Hi All,
I am building a screened in porch. The approx. dimensions are 14×21. I would like to insulate the floor (PT 2″x8″) so that if I decide to winterize the porch later it will already be done.
My concern is keeping the insulation dry until the roofs on and afterwards. I had intended on running furring strips between the floor joists down low and then laying 1/2″ PT plywood in, and installing round soffit vents into the ply for circulation. This would protect the insulation from underneath the porch. The porch is approx. 6″ to 24″ off the ground.
After that I would install R-19 fiberglass insulation and then go over it with 3/4″ T&G plywood. I am going to run kneewalls approx. 42″ and then screen the rest. I am concerned about rain either getting to the insulation before the roofs on or perhaps heavy blowing rain once the porch is complete. I intend on running overhangs of approx. 14″ on either side of the shed roof that will tie into the 2nd floor of the main house. Once I put the 3/4″ T&G plywood on I was going to staple a tarp over the deck and build the walls right on top of the tarp and only cut it out after the roof’s dried in. However, I just heard a horror story from my electrician about someone else who did exactly what I just described and rain still soaked the insulation before they had a chance to put the roof on.
Should I just skip the fiberglass insulation and run some rigid foam in between the floor joist ?? Could I double or even triple the rigid stuff to jack up my R value ? Or was the horror story because of stupidity on the part of the carpenters who maybe didn’t tie the tarp into the sidewalls of the house thoroughly ???
I worked as a carpenter professionally for 18 years before leaving the trades so I know what I’m doing but now I’m a little paranoid…..
Thanks !!
Joe in Oxford, CT.
Replies
"I am concerned about rain either getting to the insulation before the roofs on or perhaps heavy blowing rain once the porch is complete. "
I'm confused about exactly what you are planning to do, but I think you can count on rain blowing in at least occassionally. Frankly, I can't think of a safe way to insulate now.
tea,
Right now the screened in porch will be just that, screened in. No glass and/or window units of any type. My concerns are two fold. One is protecting fiberglass insulation prior to the walls & roof being built. The other is, once built, heavy blowing rain seeping through the 3/4" T&G plywood floor and getting to the insulation.
So I am wondering if perhaps I should just forego the fiberglass insulation completely in favor of laying in rigid foam board insulation in between the floor joists in the floor prior to the T&G ply being installed. Like I said, the deck is only anywhere from 6" to 24" off the ground so I don't want to have to try and insulate later should I decide to close in the porch and heat it.
Thanks !
Joe
"So I am wondering if perhaps I should just forego the fiberglass insulation completely in favor of laying in rigid foam board insulation in between the floor joists in the floor prior to the T&G ply being installed. Like I said, the deck is only anywhere from 6" to 24" off the ground so I don't want to have to try and insulate later should I decide to close in the porch and heat it."
I definitely wouldn't do fiberglass insulation. I'm still concerned though that moisture is going to get trapped between your foam and the floor. Maybe you could install it at a tilt so that water would drain to small weepholes which you could plug up once you actually enclose the porch? That might work.