Most New England homes have a sea of fiberglass batting insulation in them. Even with 6,8, or even 10" or more of fiberglass insulation, if the conditions are not right then that insulation will be severely devalued. What is the wrong condition for fiberglass insulation? Any scenario where air is allowed to move through it. When air moves through fiberglass it strips it of its ability to hold heat. So when you vent an attic and introduce cold air into an attic space, you're effectively promoting the devalued performance of your fiberglass insulation.
This client has a very nice small ranch that theoretically should be extremely efficient to heat. What the thermal photos below show is devalued fiberglass insulation due to poor installation and air leakage. A properly air sealed and insulated attic will have one solid color with no temperature variation. On this summer day, the temperatures of the attic were easily affecting the performance of the insulation and comfort of the home. This home had soffit vents with classic proper venting and when the air enters the fiberglass insulation it continues to wash across the entire attic floor. When the insulation is devalued, as shown below, heat easily conducts through the ceiling and insulation, promoting excessive summertime heat transfer into the home and heat loss into the attic in the wintertime, leading to ice damming and energy inefficiency (remember, heat goes from hot to cold).
In order to properly install fiberglass batting insulation it needs to abut perfectly on all 4 sides without gaps, kinks, or being stuffed into place - even without air movement from the soffit or gable vents, improperly installed fiberglass insulation will devalue significantly. (The photo below shows improperly installed fiberglass insulation)
ther issues occurring in this home were extensive attic hatch air leakage and unsealed window and door trim, shown below.
gain, a warm summer day. We had the blower door running when this photo was taken, so due to the depressurization of this house we were drawing in the warm attic summer air. Under normal conditions these gaps and cracks will allow winter time heat OR summer time Air Conditioned air to exit into the attic. Beyond being awfully wasteful, it can easily lead to roof top snow melt and ice damming in the wintertime.
his photo shows two scenarios of window and door air leakage; through the unsealed door jamb and around the unsealed/caulking trim. Once you've read this, walk around your home and take a look at all your interior window and door trim. Is it sealed/caulked on the sides? Now run your hands on the top and bottom of the trim where it meets the wall, is it sealed there? Most of the time there is a small 1/16" - 1/8" gap on the top and bottom with small cracks on the side. Those gaps allow this type of energy transfer and lead to energy efficiency. If you have drafty windows and want to replace them, take a look at the air sealing first and potentially save yourself tens of thousands of dollars!
Attic: Remove all the existing fiberglass insulation, air seal all penetrations (lights, electrical wiring, bath fans, chimney chases), install Accuvent/Durovent style proper venting (make sure a ridge vent exists), air seal and insulate the attic hatch, and install R49 (or more) loose pack cellulose insulation.
Windows & Doors: Air seal all the trim (preferably interior and exterior) with caulking and/or silicon