Upgrading the insulation and ventilation of an existing attic?
I have a client with a simple 42’x36′ Ranch home in SE Pennsylvania. They have an attic that has 2×6 ceiling joists @ 16″ OC and 2×8 rafters @ 24″ OC. The roof is asphalt shingles over 1/2″ plywood. There is a continuous ridge vent AND gable end vents at each end wall…one that has a thermostatic exhaust fan. There appears to be no soffit vents as the fiberglass insulation extends all the way to the roof sheathing at the bottom of the roof. The ceiling is insulated with R-19 fiberglass batts between the joists and they have have a pull down attic ladder with no insulation or cover. They are looking for the following work to be done…
– Replace the entire roof with new asphalt shingles…replace a section of plywood that has been water damaged
– Have (3) Skylites replaced at the same time…and improve the insulation at these light wells which go from the roof to the living space below
– And improve their attic insulation
– Replacing the asphalt shingles is easy enough….but do you keep the ridge vent if there are no soffit vents? Reading some of JListebrik’s articles the answer is NO since the air pressure change occurring at the ridge vent causes air to be sucked up thru the house ceiling and all of the penetrations that exist in that ceiling.
—-so if you eliminate the ridge vent, do you keep the (2) gable vents and exhaust fan?
– We would plan to reframe and re-drywall the skylite light wells and then wrap them with 2″ XPS foil faced rigid foam on the attic side of the assembly with all joints taped or spray foamed. Would this be appropriate?
– Can we just install 12″ of blown in cellulous on top of the fiberglass installation to bring it up to R-49…or is that wasting money if we don’t first do air sealing at the ceiling drywall?….which would require that we pull back (or pull out completely) all of the fiberglass to get to the penetrations which need to be sealed. I know this would be the BSET thing to do but is the ROI worth it verses just adding the 12″ of loose cellulous? I have a quote for the new cellulous of $1350
—-OR would it make best sense to eliminate both the ridge vent AND the Gable Vents and then spray foam the underside of the roof system and the gable end walls with 4″ of closed cell spray foam and forget about the blown-in cellulous and air sealing at the ceiling. I have a quote of $5300 to do this.
– We will plan on building an insulated hatch box using 2″ rigid foam to cover the access ladder
– The client will eliminate all storage of belongings in the attic
See Photos inside the attic space attached.
Thanks for your comments,
GBA Detail Library
A collection of one thousand construction details organized by climate and house part