Attic Insulation
The attic is the most critical area of the house to be insulated. It keeps you warm in winter and cool in the summer. Since heat rises, an un-insulated or under-insulated attic allows heat from the living space of your house to escape during the winter. During the summer, a sweltering attic can reduce your ability to keep your house cool. In the cold Northeast, an R-value of 49 is recommended for adequate attic insulation. In warmer climates, an R-value of 30 is recommended. Fiberglass insulation has an R-value of about 3.0 per inch of thickness. Blown-in cellulose is has an R-value of almost 4.0 per inch. This means up to 16 inches of batt or 12 inches of cellulose in the Northeast. It is essential to get an even amount of insulation over the entire roof surface. Hot and cold spots can cause ice dams. The most likely spots for ice dams are; projecting roof eaves, dormers, skylights, chimneys, cathedral ceilings, and partially finished attics. A separate unheated garage with its own separate roof is not a problem.
Cold Attic: For insulation just above the ceiling, this means you should allow a free flow of outside air from the soffit vents, all the way to the gable or ridge vents. The trick here is to provide continuous insulation from the exterior wall to the attic ceiling, without gaps in the insulation (that create cold spots) and without blocking up the soffit vents (which prevent the attic from cross ventilating, and causing humidity and mold problems). See link for soffit baffle below to solve this problem.
Warm or Finished Attic: For insulation in between the rafters, In areas where insulation butts up against rafters or roof sheathing, use rafter vents to maintain free airflow. Install batt insulation between the rafters. Do not push insulation up against roof deck or sheathing, let the rafter vents do their job of maintaining an air space to keep the cross ventilation from soffit vent to ridge vent. Finish with a layer of rigid insulation applied across the rafters and batt, and finish with the layer of drywall. Make sure that any batt or cellulose insulation that was in the floor of the attic has been removed. Leaving the old “cold attic” insulation in the floor will cause the finished attic space to become excessively humid.
Batt insulation is the easiest to install yourself. Blown-in cellulose can be done as a DYI, but it is a two man job and you will need to rent the blowing equipment. If there is old vermiculite insulation in place (it looks like a fine gravel) leave it. It may contain asbestos. Just cover it up (with floor boards or batt/cellulose insulation), and don’t agitate it or cause it to raise any dust. You will be using breathing protection for any insulation project anyway.
Good instructional graphics for batt insulation projects.
http://www.owenscorning.com/around/insulation/whatis.aspSafety instruction for DYI insulation projects. How to protect yourself when working with fiberglass.
http://www.ornl.gov/sci/roofs+walls/insulation/ins_12.htmlSoffit baffle – to prevent insulation from clogging up your soffit vents, while maintaining continuous insulation from wall to attic.
http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10051&langId=-1&catalogId=10053&productId=100388319Finished Attics and rafter vents.
http://www.hometips.com/articles/sunset_books/saving_energy/insulate_finishedattic075.htmlRoof Insulation
The other place to insulate is on the roof itself. This must be done as part of building a new roof or as part of a re-roofing job. The great advantage here is that the entire roof is insulated, no worrying about blocked soffit vents or uneven insulation. It is done with 2 to 4 inches of highly efficient rigid insulation (polystyrene or polyisocyanurate) rather than over a foot of batt or cellulose. A flat roof will have rigid insulation on the roof deck with a membrane roof on top. It is also possible to buy rigid insulation that is glued to a sheet of plywood, to give a nailable surface for re-roofing with shingles on a sloped roof. This can also be bought with vents incorporated into the “sandwich” panel.
Best web site for designers and other professionals working on new projects. Roll over the drawing of the building on the left to get menu for different building systems.
http://www.pacerepresentatives.com/ A few definitions of roofing accessories and terms:
Dew Point – A wall or roof has a warm side and a cold side. This means that at some point in the roof construction the moisture in the air will form condensation and become liquid water. This can cause many problems, especially mold growth.
Vapor Barrier – Usually some kind of paper or plastic sheet, to prevent the water from condensation from entering the living space. Needs to be combined with some form of drainage.
Underlayement – Any kind of board laid over the existing roof deck before installing new insulation and roofing. Noncombustible underlayment such as gypsum protects the interior of the building from the flammable rigid insulation.
Warning; Rigid insulation is flammable. It must be covered by a finish layer, such as gypsum. Batt insulation with paper or foil facing is also flammable. The same precaution applies.
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