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QToo
Insulating Ceiling in converted screen porch
QToo

Hi,

A long time follower of This Old House, but a first time poster. I have a question on insulating the ceiling of a converted screen porch. This is on a 100+ year old lake front cottage in Maine that had little insulation anywhere, so even some stuffed newspapers would be an improvement.

The porch is made with 2x4 walls and then 2x6 rafters (attached to side of the house with deck hangers), all fully open. The roof is old 1x6 boards on top of the rafters with a full metal roof. To convert the porch, I have fully rebuilt the side walls with large double pane thermal windows. Kept the 2x4 walls to maximize space, with 3/4" plywood sheathing and also 1" foil poly iso on the outside. Planning to install R-13 pink inside for the walls.

My question is, How do I insulate the ceiling regarding airflow or not? Because it was a screen porch, no need to worry about moisture per se, because it was always vented. By adding the windows and then insulation, I obviously will be sealing the envelope.

The intent is not to make this a showplace of energy efficiency with R-345 ceiling and R172 walls so I can warm with an LED lightbulb. I would like to make this more comfortable so it could eventually be a year round house (on piers), but that is another chapter. Need to keep in mind moisture issues and making sure the insulation stays in proper shape.

I know I just cant staple a bunch of R-24 to the rafters as eventually the moisture would make it useless. Should the rafters be ventilated with air channels built in? How would I vent this at the top as the metal roof is sealed to side of the house? Maybe go a sealed route with 1.5" of foil poly iso on the underside of the rafters with R-?? stapled behind that? Woudl this also need a vapor barrier or tyvek on the inside?

Any help would be appreciated. I have seen a number of different solutions, but most are new, or newer, construction.

Thanks so much.

QToo
Re: Insulating Ceiling in converted screen porch
QToo

Lots of views. Any insulating guys or gals out there with a tip or a push in the proper direction?

dj1
Re: Insulating Ceiling in converted screen porch
dj1

Wait for Keith to respond, he knows a thing or two about insulation.

Mastercarpentry
Re: Insulating Ceiling in converted screen porch
Mastercarpentry

Ditto on Keith, but I would insulate with an eye on future purpose. It is much easier to do that now that it will be to add more later and the cost won't be much more.

Phil

QToo
Re: Insulating Ceiling in converted screen porch
QToo

Thanks for the advice on waiting for Keith to take a look. I see that he has posted on several other threads re4cently so I am bringing this back up to the top so hopefully he sees it.

Enjoy the day.

QToo
Re: Insulating Ceiling in converted screen porch
QToo

Bumping for anyone with some ideas on what to do. Mastercarpentry had mentioned about insulating with eye to the future, but that is what I am trying to do. Looking for the proper way to handle this with the limited ability to have ventilation in this style setup. Should this be done like an unvented cathedral ceiling?

In the ceiling, should I install poly iso panels between the rafters, and air seal each panel with spray foam? 2" will get me to R-12 which is above dew point. I can then install either the pink or stone wool over that.

Thoughts? Suggestions? Warnings?

Thanks

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