Insulating existing metal roof

[Kitt]

Anybody have suggestions? I want to avoid spray-foam.

Wondering how to get an effective vapor barrier in place from inside, and what others have done.

Thanks!

[BMFR6]

Don't quote me on this, I'm not a contractor by any means.
Are the rafters exposed inside? Could you just use a high R value rolled insulation w/paper a paper face, then staple the plastic vapor barrier up? I though vapor barrier was intended to go on the warm side of insulation due to condensation.

[Kitt]

Don't quote me on this, I'm not a contractor by any means.
Are the rafters exposed inside? Could you just use a high R value rolled insulation w/paper a paper face, then staple the plastic vapor barrier up? I though vapor barrier was intended to go on the warm side of insulation due to condensation.

I'm thinking the condensation on the roof itself may drip onto the fiberglass/paper backing if I did it that way...

[DesmoTull]

My company has used Johns Manville products in the past in DPW garages.

http://www.jm.com/insulation/buildin...icrolite_l.pdf

[slammp]

Metal in/out as in shed style or house with metal shingles?

If its the latter why not use the plastic channels they sell for vaulted ceilings (home depot or lowes) you run them between the studs from top to bottom then put the insulation behind it so there is a channel of air against the inside of the roof line. I would use the insulation that comes wrapped in plastic - easier to use and no worries on the condensation - although you shouldnt get any with the channels in place.

You would need to drill soffit vents and make sure you have a ridge vent too.

[fjrrider RI]

whatever insulation fits you will need to provide air flow from the bottom up and out or you will get much condensation and carpenter ants ie roof vent or side vent. Best to use the fiberglass if possible then look at others. consider insulating the cieling rafters instead of the roof frames, much easier dropping in insulation than stapling up! Either way protect yourself from the glass fragments they do not degrade and stay with you!!! (in skin pores and nose and lungs) Use a mask and wear turtle neck evenwhen hot.) Good luck

[slammp]

Second thought (sorry for the A.D.D) what about rigid foam - it comes as thick as 1 1/2 inch with tongue and groove - you could spray adhesive it up.

[BMFR6]

I'm thinking the condensation on the roof itself may drip onto the fiberglass/paper backing if I did it that way...

I agree with that but I think we are missing something about how it works. I'm about 99.9% certain this is the way it's done on exterior walls so I'm not sure why (beyond gravity) a roof would be different. Is it going to be a cathedral ceiling? Guess I am wondering why you actually want to insulate it as most roofs should be designed to stay cold, in turn preventing melting snow and ultimately preventing ice dams.

[DesmoTull]

whatever insulation fits you will need to provide air flow from the bottom up and out or you will get much condensation and carpenter ants ie roof vent or side vent. Best to use the fiberglass if possible then look at others. consider insulating the cieling rafters instead of the roof frames, much easier dropping in insulation than stapling up! Either way protect yourself from the glass fragments they do not degrade and stay with you!!! (in skin pores and nose and lungs) Use a mask and wear turtle neck evenwhen hot.) Good luck

Insulate & Ventilate. Lstiburek talks at great length about that.

Question. Is there an attic space, or is it all open?

[DesmoTull]

I agree with that but I think we are missing something about how it works. I'm about 99.9% certain this is the way it's done on exterior walls so I'm not sure why (beyond gravity) a roof would be different. Is it going to be a cathedral ceiling? Guess I am wondering why you actually want to insulate it as most roofs should be designed to stay cold, in turn preventing melting snow and ultimately preventing ice dams.

Mark, everything you ever wanted to know about ice dams.

John Straube is a principal of the Joe Lstiburek firm. Building Science Digest is published by Lstiburek.

Lots of geeky engineering stuff in the attachment.

[SSearchVT]

Is it in an unfinished attic space or are you trying to make a vaulted ceiling?

The unfinished attic - roll out the fiberglass batting. Leave room at the soffits for air flow. There's arguments both ways about vapor barriers... I don't have it - haven't had any concerns and my heat bill is pretty cheap...

Making a vaulted ceiling - You want the vapor barrier on the warm side of the insulation in cold weather. Use channeling to allow airflow from your soffit vents to either the ridge or gable vents depending on how your roof is set up. Put in the insulation (paper backed batting is the easiest and fastest DIY in my opinion. Put up a layer of plastic sheeting.

The airflow is supposed to minimize condensation on the back of the roof.

[DesmoTull]

The unfinished attic - roll out the fiberglass batting. Leave room at the soffits for air flow. There's arguments both ways about vapor barriers... I don't have it - haven't had any concerns and my heat bill is pretty cheap...

