Insulating and Existing Metal Roof

Guest User
7/5/2017
Hi there, We have a very well-built carport/shed building that we need to convert into a livable studio space. The entire structure is sound and very solid with a concrete floor and sturdy timbers throughout. It has a metal roof, installed directly over the trusses/beams, though, which we need to insulate. Looking around the internet, I've seen ambiguous and conflicting advice about what type of insulation material to use: some say that the double-bubble reflective barrier over the inside of the uppermost timbers with reflective tape at the joints is the way to go, while others think it's better to place sheets of regular insulation — albeit foil-faced — between the roofing timbers. We want to DIY this project and have the tools and experience to do a good job (my husband's father built/designed four houses and my husband helped, so we are confident we can get this done!). We want to ensure, though, that the roof stays rust free and that we can maintain a decent temperature in the building year round. We're prepared to create extra ventilation if we need to. Please find attached a picture of the roof itself, taken from the inside. What would you advise we use and where would you advise we attach it? Many thanks in advance for your expert help!
Info @windowsonwashington.net
An informed customer is our best customer.
7/5/2017
The double bubble stuff you read about is more of a radiant barrier and while it has application value in many cases, it provides little to no insulation against heat (conduction and convection) transfer. I am guessing that the roof is not vented and does not have a soffit? How about a picture from the outside? Will you be drywalling the ceiling here? Living space and what sort of activities and heating and cooling are we looking at? Thanks.
Guest User
7/5/2017
Thanks for your swift reply! So, we're hoping to maintain the architectural look of the inside — i.e. the beams, which we want to paint. We'd like to preserve as much space as possible up there, so while installing drywall on the inside is an option, we'd like it to be as close to the roof as possible. We are turning the building into an art studio, so we do need to ensure that the temperature in there doesn't fluctuate too much and that it remains usable and watertight in any season. There are no leaks at this point, and everything appears to be sound. There's no soffit on the roof at the moment — I'm going to attach a picture of what the edges of the roof look like from the "outside" (I use quotes because it's mostly open at the moment) here and I will also reply with other pictures asap. We're planning to install a ductless heating and cooling unit. The entire building measures roughly 36x24 feet, so it's just a little over 860 sq ft in there, with the space divided into the future art studio at the front (presently a space of cars with a concrete floor) and a machine shop in the back.
Guest User
7/5/2017
Another photograph of the inside here, in case it helps — this time facing the exterior edge of the building.
Guest User
7/5/2017
Just an amendment to the above — looking at the building it does seem to have functional soffit on it, albeit very rudimentary I suppose?! Here's a picture of the outside — hopefully I'm up enough that you can see what's going on? If not, please let me know and I'll get on a ladder!
Jeanne Loganbill
7/5/2017
(I've now created an account!) Another addendum: Apparently what I'm seeing there isn't soffit after all. It's just the underside of the metal roofing, so please disregard my previous reply — sorry for the confusion!
Info @windowsonwashington.net
An informed customer is our best customer.
7/6/2017
You are right. That building appears to be well constructed. You are also right that there isn't a "soffit" in the read to vent capacity. Could you vent that space with some modifications, yes. You could also run some foam board between the trusses if you created a bit of a vent space and sealed it. You would need to open up the ridge cap and cut back the roof some measured amount to allow the air to flow through continuously. Short answer...it is possible but it will be some work to get it done and make it work properly.
Jeanne Loganbill
7/6/2017
Thanks so much for your reply! What are your thoughts on using spray-foam insulation to actually seal the gaps and bring the entire roof structure into the conditioned space? Terrible idea, or potentially workable if we keep the roof exterior a lighter color?
Info @windowsonwashington.net
An informed customer is our best customer.
7/6/2017
Spray foam works quite well in these situations. I prefer to spray to the back of something (i.e. a slip layer) other than the metal so that if a panel ever gets damaged that you can pull the roof without scrapping the foam.
Jeanne Loganbill
7/6/2017
Oh good point re. the slip panel! That might be a fairly simple way to solve things. Would you anticipate there would be any need to vent the metal any more than it already is (i.e. via the grooves in the metal roof, which obvious run all the way up to the ridge) if we decided to go the spray insulation route?
Info @windowsonwashington.net
An informed customer is our best customer.
7/6/2017
If you are sealing the roof and insulating it, there is no need to vent.
Jeanne Loganbill
7/6/2017
Thank you so much for your helpful advice! We feel much more prepared to tackle this project now, and very much appreciate you taking the time to answer our (many) questions. :)
Info @windowsonwashington.net
An informed customer is our best customer.
7/6/2017
Our pleasure. Tell all your friends and thank you for using metal roofing.

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