Posted by Mike Ciavattieri on Tue, Feb 10, 2009 @ 11:32
It's been a long, cold, and snowy winter here in Massachusetts and over the past months of performing home inspections I have run into numerous instances of ice dam formation and the subsequent questions from prospective buyers and sellers.
So what causes ice dams? Simply put, ice dam formation is caused when melting snow runs down the roof and then refreezes at the roof edge. The water runs down the roof slope underneath the blanket of snow and then refreezes into a band of ice at the roof edge creating a "dam". Additional snow melt can then pool against the dam and leak into the building through the roof or roof trim. Ice dams can actually form with as little as 1 or 2 inches of snow accumulation given the right weather circumstances.
The question I receive most often is, "what can I do to prevent ice dams?" The answer, while it may sound contradictory at first, is increased amounts of insulation and increased attic ventilation. In order to understand why, one needs to fully understand the mechanisms of ice dam formation: The upper roof (or attic) surface is typically at a temperature that is above freezing - this is what causes the melting at the upper roof surfaces. The lower part of the roof (or attic) surface (along the eaves) is typically below freezing - this is what causes the refreeze. It is heat lost from inside the house is the source of the melting at the upper roof surfaces! Because the lower roof surfaces (particularly the overhangs) are not warmed by indoor heat-loss, these regions can remain at below freezing temperatures, especially during periods of very cold outdoor temperatures.
Check your home carefully when ice dams form, even when there doesn't appear to be a leak. Get in your attic and look at the underside of the roof sheathing and roof trim to make sure they haven't gotten wet. Check the insulation for dampness. And when leaks inside your home develop, be prepared. Water penetration often follows pathways difficult follow. You may wish to hire an inspector that is equipped with an infrared or thermal imaging camera, as this equipment may be able to spot water penetration that is not readily visible with the naked eye. Ultimately, however, you will want to correct the problem to prevent future occurrences:
Insulation: Houses in this region of the country should have attic insulation of at least R-38, or about 12 inches depth of fiberglass or blown in material. The most notable problem area is at the far eaves, or right above where the exterior wall is.
Ventilation: A ‘ridge/soffit' ventilation system is currently the most effective ventilation system, and is the system found in most new construction. If you have an older home, you may still be using a power fan, static roof vent(s) and/or gable end louvers - these simply aren't as good and will have a more difficult time retarding ice dam formation. Ridge/soffit systems should also include foam or plastic baffles at the far eaves to prevent insulation from blocking the soffit intake vents. If you have soffit baffles currently installed, make sure they are not crushed or displaced - they are relatively flimsy items yet they perform a very important function.
Air Leakage: Although insulation is what primarily keeps warm air in our house, small (or large) holes can allow significant volumes of warm indoor air to pass into attic spaces. Some of these sources can include: pull-down staircases, doorways leading to attic staircases, recessed lighting, bathroom exhaust fans, and various holes for cable TV, internet, etc. Take the appropriate measures to seal up or insulate these areas, it may be the difference maker!
Remember: Always wear personal protective equipment when making repairs of any nature. And when in doubt, always hire a professional. Winter is almost over!
Mike Ciavattieri is a Massachusetts Home Inspector and owner of BONSAI Inspection Company, of Abington, MA
Posted by Mike Ciavattieri on Thu, Dec 18, 2008 @ 11:40
The clock is ticking and winter is not that far off, so now is a great time to prepare your home for the long cold winter months ahead. Tackle these tasks one at a time and you will not be overwhelmed. Do not wait until the last minute to take care of basic tasks! Do not wait until the snow and rain is coming down to start thinking about what needs to be done.
- Test your smoke and carbon monoxide detectors so you are sure that they are in good working order. They can save your life and do save thousands every year. If you do not have detectors on every floor of your home, get them! This one item should be a top priority!
- Have your fireplace inspected by a qualified/certified chimney sweep to verify that it is safe to use. If you use your fireplace regularly, have it inspected annually. Don’t rely on a ‘cleaning log’. Logs do not see or correct flue damage! Get a hold of some good firewood not only for that warm comfortable feeling that a fireplace can provide, it is a good idea to have that on hand, instead of having to brave the cold weather in a search for wood to burn during the winter. Don’t store firewood inside- it’s a great way to bring insects in! I’ve seen several instances where stored wood led to termite damage!!
- Close all the air conditioning vents if they are separate from the heating system and secure and put away any window air conditioners. Cover your air conditioning compressor (the outdoor unit) with a tarp or custom fit cover. Don’t forget to secure the cover from wind!
- Turn off and drain your outside water faucets. There should be a shutoff valve just inside the house where the faucet enters the siding. Turn this valve off then turn the outside valve on and leave it on. This will drain the faucet fixture of water and prevent freezing. For added protection you can install a screw-on end-cap to the faucet.
- Now is a great time to change your hot air furnace filter- I recommend a good quality HEPA or allergen filter unit - it’s worth the extra cost. The cheap blue 99-cent filters just don’t cut it.
Make yourself a list of any repairs around the house you may need – before winter comes. Find and fix any heating leaks that exist. On a brisk windy day check every outside door, and window to determine areas that leak or let in cold air, and repair as needed.
Assemble all the tools you might need this winter; snow blower or shovel, rock salt or ice melt, sand, warm gloves, hat, etc. Make sure the snowplow is tuned up and is in good working order.
Some more important items to consider:
- Caulk around all windows and door glass and do not overlook all exterior trim. Put weather stripping on all doors and around all windows. Check for cracks in the putty insulation around pipes and electrical outlets.
- Install storm windows and doors if you do not already have them. Use storm windows that are made from modern insulated glass. If you have older windows with screens and storm window panels, don’t forget to raise the screens and close the storms!
Have your heating system inspected and or tuned up by a licensed heating/air-conditioning professional.
- Check all your gutters and downspouts; fix or clean them if needed. Make sure downspouts discharge away from the foundation by at least 3 feet.
- Trim any bushes and trees away from the house.
- Check all fire extinguishers and replace as needed.
- Check your sump pump. If it grinds or sounds noisy, think about a replacement. Like your downspouts, be sure the discharge is routed away from the foundation by at least 3 feet!
Following these tips and tasks will help make your home safer, more comfortable, and more economical this winter.