Attic Ventilation / Insulation

Causes and Repairs for Attic Leaks

Attic Vent Fan

Attic insulation is obviously important when it comes to energy bills. Small leaks surrounding all doors and windows allow cold air to enter a home with or without wind based on the openings along the highest ceilings in the home. 

Attic Vent Louvres

If hot air rises (chimney effect) and you are heating up air on a cold day, it rises. If you have holes in your ceiling, lights, Knee wall closet (in cape with closets upstairs), air will shoot through these holes, through attic and outside, literally sucking air in from all exterior walls at the bottom level of home. Remember Hot air balloons have holes in the bottom that mean nothing, until the hole at the top is opened (chimney effect). This issue is vital to the elimination of the most damaging roof leak, The Ice Dam.

The facts behind insulation:

Insulation can do more harm than good if not used properly, put in the wrong place or when the wrong type is used

Improperly installed insulation or insufficient attic insulation are key factors in many roofs demise. Low R value allows for condensation, mold growth and energy loss. Too high R value obstructs air flow between roof deck and insulation preventing proper venting which saves energy but causes condensation, rot and roof blistering (premature failure and VOID LIMITED LIFETIME WARRANTY).

Insulation installed under roof deck has to have baffles (to protect the roof) that create space for air passage from intake vent to ridge vent. Spray foam should never be installed directly onto the bottom of roof decking as the sun’s heat cooks the roof (voiding all Manufacturers’ but CertainTeed’s Roof warranty). Spray foam salesmen do not understand the roof warranty requirements. They only know how to sell spray foam. Insist on baffles if the foam has to go under the roof deck.

Insulation does not save money when the bathroom fan is pumping into attic, when HVAC ducts have leaks or if the attic access door is not airtight. The hot air simply goes right around the insulation (through these holes) and out the attic’s roof vent. I call this: The HOT AIR BALLOON effect (to make things easy to understand):

  • **If there are holes in the top of a hot air balloon either from a tear (bad stitch) or the balloon flyer pulling the string (to descend) which opens a hole (flap) on the top of the balloon, hot air will shoot out these holes allowing cool (cold) air in the opening at bottom of the balloon. Just like the holes in the top of a hot house (in winter), air rushes out the bathroom fan, cracks around access doors, openings in old recessed lighting, missing duct tape… causing cold drafts as cold air is SUCKED in to replace the HOT AIR that is Rising. When the homes Ceiling has no openings (because we weather-strip, duct tape, vent out bathrooms and change lights to air tight LEDs) There are no cold drafts being sucked in. **Remember the hot air balloon flies very efficiently with a hole in the bottom. The top (CEILING) is most important (Sorry Anderson Windows but the attic is more important).

Whenever possible we utilize batt insulation and Attic-Cat Owens and Corning blown fiberglass insulation to create a minimum R30 under our roofs. For situations where a vapor barrier or air block is needed (Tongue and groove wood ceilings) we utilize closed cell spray foam.

Most common mistake in regards to attic ventilation:

People think that their gable vents (sides of house near peak) and Ridge vents (included in 95% of roof installs) give them attic ventilation.  Yes. They’re right. They have vents. Problem is, little air is moving through them. Remember air rises and that is why the exhaust vents are at the top. Vents are not 2-way.   So ask yourself. How much air can come out of vents if there is no air going into the attic to replace it. Answer: Not much.

Roofs with gable vents and ridge vents, vent the top portion of attic only, as air entering gable shoots across ridge and out ridge vent.  This does not create any ventilation for the bottom majority of attic and is very limited in flow. Condensation and wood rot is common in this situation as warm moist air from home that enters the attic slowly moves across plywood (leaving moisture on wood). Power fans that can help cool these poorly cross-vented attics in the hot months (4-5 months) do not run in the cool or cold months so they only work 1/3 of the time (paying for electricity all day).  Some people think that power fans are counter-productive to ridge venting. This is just not true. There is nothing counterproductive about power fans it’s just a waste of money.

If an attic doesn’t have proper soffit and ridge vent to create ‘The chimney effect’ (Chimney effect refers to the fact that hot air rises), a power fan will help ventilate the attic. Counter-productive is incorrect. Inefficient is a better word. Attic fans are 15 inch holes that provide extra exhaust venting with power on or off.  If a home has a fan, we keep it and set the thermostat to 110 degrees. The fan’s motor will only be called upon on the hottest of summer days, only at peak heat of day. Keeping central air conditioning units and ducts (out of the oven). If a home does not have an attic fan, but can be properly cross vented with soffit and ridge vent, then a power fan is not necessary. This cross vented, non-power fan assisted venting from soffit to ridge vent vents year round for free. Today it is code on new homes and necessary to avoid having your LIMITED ROOF WARRANTY being VOID.

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Other Common Roof Leak Situations

Click the links below to read about other common leaks that can affect your home.