Spray Foam Insulation

[ovrszd]

Skylights are like holes in the bottom of a ship. You cannot do anything with them until they leak, then the best thing is to throw them away and put on a new roof.

I've never understood them. And I had never heard someone ask about how to insulate a column going to one. That's why I asked of it's R value.

 

[goeduck]

Skylights are like holes in the bottom of a ship. You cannot do anything with them until they leak, then the best thing is to throw them away and put on a new roof.

Not the skylights themselves, but insulating the columns (for lack of a better description) in the attic. The sheetrocked walls up to the shylights on non-vaulted ceiling. On the attic side, what is the best way to insulate? Obviously you cannot use blown in. Bats sag and pull away exposing gaps to the attic. Is spray on closed cell appropriate here?

 

[goeduck]

What R value are the skylights?

I do not know, they are existing. Surface area wise, the columns going up to the shylights are way more than the skylights themselves. At some point I may replace the skylights but as a separate effort than re-insulating the attic. If I had vaulted ceilings and skylights it would make more sense as Eddie says to remove them. But the non-vaulted ceiling geometry makes that more difficult and they are architecturally important (at least two of them anyway). Plus SWMBO says no way the skylights are going away.

 

[ovrszd]

This goes back to what Eddie has mentioned several times. "Walls", meaning vertical surfaces require less R value than "ceilings", meaning horizontal surfaces.

So, if you are talking about insulating the vertical walls going up to the horizontal skylights I would say you need to stop air movement thru those walls. Beyond that, R value is of less importance.

So, if you are saying the vertical walls going up to the horizontal skylights are not insulated, I would say you need to stop air movement thru those walls. Closed Cell Spray Foam would best accomplish that in regards to an existing vertical wall.

 

[LouNY]

I believe the OP may be talking about something like a Sola Tube it has a collection dome on the roof,
with a polished tube that comes down to a distribution panel in the ceiling.
They have no insulation value relying on the trapped air to prevent or slow thermal movement.
I would think that any kind of spray on would help or even batting that was attached high and allowed to hang.

 

[ovrszd]

I believe the OP may be talking about something like a Sola Tube it has a collection dome on the roof,
with a polished tube that comes down to a distribution panel in the ceiling.
They have no insulation value relying on the trapped air to prevent or slow thermal movement.
I would think that any kind of spray on would help or even batting that was attached high and allowed to hang.

Awww,, got it,, thanks for the clarity Lou. And I agree with your solution.

 

[goeduck]

This goes back to what Eddie has mentioned several times. "Walls", meaning vertical surfaces require less R value than "ceilings", meaning horizontal surfaces.

So, if you are talking about insulating the vertical walls going up to the horizontal skylights I would say you need to stop air movement thru those walls. Beyond that, R value is of less importance.

So, if you are saying the vertical walls going up to the horizontal skylights are not insulated, I would say you need to stop air movement thru those walls. Closed Cell Spray Foam would best accomplish that in regards to an existing vertical wall.

I attached a picture of one of the skylight areas. I am interested in the insulation of the areas marked in red on the attic side. Below the red horizon line they are insulated by ceiling bats and I am thinking about adding blown in insulation on top of that as Eddie recommended in a post above. Above the horizon like line they are insulated by vertical bats between studs loosely supported by strings wrapped around the column going up to the skylight. Not the best fastening method. The bats over the years have sagged a bit and some sheetrock is exposed to the attic temperatures. One advice I had was to resupport and add another layer of bats horizontal. Reading this thread spray on closed cell seems to make sense. Since heat rises, these skylight areas could lose more heat than my walls depending on attic temperatures.

 

[LouNY]

Awww,, got it,, thanks for the clarity Lou. And I agree with your solution.

Nope, I guess not looking at his picture it looks like a conventional skylight boxed in with convention sheet rock construction.

I have a couple of dark rooms and have looked at the Sola Tubes a few times.

 

[aczlan]

Nope, I guess not looking at his picture it looks like a conventional skylight boxed in with convention sheet rock construction.

I have a couple of dark rooms and have looked at the Sola Tubes a few times.

Looking at the picture that was posted, I agree that spray foam is probably the best route to insulate the backside of it. I would probably buy a Froth Pak that is rated to cover about twice the square footage of the outside of the skylight and have at it. I would probably also pull the insulation back around the base so that you can foam around the whole sky light outside from top to bottom. The bottom part where the other insulation is I would just try to do a skim coat but the upper part you would probably want a couple of inches on.

Aaron Z

 

[YLee Kioti]

If you are building, here is something new to consider, insulated 2x6 studs. Wood only has an R value of 1/inch. You may have R19 in the walls, but with 10% of your wall being studs with only an R value of 6, the overall wall R value is about 12. You need to do something to break the thermal bridge that the 2x6 creates. I have no affiliation with this company, I just stumbled upon them a few weeks ago when researching building materials.
Tstud

I saw the T-Stud product on the Matt Risinger you toob channel.
IF, and a big IF, you can get your builder to show interest in using it it seems like a leap forward in thermal efficiency and also vertical shear strength.
We had one builder just openly tell me he hated the internet and he would only build a house his way.
We thanked him for his time and deleted his phone number. lol...

Lots of other good ideas on Matt Risinger channel as well.....good luck...