I'm with you as long as there is a proper air barrier...

[keeena]

Don't quote me on this, I'm not a contractor by any means.
Are the rafters exposed inside? Could you just use a high R value rolled insulation w/paper a paper face, then staple the plastic vapor barrier up? I though vapor barrier was intended to go on the warm side of insulation due to condensation.

This is right. Roof sheathing is supposed to be a cold zone. Vapor barrier facing living space. Insulation behind that.

If you have an open attic, insulate ceiling joists. Entire attic cold zone via ridge/soffit or gable vents.

If you have cathedral, insulate rafters but keep a air gap between insulation and roof sheathing. There are panels you can buy to help keep this gap between batt insulation and sheathing. Air gap allows circulation from soffit to ridge.

[Kitt]

Metal in/out as in shed style or house with metal shingles?

If its the latter why not use the plastic channels they sell for vaulted ceilings (home depot or lowes) you run them between the studs from top to bottom then put the insulation behind it so there is a channel of air against the inside of the roof line. I would use the insulation that comes wrapped in plastic - easier to use and no worries on the condensation - although you shouldnt get any with the channels in place.

You would need to drill soffit vents and make sure you have a ridge vent too.

any diagrams or pics?

whatever insulation fits you will need to provide air flow from the bottom up and out or you will get much condensation and carpenter ants ie roof vent or side vent. Best to use the fiberglass if possible then look at others. consider insulating the cieling rafters instead of the roof frames, much easier dropping in insulation than stapling up! Either way protect yourself from the glass fragments they do not degrade and stay with you!!! (in skin pores and nose and lungs) Use a mask and wear turtle neck evenwhen hot.) Good luck

it will be vented at the bottom, but cathedral ceiling, so other than the way the peak is vented, I wont be able to add any on end at the peak.

My company has used Johns Manville products in the past in DPW garages.

http://www.jm.com/insulation/buildin...icrolite_l.pdf

I'll check them out.

Second thought (sorry for the A.D.D) what about rigid foam - it comes as thick as 1 1/2 inch with tongue and groove - you could spray adhesive it up.

Looking for a decent R value, as this is the ceiling to a master bedroom...

I agree with that but I think we are missing something about how it works. I'm about 99.9% certain this is the way it's done on exterior walls so I'm not sure why (beyond gravity) a roof would be different. Is it going to be a cathedral ceiling? Guess I am wondering why you actually want to insulate it as most roofs should be designed to stay cold, in turn preventing melting snow and ultimately preventing ice dams.

it's the ceiling to a new bedroom I'm putting in.

[Kitt]

Making a vaulted ceiling - You want the vapor barrier on the warm side of the insulation in cold weather. Use channeling to allow airflow from your soffit vents to either the ridge or gable vents depending on how your roof is set up. Put in the insulation (paper backed batting is the easiest and fastest DIY in my opinion. Put up a layer of plastic sheeting.

The airflow is supposed to minimize condensation on the back of the roof.

If you have cathedral, insulate rafters but keep a air gap between insulation and roof sheathing. There are panels you can buy to help keep this gap between batt insulation and sheathing. Air gap allows circulation from soffit to ridge.

OK... this is what I need. pics/info on the channeling, and what type of plastic/vapor barrier? I am going to have non-mold resistant drywall put up when the insulation is done.

[DesmoTull]

OK... this is what I need. pics/info on the channeling, and what type of plastic/vapor barrier? I am going to have non-mold resistant drywall put up when the insulation is done.

Look at my attached PDF above...

[Kitt]

Look at my attached PDF above...

that just looks like a plastic-backed insulation... you saying that would work as-is plastic side towards bedroom?

[SSearchVT]

Use just about any plastic sheeting for vapor barrier. I've seen 2 mil plastic drop cloth material in rolls, and I've also seen black plastic (10 mil or so). You're in VT - Chase around with some metal roof sealant on the inside of the roof first, and maybe even expanding foam along the roof joists where they touch the metal (prevent all possible water leaks).

The air channels are available at Home Depot or any good lumber yard - Measure between the joists first - they might have a few widths. Run them the entire length of the ceiling/roof that you will have drywall on and make sure they will stick a few inches above the insulation in any attic space you have.

Get the right thickness paper backed insulation (don't compress it - it won't work as well), or stack rigid foam sheets, or have expanding foam shot in. Your choice on final insulation material.

If you don't have one yet - spend the $20 on a slap stapler... It'll be the smartest money you spend. The downside is it'll be so easy to put staples in you'll use a Sh*tload of them...