attic space can correct blocked airflow by insulation.

Another common problem is an unbalanced system. The quantity of free airflow at the eaves must be balanced with the upper roof ventilation in order to meet the 1/150 or 1/300 design parameters.

In conclusion it is best practice to properly vent attic spaces to prevent problems with moisture, ice damming, and excessive heat build up. (Note there is a hot roof theory that is beyond the scope of this discussion) Most new homes will have some kind of ventilation but that is not to say it has been properly balanced or installed. Many older homes lack ventilation entirely. Always consult with a reputably contractor about your options and do your own research. Then ask a home inspector to verify installation before making your final payment. If you follow these principals you should end up with a good working system.

When Should I Clean My Chimney?

Trying to determine when to clean your chimney or how often cannot be based on a clean set of rules. You must check the buildup of creosote in your chimney to determine this. To do this use a fire poker, when there is no fire, to scrape the inside of the chimney walls. If you find that there is only a thin film buildup, your chimney does not need a cleaning at this time. However, if there is a buildup, then you should have it professional clean. If you find a buildup over ¼” do not use the fireplace until it is serviced. As an added note, please be sure to use proper eye protection and dust mask when do this type of self inspection.

When buying a home with a fireplace it is recommended that you have the chimney inspected prior to purchase. Your home inspector may be able to identify more obvious deficiencies with your chimney but only a CSIA Certified Chimney Sweep can perform a detailed inspection of a chimney. The CSIA (Chimney Safety Institute of America) recommends that any property being transferred that has a chimney have a level two inspection. A level one inspection examines readily accessible areas of the chimney whereas a level two inspection is more in-depth and can reveal hidden hazards.

I encourage you if you have questions about your chimney to visit the CSIA website at www.csia.org and read the homeowner resources.

Is it safe to use rock salt on concrete?

If you haven’t heard it yet you will by the de-icing marketing pros that rock salt can damage concrete drives and walks. However, what you may not know is all de-icers have this potential.

The damage that usually is attributed to rock salt is a spalling of the surface of the concrete. This is more prevalent in new concrete and concrete that is poorly installed. Typically, there are two reasons for this. The first is that concrete is porous and absorbs water. This water freezes in the wintertime and the expansion causes the concrete to crack or spall. The increased introduction of water by melting ice by salts magnifies this problem. The other reason is related to chemical reactions that develop between de-icers and the concrete material or metal reinforcement within that can weaken and/or compound the freeze thaw issues naturally present.

Proper concrete installation reduces its ability to absorb water resulting in freeze thaw damage. This includes proper strength, placement, additives, and finishing. Exterior concrete should be air-entrained (tiny air bubbles); an additive that helps prevent freeze/thaw harm. Finishing can create a surface on the concrete that is weak if done incorrectly. For example if too much water is added during finishing it can spall much easier. If concrete is correctly installed and allowed to cure it typically can withstand more abuse by de-icers.

Conventional thinking is that rock salt (sodium chloride) is the worse de-icer for concrete on the market. Magnesium chloride is sometimes cited as one of the safest de-icer for concrete available. Interestingly in my own research of the subject I found a study by the Iowa State University that seems to run counterintuitive to this thinking. In part it found in testing reaction of de-icers on highway concrete the following:

“Samples were experimentally deteriorated using wet/dry, freeze/thaw, and continuous soak conditions in solutions of magnesium chloride, calcium chloride, sodium chloride [rock salt], magnesium acetate, magnesium nitrate, and distilled water in order to determine relative deterioration activities. Magnesium chloride was most destructive. Calcium chloride was next, and sodium chloride was relatively benign.”

This seems to suggest that the preferred de-icer of some may in fact be more harmful than rock salt. While I am not suggesting the use of rock salt you may not want to regard other forms of de-icers as entirely safe for concrete. Currently it appears that newest de-icer on the market, calcium magnesium acetate (CMA), may be the safest for concrete according to the most recent published information. However it has its own drawbacks. A certain chemical company had this to say:

“CMA is a dry formulation used as an ice melter on bridges, parking decks and airport runways. It does not attack rebar in reinforced concrete and is biodegradable, creating no problems in runoff water. It changes ice and snow into a oatmeal texture. This is not desirable for sidewalks, and it also may be cost-prohibitive, as it costs four to five times more than calcium chloride.”

The point is, as will all de-icers, they are designed to break up and loosen snow and ice so it can be mechanically removed. Instructions will typically say to remove excess de-icer, water, or slush. They are not designed to “burn-off” ice and snow.

If you follow the tips below you should not experience damage to your home’s concrete sidewalks and driveways.

• Never use de-icers on new concrete or concrete already showing signs of damage. Instead use sand for traction.
• If you must use a de-icer use calcium magnesium acetate (CMA) or another acetate product and follow the manufacturer’s instructions.
• CMA is rather expensive. If you need an economic solution you can use rock salt but remove it as soon as the ice can be loosened. However again, sand may provide a better solution.
• Never leave a de-icer on concrete to “burn off” the ice, snow, or water.
• Clean your drives and walks in the morning to allow the sun to help naturally de-ice the concrete.
• Never use a shovel or other metal tools to break up ice on concrete. This can cause mechanical damage to the surface.

We hope you winter is a safe one for you, your family and your home.