building a room in my attic... how to prevent melting snow?

[MrDanky]

I am currently building out my attic... i live in a northern region where it gets very cold in the winter time... I recently put up some r-13, and some r-4 sheets and im hoping that will be enough insulation to allow snow to sit on top of the roof without melting. I will be running 4k watts, and cooling with 2- 8inch 747cfm vortex fans. I am really concerned about the snow and was wondering if I should be ok or if there is more that I should do in order to safeguard myself from heat escaping the sectioned off room in this attic and causing icicles and melted snow on my roof. So basically what i have is the r-13 in between the skeleton of the roof, then the r-4 sheets (the shiny/sturdy/styrofoam stuff) on top of the r-13. then I plan on putting up some panda film (dont tthink that will really help me much)...

i am hoping that I will not have any problems with melting snow and the point of me writing this thread is to see what anyone with experience has to say about it. (such as, yeah man, youll be ok... or... no way dude, you are doomed, you need more insulation)

In the summer time I plan on hookin up a ductless mini split to handle the heat...

what do you all have to say??

 

[Throwgar]

Don't do it! The snow will be the least of your problems. Ventillation and AC is a KILLER!

 

[madpenguin]

Don't do what? He has already setup the attic. Plus, with winter arriving, AC will be the least of his worries. He's going to need a space heater hooked up to a T-stat more than likely. Hopefully the lights will keep things warm enough during the light cycle but when the lights go out, it's going to get REALLY cold up there.

Do you live in an old house? Do you live in a neighborhood that is full of old houses? If so, I wouldn't worry about melting snow on the roof. My next door neighbors 3rd floor roof space on the north west side always melts snow and it does get me thinkinging but I live in a neighborhood where ALL the houses are atleast or close to 100 years old. If the attic is finished and being lived in with baseboard heaters installed, then you'll see bare spots on peoples roofs all the time.

I think you might be alright. There's only one way to tell. The first good snow you get, take a walk across and down the street and see what it looks like. This is something I always worried about periodically last year but I always forgot to look at my roof to see if it was holding snow or not...

You probably should have splurged for the more expensive stuff if you were really worried about it. Like the R-30 whatever crap. Bout 5 times as expensive as the R-13 but.....

 

[boroboro]

Is this a room-in-a-room? If so, I would move a lot of air around the outside of the room, especially above the room-in-a-room. Hopefully that would dissipate the extra heat coming off of the walls enough to keep snow from melting.

I think a room-in-a-room in an attic could work. Clearly there would be extra a/c requirements in summer, though. You would need to cool it 30-40F under ambient, instead of maybe 10F under ambient in a regular room.

I would sure have a lot more than R-13 insulation, though... maybe 2 layers of it...

 

[Sam the Caveman]

You could line the walls and ceiling with prodex. Prodex is 5mm thick with a R value of 15.6 and has a reflective side and is relatively cheap. 700 sq. ft for ~$200 + shipping.

I'm not affiliated with the company in any way, just do a google search to find it.

 

[Rysam]

If you insulate the ceiling it is critical to make sure you have plenty of airflow between the insulation and the roof sheeting. THIS IS VERY VERY IMPORTANT!!!!! it will keep the mold and funk from growing in-between your insulation and roof from condensation. This will also prevent the roof from melting(or rotting off in a few years). They sell a foam baffle doohickey that looks like a "W" that you staple to the underside of the roof for just this reason. they go from the eave vent to the ridge. then when you install the insulation put as much as you can in the bay without compressing the insulation. compressing it lowers its R-value. 2x4=R13 2x6=R19 and on and on....(you can get HD batts too but they arent cheap.)
To qualify myself, I was a Journeyman insulator for 10+ years in all climates from Michigan to California.

Edit:with proper airflow like i posted earlier i think a total of R-17 would be fine.