If there's condensation it seems like it would develop primarily on the top of the beam and drip down? The beam top is where the greatest temperature differential lies. Will the roof vents prevent condensation, anyway?

It looks like it wouldn't be possible to encase the top of the beam because it's likely flush against the rafters? So, there may be condensation whether it's "naked" or surrounded by drywall or wood anyway. If there's drywall or wood it would really be a mess assuming the water drips down from top of i-beam.

So, might as well leave it exposed for a winter and check it out? See if it stays dry? If your house maintains a regular temperature it would surprise me if water condenses on the beam. You could also cover it over in the spring if need be?

We have several interior beams and really like the feeling. In our case they aren't quite so close to the ceilings - there's insulation above them. We also used metal in other ways, too: as a fireplace bench and above sliding doors.

There is wooden block sitting on the top of the beam which is about 2 inch thick and then 2x8 rafters are sitting on that wooden block. Roof plywood is on the other side of the rafter and then there is roof after that. Basically a typical attic-less cathederal ceiling.

Condensation happens when hot air hits the colder surface. So his theory is beam is going to get cold enough in the winters that hot air from inside the house is going to hit the colder surface of the beam and it will create condensation.

I am betting my money on the fact that beam might just never get cold enough since it is mostly inside. I am afraid to be wrong on that.

Thermal bridging in my opinion usually happens when one side of the material is eposed completly to outside weather and other side of it is inside. With ridge vent on top and 2x8 rafters I see a clearing of good 10-12 inches of air space betweem roof surface and the beam. It would be interesting to see of that makes it cold enough. 10 inches bein in the case where ridge vent is absent since it does not run all the way across the roof.

If you touch your drywall on the ceiling in the winter you will notice it cold. But it is not cold enough to cause thermal bridging. I was hoping that will hold true in case of steel beam as well, but steel is much better conductor than wood or drywall. So we never know.

His logic behind putting covering beam with drywall or wood is the hot air will not be in direct contact of the steel surface. It has logic.

I could try to break any potential thermal briding by putting insulation that will run over that wooden block sitting on beam. But I wonder what kind of insulation I can use in this application, which will leave adequate space for roof ventilation. In theory I should have a minimum of 2-3 inch space to work with insulation.

your place looks great, what kind of insulation do you have on the top behind the steel beams? I love the exposed ceiling. I wish I could have that.

The air around the beam will keep it warm enough to prevent condensation.

Why is there a ridge vent if the joist bay is full of insulation? If there is a channel for fresh air above the insulation fine, I still wouldn’t worry about the beam once it was wrapped since there is insulation above it plus that wood spacer will help. We used drywall to wrap our beam so it wouldn’t dominate the space.

yes there is around 3 inch channel after the insulation to keep the roof vantilated. Rafters are not completly filled with insulation because it is a vantilated roof. I know people are doing closed cell polyeurothene these days which I am never really sure about and in my opinion will make roof really hot in the summer and coock your roof's shingles or membrane. Which is why maybe guys doing metal roof these days.

Anyways I am getting side tracked here.

So verdict seems to be that beam might just never get cold enough to cuase the condensation.

To be on safe side I will run a 3 inch rockwool insulation from rafters to the point where that wooden blocks sits on the beam on both sides of the beam and count on that wood block to break the thermal bridging on point of contact where it sits & will update you guys how it goes in winters.

If anyone have better ideas please feel free to comment.

Thank you.

@jony Thanks for explanation. A ceiling fan could be useful, too, IF there's condensation. The fan would obviously reduce the temperature near highest point of ceiling.

All of what is seen in the pics is "fake", that is non-functional. Above the exposed beams are a bunch of wooden engineered i-beams as rafters on 16" centers. Those beams support the ceiling and then there's extensive bat insulation with foam sprayed around corners. The metal i-beam is non-functional, too, ha ha; if today's prices (not 2 years ago) we probably would've bought a rubber or plastic i-beam to save costs.

As an aside the whole wall facing mountains is windows or doors (shed roof shape), so there's a welded steel frame that's invisible but the engineers scoped it so wind wouldn't just blow the whole wall in; plus the metal frame gives vertical structural support to that wall span.

I wanted that I spent whole Canadian winter with it. No condensation what so ever.